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I ,. .,,. SUSITNA HYDROELECTRIC PROJECT :?~
·,,· = FINAL REPORT e;11
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•• ~~ BIG GAME STUDIES 110.'11~1
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by
Ronald D. Modaferri
Alaska Department of Fish & Game
333 Raspberry Road
Anchorage, Alaska 99518
December 1988
ARLIS
Alaska Resources.Lihrarv & Information SeIVlces
Libra!)' Build1ng, Suile 111
3211 Providence D rive
Anchorage, AK 9950&4614
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PREFACE
Between January 1980 and June 1986, the Alaska Power Authority
(APA) contracted with the Game Division of the Alaska Depart-
ment of Fish and Game (ADF&G) to provide field data and
recommendations to be used for assessing potential impacts and
developing options for mitigating impacts of the proposed
Susitna Hydroelectric Project on moose, ·caribou, brown bear,
black bear, Dall sheep, wolf, wolverine, and belukha whales.
ADF&G was only one of many participants in this program.
Information on birds, small mammals, furbearers, and vege-
tation was collected by the University of Alaska and private
consulting firms.
Formally, ADF&G's role was to collect data which could be used
to describe the baseline, pre-project conditions. This infor-
mation was supplemented with data from other ADF&G studies.
Baseline conditions were defined to include processes which
~ight be sufficiently sensitive to either direct or indirect
project induced impacts to alter the dynamics of the wildlife
populations. The responsibility ·of impact assessment and
mitigation planning was assigned by APA to several private
consulting firms. ADF&G staff worked closely with these
firms, but only in an advisory capacity.
The project was .cancelled before the impact assessment and
mitigation planning processes were complete. In an effort to
preserve the judgments and ideas of the authors at the
termination of the project, the scope of this report has been
expanded to include material relating to impact assessment and
mitigation planning. Statements do not necessarily represent
the views of the APA or its contractors. Conjectural state-
ments sometimes are included in the hope that they may serve
as hypotheses to guide future work, should the project be
reactivated.
The following list of reports completely cover all of the Game
Division's contributions to the project. It should not be
necessary for the reader to consult the many progress reports.
Moose
Modaferri, R. D. 1987. Susitna Hydroelectric Project, Big
Game Studies, Final Report Vol. I -Moose -Downstream.
Alaska Dept. of Fish and Game.
Ballard, W. B .. and J. S. Whitman. 1987. Susitna Hydroelec-
tric Project, Big Game Studies, Final Report, Vol. II -
Moose -Upstream. Alaska Dept. of Fish and Game .
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ARLIS
Alaska Resources
Library & Information SerVices
Anchorage, Alaska
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Becker, E. F. and W. D. Steigers. 1987. Susitna Hydroelec-
tric Project, Big Game Studies, Final Report, Vol. III -
Moose forage biomass in the middle Susitna River basin,
Alaska. Alaska Dept. of Fish and Game.
Becker, E. F. 1987. Susitna Hydroelectric Project. Big Game
Studies. Final Report. Vol. V. -Moose Carrying
Capacity Estimate. Alaska Dept. of Fish and Game.
Caribou
Pitcher, K. W. 1987. Susitna Hydroelectric Project, Big Game
Studies. Final Report. Vol. IV -Caribou. Alaska Dept.
of Fish and Game.
Black Bear and Brown Bear
•Miller, S. D. 1987. Susitna Hydroelectric Project. Big Game
Studies. Final Report. Vol. VI -Black Bear and Brown
Bear. Alaska Dept. of Fish and Game.
Wolf
Ballard, w. B., J. S. Whitman, L. D. Aumiller, and P. Hessing .
1984. Susitna Hydroelectric Project, Big Game Studies.
1983 Annual Report. Vol. V -Wolf. Alaska Dept. of Fish
and Game. 44pp.
----, , and C. L. Gardner. 1987. Ecology of
an exploited wolf population in southcentral Alaska.
Wildlife Monograph No. __ (In press).
Wolverine
Whitman, J. S. and W. B. Ballard. 1984. Susitna Hydroelec-
tric Project, Big Game Studies. 1983 Annual Report.
Vol. VII -Wolverine. Alaska Dept. of Fish and Game.
25pp.
Dall Sheep
Tankersley, N. G. 1984. Susitna Hydroelectric Project, Big
Game Studies. Final Report. Vol. VIII -Dall Sheep.
Alaska Dept. of Fish and Game. 9lpp.
Belukha Whale
Calkins, D. 1984. Susitna Hydroelectric Project. Big Game
Studies. Final Report. Vol. IX -Belukha Whale. Alaska
Dept. of Fish and Game.
ii
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SUMMARY
Recent demand for nonfossil fuel energy in southcentral Alaska
has stimulated public interest and initiated formulation of a
proposal to develop the hydroelectric potential of the Susitna
River. The proposal is based on construction of two impound-
ments: (1) an earth/rock filled dam at a site between Tsusena
and Deadman Creeks and (2) a concrete arch dam at Devil
Canyon. Each would have electric generating facilities, with
a combined capacity of about 1200 megawatts.
Feasibility of the proposed project will be determined by
evaluating environmental impacts as well as economics.
Environmental impacts may be linked to alterations in
hydrological characteristics of the Susitna River or to other
nonhydrological factors associated with construction and main-
tenance of the proposed project.
Impacts resulting from alterations in river hydrology can be
divided into two categories: (1) those occurring upstream
from the impoundments and (2) those occurring downstream from
the . impoundments. Impacts upstream from impoundments will
primarily involve immediate ·loss of habitats through
inundation. Impacts occurring downstream from impoundments
will probably involve gradual and less dramatic changes in
riparian environments through altered flow regimes and charac-
teristics of the water itself. Altering hydraulics of the
Susitna River may affect wildlife directly or indirectly
through several intermediate environmental components. The
ultimate impacts, arising from the direct or indirect effects
of hydroelectrical development on migratory species of wild-
life, may occur over a long period of time.
In a 215-km course from Devil Canyon to Cook Inlet, the
Susitna River and its tributaries drain about 800,000 km 2 of
watershed in the Susi tna River valley. Perhaps the innate
value of the Susitna River floodplain as wintering habitat for
moose (Alces alces gigas Miller) is unsurpassed elsewhere in
the state.
The general objective of this study was to determine the
probable nature and approximate magnitude of impacts of the
proposed Susitna River.hydroelectric project on moose subpopu-
lations downstream from the prospective Devil Canyon dam site.
To accomplish this, one must understand how moose subpopu-
lations utilize habitats on the Susitna River floodplain
(i.e., what is the ecological value of these habitats to
moose?) and other more distant habitats that may be indirectly
altered by the proposed hydroelectric project. Ecological
values of floodplain environments to moose must be identified
iii
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and understood before impacts of the proposed hydroelectric
development can be knowledgeably evaluated.
Specific study objectives were the following: (1) determine
t.iming, duration, and magnitude of moose use of floodplain
habitats along the Susitna River downstream from Devil Canyon;
(2) identify moose subpopulations that are ecologically
affiliated with the Susitna River downstream from Devil
Canyon; (3) determine seasonal distribution and movement
patterns for identified moose subpopulations; (4) identify
mechanisms through which proposed hydroelectric development
1;vill impact moose subpopulations; ( 5) determine probable
nature and approximate magnitude of impacts on identified
Jmoose subpopulations; (6) delineate a geographical zone encom-
passing moose subpopulations impacted by proposed hydroelec-
tric development; (7) discuss potential options for mitigating
impacts from hydrological development with moose; and
(8) quantify potential of various mitigation options.
This report is primarily based on data from relocations of
radio-marked moose collected between 4 April 1980 and 19 June
1985 and from supplemental moose censuses and surveys
conducted from 9 December 1981 through 24 December 1986.
Pertinent findings detailed in Phase I progress (Arneson 1981)
and fin~l reports (Modafferi 1982) and Phase II ~regress
(Modafferi 1983) and annual reports (Modafferi 1984) are also
included.
Timing, duration, and magnitude of seasonal and annual moose
use of floodplain habitats were primarily assessed from 6, 11,
7, and 11 aerial censuses conducted during five winter periods
between ·December 1981 and April 1985, respectively.
Patterns of movement, habitat use, productivity, survival, and
identity of moose subpopulations ecologically affiliated with
the Susi tna River floodplain were determined primarily from
relocations of 18 male and 51 female radio-marked moose.
Moose were radio-marked along the Susi tna River floodplain
between April 1980 and January 1985 along the Susitna River
floodplain. Five moose marked in 1980 were recaptured in 1984
and collared with new radio-transmitters.
Some moose used Susitna River floodplain habitats throughout
the year. Large numbers of moose occurred on the floodplain
in winter when snow and foraging conditions became unfavorable
to subpopulations in adjacent habitats. Numbers of moose
utilizing floodplain habitats were closely related to severity
of climatic conditions in the surrounding watersheds.
Findings presented here must be considered cautiously, since
they are only representative for winter weather conditions in
iv
which sampling and surveys occurred. During the study, annual
winter weather conditions varied widely.
In the mild winter of 1981-82, a maximum of 369 moose were
observed on six censuses of Susitna River floodplain habitats
downstream from Devil Canyon. During relatively inclement
winters, maxima of 934 and 819 moose were observed on similar
censuses in November 1982 and March 1.984, respectively. In
1985, following extremely heavy snowfall, a portion of the
floodplain contained 50 percent more moose then were observed
in the previous three winters. Because other data indicate
that moose may not utilize the floodplain daily and annually,
numbers of different moose affiliated with the floodplain are
probably greater than the projected estimate.
Within and between year variations in moose occurrence on the
floodplain in winter were primarily associated with effects of
snowfall on moose behavior. Number of moose observed on the
floodplain correlated with snowpack depth in adjacent areas.
Moose rapidly responded to large increases and decreases in
snow depth. Theoretically, gradual increases in snowpack
depth would promote maximal moose use of the floodplain winter
range. Abrupt heavy snowfall may impede moose migrations to
traditional lowland winter ranges. Winter mortality and other
·factors which affect population levels may contribute to
annual variation in moose use of floodplain wintering areas.
Data from individuals radio-marked on the floodplain in winter
were used to identify areas that these moose subpopulations
ut.ilized during open hunting season, calving, and summer
se~asonal periods. These data were used to predict where
impacts to moose from hydroelectric development would become
evident during various seasonal periods. Radio-marked moose
ranged far from the floodplain during nonwinter seasonal
periods.
Lowest winter moose densities on the floodplain occurred in
mature forested habitats where forage was limited and snow was
deep. Greatest . moose densities occurred in open forest
habitats on high relief islands near Cook Inlet where
prevailing winds precluded accUmulation of a deep snowpack.
Largest numbers of_ moose were observed in low relief flood-
plain areas where dynamic river flow regimes maintained early
successional plant corrununities which provided high-quality
moose forage.
Moose from fourteen different subpopulations were identified
to utilize the Susitna River floodplain in winter. Behavior
patterns for moose that utilized floodplain habitats varied
within and between subpopula tions. Some moose of each sex
migrated up to 25 km from summer-fall range to winter on the
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floodplain. Summer-fall ranges of other moose of each sex
occurred syrnpatric with floodplain winter ranges.
Many female moose radio-marked downstream from Talkeetna
utilized wet muskeg habitats west of the floodplain during
parturition. Most females radio-marked north of Talkeetna
departed the floodplain in early spring but returned at the
time of parturition. Movements in both areas may be related
to predator avoidance and/or availability of high-quality
herbaceous forage for both females and offspring.
The Susitna River was not a barrier to moose movements. Moose
commonly crossed the river. Many moose had activity centers
on both sides of the floodplain. Moose north of Talkeetna
crossed the floodplain most frequently during May and June.
Moose south of Talkeetna crossed mostly between February and
April.
Moose north of Talkeetna generally had smaller annual ranges
than moose south of Talkeetna. Some moose in large islanded
habitats south of Talkeetna seldom moved off the floodplain
and had small annual ranges that lacked discrete activity
centers. Other moose exhibited two activity centers: a
winter one on the floodplain and another one removed from the
floodplain. Data from a few individuals indicated three or
four seasonal activity centers. Most moose consistently
utilized the same activity centers annually. Some moose
exhibited movements that were 11 extraordinary 11 with respect to
documented activity centers.
Mortality of moose in the lower Susi tna River valley was
at.tributed to a variety of causes. Large numbers of moose
were killed by collisions with trains and vehicles in the
Alaska Railroad and highway rights-of-way, respectively, when
snowpacks became deep in adjacent areas and surrounding
uplands. In winter 1984-85, 325 moose were reported killed by
trains in the project impact area. About 100 moose may be
killed by highway vehicles in the same sized area. Mortality
rates varied along rights-of-way and between different moose
subpopulations. Use of deicing salts on roadways may attract
moose and increase mortality rates from collisions with
VE~hicles. Five of 21 moose radio-marked north of Talkeetna
WHre subsequently killed by trains.
Death of six radio-marked moose was attributed to "winter
kill," a catch all category for moose that died in winter
presumably from inadequate nutrition.
Mortality of other radio-marked moose was attributed to
slipping on glare ice; falling through open water leads or
thin ice while crossing frozen rivers; drowning while
vi
attempting to cross sections of open water, log jams, or ice
jams: and injuries sustained from intraspecific fights during
the rut or from bullets during the open hunting season.
One radio-marked moose was killed in defense of life and
property. Inclement winter weather conditions can stress
moose and cause them to become aggressive towards humans.
During inclement winters, it is not uncommon for moose to be
killed in defense of life and property. About 50 percent of
the radio-marked male moose were subsequently killed by
hunters during open hunting season.
Although brown and black bears occurred throughout the area
and wolves occurred north of Talkeetna, predation on adult
radio-marked moose in the project area was negligible. Brown
and black bear predation on neonate moose was suspected to be
a significant mortality factor in the project area. Death of
only one radio-marked adult moose was suspected to be the
result of brown bear preda.tion.
Losses to habitat or wildlife from the proposed hydroelectric
development were to have been mitigated by increasing or main-
taining moose carrying capacity above projected levels through
habitat enhancement and habitat protection, respectively. For
habitat enhancement to be a successful mitigation procedure,
target moose subpopulations must be limited by winter forage.
Enhancement of moose winter range would be ineffectual in
increasing carrying capacity if the target moose subpopula-
tions are limited by predation. If subpopulations are limited
by forage in winter, dead moose should be observed in
relatively severe winters. Surveys determining distribution
of dead and live moose and snowpack depth were used to
identify areas that are acceptable for mitigation.
Observations of extensive winter kill, poor femur marrow fat
indices, and low calf: cow ratios in wintering areas on the
lower Susitna River floodplain and several tributary streams
suggested that range quality was inadequate during inclement
winters -and thus limited moose subpopulation growth. These
data indicated that habitat enhancement would be an acceptable
mitigation procedure.
Moose distribution-abundance surveys conducted 13-15 and
18 March 1985 identified important winter range in a
10,600-km 2 area of the lower Susitna River valley. Seventy
percent of the moose observed occurred in 18% of the area
surveyed. Areas with high moose densities were identified as
potential replacement lands, and areas adjacent to replacement
lands should be considered for implementing habitat enhance-
ment procedures (enhancement lands).
vii
Surveys assessing snowpack depth patterns in the lower Susitna
River valley watershed were conducted 24-27 March 1985.
During this inclement winter, snowpack depth measurements
varied from 25 to 225 ern. Snowpack depths greater than 76 and
90 ern were considered critical for survival of calf and adult
moose, respectively. More than 80% of the 12, 000-km 2 area
surveyed had snowpack depths considered unacceptable for
moose winter range. Moose distribution and mortality were
related to s·nowpack depth. Snowpack depths were used to
delineate areas unacceptable for mitigation.
Periodic moose surveys in two alpine areas, floodplains of
thi:ee Susi tna River tributary streams, six areas on the
Susi tna River floodplain, and three areas characterized by
disclimax plant communities provided baseline infoz:rnation for
quantifying the potential of habitat protection and habitat
enhancement for mitigating with-project losses in wildlife or
wildlife habitat with "units" of moose carrying capacity.
The~se surveys also provided information on moose use of those
habitat types.
Six surveys on three Susitna River tributary streams indicated
that a maximum of over 23,000 moose days use occurred during a
140-day period from late November to mid-April 1984-85 on an
estimated 17 km 2 of winter range habitat along Alexander
Creek. Dead moose were commonly observed in this wintering
area.
Nineteen surveys conducted over a 4-year period on Bell
Island, a 12. 5-km 2 island on the Susi tna River floodplain,
indicated that over 10,700 moose days use occurred during a
139-day period between late November and mid-April 1984-85.
Dead moose were seldom observed in this wintering area.
Ei,ght surveys in two alpine areas indicated that a maximum of
over 45,000 moose days use occurred during a 196-day period
from late October to mid-April 1985-86 on ah estimated 73 krn 2
of winter range habitat on Bald Mountain Ridge. Dead moos·e
were seldom observed in this wintering area.
Eight, 23, 21, and 19 moose surveys were conducted during the
winters of 1981-82, 1982-83, 1983-84, and 1984-85, respec-
tively, on sites where human activities had altered climax
vegetation to favor regrowth of early successional disclirnax
plant communities. One 2.5-km 2 disclimax site provided over
6, 200 moose days use during a 162-day period between late
October and mid-April 1982-83. Several dead moose were
observed at this site.
These data suggest that prime alpine habitats (Bald Mountain
Ridge) may provide about 600 moose days carrying capacity per
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km2 per winter, prime riparian habitats may provide about
1,4.00 moose-days carrying capacity per km 2 per winter, prime
habitats on the Susitna River floodplain may provide about 900
moose-days use per km 2 per winter, and about 2,500 moose-days
use could be provided on 2. 5 km 2 of selected lands through
habitat enhancement techniques.
Fol,low-up field studies would be necessary to evaluate level
of success of mitigation on compensation lands. If moose use
and/or carrying capacity on compensation lands is determined
to be lower than projected, additional (secondary) mitigation
will be necessary. ·
Bald eagle nest sites were located throughout the study area.
Federal law prohibits activities that might cause eagles to
desert traditional nest sites. Locations with eagle nest
sites should not be considered for habitat enhancement.
The following hydrological mechanisms were identified as
having the potential for negatively impacting moose subpopu-
lations downstream from Devil Canyon: flow regimes;
inundation of habitats; incidence of open water; river ice
regimes; river water temperature regimes; river silt loads;
occurrence, transportation, and disposition of riverine
debris; incidence of fog; dissolved nutrient regimes; and
incidence of salt water encroachment and ecosystem alteration.
The following nonhydrological mechanisms were identified as
the potential for negatively affecting moose subpopulations:
direct alteration of habitat; increased access; human
encroachment; and ecosystem alteration. Potential negative
effects of these variables were discussed in relation to
specific moose subpopulations. Most variables would impact
moose by alternating occurrence and/or species composition of
plant communi ties preferred by moose for winter range. Some
variables could directly result in moose mortality.
Knowledge about life history, biology, environment, ahd
manage~ent for moose subpopulations identified to utilize the
Susitna River floodplain downstream froi:n Devil Canyon were
summarized in narratives. Subjects discussed in narratives
included: subpopulation size and annual range, human inter-
action in the area, significant subpopulation movement
patterns, noteworthy subpopulation behavior patterns, signifi-
cant mortality factors affecting subpopulation, and concerns
a:nd potential with-project conflicts for the subpopulation.
I:n this section relevant research findings are partitioned by
identified moose. subpopulations.
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ACKNOWLEDGMENTS
The following persons deserve special thanks for various
phases of this study:
K. Schneider, Alaska Department of Fish and Game, for
providing numerous helpful suggestions and comments on all
aspects of the research, for his willingness to ease the
burden of administrative tasks and meetings which frequently
conflicted with fieldwork, for supporting the many varied
field activities that went into preparation of this final
report and for being so very patient while I nurtured this
final report.
D. C. McAllister, Alaska Department of Fish and Game, for
willing and able assistance and suggestions and comments in
all aspects of this study. Mr. McAllister's assistance was
invaluable in field aspects of the research. He also prepared
many of the figures included in this report.
J. Swiss, John Swiss and Family, Big Game Guiding, Outfitting
and Air Charter Service; C. A. Allen, Charlie Allen Flight
Service, L. Rogers, M. Houte, V. Lofsted, arid C. Lofsted,
Kenai Air Alaska for piloting aircraft on many long and
tedious moose ~elocating surveys or for live-capturing moose.
They deserve _special recognition for ability, desire, and
safety.
D. Anctil, T. Wettin, S. Miller, and R. Strauch, all Alaska
Department of Fish and Game employees, for assistance in
management and analysis of data.
c. Schwartz, T. Spraker, W. Ballard, J. Lewis, B. Taylor, N.
Tankersley, M. Chihuly, and S. Albert, all Alaska Department
of Fish and Game employees, for occasional assistance in field
operations.
B. Steigers and R. Sener, of LGL Consultants and R. Fairbanks,
and R. Densmore of Harza-Ebasco, for providing mariy useful
suggestions and for participation on several field excursions.
S. Lawler and P. Miles, Alaska Department of Fish and Game
employees, for tolerating the typing of this report.
C. Hepler, Alaska Department of Fish and Game, for drafting
some original figures that were used repeatedly in my reports.
X
TABLE OF CONTENTS
PFlEFACE. • • • • i
SUMMARY. . . • . .
ACKNOWLEDGEMENTS . • • •
LIST OF APPENDICES . • • •
LIST OF TABLES • . . • . . • •
LIST -OF FIGURES. . • •
INTRODUCTION . • • . • •
. . -. . . iii
X
4
5
7
S~~UDY AREA • • • . . • • • • .
Susitna River Floodplain. • . ..
11
• . . 14
14
Zone I . . . . . . . . . . • • . 15
Zone II. . . . . . . . . . .
Zone III . . . . . . . . . . . . . . . .
Zone IV. . . . . . . . . . . . .
Climate . . . . . . . . . . . . . . . . .
Project Impact Area • • • . . • • . • • •
Substudy Locations. . • .•.
Comparisons of Moose Density and Age
Composition. . . . . . . . . . . . . . . .
Moose Use of Disclimax Habitats .•.••
Moose Winter Use of the Susitna River
Floodplain . • • . . • • • . • . .
Moose Use of and Mortality on Riparian
Wintering Areas Adjacent to the Susitna River.
Moose Us~ of Alpine Wintering Areas .•.••
Other Important Moose Wintering Areas in the
Lower Susitna River Watershed ....••.
Snowpack Depth in Lower Susitna River Valley •.
Moose Mortality in Highway and Railroad
Rights-Of-Way •.•••.••••...••
METHODS • • • • • • • • • • • • • • • • • • • • • • • • • •
Subpopulation Identity, Behavior, Ecology, and
Mortality Factors • . . . ..•..•.
Radio-Marking Moose ••••.••......
Moose Censuses . . . • . • . • . . . • • . . • .
Variation in Moose Use Among Areas on the
Susitna River Floodplain . . . . . . . . • . .
Ecological Basis of Moose Subpopulation
Behavior . . . . . . . . . . . . . . .
Moose Moitality in Railroad and Highway
Rights-Of Way. . . . • . . • • . . . . . . . .
Alaska Railroad Right-Of-Way .•..
Highway Right-Of-Way. • . . . • . . . . . .
Mitigation ..••...•.•...•.•.
·-·~··--···---·-· -' _. ·---'-··---'--~·
Selecting and Evaluating Compensation Lands.
Land Ownership and Revegetation Potential ..•
Moose Subpopulation Behavior and Ecology . • . .
Moose Abundance and Distribution Survey.
Riparian Wintering Areas Adjacent to the
Susitna River ......••••.....
Snowpack Depth Survey. . . • . • . . . . • .
1
15
15
16
17
18
18
18
18
19
19
19
19
19
19
20
20
20
21
22·
23
23
24
24
24
26
26
26
26
27
28
Food-Related Winter Moose Mortality; • . . • . . 29
Moose Herd Age Composition and Winter Mortality. 30
Bald Eagle Nest Sites. • . . • • • . • • . • • • 31
Quantifying Compensation Potential.of Mitigation
Lands • . . • . . . . . . . . . . . . . 31
Enhancement Lands • . . . • • . . . . . • . 32
Replacement Lands . . • . • . . . • 33
Incorporation of Parallel Data on Impact
Assessment and Mitigation Planning From
Other Disciplines. . . • . • . • . • . . . . . 34
Moose Subpopulattion Narratives • • . • . • . . 34
Limitation of Samples and Sampling Effort . . . . • 35
FINDINGS AND DISCUSSION. . . • . . • . • . • . . . . . 35
Timing, Duration, and Magnitude of Floodplain Use by
Moose in Winter . . • . . . • . . . • • . . 35
Locational Differences in Moose Winter Use of the
Susitna River Floodplain. . . . . . . . . . 39
Moose Subpopulation Behavior and Movement Patterns. . 40
Annual Ranges for Moose that Winter on the Susitna
River Floodplain. . . . . . . • • . . . . . . . • . 40
Seasonal Ranges for Moose that Winter on the Susitna
River Floodplain . . . • . . . • . . . . . . . . 42
Calving Range. . • . . . . . 4 2
Summer Range . . . . . . . . . . . . . . . . 4 4
Fall Range . . . . . . . . .. . . . . . . . 11 44
Frequency and Seasonal Timing for Moose Crossings of
the Susitna River Floodplain. . • . . . . . . • . . 44
Size, Shape, and Spatial Arrangement of Annual
Ranges for Moose Radio-marked on the Susitna
River Floodplain. . . • . . . •. • . . . . . . . 45
Movement Patterns and Spatial Relationships Between
Seasonal Ranges for Moose Radio-marked on the
Susitna River Floodplain. . . • . . . . . . • . . . 46
Consistency in Use of Annual Ranges by Radio-marked
Moose . . . . . . . . . . . . . . . • . . . . . 47
Apparently "Erratic" Movements for Radio-marked
Moose • • • . . . •. . . . . . . . . . . . . . .. 48
Affinity of Radio-marked Moose for the Susitna River
Floodplain. . . . . . . . . . . . . . . . . . . . . .
Mortality Factors for Unmarked and Radio-marked Moose
in the Lower Susitna River Valley . . . . • . . . .
Moose Collisions With Trains and Highway
Vehicles . . . . . . . . . . . . .
Alaska Railroad Right-Of-Way.
Highway System Right-Of-Way
Accidental Mortality ...
Hunting ..•....•...
Predation ......... .
Winter Kill •..•.•
Defense of Life and Property
Illegal Kill . . . . . • . .
2
49
50
51
51
53
55
56
56
57
59
60
Mitigation for Loss of Wildlife and/or Habitat. • . . 60
Identification of Potential Compensation Lands . 61
Moose Distribution and Abundance. • . . 61
Snowpack Depth. • • . . . • . . • . • • 62
Procedures for Conducting Mitigation on
Compensation Lands • • • . . • . . . . . . 63
Replacement Lands . . • • . . . . . 63
Enhancement Lands . • . . . . . • . • . 63
Quantifying Mitigation Potential for Compensation
Lands ..•...•.
Replacement Lands . • .
Enhancement Lands . • . • . • .
Avoidance of Bald Eagle Nest Sites~
Potential Impact Mechanisms Incidental to With-Project
Alteration in River Hydrology . . . . . .•
Flow Regimes • . . . . . . • . . . . . . . . . .
Inundation of Habitats . • . . . . . . . ..
Incidence of Open Water .......... .
River Ice Regimes. . . . . . . .
River Water Temperature Regimes ........ .
River Silt Loads . . . . . . . . . . . .
Occurrence, Transportation, and Disposition of
Riverine Debris .........•.•....
Incidence of Fog . . . . . . . . . . . . . . . .
Dissolved Nutrient Regimes . . . . . . .
Incidence of Salt Water Encroachment .
Alteration of Ecosystem. . . . . . . . . ~ . . .
Potential Impact Mechanisms Not Related to
65
65
66
67
68
68
69
69
70
71
71
73
73
74
74
75
With-Project Alterations in River Hydrology . . • . 75
Direct Alteration of Habitat . . . . • . 75
Increased Access . . . . . . . . . . 75
Human Encroachment . . . . . . . . . . . 75
Altered Ecosystem. . . . • . . . . . 75
Moose Subpopulation Narratives. . . . . . . . 76
Devil Canyon-Talkeetna . . . . . . . 76
Chunilna Creek . . . . . . . . . . . 83
Lower Talkeetna River-Iron Creek-Sheep River . . 87
Montana Creek-Sheep Creek-Kashwitna River. • . . 91
Willow ~ountain-Bald Mountain Ridge. . . . . 96
Little Susitna River . . . . . . . . 101
Little Susitna Flats-Susitna River ....... 105
Beluga River-Susitna River . . . • . . . . . . . 107
Mount Susitna-Little Mt. Susitna ........ 109
Big Island-Bell Island (floodplain) ....... 113
Kroto Creek-Moose Creek. . . . . • . . . . . 115
Delta Islands-Caswell Islands (floodplain) ... 119
Little Peters Hills-Petersville .......•. 122
Remainder of Susitna River Floodplain. . 125
LITERATURE CITED . . . . . . . . . . . . . . . . • . . 128
Personal Communications. . . . . . . . . . . . . . .. 133
3
LIST OF APPENDICES
A. Identification number and location for sample units
in the eastern portion of the stratification survey,
March 19 8 5 • • • . • • • . • • . . • . . • • . . • 13 4
B. Identification number and location for sample units in
the western portion of the stratification survey,
March 19 8 5 • . . • • • . . • . • . • . . • • • 13 5
C. Number and density of moose and moose tracks observed
in different size sample units during a stratification
survey in the lower Susitna River valley watershed,
13-15 and 18 March 1985 . • • . . • . . . • • . . 136
D. Frequency distribution of moose density classes for
numbers of moose observed in various size sample units
on a stratification survey in the lower Susitna River
valley watershed 13-15 and 18 March 1985. . . 144
E. Numbers of moose observed on periodic surveys in two
alpine areas o£ the western foothills of the Talkeetna
Mountains, Alaska, 1985-87. • . . . • . .•... 145
F. Numbers of moose observed on sites in the lower
Susitna River valley where natur~l vegetation has been
altered by activities of man, 1981-85 ........ 146
4
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
T•3.ble 10.
Table 11.
LIST OF TABLES
Physical and geographical characteristics
for selected zones along the Susitna River
from Devil Canyon dam site to Cook Inlet,
Alaska. . . . . . . . . . . . . . . . . . 14 8
Vegetative characteristics for general haoitat
types which occur in the Susitna River
watershed from Devil Canyon to Cook Inlet,
Alaska .•...•.
Total precipitation and snowfall for various
locations in geographic zones along the
Susitna River downstream from the prospective
.149
Devil Canyon dam site . . . . . . . . .150
Mean daily, monthly mean, and mean daily
minimum temperatures (°C) for Anchorage
(1953-80) and Talkeetna (1940-80), Alaska .151
Inclusive calendar dates for significant life
histoiy events for moose subpopulations along
the Susitna River from Devil Canyon to Cook
Inlet, Alaska ................. 152
Numbers of moose observed on periodic
censuses of floodplain habitat along four
zones on the Susitna River between Devil
Canyon and Cook Inlet, Alaska, 1981-85 ..... 153
Winter density of moose in 4 zones along
the Susitna River floodplain between Devil
Canyon and Cook Inlet, Alaska, 1981-85 ..... 154
Density of moose observed in floodplain and
large island habitats on the Susitna River
floodplain between Montana Creek and Cook
Inlet, Alaska, 1981-85. . . . . . • . . .. 155
Fate for 55 female and 22 male moose
captured and radio-marked along the
Susitna River floodplain downstream from
Devil Canyon, Alaska, 1980-86 . . . . ... 156
Numbers of moose killed by trains in the
Alaska Railroad right-of-way between
Seward and Fairbanks during winter (October
through April) and summer (May through
September) seasonal periods, 1963-86 . . 157
Annual total, monthly percent, monthly
totals for four annual periods and average
period percent (average for percents of four
5
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
annual periods) of moose killed by trains
in the Alaska Railroad right-of-way
between Seward and Fairbanks, 1963-86. . . 158
Location, number, and average percent (mean of
percents for each of three winter periods) of
moose killed by trains in the Alaska Railroad
right-of-way between Seward and Fairbanks
during winter 1978-79, 1982-83 and 1984-85 159
Numbers of moose reported killed by
collisions with vehicles on highway
rights-of-way in Game Management
Subunits 14A and B, 1970-86 ..... . . . 160
Live moose, dead moose (D) and percent calf
moose (%C) observed on riparian areas adjacent
to the Susitna River floodplain in winter
1984-85. . • . . . . . . . . • . . .... 161
Live moose (LM) , dead moose (DM) and percent
calf moose (%C) observed on large island and
floodplain areas of the Susitna River in
winter 1984-85 . . . . . • . • . . . . . . . . 162
Femur bone marrow fat content (percent fat in
marrow) for moose found dead on the study area
in winter. . . . . . . . 163
Numbers and densities for moose observed
during a late winter distribution survey
conducted in the lower Susitna River
valley, Alaska, 25-28 March 1985 ..... . 164
Moose use (moose-days, monthly, and accumula-
tive) of two alpine areas in the western
foothills of the Talkeetna Mountains calculated
from 8 periodic aerial surveys conducted between
4 October and 17 April, 1985-86 ........ 165
Moose use (monthly and accumulative monthly
moose-days) of riparian areas adjacent to
the Susitna River floodplain calculated
from periodic aerial surveys conducted
between 29 November and 16 April, 1984-85 ... 166
Moose use (monthly and accumulative total
moose-days) of areas adjacent to and on the
Susitna River floodplain calculated from
periodic aerial surveys in winter, 1981-1985 . 167
Estimates of annual range size for moose
subpopulations identified to utilize habitat
on the Susitna River floodplain. . 168
6
..
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
LIST OF FIGURES
Map showing location of the study area in
Alaska with names listed for rivers, lakes
and other prominent landscape features ••..• 169
Locations of riparian areas and subsections
of the Susitna River floodplain {I-IV) where
moose surveys were conducted. . • • • .170
Idealized habitat map showing the
distribution of vegetative types which
occur in the Susitna River watershed
between Devils Canyon and Cook Inlet. . . .171
Map of study area showing locations of game
management subunits (13E, 14A, 14B, 16A and
16B), state and national parks, and weather
stations. • . . • . . . . . • . . .172
Location of floodplain and islanded areas
along the Susitna River, Alaska, where
densities and calf composition were
determined for wintering moose, 1981-83 ... 173
Location of sites adjacent to the Susitna
River, Alaska, where climax vegetation has
been altered by man and numbers of moose
were counted periodically during the
winter, 1981-84 •............... 174
Location of alpine areas where moose use
(moose days) was calculated-for winter
1985-86 • • . . . . . • . . . . • . . .175
Areas surveyed for moose distribution and
snowpack depth in the lbwer Susitna River·
valley, March 1985. . . . . . . . . . •.. 176
Figure 9. Locations where moose were captured and
radio-marked in 5 different annual
samples . . . . . . . . . . . . . . . . . 17 7
Figure 10. Numbers of moose observed during periodic
censuses of floodplain habitat between
Devil Canyon and Talkeetna (Zone 1), Alaska,
1981-85 . . . . . • . . . . . . . . .178
Figure 11. Annual variation in.distribution of moose
radio-marked on the Susitna River
floodplain during December in 1981-82
1982-83, 1983-84, and 1984-85 ......•.. 179
7
Figure 12. Late winter distribution of moose radio-
marked along the Susitna River floodplain
and relocated from 1980-85 .....•..
Figure 13. Polygon encompassing 3852 relocation points
for 51 female and 18 male moose captured
and radio-marked along the Susitna River
floodplain between Devil Canyon and Cook
.180
Inlet, Alaska, 1980-85 ••..•.•••...• 181
Figure 14.
Figure 15.
Relocation points (3852) for 51 female
moose radio-marked along the Susitna River
floodplain between Devil Canyon and Cook
Inlet, Alaska, 1980-1985. . . • . . . . . . .182
Relocation points (946) for 18 male moose
radio-marked along the Susitna River
floodplain between Devil Canyon and Cook
Inlet, Alaska, 1980-85. . . . ....•.. 183
Figure 16. Locations ·where female moose radio-marked on
the Susitna River floodplain in winter
were relocated during the calving period
(May-,_Tune) •..•...•.•......... 184
Figure 17. Locations where male moose radio-
marked along the Susitna River floodplain
were relocated during September (open
hunting season) 1981-85 ....••..•... 185
Figure 18. Locations where male and female moose
radio-marked on the Susitna River floodplain
in winter were relocated during the summer
period (July-16 August), 1980-85~ . . . • .186
Figure 19. Frequency and seasonal timing of Susitna
River crossings by moose radio-marked in
2 areas between Devil Canyon and Cook Inlet
and relocated between 1980-85. (Numbers =
percent of observations in respective area
category) . • . . . . • . . . . . . . .187
Figure 20. Spatial relationship of radio-marked moose
annual ranges with the Susitna River
floodplain .••...•...••....... 188
Figure 21. Spatial relationship of radio-marked moose
annual ranges with the Susitna River
floodplain .(underline =male moose) ...... 189
8
Figure 22. Spatial relationship of radio-marked moose
annual ranges with the Susitna River
floodplain (underline =male moose) .•. 190
Figure 23. Polygons enclosing relocation points for
radio-marked moose which exhibited grossly
different patterns of seasonal range use. .191
Figure 24. Variation in spatial relationships of
seasonal ranges for moose radio-marked on
the Susitna River floodplain (underline =
male moose) . . . . . . . . • . . • . . . 192
Figure 25. Polygons enclosing reloc~tion points for
radio-marked moose which ranged over
relatively large areas (underline = male
moose) . . . . . . . . . . 193
Figure 26. Polygons encompassing annual ranges for
radio-marked moose which exhibited
relatively little "between year"
variation in movement patterns . .
Figure 27. Polygons encompassing annual ranges for
radio-marked moose which exhibited
noteworthy "between year" variation in
. 194
movement patterns. . ... -. . 195
Figure 28. Polygons enclosing relocation points for
radio-marked moose which exhibited an
"erratic" movement (underline = male moose) .. 196
Figure 29. Monthly variation in proximity to the
Susitna River floodplain for female moose
radio-marked in winter along the floodplain
between Talkeetna and Cook Inlet and
relocated periodically from April 1980
through July 1985. (No. moose summed over
-years) . . . . . . 197
Figure 30. Monthly variation in proximity to the
Susitna River floodplain for male moose
radio-marked on the floodplain between
Talkeetna and Cook Inlet and relocated
periodically from April 1980 through July
1985. (No. moose summed over years). . .. 198
Figure 31. Monthly variation in proximity to the
Susitna River floodplain for male and
female moose radio-marked in winter along
the floodplain between Talkeetna and Devils
Canyon and relocated periodically from
April 1980 through July 1985. (No. moose
summed over years) . . . . 19 9
9
Figure 32. Distribution and number of moose killed by
trains in the Alaska Railroad (ARR)
right-of-way between milepost 160.0 (near
Wasilla) and 278.0 (near Chuiltna Pass)
during winter (October-April) 1978-79,
1982-83 and 1984-85 ••••••••••••. o 200
Figure 33. Locations of moose carcasses observed
during aerial surveys in winter 1981-82 .••• 201
Figure 34. Locations of moose carcasses observed
during aerial surveys in winter 1982-830 .•• 202
Figure 35. Locations of moose carcasses observed
during aerial surveys in winter 1983-84. • 203
Figure 36. Locations of moose carcasses observed
during aerial surveys conducted in winter
1984-85 .•.•..••...•• 0 ...... 204
Figure 37. Locations of areas that encompass lands with
-enhancement and/or replacement potential
for mitigation with moose. . . . . . . . . 205
Figure 38. Snow depth (em.) measurements recorded in
lower Susitna River valley~ March 1985 . . 206
Figure 39. Histogram of snow depth measurements
{em. ~ table interval) recorded in lower
Susitna River valley, 24-27 March 1985
(n = 138) ..•...... o ••••••••• 207
Figure 40. Accumulative frequency distribution for
snow depth measurements (em. ~ table
interval) recorded in lower Susitna River
valley, 24-27 March 1985 (n = 138) . . . . .. 208
Figure 41. Geographical areas in the lower Susitna
River vall~y where snow depths of ~70 em.
(A) , > 7 0 ~ 1 0 0 em • (B) , > 1 0 0 :;:; 12 0 em . {C) ,
>120 em. :;:;155 em. (D), or >155 em. :;:;212 em.
{E) were recorded on 24-27 March 1985 ...... 209
Figure 42. Location of eagle nests in the lower
Susitna River valley . . . . . .... 210
Figure 43. Delineation of annual ranges for 13
hypothetical moose subpopulations
identified to use the Susitna River
floodplain ................... 211
10
INTRODUCTION
More than 30 years ago, the search for an economical source of
power to serve Alaska's railbelt region stimulated interest in
qonstruction of a hydroelectric facility on the upper Susitna
River. Feasibility assessments, then by the U.S. B1;1.reau of
Reclamation, and subsequently by the u.s. Army Corps to
Engineers, indicated that the proposed project was economic-
ally feasible and that environmental impacts would not be of
sufficient magnitude to affect its authorization.
More recently, in response to an anticipated demand for a
nonfossil fuel source of energy, previous ideas and plans were
rejuvenated in 1976 as attention was again focused on a
Susitna River hydroelectric project. At that time, the Alaska
state legislature created the Alaska Power Authority to
administer detailed studies to reevaluate the feasibility of
developing the hydroelectric potential of the upper Susi tna
River, since environmental impacts of the project were not
adequately addressed in initial technical field research
st:udies and in recent times, regulations and public sentiment
for envi-ronmental conservation have become increasingly more
ccmserva ti ve.
Environmental impacts of the proposed hydroelectric project
can be divided into two hydrological categories: (1) impacts
upstream and ( 2) impacts downstream from the proposed Devil
Canyon impoundment.· Initial environmental impact assessments
emphasized concern in the pre-impoundment area; concern in the
post-impoundment area was considerably less and environmental
assessments were "token" in nature. Perhaps, conceptually,
acute effects involving loss of habitats through inundation
were considered to be more significant than indirect,
long-term, chronic type effects that would occur in habitats
downstream as a result of altered characteristics of the water
and hydrologic flow regimes.
Though impoundments will be located in the upper portion of
the Susitna River, environmental impacts resulting from
altered flow regimes will be realized along the 215-km section
of downstream floodplain. Indirect effects may occur in a
much wider corridor of terrestial habitats adjacent to the
river and removed from the floodplain. An assessment of the
types and magnitude of influence of the Susitna River hydrau-
lics on environments at perpendicular distances from the
floodplain is as important to determine as those impacts that
occur within the riverbed. For migratory species of wildlife,
ultimate effects of proximate impacts may be geographically
distant and less obvious, but should not be overlooked nor
regarded lightly.
11
The Susitna River flows about 215 km downstream from Devil
Canyon before entering Cook Inlet. In a narrow sense,
watershed of the Susitna River encompasses roughly 800,000 km 2
of extremely productive habitat for many species of wildlife.
Perhaps, the potential year-round carrying capacity of the
lower Susitna River valley for moose and the innate value of
the Susitna River floodplain as winter habitat for moose
(Alces alces gigas Miller) are unsurpassed elsewhere in th~
state.
Prior to statehood, the Susitna Valley was ranked as the most
productive moose habitat in the territory (Chatelain 1951).
During the same time period, some wintering areas were said to
sustain moose at concentrations greater then 22/km 2 (Spencer
and Chatelain 1953) . More recent evidence indicates that
concentrations and densities of moose in the Susi tna valley
are greatest when deep snows in surrounding areas and at
higher elevations persist into the late winter early spring
period and obscure browse species (Rausch 1959). Such dense
,.,inter aggregations are the probable result of moose from
numerous subpopulations, some as remote as 30-40 km (LeResche
.19 7 4) , to perhaps more than 110 km . away (Van Ballenberghe
197j), gathering to seek refuge and iorage in lowland
habitats. It appears that many moose, from an extensive area
and numerous subpopulations, utilize winter range in the
Susitna River valley and on the Susitna River floodplain.
In addition to the occurrence of preferred lowland riparian
winter range on the Susitna River floodplain, it is said that
the desirability of the Susitna River valley for moose in the
early 1950s was greatly enhanced by early successional stages
of vegetation which resulted from wildfires, mild winters, and
abandonment of lands cleared for homesteads, highway and rail-
road construction and rights-of-way (Chatelain 1951).
By the early 1970s, browse available on previously cleared
land had been lost through succession and strict fire
suppression efforts precluded replacement of fire subclimax
plant conununities. In response to the .decreased availability
of winter browse, moose populations had begun to decline.
Several severe winters and possibly a low proportion of males
in the population (Bishop and Rausch 1974) compounded the
decline in moose numbers. Presently, many habitats in the
Susitna River valley have reverted to the pre-1930 pristine
state where floodplains and riparian areas provide the
majority of winter browse for moose. Moose populations have
adapted accordingly and now exist at lower levels. Lower
moose population levels do not mean that the area is any less
important to moose than it was in the early 1950s. It simply
indicates that fewer moose are using the area now because of
present land management policies. Different land management
12
practices could increase moose populations to levels higher
than those previously documented.
It appears that, in the past, results of activities of man,
such as wildfire and extensive land clearing, were the
dominant factors involved in creation and maintenance of young
se:cond-growth species for moose browse. During that same time
period, other ("natural") phenomena, such as beaver activity,
periodic flooding, ice scouring, riparian erosion, and
alluvial or loess translocation of soil, which also stimulated
growth of moose browse were viewed as insignificant because
they were primarily restricted to riparian habitats and acted
on a smaller, less dramatic scale.
In the near future, habitats in the Susi tna River basin may
again experience a broad ecological perturbation if flow
regimes and other hydrologic characteristics of the Susi tna
River are altered to accommodate hydroelectric development and
production of electric power. Alterations in the flow regime
and other hydrologic characteristics of the Susitna River
(t:emperature, turbidity, substrate erosion and deposition, ice
formation and scouring, ice fog, icing of vegetation, ice free
channels, dissolved nutrients, tree debris, etc.) could impact
moose in a ·number of ways. Impacts· to moose would be most
profound if vegetative communities which occur along the
floodplain were altered so that critical seasonal habitats
and/ or winter browse species were no longer available to
various subpopulations o1 moose.
A mitigation option under consideration by the Alaska Power
Authority includes compensation for with-project losses to
wildlife and wildlife habitat and implementing habitat
management techniques on preselected lands in the lower
Susi tna River valley. Habitat management programs would be
de!signed to increase and/or maintain higher moose carrying
capacity then presently exists on designated lands.
~he present research study was imple~ented: (1) to assess the
impact of the proposed Susitna River hydroelectric project on
moose subpopulations between the Devil Canyon damsite and Cook
Inlet and to suggest possible actions to mitigate those
impacts, and ( 2) to identify and evaluate lands in the lower
Susitna River valley on which habitats could be protected or
enhanced to mitigate for loss of moose or other wildlife
carrying capacity elsewhere.
Primary objectives of the first part of this study were:
( 1) to identify and delineate moose subpopulations that are
ecologically affiliated with the Susitna River downstream from
DE~vil Canyon; ( 2) to determine how, when, where, and at what
rnagni tude those subpopula tions interface, directly and
13
indirectly, with the Susitna River; (3) to identify mechanisms
through which with-project impacts may be transferred to moose
subpopulations; (4} to determine the probable nature and
approximate magnitude of identified impacts on each particular
moose subpopulation; and (5) to determine and suggest poten-
tial options for actions to mitigate. negative with-project
impacts.
Objectives of the second part of this study were: (1) to
identify lands in the lower Susitna River valley watershed on
which high moose carrying capacity could be maintained through
habitat protection (replacement lands) or on which low moose
carrying capacity could be.increased through habitat manage-
ment (enhancement lands}; (2) to develop criteria for selec-
ting and evaluating replacement and enhancement lands; and
( 3) to quantify the potential for mitigation on replacement
and enhancement lands.
Knowledge and understanding of moose subpopulation
distribution, mortality factors, behavior patterns, habitat
use, and limiting factors acquired during study of the primary
objectives, in part, facilitated fulfillment o£ the secondary
study objectives.
The following final project report contains relevant findings
from the Annual Progress Report Phase I (Arneson 1981), the
Phase ~ Final Report (Modafferi 1982), the Phase II Progress
Report (Modafferi 1983), the 1983 Annual Report (Modafferi
1984) and through August 1986 field studies. This report
includes a discussion of findings pertinent to the primary and
secondary study objectives. More detailed and specific
accounts of the Study Area, Methods and Findings pertinent to
data collection and data available occur in aforementioned
reports.
STUDY AREA
Susitna River Floodplain
The Devil Canyon damsite lies about 215 km upstream from where
the Susi tna River empties into Cook Inlet (Fig. 1) . While
traversing that distance the river descends from about 300 m
in elevation to sea level. In its course to Cook Inlet,
characteristics of the river, the adjacent floodplain, plant
communities, and associated habitats for moose undergo a
pattern of change. These changes can be roughly separated
into four (I-IV) physiographic zones along the rivercourse
(see Fig. 2 and Table 1}:
14
Zone I:
An 80-km section of river from Devil Canyon to Talkeetna.
Through this stretch, the river changes elevation from 300 to
105 meters and maintains a narrow (generally less than 150 m
wide) channel, interrupted by relatively few, widely
separated, seldom abreast, islands. Along the northern 3/4 of
this route, the river is flanked on each side by mountains
commonly ranging over 700. m. Further downstream as the river
approaches Talkeetna, these mountains grade into a lower alti-
tude plateau. Cottonwood and alder dominate the river margin.
A spruce-birch vegetative complex occurs in the river basin.
Extensive stands of alder dominate the steep valley slopes
which at higher elevations grade into a moist tundra plant
community of sedge, alder, willow, and dwarf birch. Several
islands immediately north of Talkeetna support stands of
second-growth willow and cottonwood.
Zone II:
A 30-km section of river from Talkeetna to Montana Creek. At
Talkeetna, the Susitna River broadens to abo~t 2 km in width.
as a result of the increase in water volume contributed by its
confluence with the Chulitna and Talkeetna Rivers, a decrease
in grade and a general flattening in relief of adjacent flood-
plain terrain. It is here that the Susitna first exhibits a
"braided" character where many small islands break up and
divert the mainstream flow. Apparently, these islands form
from combined silt loads of the three converging rivers and a
re:duced general flow rate from the more gradual elevational
de~scent. Seasonal purges by high volume water flows cause
these first islands to be relatively small and temporary. The
Susi tna River maintains this braided character, as it drops
only about 30 m in elevation from Talkeetna to its confluence
with Montana Creek. Wet, treeless, sedge, and grass bogs and
open black spruce-paper birch forests combine to dominate the
VE!getative complex on the flat plateau which extends roughly
25, km west of the floodplain. Beyond this distance, slight
increases in elevation are accompanied by a disappearance of
open bogs and an increase in the overall size, density, and
tree size of the spruce-birch forests. East of the Susi tna
River, open bogs occur less commonly, spruce-birch forests are
more dense· and tree size increases before giving way to dwarf
birch, willow, and ericaceous shrub dominated alpine tundra
plant communities about 25 km away in the western foothills of
the Talkeetna Mountains.
Zone III:
A 65-km section of river between Montana Creek and the Yentna
River. Through this stretch of the Susitna River floodplain
15
extensive tributary streams enter from the east and west.
Several of the eastside tributaries originate 40 km or more
away at elevations near 1700 m in the Talkeetna Mountains.
Apparently, a further decrease in gradient and flow rate of
the Susitna River alfd cumulative silting from upstream and
local tributaries have acted together to form very extensive
and relatively permanent island systems. Here the floodplain
frequently exceeds 5 km in breadth, the river occasionally
braids into 15 or more channels and islands larger than 2 km 2
are common. Vegetative types adjacent to the west side of the
river in this zone are similar to those in Zone II but the
extensive wet treeless bogs are less common and are replaced
by spruce-birch forests in both the lmver half and the more
remote parts of this zone. Wet treeless bogs are common east
of the floodplain. In the north, the treeless bogs give way
to spruce-birch forests as elevations begin increasing about
10 km from the floodplain. Superimposed within the former
habitats and within a 5-km band along the east side of the
river south to Willow Creek are an abundance of sites where
climax vegetation has been reverted to more seral plant commu-
nities incidental to construction of the Alaska Railroad, the
Parks Highway, farms, homesteads, and other land developments.
a prominent vegetative type 20 km east
floodplain at 650 m elevation in the
Tributary streams originating in the
are commonly paralleled by a mix of
Alpine tundra becomes
of the Susi tna River
Talkeetna Mountains.
Talkeetna Mountains
cottonwood, alder,
components.
willow, spruce, and birch vegetative
Vegetation in the southeastern part of this zone is
characterized by a combination of open treeless bogs, numerous
small lakes and open spruce-birch forests. These habitat
types prevail up to 30 km from the floodplain, as the latter
begins to track to the west at the southern extent of the
Talkeetna Mountains.
Zone IV:
A 40-km section of river from the Yentna River to Cook Inlet.
The islanded and braided characteristics of the Susitna River
are temporarily obliterated after its confluence with the
Yentna River. For about 15 km downstream from this confluence
the Susitna River becomes a single channeled river less than
1 km wide. However, in the terminal 25 km, the Susitna River
again becomes very braided, attains 18-km width and contains a
series of very large islands with surface areas exceeding
65 km 2 •
Vegetation in the northeastern part of this zone is a
continuation of the open treeless bogs and open spruce-birch
16
forests from the north. The northwestern quarter of Zone IV
is dominated by fairly dense mature spruce-birch forests
interspersed with riparian wetlands. Alpine tundra is found
within 8 km west of the river on Mount Susitna, which rises
abruptly to over 1300 m elevation. Habitats adjacent to the
Susitna River, in the lower half of Zone IV, are characteris-
tically wet grass-sedge marshes interspersed with shallow bog
ponds.
Figure 3 schematically illustrates the location and
distribution of various habitat types within the study area.
A more complete characterization of vegetation that occurs in
these habitat types appears in Table 2. A more specific
de~scription of plant species which comprise these habitat
types is available in Viereck and Little (1972) and Viereck
and Dyrness (1980).
Climate
Historical climatic records for the lower Susitna River valley
vary from extensive and complete to ·spotty and scanty,
depending on the specific locality. Records for Anchorage and
Talkeetna, which are ·probably representative of areas near
Cook Inlet and more interior areas, respectively, are complete
for more than 20 years. Data from other locations are consi-
dE!rably less complete.
In general, climatic · conditions
grade from those strongly under
Inlet, to those where continental
dominant, at Devil Canyon.
throughout the study area
oceanic influence, at Cook
weather patterns become more
Summaries of precipitation (Table 3) and temperature (Table 4)
records are presented for various locations (Fig. 4) in the
s1:udy area. These data document general weather characteris-
tics and demonstrate the gradient from a moderated, maritime
climate to a more harsh and extreme continentally influenced
climate, as one moves inland from Cook Inlet (Zone IV) and up
the Susitna River to more interiorly located areas near Devil
Canyon (Zone I) (Fig. 2).
Climatic regimes are known to have direct and indirect effects
on moose (Bishop and Rausch 1974, Coady 1974, and Des Meules
1964) . It can be expected that ameliorated maritim~ climatic
patterns near Cook Inlet are more favorable for moose popula-
tions than the characteristically interior weather patterns
encountered as one moves farther up the Susitna River toward
DE:vil Canyon.
One would expect that thermoregulation may be less problematic
for moose subpopulations near Cook Inlet than for
17
subpopulations in more interior
temperatures are more extreme.
areas where ambient
Similarly, direct and indirect effects of snowfall on moose
must increase substantially as one moves away from Cook Inlet,
north, to more interior regions where snowfall is greater and
snowcover more persistent.
Strong prevailing cold northeasterly winter winds from the
Matanuska River valley eliminates the snowcover in most areas
between Palmer, the Yentna/Susitna River confluence and the
mouth of the Susitna River. Warm southeasterly winter winds
from the Knik and Turnagain Arms frequently cause snowpacks in
Zone IV to melt and settle unseasonably early. Lack of snow
cover makes portions of this area very favorable for moose
winter range.
Project Impact Area
The study area for assessing impacts of Susitna River
hydroelectric development on moose was delineated by the
extent of movements documented for moose which were known to
utilize habitats on the Susitna River floodplain.
It was assumed that moose which utilize Susitna River
floodplain habitats in any manner, during any seasonal period,
for any length of time, may be impacted by hydroelectric
development. Ultimately, that area encompassing all
relocations. of moose radio-marked on the Susitna River
floodplain was considered as the zone where impacts could
potentially occur.
Substudy Locations
Information on specific aspects of moose ecology were
collected from isolated geographical areas located within the
overall study area.
Comparisons of Moose Density and Age Composition:
Data for comparing densities and age composition of moose
wintering in different geographical areas and habitats were
collected from two predominantly small islanded, low relief,
floodplain areas and four primarily large islanded, high
relief, floodplain islands located on the Susitna River south
of Talkeetna (Fig. 5).
Moose Use of Disclimax Habitats:
Data for determining moose use of habitats where "natural"
plant succession had been altered by man, were collected from
18
12 sites located adjacent to the Susitna River floodplain
south of Talkeetna (Fig. 6).
Moose Winter Use of the Susitna River Floodplain:
Data for delineating moose distribution and quantifying use of
the Susi tna River floodplain were gathered for four subsec-
tions (Zones) of the floodplain (see Fig. 2).
Moose Use of and Mortality on Riparian Wintering Areas
Adjacent to the Susitna River:
Data for identifying and locating important non-Susitna River
riparian moose wintering areas and for documenting moose
winter mortality were gathered from four Susitna River tribu-
tary streams (Fig. 4). These tributary streams originate from
extensive watersheds west of the Susitna River floodplain.
Moose Use of Alpine Wintering Areas:
Data for determining moose use of alpine winter range areas
were gathered from two locations in the western foothills of
the Talkeetna Mountains (Fig. 7) . These areas were located
about 25 km east of the Susitna River floodplain.
Other Important Moose Wintering Areas in the Lower Susitna
River valley:
Data for identifying and generally locating
non-Susitna River floodplain moose wintering
gathered from a 10,600-km 2 · area including most of
River watershed downstream from Devil Canyon (Fig.
Snowpack Depth in Lower Susitna River Valley:
important
areas were
the Susitna
8) •
Data for assessing snowpack depth were gathered
approximately 12.,000-km 2 area in the Susitna River
downstream from Devil Canyon (Fig. 8).
from an
valley
Moose Mortality in Highway and Railroad Rights-Of-Way:
Data for moose killed by collisions with trains or vehicles in
Alaska Railroad or highway rights-of-way, respectively, were
gathered and analyzed primarily for sections of railroad
be:tween Wasilla and Chuliltna Pass and for sections of the
highway in Game Management Subunits 14A and 14B, respectively
(F'ig. 4).
19
• _.,:. _________ .~_...:...:.o.:_ __ ---· _. _. _·· -~---·-· ·-· -·· _-_,_. --'--~"'-'----"--~"-'--'-"'---~· .~~~--~~~
METHODS
Subpopulation Identity, Behavior, Ecology and Mortality
Factors
Radio-Marking Moose:
To identify moose subpopulations that are ecologically
affiliated with Susitna River floodplain habitat downstream
from. Devil Canyon; to assess the ecological importance of
these habitats to individual moose subpopulations; to deter-
mine timing, location, duration, and magnitude of moose use;
and to identify seasonal and annual patterns of moose use for
those habitats, it was necessary to periodically locate and
observe individually identifiable moose.
To provide identifiable individuals that could be periodically
relocated, samples of moose were captured by immobilization
and marked with visual and radio-transmitting collars. Each
collar featured a discrete visible number and radio frequency.
Moose were typically immobilized with an Etorphine
(M-99) :Rompum (xylazine hydrochloride) mixture (10-12cc:lcc @
9 mg and 100 mg/cc, respectively) administered intramuscularly
with Palmer Cap-Chur equipment by personnel aboard a hovering
Bell 206B helicopter. Immobilized moose were revived with an
intravenous injection of Diprenorphine (M50-50, 10-12cc @ 2
mg/cc) .
While immobilized moose were collared, measured, marked with
ear tags, their age was estimated by incisor tooth wear, and
their sex was determined; for females, associations with young
were noted.
Ten, 2 9, 18 , 7 , and 12 moose were captured and marked in
winter on the ice and snow covered Susi tna River floodplain
between Sheep Creek and Sherman in 1980 (Arneson 1981),
between Delta Islands and Portac_:re in 1981 (Modafferi 1982),
between Delta Islands and Cook Inlet in 1982 (Modafferi 1983),
at the Montana West "disclimax" site in 1983 and between
Talkeetna and Chase in 1984, respectively (Fig. 9). Due to
the relatively unavailability of moose on the floodplain north
of Talkeetna in 1980 and 1981, some individuals were captured
up to 400 m off the floodplain.
Radio-marked moose were relocated with Cessna 172, 180, or 185
aircraft equipped with a Yagi or "H" type antenna on each
wing. Relocation surveys were conducted at intervals of about
three weeks in 1980 and about _every two weeks thereafter.
Inclement weather occasionally altered this schedule.
20
Relbcations (audio or audio-visual) of radio-marked moose were
initially noted on 1:63,360 scale USGS topographic maps and
subsequently transferred to transparent map overlays for
computer digitization. Data on elevation, vegetation,
snowcover, and other moose at the relocation site were also
re~corded. For more complete details of data management, see
Miller and Anctil (1981).
Fiv~ moose (Nos. 22, 23, 26, 27, and 91) originally captured
and radio-marked in April 19 8 0 were located, captured, and
marked with new visual and radio-transmitting collars on
27 March 1983. Original ·radio-transmitters on these moose
WE:!re expected to expire within several months. Some
individual moose provided over 150 points of relocation.
Moose Censuses:
River censuses were conducted to complement data on
relocations of individual radio-marked moose by providing more
quantitative data on behavior patterns for moose subpopu-
lations.
Moose were known to use the Susitna River floodplain
year-round. Previous research indicated that the magnitude of
use was significantly greater during winter and, particularly
so during winters characterized by deep snowpacks which
persisted for a long period of time (Rausch 1958). In
consideration of this a priori knowledge, periodic aerial
c1:nsuses were conducted over the Susitna River floodplain from
Devil Canyon to Cook Inlet, to assess the magnitude, delineate
timing and determine location and spatial distribution of
moose use of floodplain habitats. These surveys were
conducted throughout the winter period as snowcover permitted
observation of moose.
I did not initiate river censuses in the winter of 1980-81.
Mhen I became familiar with this project in early 1981,
radio-marked moose had already begun to abandon ·the Susi tna
River floodplain and censuses at that time would have ·been
Eutile. In the winters of 1981-82, 1982-83, 1983-84, 1984-85,
respectively, 6, 11, 7, and 11 river censuses were conducted.
In winter 1984-85, censuses were limited to portions of the
Susitna River floodplain near Caswell, Kashwitna, Delta
Islands, Bell Island, and between Devil Canyon and Sunshine
Bridge. River Zones I and IIa correspond to that portion of
the Susitna River floodplain between Devil Canyon and Sunshine
Bridge (Fig. 2).
Aerial river censuses were conducted with a PA-18 aircraft
flown at low elevation in a parallel transect pattern between
opposing banks of the Susi tna River floodplain and upstream
21
from Cook Inlet to Devil Canyon. Though limitations of aerial
moose survey techniques were known (LeResche and Rausch 1974),
the object of river censuses was to count all moose on the
Susi tna River floodplain (including interconnecting sloughs)
in the designated survey area.
River censuses were conducted over a time period to encompass
the buildup, peak and decline in moose use of winter range on
the Susitna River floodplain. During river censuses, moose
observed were assigned to the following categories: antlered
moose, antlerless moose, females with one calf, females with
two calves, and lone calves. Locations for all moose obser-
vations were noted on 1:63,360 scale USGS topographic maps.
Weather and numbers of moose observed affected duration of
individual censuses. Inclement weather and inadequate
snowcover for observing moose frequently disrupted continuity
within and between surveys.
To account for obvious variation in ecological characteristics
of the Susitna River floodplain between Devil Canyon and Cook
Inlet, results of river censuses were reported for four
physiographic zones (Fig. 4). To facilitate comparison of
moose densities between physiographic zones, surface area of
terrestrial and aquatic habitat available on the floodplain
within each physiographic zone was visually ·estimated from
1:63,360 scale USGS topographic maps. Surface areas of 28 and
31, 23 and 21, 65 and 104, and 65 and 29 km 2 , were estimated
for aquatic and terrestrial habitats, respectively, in
Zones I, II, III, and IV, respectively.
Variation in Moose Use Among Areas on the Susitna River
Floodplain:
After conducting aerial river censuses over several years, it
appeared that moose were not distributed evenly throughout the
Susitna River floodplain. Moose use (moose density) appeared
to vary between different areas and habitat types on the
floodplain.
To examine this contention and to identify and substantiate
the relative importance of different geographical areas and/or
habitat types for moose winter range on the Susitna River
floodplain, data on moose density collected on river censuses
in 1981-82, 1982-83, 1983-84, and 1984-85 were compared
between two predominantly small islanded, low relief, braided
floodplain areas (Caswell and Kashwitna) located north of the
Kashwitna River and four higher relief, large islanded, more
deeply channeled floodplain areas (Delta, Bell, Alexander, and
Beaver) located south of the Kashwitna River (see Fig. 5).
22
Ecological Basis of Moose Subpopulation Behavior:
The ecological basis of moose subpopulation behavior and
movement patterns was assessed by relating inclusive calendar
dates for significant moose life history events to seasonal
timing for documented moose movements. This methodology
enabled me to relate the timing of moose use or nonuse of
Susitna River floodplain habitats with significant events in
moose life history. A description of life history events
utilized in this analysis and assigned inclusive calendar
dates are presented in Table 5.
Time periods for life history events did not encompass the
entire calendar year. Transitory intervals were delineated
between range use periods to accommodate movement or transi-
tion from one range or period to another. To remove effects
of transitory movements on identifying locations of seasonal
ranges, a very narrow spread of calendar dates was used to
encompass life history events. Data provided from this
analysis may be interpreted to illustrate how and where
impacts from hydroelectric development would most likely be
realized in relation to moose subpopulation geography and
ecology (i.e., with-projeqt losses to moose or winter habitat
on the Susitna River floodplain may impact hunters in a parti-
cular area, affect fall moose sex-age composition surveys in
another area and alter results of spring an(l winter calf
composition surveys in yet other geographical areas) . These
data also provided indirect information on the ecological
importance of ·floodplain habitats to moose (i.e., why do moose
ut:ilize floodplain habitats?, what do floodplain habitats pro-
vide to moose subpopulations?, etc.).
Moose Mortality in the Railroad and Highway Rights-of-Way:
Hydroelectric development of the Susitna River will involve
transporting large quantities of equipment and materials on
freight trains and highway vehicles from Anchorage and more
southern sea ports, northward along the Alaska Railroad and
highway rights-of-way, respectively, to the prospective dam
sites. Railroad and highway rights-of-way are located east of
and parallel to the Susi tna River from Willow to Gold Creek
(Fig 1). During construction of this project, amount and
frequency of train and vehicular traffic in these rights-
of-ways is projected to increase greatly.
Large numbers of moose have reportedly been killed by
collisions with trains and and vehicles in the Alaska Railroad
and highway rights-of-way, respectively, (Rausch 1958 and
ADF&G files) . Mortality of moose from these sources is
particularly great during winters characterized by deep and
23
persistent snowpacks which cause moose to concentrate in
lowland areas near rights-of-way.
Alaska Railroad Right-of-Way:
To obtain information on moose mortality in the Alaska
Railroad right-of-way, historical train dispatch record files
were obtained and reviewed (Alaska Railroad files) . Accuracy
of dispatch records for numbers of moose killed by collisions
with trains prior to acquisition of the railroad by the state
of Alaska have been questioned. Kill estimates may be
inaccurate and inordinately low (Rausch 1958}. Kill records
and the recording system utilized after state acquisition
(1983} of the then federally-owned railroad are considered to
be more accurate.
The Alaska Department of Transportation dispatch records for
train killed moose between Seward and Fairbanks from 196 3
through 1986 were reviewed and analyzed by year, winter period
and location. Coincidentally, the 1984-85 wiriter, charac-
terized by a very deep snowpack which persisted well into
April, caused large numbers of moose t~ concentrate in lower
areas and resulted in a large moose kill by collisions· with
trains. Available data were analyzed to document the timing,
location, and magnitude of the moose kill by trains in the
railroad right-of-way. The resulting data also provided
baseline information from which to make recommendations for
minimizing this with-project source of moose mortality.
Highway Right-of-Way:
Moose killed by collisions with vehicles in highway
rights-of-way are reported to the Alaska State Troopers. Data
on moose mortality in highway rights-of-way are provided to
the Alaska Department of Fish and Game by the Alaska Depart-
ment of Public Safety. The actual number of moose killed by
collisions with vehicles is more than that which is reported
and recorded. Many moose are hit, injured, and die undetected
away from the roadway. Other-moose that are hit. and killed
are not reported. Data on moose killed by collisions with
vehicles in highway rights-of-way in Game Management S~bunits
14A and 14B from 1970 through 1986 were obtained from
Department of Fish and Game files. Game Management Subunits
14A and 14B extend from the Knik River, south of Wasilla,
northward parallel with the Susitna River to Talkeetna
(Fig. 4} .
Mitigation
Hydroelectric development of the Susitna River will eliminate
and/or alter wildlife habitat and result in an overall
24
"
de,crease in wildlife carrying capacity of the Susitna River
valley.
To address this possibility, the Alaska Power Authority
initiated a process of identification and evaluation of
"compensation lands" which corild be managed to offset unavoid-
able "with-project" losses in wildlife carrying capacity.
Under this plan, compensation for "with-project" losses in
wildlife carrying capacity would involve: (1) securing and
protecting productive habitats from future alteration as
"replacement lands," or (2) securing less productive habitats
and secondarily increasing their carrying capacity as
"enhancement lands."
Re!placement lands are lands that, in their present state,
be!cause of location or habitat type, are determined to be
important to moose. Preservation or protection of such lands
from alternate or different land uses which would degrade
their value to moose, would in fact, be an acceptable form of
mitigation. Replacement lands may be lands used by moose for
calving, winter range, or rutting, etc., and for those reasons
protection of them is determined important for maintaining and
sustaining the integrity of specific moose subpopulations.
Enhancement lands are lands where moose carrying. capacity
could be maintained at high levels or increased to higher
levels through habitat management techniques. The net affect
of habitat management (enhancement) would be a positive gain
in moose carrying capacity. Considering the present state of
knowledge on habitat enhancement, enhancement activities would
bE: limited to lands with potential for moose winter range
(Harza-Ebasco Susitna Joint Venture 1984) . In the absence of
high levels of predation, quantity and/ or quality of winter
range (usually browse quality) affects annual recruitment to
moose subpopulations. Long-term moose population levels are
l:Lmi ted by interaction of severe winter weather conditions
(depth and persistence of the snowpack) and .range quality. If
winter range quality . can be improved or maintained through
habitat manipulation to increase the carrying capacity, then
greater numbers of moose wili survive severe winter weather
conditions and long-term subpopulation levels will be
elevated.
To provide information on mitigation options, studies were
initiated in the Susitna River valley downstream from
Talkeetna to: (1) develop criteria for selecting and evalua-
ting replacement and enhancement lands~ (2) identify potential
replacement and enhancement lands~ and (3) quantify mitigation
potential for replacement and enhancement options.
25
Selecting and Evaluating Compensation Lands:
Land Ownership and Revegetation Potential.
Related but independent studies were undertaken to identify
ownership status (LGL Consultants files) and revegetation
potential of lands (Harza Ebasco Susitna Joint Venture 1984)
in the lower Susitna River valley consideration. Information
on ownership status was used identify lands that could be
considered for procurement and alternative management
patterns. Information on revegetation was utilized to further
identify lands that did or did not have potential for
vegetative enhancement.
Moose Subpopulation Behavior and Ecology.
In this study, criteria and procedures for selecting and
evaluating the enhancement and replacement potential of
specific lands in the lower Susitna River valley were
primarily gleaned from information on behavior and movement
patterns of radio-marked moose and from observations on
distribution and habitat use. of unmarked moose obtained from
aerial surveys. Additional information was obtained from
-secondary analyses of data gathered for other aspects of this
study.
Moose Abundance and Distribution Survey.
Enhancement and replacement potential of specific lands was
appraised by quantifying distribution and abundance of moose
in winter. Lands which were utilized by large numbers of
moose in winter were assumed to have a high innate carrying
capacity and a high potential as replacement lands. It was
further assumed that lands which were utilized by large
numbers of moose in winter were probably at or near carrying
capacity and would be "relatively unresponsive" to enhancement
techniques. However, lands adjacent to areas which were
utilized by large numbers of moose in winter were considered
to have a high enhancement potential.
To identify specific
replacement potential, a
survey was conducted in a
River watershed downstream
lands which had enhancement or
moose distribution and abundance
10,600-km2 portion of the Susitna
from Devil Canyon (see Fig. 8}.
Procedures for conducting the moose distribution and abundance
survey were similar to those utilized for stratifying sample
units in a stratified random census method developed for moose
(Gasaway et al. 1986). The survey area was divided into 30-40
km 2 sample units discernible from low flying aircraft
(Appendices A and B). Sample units were surveyed for moose
26
"
and moose tracks. A "moose track" was indicated by fresh
mc,ose tracks in the snow. "One" moose track theoretically
indicated that one moose was present in the sample area but
was not observed. The survey was conducted at low level
flying in Cessna 180/185 aircraft with a_ crew of a pilot,
natvigator, and two observers. Observations of moose and moose
tracks were "called out" to the navigator who recorded them on
1:63,360 scale USGS topographic maps. The navigator also
directed the pilot through the survey area and plotted the
flight path on the same topographic maps. Sample unit boun-
dc:tries were delineated on the survey map so that none were
overlooked. Typically, the search effort lasted two to three
minutes and involved two to three aerial transects through
representative habitat types in each sample unit.
BE~cause sample units vary in size (3-23 mi 2 ), raw survey data
wE~re adjusted. To obtain adjusted estimates of moose use
among different size sample units, values for moose and moose
track density were calculated for each sample unit by dividing
the number of moose and moose tracks observed by area of the
sample unit. Area for sample units was calculated with
computer software from data of computer-digitized sample unit
boundaries.
affect observabili ty of
to enumerate "all" moose
However-, for many sample
habitats, almost all moose
Be~cause overstory and habitat type
moose, these survey procedures fail
present in particular sample units.
units in alpine tundra or low shrub
present were observed and counted.
Number of "moose tracks" in sample units with high moose
demsi ty are of little value because when moose were readily
observed "track calls" were neglected. However, in sample
un~ts where few moose or no moose were observed, "track
counts" accurately reflect previous moose use or movements
through the area. Sample units or habitats of the latter type
are probably much more important to moose than areas where
both few moose and few tracks were observed.
This survey technique provided an economical means of
delineating distribution and relative abundance of moose
throughout a major portion of the lower Susitna River valley.
RE:sul ts of this survey also contributed circumstantial
evidence that was used, in part, to make estimates of moose
subpopulation size.
Riparian Wintering Areas Adjacent to the Susitna River.
To refine identity and location of important riparian moose
wintering areas adjacent to the Susitna River, aerial surveys
wE:re conducted along floodplains of Susi tna River tributary
27
streams (Fig. 2) and in alpine areas of the western foothills
of the Talkeetna Mountains (Fig. 7). Tributary stream
floodplain areas surveyed were the Yentna River and Alexander,
Kroto, and Moose Creeks. Alpine areas surveyed were Bald
Mountain Ridge and Willow Mountain. Twelve and eight periodic
moose surveys were conducted in tributary stream floodplain
and alpine areas, in the winters of 1984-85 and 1985-86,
respectively. One moose survey was conducted in alpine areas
in the winter of 1986-87. Survey procedures and data recorded
were similar to those for river censuses.
Snowpack Depth Survey.
Snowpack depth affects the quality of moose winter range.
Deep snow impedes movements of moose, buries forage, reduces
availability of forage, and increases. energetic costs of
obtaining forage. Regardless of forage availability, areas
that traditionally have a deep and persistent snowpack are of
little value as moose winter range. Ideal moose winter range
may be characterized by a shallow snowpack and an abundance of
forage. To evaluate the enhancement or replacement potential
of specific lands with respect to snowpack conditions, a
survey was proposed to determine snowpack depth over an
extensive portion of the Susitna River watershed downstream
from Devil Canyon (Fig. 8).
A technique based on systematic sampling design was utilized
to assess snow depths throughout the study· area. This tech-
nique involved measuring and recording snow depths in a grid
pattern defined by the points of intersection of
range/township coordinate lines on 1:250,000 scale USGS
topographic maps.· This methodology provided snow depth
measurements at about 10-to 14-km intervals in the area
sampled. It was believed that this sampling intensity would
adequately describe snowpack configuration throughout the
study area.
At locations of particular interest, the Bell Island area, the
Chijuk Creek area, and the Chulitn~-Susitna River ~triangle"
area, additional representative sampling sites were selected
during field operations. Sampling was intensified in the
former area because it was known to be a heavily utilized
moose wintering area. The latter two areas were sampled
intensively because they were specifically being considered
for enhancement in the Susitna Hydroelectrical Project Moose
Mitigation Plan {LGL Consultants files) .
In theory, sampling sites were indicated by the point of
intersection of range/township coordinate lines on 1:63360
scale USGS topographic maps. In the field, sampling sites
were located by reference to topographic map features. A
28
Bell 205B helicopter was used to navigate two field personnel
as near as possible to each predetermined sampling site. When
vegetation or topography precluded landing the helicopter at
the predetermined sampling site, an alternate site was
selected. Alternate sites were the next nearest area where
the helicopter could be landed. In most cases, sampling
occurred within 200 m of the preselected site. Since
glaciation affected actual snow levels on lakes and.waterways,
sampling over those substrates was avoided and an alternate
site was selected.
At each· sampling site, snow depth was measured· with a
graduated two-piece, 250 em length of 2 em width aluminum U
stock. This aluminum probe was "jabbed" through the snowpack
until its tip contacted a firm substrate. Frequently the
probe had to be forced through compacted and/or crusted layers
of snow before a solid substrate was reached. Five snow-depth
measurements spaced about 30 em apart were obtained and
recorded at each sampling site. In most cases, measurements
were taken from aboard the helicopter or in forest openings
less than 50 m in diameter. Results of each ·series of
measurements were called out to and recorded by the person
navigating the pilot to sampling sites.
A single value for snow depth was ultimately associated with
each sampling site. To obtain this value the high and low
values were discarded. If two or three of the remaining
measurements were common, that value was utilized; if not, the
arithmetic mean of the three measurements was calculated and
utilized. The resulting number was associated with the
sampling site.
Field sampling was timed to correlate with both annual maximum
snow accumulation in the study area and the time period when
most moose subpopulations are distributed on "late winter"
winter ranges. Data obtained during ·earlier phases of this
study indicated that some moose subpopulations do not move to
winter range until late January. Field survey procedures were
conducted on 24-26 March 1985. Circumstantial evidence
indicated that seasonal and annual timing of the snowpack
depth survey coincided with maximum snow depths recorded for
the study area in a ten-year period (SCS 1985).
Food-Related Winter Moose Mortality.
Habitat enhancement techniques are usually designed to produce
additional winter food for moose. For habitat enhancement
techniques to be affective in increasing moose carrying
capacity, "target" moose subpopulations must be directly or
indirectly limited by winter food resources. Habitat enhance-
ment targeted for a moose subpopulation that is limited by
29
factors other than winter browse (as predation) would be
inappropriate mitigation. Before habitat enhancement is
considered an acceptable method of mitigation for a moose
subpopulation, it should be demonstrated that the moose
subpopulation is limited by availability of winter forage or
that availability of additional forage will have positive
effects on moose carrying capacity.
Inadequate winter range conditions are typically evidenced by:
an overall scarcity of browse; browse available above the snm'l
level is primarily large diameter branches and evidence of
feeding on tree bark may be obvious. Inadequate winter range
may initially affect moose nutritive condition and produc-
tivity. As quality of the winter ranges deteriorates further
dead moose are observed in wintering areas. Moose mortality
is particularly evident during winters with deep and persis-
tent snowcover. Moose that die from inadequate winter browse
(quality or quantity) are typically calves and/or individuals
with low bone marrow fat content.
To evaluate if habitat enhancement would be considered an
effective form of mitigation in the lower Susitna River
valley, preliminary investigations were conducted to determine
if moose subpopulations in the lower Susitna River valley were
limited by inadequate winter range. Moose mortality was docu-
mented, availability and condition of browse. on winter range
was assessed subjectively, and nutritive condition and age
composition of moose that died on winter range were
determined.
To document and quantify moose mortality in wintering areas,
observations and locations of dead moose (carcasses) were
recorded on all moose surveys.
To appraise status of winter range browse and to determine
nutritive condition and age of moose that died during the
winter, field . excursions were conducted to moose wintering
areas in April and May of 1985. Wintering areas visited were
Alexander Creek, Moo~e Creek, Kroto Creek, Lake Creek, and the
"Caswell" and "Kashwitna" floodplain portions of the Susitna
River floodplain (Figs. 2 and 5) . Winter forage conditions
were subjectively appraised by looking for signs typical of
winter range inadequacy: evidence indicating utilization of
large diameter browse, utilization of tree trunk bark, and
utilization of forage that is out of normal browse level for
moose. Browse which was broken down before being consumed by
moose constituted evidence in the latter category.
Moose Herd Age Composition and Winter Mortality.
Data on numbers of dead moose
calves observed on surveys at
(carcasses) and percentage of
four locations on the Sus i tna
30
River floodplain (Fig. 5) and along three tributary streams
(Fig. 2) were used to identify potential replacement and
enhancement lands. Two locations represented habitats on
large, relatively high relief floodplain islands and two
locations represented habitats on small low relief floodplain
islands. The former locations were near to Cook Inlet and the
latter areas were located about 85 km upstream (north) • The
three tributary streams represented riparian areas adjacent to
the Susitna River floodplain.
These data also verified that some floodplain areas contained
potential replacement lands whereas other floodplain areas
contained potential enh~ncement lands.
Bald Eagle (Haliaeetus leucocephalus) Nest Sites.
Bald eagle nest sites occur commonly along the Susitna River
floodplain. Federal law prohibits disturbances and alteration
of: habitat within about 90 m of an eagle nest. Because
mitigation procedures may involve manipulation of vegetation,
it: ~ras important to identify location of eagle nests in areas
where habitat enhancement might occur. Locations of eagle
nests observed on all aerial surveys were noted on 1:63,360-
scale topographic maps. Each year observations of nest
locations were consolidated onto one map. After all field
re~search terminated, observations of nest locations for all
years were combined and indicated on a single map. Combining
ne~st location data from numerous maps resulted in some nests
being in close proximity to others. In some instances, such
"duplicate" observations obviously represented the same nest
that had not been precisely located on the map; in other
instances the observations may have represented two different
nest sites. I know of several locations that had two
different nests in very close proximity.
Quantifying Compensation Potential of Mitigation Lands:
Losses of wildlife or wildlife habitat that result from
hydroelectric development of the Susitna River will be
compensated for through mitigation. The mitigation plan under
consideration is designed to compensate with-project losses
with sustained increases in moose carrying capacity on
replacement lands or enhancement lands.
I used moose densities to indicate areas (habitats) that had a
high likelihood of being important as compensation lands.
However, these data do not indicate that other areas were
unimportant. Supplementary data on life processes (reproduc-
tion, seasonal nutrition) and factors that might influence
these processes (e.g., snowpack depth} were used to const:r-uct
a rationale supporting the concept that these areas were
31
important. Quantification of value of compensation lands
might have required further investigation.
Enhancement Lands.
Enhancement lands are lands where moose carrying capacity can
be maintained at high levels or increased to higher levels
through h~bitat management of winter range. The goal of
habitat management (enhancement) would be to increase the size
of a moose subpopulation by increasing winter range carrying
capacity. If winter carrying capacity is increased, then
greater numbers of moose would survive through severe winter
conditions and long-term subpopulation levels would be
elevated. Success of enhancement procedures would be
evaluated by quantifying long term increases in numbers of
moose utilizing a given winter range.
The potential for increasing moose winter range carrying
capacity through habitat management (enhancement) was assessed
by studying and quantifying moose winter use of sites where
activities of man had disturbed natural plant succession
( "disclimax sites") and resulted in regrowth of early
successional, disclimax plant species preferred by moose for
\'Tinter browse. It was assumed that similar disturbances to
like habitats would result in similar winter ran<!es with
comparable moose carrying capacity. If a specific size
disturbed site supported (provided range for) 50 moose
throughout the winter, then creation of a similar size site
would l.:j..kewise be expected to provide winter range for 50
moose. It could be assumed that such a site would compensate
for a loss of 50 moose or winter range for 50 moose.
To document and quantify moose use of disclimax sites, data
were collected from six sites in 1981-83 and from seven addi-
tional sites in 1983-85. Eight, 23, 21, and 19 periodic moose
censuses were conducted on "disturbed" sites during the
1981-82, 1982-83, 1983-84, and 1984-85 winters, respectively.
"Disclimax" sites studied were located adjacent to the Susitna
River floodplain downstream from Talkeetna (see Fig. 6) '!..
To census moose on "disclimax" sites, aerial surveys were
conducted by flying low-level transects over each area in a
PA-18 aircraft. A 100 m band around the perimeter of the site
was also surveyed to include moose which were utilizing the
area but were "bedded down" in denser adjacent vegetative
cover when the survey was conducted. Moose observed were
classified into sex and age categories similar to those
utilized on river censuses.
Numbers of moose observed on periodic censuses
disturbed sites (Montana west and Montana middle,
32
of two
Fig. 6)
along the Susitna River floodplain were utilized to calculate
monthly and accumulative days of moose use. Numbers of moose
utilizing sites during intervals between consecutive surveys
were estimated by assuming that numbers of moose observed on
sequential surveys also occupied the site prior to and after
the: midpoint day between any two consecutive surveys (i.e., if
50 moose were observed on a 'site on 1 November and 75 moose
were observed on 30 November, I assumed that 50 moose occupied
the' site from 1-15 November and that 75 moose occupied the
sit~e from 16-30 November). It was assumed that habitat
management techniques similar to original "disturbances" in
similar habitats would produce like second growth·vegetative
communi ties and provide winter browse for like numbers of
moose.
Replacement Lands.
Lands with replacement potential are lands · which· in their
present state, because of location or habitat type, are
det:ermined to be important to moose. These lands may be of
sisrnificant importance to a particular moose subpopulation for
calving, rutting, or winter range, etc. If these habitats are
important to moose and future land uses may degrade that
importance, then protection and preservation of such lands
would be judged critical for maintaining and sustaining the
integrity of specific moose sqbpopulations and be considered
acceptable mitigation.
Pot:ential replacement lands identified in the lower Susitna
River valley include moose winter and post-rut ranges.
Specific habitat types utilized by parturient females during
calving were identified but the importance of a unit of land,
based on density of moose utilizing them, was significantly
less than for winter and post-rut ranges.
Benefits derived from this type of mitigation can be estimated
by quantifying moose use of the specific parcel of replacement
land. One must asstime that, if the parcel of land were not
acquired ("set-aside") · sole·ly for management of a particular
moose subpopulation, its habitat could be altered inunediately
and its value to moose. would be degraded entirely. If 50
moose utilized a particular parcel ·of "potential replacement
land," then preventing degradation of that land parcel could
compensate for a with-project direct loss of 50 moose or
indirect loss of habitat (carrying capacity) for 50 moose.
"Time frames 11 (years) for compensation would have to be
established for various mitigation measures. Perhaps 11 moose
years" is a useful unit for which to calculate "credit and
debit 11 accounts for moose carrying capacity. The Susitna
hydroelectric project would have a life of 50 years.
Environmental impacts could be realized throughout that entire
33
50-year time period or for shorter time periods. Likewise
individual mitigation measures may be relevant for the life of
the project or only a portion of the life. Some forms of
habitat degradation might not occur for 20 years but
mitigating that degradation would still have some compensatory
value.
Densities of moose observed on periodic censuses conducted in
six areas on the Susitna River floodplain, in two areas above
timberline in the western foothills, and the Talkeetna
Mountains east of the Susi tna River were. utilized as indica-
tors of probable value of habitats and as a quantifier of
potential habitat carrying capacity for replacement lands.
Numbers of moose observed on these periodic censuses were used
to calculate monthly and accumulative monthly moose days use
for specific habitats and potential replacement·lands.
Numbers of dead moose (carcasses) and percentage of calves
observed on censuses at four locations from two areas of the
Susitna Rivex floodplain were also used as indicators of
probable habitat value for consideration when identifying
potential replacement and enhancement lands. These data were
also-used to illustrate that some floodplain areas contain
potential replacement lands and other floodplain areas contain
potential enhancement lands.
Incorporation of Parallel Data on Impact Assessment and
Mitigation Planning From Other Disciplines.
Impact assessment and mitigation planning should
solely on information gathered from wildlife
Wildlife populations can be used as an indicator
impacts and for selection of compensation lands.
not be based
populations.
of downstream
Ideally, parallel data on downstream impacts and mitigation
planning should be provided from hydrological, botanical,
demographical, sociological, etc., research studies. Data
from all disciplines should then be integrated to provide a
unified assessrnent·of potential downstream impacts and options
for mitigation planning. The latter data were not available
when project environmental assessment studies were precluded.
Moose Subpopulation Narratives
Narratives describing behavior patterns, mortality factors,
interfaces with human activities, geographic settings, poten-
tial with-project impacts, and other outstanding or peculiar
ecological factors were prepared for moose subpopulations
identified to utilize the Susitna River floodplain. In these
accounts, I discuss information that I believe is pertinent
and needed for assessing with-project impacts to moose.
34
'.",' . •; ...
A large part of these accounts are based on circumstantial or
substantiated data obtained in other aspects of this study.
However, other portions of the accounts may be factually
unsubstantiated and are my best "guesses," "estimates," or
"speculation" as to the exact situation or its magnitude
(i.e., mortality factors, subpopulation size, etc.).
Limitations of Samples and Sampling Effort
Samples are only representative of the population from which
they are drawn. Moose subpopulation use of the Susitna River
floodplain is greatly influenced by winter conditions,
photoperiod (seasonal time), and location. Radio-marked moose
are only samples of groups of moose using specific areas on
specific dates during specific types of winters. Subpopu-
lations which winter on the Susitna River floodplain but were
not present on those dates or utilize the floodplain during
other seasonal periods may not have been adequately sampled.
Only a small sample of radio-marked moose was maintained north
o1: Talkeetna where impacts from hydroelectric development were
expected to be greatest. A high proportion of moose from this
subsample were lost due to mortality by hunters ( 1) , trains
(4), winter kill (2), and natural accidents (2). Additional
moose were radio-marked in this area in January 1984, but only
one additional year of data was obtained from those
individuals and some succumbed to similar mortality factors.
For these reasons, I believe that baseline data presently
available to identify and assess habitat use for moose sub-
populations which use this portion of the Susitna River flood-
plain may be inadequate.
FINDINGS AND DISCUSSION
Timing, Duration, and Magnitude of Floodplain Use by Moose in
Winter
Interaction between hydraulics of the Susitna River and
adjacent terrestial habitats have, over time, resulted in a
heterogeneous assemblage of early and late successional plant
communities which, along with local climatic conditions,
appear to provide attractive winter range for moose (Collins
1983).
Some moose use Susi tna River floodplain habitats throughout
the year but greatest use of .the floodplain occurs in winter
when snow and foraging conditions become unfavor~ble to moose
subpopulations in adjacent habitats (Rausch 1958). A
shallower snowpack and greater availability of high quality
browse encourage large numbers moose to immigrate great
35
distances to winter on ·the floodplain. Timing, duration, and
magnitude of moose use of the Susitna River floodplain as
winter range are strongly influenced by snowpack depth in the
surrounding Susitna River valley. However, I believe that
activities and movements associated with rutting (pre-winter)
and calving (post-winter) would preclude the effects of
extreme variation in weather and snowpack depth on timing of
moose migratory behavior. Considering these factors, early
winter migratory behavior would not occur until late October
when the rut is completed and early spring migratory behavior
which precedes calving would not be delayed later then late
April.
Periodic censuses of moose in floodplain habitats within a
given winter and during several winters provide information
on: (1) timing of moose use of these habitats; (2) habitats or
areas that are most attractive to moose; (3) numbers of moose
that utilize floodplain habitats; ( 4) numbers of moose that
floodplain habitats may potentially support; ( 5) sex and age
composition of moose which use specific riparian habitats; and
(6) duration of moose use of these habitats. Surveys con-
ducted prior to and/or after a major migration of moose may
provide indirect information on numbers of moose and identity
of subpopulations which are year-round "residents" to flood-
plain habitats.
Information obtained from 35 moose censuses, gathered during
contrasting annual winter \veather conditions in floodplain
habitats along the Susitna River between Devil Canyon and Cook
Inlet (Table 6 and Fig. 10) , substantiated observations of
Rausch (1958) and others (Chatelain 1951 and LeResche 1974)
about effects of weather on behavior of "railbelt" moose sub-
populations and moose use of lowland winter ranges such as
those along the lower Susitna River. Six censuses were
conducted from 9 December through 12 April during the
relatively mild and snow-free winter of 1981-82. Eleven
censuses were conducted from 29 October and 13 April during
the relatively early and inclement winter of 1982-83. Seven
censuses were conducted from 17 November .through 15 March
during the relatively late and severe winter of 1983-84.
Eleven censuses were conducted from 27 November through
17 April during the relatively late but long and very
deep-snow winter of 1984-85. Snowpack depth in the lower
Susitna River valley in winter 1984-85 was greater than that
recorded in the previous ten years (U. s. Department of
Agriculture 1985) .
During the mild winter of 1981-82, a maximum of 369 moose were
observed along the entire length of the floodplain and a
maximum of 36 moose were observed between Devil Canyon and
Talkeetna.
36
Following substantial snowfall early in winter 1982-83, a
maximum o:E 934 moose were observed on the entire floodplain in
early January. At that time, 84 moose were observed in the
survey area between Devil Canyon and Talkeetna. From late
January through the remainder of the winter, numbers of moose
observed on the floodplain decreased in response: (1) to
absence of additional major accumulations of snow, and (2) to
settling of the accumulated snowpack. On eight of the ten
surveys conducted that winter, more moose were observed than
on any survey conducted in a previous year.
River surveys provided evidence that large numbers of moose
can and do rapidly respond to an early and extensive accumu-
lation of snow and a gradual dissipation of the snowpack with
migrations to and from the floodplain, respectively. In 1982,
deep snow~acks in October initiated a major movement of moose
to floodplain habitats. In 1985, persistence of a snowpack
into April apparently resulted in large numbers of moose
remaining on the floodplain in mid-April.
During the winter of 1983-84, little snowfall occurred in the
study area prior to late December. However, from January
through February, the snowpack increased substantially.
Extremely mild and warm weather in early March rapidly
dissipated the snowpack. Data obtained from moose surveys
indicated that few moose were observed on the floodplain
through e~arly January. Between January and early March the
numbers of moose observed on the floodplain increased
dramatically (from about 350 to 819). By mid-March the
numbers of moose on the floodplain had decreased sharply and
most survey areas contained few moose and snowcover was
insufficient for intensive moose counts.
In winter 1984-85, other field activities precluded conducting
moose surveys along the entire Susitna River floodplain down-
stream from Devil Canyon. Only floodplain areas between Devil
Canyon and Sunshine Bridge (Zone I ahd part of Zone II) were
periodically surveyed that winter.
Snowfall in the lower Susitna River Valley in the winter of
1984-85, was the greatest recorded in the previous ten years.
By February, the snowpack was nearly twice the normal depth
(U. S. Department of Agriculture 1985). A substantial snowpack
remained in most areas through mid-April. Numbers of moose
observed in Zone I on 18 January were 50 percent higher than
for any previous survey { 13 2 vs. 8 8 moose) . Though only a
portion of Zone II was surveyed, the number of moose observed
on 18 January was the second highest number observed for that
entire zone on . any previous survey. Large numbers of moose
continued to be observed in both those floodplain zones
through mid-April.
37
I suspect that moose subpopulations in the lower Susitna River
valley in general were at lower levels in winter 1984-85 than
in prior years due to mortality incurred during the previous
two relatively inclement winters. Therefore, I believe that
many more moose would have been observed on the floodplain in
winter 1984-85, had subpopulations not sustained relatively
high mortality in the winters of 1982-83 and 1983-84,
respectively·. In addition loss (death) of moose to starvation
(inadequate nutrition), and collisions with highway vehicles
and trains in the winter of 1984-85 also contributed to reduce
the number of moose moose available for observation that
winter.
In total, data from river surveys suggest that about 150-200
moose are resident to the Susi tna River floodplain between
Devil Canyon and Cook Inlet. Other moose observed on the
floodplain are migrants from adjacent subpopulations which
move into the area to utilize floodplain habitats for winter
range. The data suggest that, even without a significant
accumulation of snow, an additional and equal number of moose
move to the floodplain by mid-December. Large amounts of
snowfall and the accumulation of a deep snowpack in adjacent
areas can initiate a major immigration of moose from other
subpopulations to the floodplain. The latter immigration
occurs in response to snowfall and snowpack depth and may
occur as early as mid-November. If this immigration movement
occurred any earlier than this date, it may interfere with and
cause moose to prematurely abandon normal fall rutting beha-
vior and associated activities. I doubt if this mi.gratory
behavior would take precedence over and ·preclude rutting
activities.
Timing and progression of snowfall may affect the number of
moose that immigrate to the Susitna River .floodplain for
winter range. If snowfall occurs in numerous small storms
over an extended period of time, I believe that more moose
will be physically able to ·immigrate to the floodplain. A
gradual increase in the snowpack will stimulate moose to
immigrate and yet not hinder or prevent their migrat~on
because of extreme snowpack depths. Conversely, a rapid
increase in the snowpack to a deep level may impede moose
movements and preclude a typical and desirable (as far as
moose are concerned) migratory pattern. Settling or
dissipating of a deep snowpack probably would stimulate those
moose subpopulations that immigrate in response to excessive
snowfall to emigrate from the floodplain. The number of moose
utilizing the Susitna River floodplain in a winter
characterized by a small, incremented, but deep snowpack is
probably three times that number which may utilize the
floodplain in a winter with little snowfall and six times as
many as are resident to the floodplain. In the inclement
38
1984-85 winter, nearly four times as many moose were observed
on the floodplain in Zone I as were observed in the mild
1981-82 winter.
Moose captured and radio-marked in late winter on the Susitna
River floodplain exhibited within and between year differences
in timing· of return movements to floodplain areas in
subsequent winters (Fig. 11). In most winters, many moose did
not move to floodplain areas before January and timing of
immigrations of moose radio-marked on the floodplain varied
among years. In the winter of 1982-83, most radio-marked
moose had returned to floodplain winter range by December.
The former movement was preceded by substantial snowfall in
late October and early November. In contrast, few
radio-marked moose returned to floodplain wintering areas by
December in the winters of 1981-82, 1983-84, and 1984-85.
These data indicate that local weather conditions (snowfall
and snowpack depth) strongly influence the timing of moose
immigration to the Susitna River floodplain and secondarily
affect the duration of time moose spend in floodplain
wintering areas.
In most winters, many radio-marked moose did not immigrat·e to
floodplain. wintering areas before January; most moose were
usually on floodplain winter ranges by February, and rela-
tively more modse were on floodplain wintering areas in March·
than in J'anuary (Fig. 12). These data may be "atypically"
skewed by the late winters (snowfall and snowpack) in 1982-83
and 1984-!35. However, evidence provided by this study indi-
cates that "winter" and use of winter range for most moose in
the lower Susi tna River valley did occur until February or
March. Depending of timing and extent ·of winter snowfall,
moose in the lower Susitna River valley may utilize winter
range on the Susitna River floodplain as early as November, or
as late as February through March, for periods of five and two
months duration, respectively.
Numbers (magnitude) of moose utilizing the floodplain in
winter are, in part, ~ependent on the standing crop of moose
subpopulations. If subpopulation levels are dow~ from a
series of inclement winters (or for whatever other reason),
fewer moose will be observed in floodplain areas merely
because of depressed subpopulation levels. If importance of
floodplain habitats to moose is based on magnitude of use,
invalid interpretations could result if information was
gathered after an (or several) inclement winter(s).
Locationa1 Differences in Moose Winter Use of the Susi tna
River Floodplain
Considering the quantity of habitat available in
zone along the Susitna River floodplain, the
39
each river
calculated
magnitude of use was similar for Zones I-III. Moose densities
in the former zones were considerably lower than for Zone IV.
Maxima calculated densities for moose observed in river Zones
I-IV were 4, 5, 4, and 14 moose per kmz of floodplain habitat,
respectively (Table 7).
I believe that three environmental factors account, in part,
for differences in densities of moose observed wintering on
different sections of the Susi tna River floodplain between
Devil Canyon and Cook Inlet. In its course toward Cook Inlet,
physiography of the Susitna River changes greatly (Table 1).
As the streambed gradient lessens, the instream flow rate
decreases, the floodplain widens, and· the main channel braids
into many smaller subdivisions. These factors result in the
occurrence of high relief, relatively stable islands upstream
from Talkeetna; numerous, shallow relief, relatively instable
islands from there downstream; and another series of large,
high relief, and stable islands near Cook Inlet.
Early successional browse plants preferred by moose in winter
occur more commonly on the wide, braided, shallow relief
portions of the floodplain nearer to Cook Inlet. Other impor-
tant nonbrowse food plants occur as understory vegetation on
the more permanent, larger, high relief islands.
Snowfall and snowpack persistence decrease from Devi-l Canyon
to Cook Inlet (Table 3) . Effects of these parameters
(snowfall and snowpack) appear to override the influence of
habitat type on moose distribution. Though the quality and
quantity of winter moose browse (second-growth vegetation)
were likely more desirable in the braided, low relief sections
of the floodplain, densities of wintering moose were found to
be greater on large islanded habitats nearer Cook Inlet
(Table 8) . Annual snowfall. is less and the snowpack is less
persistent on the latter downstream floodplain areas.
Of the floodplain areas intensively studied, moose densities
were lowest on the Delta Islands . (Table 8) . Dense, mature
cottonwood forests and a relatively deep snowpack probably
contribute to make the Delta Islands relatively· undesirable
winter habitat for moose.
Moose Subpopulation Behavior and Movement Patterns
Information on moose behavior and movement patterns was
gleaned from 3,852 relocations of 18 male and 51 female
radio-marked moose studied from April 1980 through July 1985.
Annual Ranges for Moose that Winter on the Susitna River
Floodplain
Data presented in Fig. 13 illustrate spatial distribution of
radio-relocations for all moose captured and radio-marked
40
along the Susitna River floodplain between Devil Canyon and
Cook Inlet:. It may be interpreted that these data indicate
the minimum area or zone within which impacts incurred by
moose that utilize the Susitna River floodplain may be
realized. More specifically, these data show that impacts to
moose on t.he Susitna River floodplain between Devil Canyon and
Cook Inlet may ultimately become obvious in areas as far west
as Beluga Lake, Little Peters Hills, the Chulitna River; as
far north as Hurricane; or as far east as Chunilna Creek,
Sheep River, the headwaters of Sheep Creek, Palmer, and Big
Lake. This "impact zone" broadens widely in areas south of
Talkeetna, where it is apparent that impacts to moose from
hydroelectric development of the Susitna River are likely to
be realized in areas up to 30 km from where they were incurred
on the floodplain.
Likewise, positive effects of hydroelectric development or
mitigation activities may be realized throughout this same
area or may be directed at locations distant from the flood-
plain and still benefit moose subpopulations which utilize
floodplain habitats.
In October through December, large numbers of moose (probably
over 1,500) have been observed in areas east of the Susitna
River floodplain in the foothills of the Talkeetna Mountains
between the Little Susitna River and the Kashwitna River
(ADF&G files) . I am unsure why no moose in the radio-marked
sample later utilize habitats in that area (i.e., why did
moose front that subpopulation(s) not utilize the Susitna River
floodplain as winter range?) . Perhaps moose from this
subpopulation: (1) do not winter on the floodplain~
(2) winter on the floodplain but for periods of time not coin-
cident with sampling; or (3) winter on the floodplain only
when a de~ep snowpack occurs in. that portion of the Talkeetna
Mountains; however, the latter conditions did not occur during
this study.
Figures 14 and 15 illustrate points of relocation for female
and male radio-marked moose, respectively. These data
indicate that the extent and spatial relationships of impacts
will, in part, depend on the sex of affected moose. Though
the sample of radio-marked males ( 18} was considerably less
than for females (51), males appeared to range over the same,
similar-sized area as females. The "bounds n or maxima for
movements of both sexes was similar but, since the extremes in
range size for females was displayed by a smaller sample of
males, distance of male movements varies more between
individuals.
Changes in environmental conditions along the Susi tna River
floodplain as a result of hydroelectric development may affect
41
productivity of some moose subpopulations. The effects may be
direct by mortality of productive females, or indirect by
affecting quality of floodplain habitats which, in turn,
affects female nutritive condition and reduces female
reproductive success. In either case, decreased productivity
may result in reduced moose densities near or distant from the
floodplain. Likewise, mitigation measures that improve
calving environment or winter range on the floodplain may
increase productiv~ty and sizes of moose subpopulations within
that same extensive area. However, it should be noted that
resulting increases in moose subpopulation size may
subsequently place· addi t.ional "stress" on environmental
components used by these moose subpopulations during other
seasonal periods.
Seasonal Ranges for Moose that Winter on the Susitna River
Floodplain
Calving Range:
Figure 16 illustrates locations where female moose captured
and radio-marked in winter on the Susitna River floodplain
were ·relocated during· the calving period (May-June) . These
data indicate that most female moose south of Talkeetna leave
the floodplain in spring to calve, that female moose north of
Talkeetna return to the floodplain to calve, and that females
inhabiting large islanded areas south of Talkeetna may remain
in those areas (on the floodplain) for calving.
Previous studies in the lower Susitna River valley (Modafferi
1982) indicated that radio-marked female moose south of
Talkeetna were commonly located in "typical" moose calving
habitat (Bailey and Bangs 1980, Rausch 1958) composed of black
spruce, sedge, and mQskeg by mid-May. This type of habitat
was not readily available to female moose north of Talkeetna
where Susitna River floodplain habitats were used during
parturition.
One feature common to floodplain calving sites north of
Talkeetna and riparian and nonriparian sites south of
Talkeetna was their proximity to water. These data indicate
that one of the most important attributes of a calving site
may be the presence of water. It is possible that female
moose seek wet areas during calving because of the availa-
bility of newly growing, succulent, nutritious, herbaceous
vegetation and not specifically because of the presence of
water. It is probably important for lactating females and
neonate moose to have a readily available source of easily
digestible, highly nutritious, forage plants. It has been
reported that in early spring near parturition moose prefer to
consume newly growing emergent marsh forbs, sedges, or
42
horsetail and that they have been observed to gather in groups
on muskegs to consume those types of vegetation in pre-flower
and early flowering stages (LeResche and Dav"is 1973) . Feeding
on aquatic plants in spring could also counteract any negative
sodium balance which moose may incur while subjected to high
dietary potassium levels and increased water flux associated
with feeding on newly growing succulent forbs (Weeks and
Kirkpatrick 1976, Fraser et al. 1980).
Avoiding predation (Ballard et al. 1980a and Schwartz and
Franzmann 1981) or insect harassment (Mould 1979) may be a
secondary consideration to food quality in ·selection of
calving sites. Open muskeg areas would provide relief from
insect harassment because of air movement, but air movement
may also carry moose scent to predators ~uch as black or brown
bears or wolves. The relative openness of these habitats pre-
cludes concealment from predators, reduces desirability of the
habitat for black bears (Modafferi 1978 and Schwartz and
Franzmann 1981), but promotes visual observation of
approaching predators. Riparian habitats utilized by moose
upstream from Talkeetna are less open ·than muskeg calving
habitats and would provide little relief from insect
harassment, but would provide considerably more concealment
from predators and decrease the amount of windborne scent.
Wolves are not commonly observed, but occur along the Susitna
River downstream from Devil Canyon. Brown and black bears
occur con~only in the area between Talkeetna and· Devil Canyon
and are known to utilize mid elevations on south-facing slopes
during this seasonal period (Sterling Miller pers. commun.) .
Predation from bears could be responsible for parturient
female moose moving from ridges and midslopes to lower eleva-
tions along the floodplain, as was hypothesized by Edwards
(1983) for female moose in association with wolves at Isle
Royale. High rates of predation by brown bears and wolves on
neonatal moose calves have been documented for a moose
subpopul.::ttion several miles upstream from Devil Canyon
(Ballard et al. 1980b and Ballard and Spraker 1979,
respect~vely) .
Coyote harassment and predation on moose calves is not
documente:d, .but coyotes are abundant throughout the entir·e
study ar,ea and may be involved in prompting female moose to
move to floodplain or muskeg areas during parturition.
Edwards (1983) provided evidence that while attempting to
avoid predators moose inhabited poorer quality habitat and had
to increase diet diversity to compensate for an overall
decrease in diet quality (i.e., increased diversity in dietary
constituents indicated a decrease in overall diet quality) . I
contend that increases in diet diversity may not always be
indicative of overall decreases in diet quality. It may be
43
that understory vegetation in riparian habitats provides a
variety of nonbrowse plant species which at any given time
occur at different stages of phenological development, but
when considered over time they could, in combination, provide
a continuous supply of young, tender, highly digestible, and
nutritious phenological stages of vegetation. Collins (pers.
commun.) has observed in late May and early June that ferns on
some floodplains and islands north of. Talkeetna were heavily
browsed by moose. He also believed that ferns (particularly
at the fiddlehead stage) were an excellent source of nitrogen
(see Modafferi 1984:100 for chemical analysis of fern
fiddleheads and rhizomes collected in January) .
For a period of time after calving, female moose with neonates
remain relatively sedentary. By July, moose have generally
started moving to summer range areas where they remain until
rutting activities start in late September.
Summer Range.
It is probably during the summer period when numerous people
are traveling afield picnicking, camping, fishing, boating,
and recreating outdoors that nonconsumptive values of moose in
the lower Susitna River valley are greatest. Impacts of the
proposed Susitna River hydroelectric project may be expected
to influence summer distribution and abundance of moose in
areas similar to those illustrated in Fig. 17. The greatest
impact on nonconsumptive use of the moose resource will likely
occur in the aforementioned areas.
Fall Range.
Consumptive use of the moose resource by hunters occurs
primarily during the month of September. Hunting seasons are
generally only open to the taking of male moose. Figure 18
illustrates where male -radio-marked moose were relocated
during September. These data indicate loca.tions where impacts
of the proposed hydroelectric project on moose subpopulations
will be realized· by hunters. The data further illustrate that
moose subpopulations which winter on the Susitna River
floodplain provide for consumptive use throughout an extensive
area and inc·lude locations up to 30 km from the floodplain.
Frequency and Seasonal Timing For Moose Crossings of the
Susitna River Floodplain
Information on frequency and seasonal timing of river
crossings by moose is important to assess potential impacts of
the proposed hydroelectric development if flow and ice regimes
of the Susitna River will be altered "with project."
Mortality of unmarked and radio-marked moose was attributed to
44
river crossings during spring breakup flows and ice jamming,
summer peak flows, and slush (soft) ice cover in winter.
With-project alterations in river conditions during these time
periods may have positive or n_egati ve "direct" impacts on
moose subpopulations by affecting moose mortality rates. The
net effect:s of these direct impacts must be considered along
with "indirect" impacts of altered flow regimes. Decreased
flow regimes in summer may facilitate moose movements across
the floodplain, but the lower and relatively stable flows may
negatively· affect colonization of the floodplain by early
successional plant communities.
Data in Fig. 19 further substantiate similarities and
differences between behavior patterns of moose subpopulations
north and south of Talkeetna. River crossings for moose south
of Talkeetna peaked in late winter (February through April) ,
whereas c:rossings for moose north of Talkeetna exhibited a
small peak in early winter and a much larger peak in May and
June during parturition. River crossings for moose from both
areas wer4::! minimal from July through November. These data
along \vi th that presented in the subsequent section "Affinity
of Radio-marked Moose For the Susitna River Floodplain"
suggest . that direct moose mortality could be minimized and
moose would benefit from a solid river ice cover during winter
and subdue~d peak flows during parturition (May and June).
Size, Shape, and Spatial Arrangement of Annual · Ranges for
Moose Radio-Marked on the Susitna River Floodplain
Information on size, shape, and spatial arrangement of annual
ranges for moose is useful in identifying subpopulations, in
assessing how individuals and subpopulations utilize resources
and habi·tats available on and off the Susitna River
floodplain, in considering and selecting compensation lands,
and in anticipating how moose might respond to habitats on
enhancement lands. Data presented in Figs. 20, 21, and 22
illustrate relative size, shape, and spatial arrangements of
ranges for radio-marked male and female moose studied for 1.5
to 5.5 years. These data .show that the Susitna River is not a
boundary or an impassable barrier to moose movements. Many
moose utilized areas on both sides of the floodplain (No. 87
and 22 in Fig. 20, No. 84 in Fig. 21, and No. 23 in Fig. 22).
Some moose ranged farther eastward of the floodplain (No. 26
in Fig. 20, No 100 in Fig. 21 and No. 791 in Fig. 22) and
others ranged farther westward (No. 93 in Fig. 20, No. 713 in
Fig. 21, and No. 93 in Fig. 22). Ranges of some moose
centered on the floodplain (Nos. 37, 68, and 95 in Fig. 21),
abutted the floodplain (No. 97 in Fig. 20, No. 99 in Fig. 21,
and Nos. 88 and 94 in Fig. 22) or paralleled the floodplain
(No. 92 in Fig. 22).
45
Most radio-marked moose ranged west and/or north of the
Susitna River when not on the floodplain. Moose radio-marked
north of Talkeetna ranged over considerably smaller areas than
moose south of Talkeetna (Fig. 20). Ranges of moose in the
former area were more n·circular" in shape compared to the
"oblong 11 shape for ranges of moose from the latter area. I
suspect this phenomenon is a function of the distance between
different seasonal habitats. Sui table seasonal habitats or
ranges (i.e. , winter and summer, etc:} are apparently more
dispersed for moose south of Talkeetna or circumstances are
such that some moose may have the "option 11 to travel further
to encounter required seasonal habitats. Lesser snowpack
depths south of Talkeetna may enable moose to travel greater
distances between fall-winter and winter-spring ranges. If
this contention is correct, then winter ranges which are
surrounded by areas with relatively shallow snowpacks (as the
Susi tna River floodplain south of Talkeetna) would attract
moose from greater distances (and a larger area) than winter
ranges which are surrounded by deeper snowpacks and the former
ranges would exhibit much greater moose densities.
Movement Patterns and Spatial Relationships Between Seasonal
Ranges for Moose Radio-Marked on the Susitna River Floodplain
Figures 23, 24, 25, and 26 exhibit movement patterns and
spatial relationships between seasonal ranges (activity
centers) for individual moose radio-marked along the Susitna
River floodplain.
Figures 23 and 24. illustrate variation in range size and
differences in spatial relationships between seasonal ranges
or activity centers for radio-marked moose. Some moose appear
to have a relatively consolidated annual range in which all
seasonal ranges or activity centers are in close proximity
(No. 81 in Fig. 23). Other moose exhibited a more extensive
annual range which encompassed two (No. 99 in Fig. 24), three
(No. 23 and 93 in Fig. 23) or four (No. 41 in Fig. 24)
spatially separated seasonal ranges or activity centers.
Individual moose Nos. 81 (Fig. 23), 29, 69, and 99 (Fig. 24}
exhibited increasing degrees of spatial separation and
discreteness between seasonal ranges or activity centers.
Radio-relocations for No. 81 do not indicate the existence of
spatially discrete seasonal ranges. Relocations for moose
Nos. 29 and 69, respectively, illustrate partial and nearly
complete separation between seasonal ranges. The scarcity of
relocation points between spatially separated activity centers
suggest that moose No. 99 moved rapidly between an activity
center (winter range) on the Susi tna River floodplain and a
nonwinter activity center near the Yentna River. In contrast,
radio-relocations between spatially distinct activity centers
46
r. •,_
suggest that moose No. 93 moved more "leisurely"
winter range on the Susitna River floodplain and
seasonal activity center about 40 km westward or
transitional ranges in between.
between
another
utilized
Frequently, moose which had more than two activity centers
utilized areas early in winter or during mild winters that
were discrete from areas utilized later in winter or during
inclement winters (Nos. 41 and 23, Fig. 23; No. 65, Fig. 25;
and Nos. 27 and 45, Fig. 28). With few exceptions (No. 22,
Fig. 25), radio-marked moose had late and/or inclement winter
ranges located on the Susitna River floodplain.
Several moose radio-marked on the Susitna River near the mouth
of Kroto Creek (No. 87, Fig. 20; No. 100, Fig. 21 and No. 84,
Fig. 22) were known to winter east of the Susitna River around
~uman set:tlements near Wasilla. Whether this area was their
only wintering area or an alternative wintering is unknown.
Moose seasonal activity centers were not
proximity {Fig. 25). Females (Nos. 22 and
males (Nos. 65 and 92), utilized seasonal
that were more than 50 km apart.
always in close
93), as well as
activity centers
One female moose (No. 22, Fig. 25) exhibited very intriguing
movement patterns and spatial arrangements between seasonal
activity centers. This individual utilized a winter range
above timberline between Sheep Creek and South Fork Montana
Creek in five consecutive years. Each year before
parturition, this moose migrated about 80 km southwest across
the Susi t.na River to near Wi tsol Lake. After parturition,
this individual moved about 40 km north to Trapper Lake for a
month and then returned to her calving area until the end of
September when she returned to a winter range above timberline
in the Talkeetna Mountains. Apparently, she was captured in
late winter/early spring while crossing the Susitna River
floodplain enroute to the calving area.
Consistency in Us~ of Annual Ranges by Radio-Marked Moose
Figures 26 and 27 illustrate consistency and variation,
respectively, in use o~ annual· ranges for radio-marked moose.
Annual movement patterns of some individuals (Nos. 23, 88, 40,
and 93) indicated some individual moose ranged over the same
area for three to four consecutive years (Fig. 26). Size and
shape of annual ranges for these individuals were consistently
similar. Movements for other individual moose (Nos. 42, 63,
27, 45, 37, and 95) indicated that they ranged over grossly
different: areas in consecutive· years (Fig. 27} . I believe
that relatively mild conditions in the winter of 1981-82 may
explain ·the "inconsistent" patterns of annual range use for
47
moose Nos. 27, 45, and perhaps 95. Under mild winter
conditions moose Nos. 27 and 45 did not migrate to the Susitna
River floodplain. Apparently, these individuals ranged over
smaller areas and utilized "alternate" areas in mild winters.
In the 1983-84 winter, moose Nos. 27 and 45, respectively,
remained in the foothills of the Talkeetna Mountains and near
Kroto Creek instead of immigrating to the Susitna River
floodplain. Moose No. 95 also ranged less in that year,
perhaps for the same reason.
Some moose that consistently ranged over small area~ (Nos. 63
and 37) also exhibited inconsistent patterns in annual range
use.
Inconsistent use of annual ranges by females may have profound
implications on subsequent development of behavior patterns in
their progeny. Female moose which exhibit inconsistent
patterns in annual range use will expose progeny born and
reared in different years and spatially different habitats.
Depending on weather patterns in their birth year, dependent
calf moose will be exposed to and learn different annual
~ovement patterns. Such variation in behavior by female moose
promotes the incorporation of potentially adaptive variability
in moose subpopulation behavior. Survival rates for moose
with different learned migratory behavior will be influenced
by similarity {or dissimilarity) of environmental conditions
bet\v-een their first year of life and subsequent years. During
severe winter conditions, female moose may undertake different
movements and expose their young to different winter ranges
than during milder winters. When exposed to severe winter
conditions it would seem that moose "knowledgeable" of those
("severe winter") movement patterns and alternate winter
ranges would be favored to survive. In contrast, during mild
winter conditions moose that do not undergo extensive
("unnecessary") migrations would probably be "selectively
favored" to survive.
Apparently "Erratic" Movements for Radio.:..Ma.rked Moose
Some moose exhibited movements that were "erratic" or
extraordinary compared to documented centers of activity.
Moose Nos. 42,· 64, and 95 (Fig. 28) exhibited "erratic"
movements. The extraordinary movements for females (Nos. 42
and 6 4) were recorded in July (after the normal time for
paturition) of different years. Male No. 95 made an "erratic"
movement during winter. Because extraordinary movements for
females occurred after parturition, those forays may have been
associated with the loss of neonatal young. The movement of
the male may have been in response to extreme winter
conditions as it occurred in the winter of 1982-83 when a deep
snowpack was present in early November. Other moose (Nos. 45
48
and 27, Fig. 27) are known to have altered movement patterns
in response to winter conditions. Perhaps these forays were
not extraordinary and, if the individual moose were studied
for a longer period of time, the same movements would be
repeated under similar environmental conditions.
Affinity of Radio-Marked Moose for the Susitna River
Floodplain
Figures 29, 30, and 31 illustrate moose affinity by sex, area,
and month for the Susitna River floodplain and its associated
riparian habitats. ·
Most female moose radio-marked on the Susitna River floodplain
in winter had migrated 5-15 miles from the west to winter on
the floodplain (Fig. 29). These data indicate that some
females originated from distances over 15 miles. Few migrant
females originated from areas 3-5 miles distant from the
floodplain. About one-third of the females migrated less than
three miles: to utilize winter range on the Susitna River
floodplain. Some individual females remained on the
floodplain year-round and did not have to migrate to a winter
range. Miqrant females typically began arriving on the
floodplain in November and most all immigrants were present on
the floodplain by January. Emigration commenced after March
and was completed by May. Female emigration from wintering
areas is probably timed so they arrive in calving areas by
mid-May when parturition commences. The emigration of females
from the floodplain to spring-summer ranges must be a rapid
direct movement since radio-marked individuals that traveled
relatively long distances {Nos. 41, Fig. 23; No. 99, Fig. 24
and No. 22, Fig. 25) were not frequen1:ly relocated "between"
winter and calving range activity centers.
As for females, few males radio-marked downstream from
Talkeetna emigrated from 3-5 miles to winter on the Susi tna
River floodplain. Similar to females, a small portion of
males that occur on the floodplain in winter are probably
nonmigrant, year-round residents. In some winters, some males
apparently initiated a migration, moving toward and near the
floodplain but remained 0-3 mi away rather than utilize the
floodplain. I suspect these individuals utilized early
successional habitats available on "disclimax sites"
( Identifica·tion of Potential Compensation Lands) . The data
suggest tha.t, in contrast to females, origin of male moose
that winter on the floodplain is more equally distributed
between the 0-3, 5-15, and 15+ mi zones distant from the
floodplain. The data imply that both males and females
initiate emigration from floodplain winter range in March.
However, ma.les did not appear to start immigrating to win-
tering areas until after December, two months later than
49
females. Males may remain on early winter ranges ("post-rut}
longer than females to replenish condition lost during rutting
activities. Males may be physically unable to migrate at the
same time as females.
I am uncertain why data for both sexes imply that few emigrant
moose originated between 3 and 5 mi from the floodplain.
Other notable wintering areas, Kroto and Moose Creeks, are not
located in that range but are farther west of the Susi tna
River in the 5-to 10-mi range. It may be that moose from the
3-to 5-mi range utilize wintering areas to the west rather
than the Susitna River floodplain or that habitat in the 3-to
5-mi range is low quality spring, summer, and early fall moose
habitat and supports few moose.
Male and female moose radio-marked on the floodplain upstream
from Talkeetna (Fig. 31) emigrated considerably less distance
to winter on the Susitna River floodplain than did their
counterparts downstream from Talkeetna (Figs. 29 and 30).
Less than 25 percent (vs. 50-60 percent) of the moose marked
in this area migrated from distances greater than 3 mi. Only
infrequently did moose from this area utilize habitats farther
than 5 mi from the floodplain. These data also suggest that,
for moose north of Talkeetna, major migratory movements to the
Susitna River floodplain did not occur until January and were
reversed by April. This was a much shorter time period of use
than for marked moose downstream from Talkeetna.
The most contrasting behavior between moose south and north of
Talkeetna was the apparent "reverse" movement of latter female
moose (see Modafferi 1984:59, Table 17) back to the floodplain
during May and June. The timing of this movement correlates
with parturition in females. Female moose from this
subpopulation apparently seek and utilize floodplain areas
during calving. Specific factors causing this movement have
not yet been identified but they may be related to
availability of early growing nurtitious forage plants
(Leresche and Davis 197 3) and/ or the scarcity of predators
{Stringham 1974, Ballard et al. 1980a, and Edwards 1983) in
the relatively moist and inaccessible floodplain habitats,
respectively (Calving Range} .
Mortality Factors For Unmarked and Radio-Marked Moose in the
Lower Susitna River Valley
Mortality of radio-marked moose in the lower Sus i tna River
valley was attributed to the following sources: winter nkill,"
collisions with trains, drowning, injury, hunting, defense of
life and property, capture activities, and poaching (Table 9).
Moose mortality rates from some sources will likely increase
with hydroelectric development of the Susitna River.
50
Moose Collisions with Trains and Highway Vehicles:
Access plans for hydroelectric development of the Susitna
River call for extension of railroad and vehicular roads to
Devil Canyon as well as increased traffic on existing track
and road systems. Traffic on access routes will be greatest
during the construction phase when equipment, materials, and
personnel will be transported to and from areas near the
prospectiVE:! dam sites. Presently, large numbers of moose are
killed by collisions with trains and vehicles {ADF&G files).
Moose mortality rates vary between year, season, location, and
time of day. Mortality is greatest in winters when deep
snowpacks in adjacent and upland areas cause moose to
concentratE:! on lowland winter range near railroad and highway
rights-of-~vay. Shallower snow, availability of browse and
plowed paths through snow in and near rights-of-way encourage
moose to remain in these areas while deep snowpacks persist in
adjacent areas. Mortality is accentuated at locations where
large subpopulations and/or several different subpopulations
congregate and feed during winter. Mortality is probably
greatest at all locations at night following additional local
snow accumulation. The former further restricts and impedes
moose movements and the latter is when moose are most active
and visibility by engineers and motorists is minimized.
Moose collisions with trains and highway vehicles result in
property damage and are a hazard to human safety. Hazards to
humans and mortality of moose from collisions with trains and
vehicles is not limited to Alaska. In years of heavy
snowfall, over 1,000 moose are reported to have been killed by
collisions with trains in the Omineca region of British
Columbia, Canada (Child 1983). In Ontario, Canada, road
accidents involving moose in spring are hazardous to motorists
and result in unwanted mortality of moose (Fraser 1979}.
Alaska Railroad Right-Of-Way.
Mortality of moose from collisions with trains in the Alaska
Railroad right-of-way can be a major source of mortality to
specific subpopulations. From May 1984 through April 1985,
over 380 moose were reported killed by collisions with trains
in the Alaska Railroad right-of-way (Table 10} . These data
illustrate that mortality rates in summer were relatively
insignificant and that outstandingly high mortality rates
occurred in the 1970-71, 1978-79, 1982-83, and 1984-85
winters. All these winters were characterized by above
average snowpacks.
A more refined analysis of data among those four years and
within each ~inter period indicates that mortality rates were
greatest from December through March. A mean of 87 percent of
51
the reported mortality occurred during this seasonal period
(Table 11}. These data further indicate that over 50 percent
of the mortality in each winter occurred during February and
March.
An analysis of the 1978-79, 1982-83 and 1984-85 data by
location (railroad milepost) indicated that moose mortality
was not distributed evenly throughout the right-of-way
(Table 12}. Data for 1970-71 were not included in this
analysis because moose, in part, utilize these areas because
of available winter browse. As early seral vegetation matures
its desirability as moose browse declines. Therefore, unless
subpopulation traditional use is an overriding factor, one
would expect that moose use of specific winter range areas
would change over time in relation to availability of early
seral browse. Data for all three winters indicate that the
highest percent of mortality occurred between milepost 195 and
199. This interval of right-of-way accounted for a mean of 12
percent of all railroad-based mortality. In winter 1984-85,
46 moose were killed in this section of right-of-way. A mean
of .50 percent of all mortality occurred in the milepost
section 185-225. Two hundred and six moose w·ere killed in the
latter section in 1984-85.
Figure 32 graphically illustrates numbers and locations for
moose killed within milepost sections for the three years with
the highest recorded kill in the last ten years. These
sections of right-of-way roughly correspond to winter range
areas utilized by different moose subpopulations identified in
this study (Fig. 43). The kill data indicate that relatively
high rates of mortality (4-5 moose per mile of right-of-way)
were sustained by moose in sections south of Talkeetna and
that relatively low mortality rates (0.2 to 1.5 moose per mile
of right-of-way) occurred in the 2 36-2 78 milepost sections
north of Talkeetna.
However, to realistically ·assess impacts from this source of
mortality, mortality rates and numbers of moose killed must be
related· to the size of the respective moose subpopulations
which sustain that mortality. Though higher kill rates
occurred for right-of-way sections farther south, the impact
of that mortality on those subpopulations is considerably less
due to the relatively large size of those moose
subpopulations.
Data on winter weather, mortality by month, and moose kill
rates in specific milepost sections may be integrated with
information on moose subpopulation size and movement patterns
to formulate a list of precautionary measures to follow to
minimize negative impacts of increased railway traffic on
moose subpopulations.
52
Increasing the length of traveled right-of-way or frequency of
train traffic between Anchorage and Devil Canyon will increase
moose mortality. Before measures are taken to decrease moose
mortality in railroad rights-of-way, it should be determined
whether t:he goal of these measures is to decrease overall
moose mortality or whether it is to decrease the impact on
subpopulations whose long-term integrity may be threathened
because of their relatively small size.
Precautionary measures to consider for decreasing moose
mortality from collisions with trains include: scheduling
trains during the day, decreasing the number of trains by
combining several together and/or hauling the maximum numbers
of cars per trip, slowing the speed of trains so engineers
have time to react to moose and/or moose have time to avoid
oncoming traffic, wing-plowing snow in right-of-way and
adjacent to tracks to decrease snow depths and increase the
likelihood of moose running off track areas to avoid oncoming
traffic, providing bright lights on trains so engineers may
see moose: in time to slow down, and providing winter range
type browse in strategic locations removed from right-of-way
to "intercept" and hold moose subpopulations migrating toward
winter ranges near rights-of-way. Some measures could be
employed in milepost sections where moose are particularly
vulnerable and other measures may be undertaken in areas where
small-sized subpopulations are particularly vulnerable.
Seven radio-marked moose were killed by collisions with trains
in the Alaska Railroad right-of-way. Six of the moose killed
(four females and one male) ranged in areas north of Talkeetna
where 21 moose were radio-marked. Four of the moose were
killed during the relatively severe 1984-85 winter. These
data suggrest that train kills may be a significant cause of
mortality in the subpopulation of moose which winter on the
Susitna River floodplain north of Talkeetna. These data also
indicate that rates of mortality by collisions with trains are
much higher during a winter when snowpack depth is extreme.
Highway System Right-of-Way.
Mortality of moose from collisions with vehicles along the
railroad corridor appear to be of lower magnitude than for
collisions with trains but the potential hazard for humans is
considerably greater.
Moose-highway vehicle accident problems in Canada occur during
spring and early summer and are related to the appetite of
moose for dissolved sodium originating from highway deicing
salt and available in roadside pools (Fraser and Thomas 1982).
In Alaska,
primarily
moose mortality
in winter when
in highway rights-of-way occurs
moose concentrate in lowland
53
I .
wintering areas located near major highway systems (ADF&G
files) • Occurrence of early successional vegetation in
rights-of-way adjacent to roadways attracts moose and
increases the likelihood of collisions with vehicles. Numbers
of collisions are reported to be greatest at night when moose
are more active and visibility by motorists is minimized.
Use of deicing salt is becoming more common on roadways
between Anchorage and Fairbanks. This road maintenance
practice may increase moose mortality. In recent years,
travelers using those highways frequently report observing
moose licking.the paved surface (frequently from a "kneeling"
position) or eating snow in the roadside plow berms. I
presume these moose are obtaining sodium from the deicing
salt. Continued use of deice salt may encourage moose to
remain along roadways during spring and early summer as in
Canada.
The magnitude of moose mortality in winter is affected by
snowpack depth in surrounding uplands and along highway
rights-of-way. Relatively large numbers of moose were
reported killed by collisions with vehicles in winters
(1971-72 and 1978-79, 1982-83, 1983-84 and 1984-85, Table 13)
when heavy snowfall and deep snowpacks caused-large numbers of
moose to migrate to lowland winter ranges near the Susi tna ··
River floodplain (see Table 6) and along the adjacent highway
system.
Additional development of the highway system and increases in
highway traffic projected to occur during development and
maintenance of the proposed hydroelectric project will
increase the number of moose killed by collisions with
vehicles on roadways.
Moose mortality will increase significantly if new roadways
are constructed in or across moose migratory corridors or in
lowland wintering areas.
To minimize moose mortality on roadways, highway construction
in the former areas should be avoided, use of deicing salt
should be minimized, traffic patterns should be shifted toward
daylight hours and away from periods of heavy snowfall. No
radio-marked moose were known to be killed by collisions with
highway vehicles. One moose relocated in the highway
right-of-way was relocated one week later in the Talkeetna
dump. I suspect that this moose was either killed illegally
(poached) or hit and killed by a highway vehicle. Though
large numbers of moose may be killed in highway right-of-ways
in some winters, data from radio-marked moose suggest that
very few moose which winter on the Susitna River floodplain
are killed by collisions with highway vehicles.
54
..
The fact that no radio-marked moose were killed by vehicles
appears t:o contradict data which indicate large numbers of
moose from GMU 16A migrate easterly to winter on the Susitna
River floodplain and near highway and railroad rights-of-way.
However, I believe these data may merely emphasize the fact
that moose are exceptionally traditional in use of specific
wintering sites. In this case, moose that winter on the
Susitna River floodplain, where marked individuals were
captured, do not frequently venture to rights-of-way only
another mile to the east. Likewise, moose that traditionally
winter near the rights-of-way probably spend little time on
the ·floodplain (where moose were marked) while in transit to
their wintering areas near right-of-ways one mile eastward.
I suspect: more moose were killed on roadways in GMU 14A than
on roadways in GMU 14B (Table 13) because moose densities and
highway traffic are greater in the former subunit.
Additional development of the highway system and increases in
highway traffic that are projected to occur during development
and main·tenance of the proposed hydroelectric project will
increase the number of moose killed by collisions with highway
vehicles.
Accidental Mortality:
Mortality of some radio-marked moose was attributed to
· slipping on glare ice; falling through open water leads or
thin icE~ while crossing frozen rivers; drowning while
attempting to cross sections of open water, log jams or ice
jams; attempting to swim across sections of open water in
winter; injuries sustained from fighting during the rut; or
from wounds received during the open hunting season.
Two radio-marked moose died from injuries sustained from
slipping and falling on a glare ice cover of the Susi tna
River. Another moose died from similar injuries sustained
during capture procedures while under effects of tranquilizing
substances. Field observations indicated that mortality of
other ncmmarked moose resulted from similar causes. This
source of mortality is probably most frequent on the Susitna
River downstream from the Yentna River where strong
northeas1:erly winds conunonly blow snow off the frozen
floodplain. Similar conditions may occasionally occur on
sections of the Susitna River floodplain north of Talkeetna.
Death of one radio-marked moose north of Talkeetna was
attributed to drowning after falling through an open lead or
thin ice on the ice covered Susitna River. Observations near
the site, indicated the presence of a small open lead that may
not have been visible to the moose. In any event, it was not
55
large enough for the moose to have anticipated having to swim
to the other side. I make this distinction because the death
of several moose north of Talkeetna apparently resulted from
moose attempting to swim across a section of open water.
Field evidence suggested that these moose probably succumbed
to hypothermia because they were unable to climb back out onto
firm shorefast ice after traversing open water or slush ice.
Hunting:
Roughly, 900-1,400 moose have been killed annually by hunters
in the portion -of the lower Susitna River valley watershed
utilized by moose which may also utilize the Susitna River
floodplain. The estimated number of moose killed varies
greatly with current management strategy (i.e., timing and
length of the open hunting seasons and occurrence of either
sex and special permit late season permit hunts).
Hunting seasons have always been open to the harvest of males
in September. Therefore, I will direct my comments on impacts
of hydroelectric development to the harvest of male moose
during that time period. Male moose radio-marked on the
Susitna River floodplain were distributed throughout a
relatively large area during the September open hunting season
(Fig. 18) •
Eleven moose radio-marked on the Susitna River floodplain were
subsequently killed by hunters during open hunting seasons.
One male (out of three radio-marked, 33%) was killed north. of
Talkeetna and three females (out of 35 radio-marked, 9%) and
seven males (out of 14 radio-marked, 50%) were killed south of
Talkeetna. Data from the small sample of moose north of
Talkeetna indicate that a high proportion of that subpopula-
tion which winter on the Susitna River floodplain are killed
by hunters. Data from radio-marked male moose south of
Talkeetna indicate that about half the moose which winter on
the Susitna River floodplain south of Talkeetna are subse-
quently killed by hunters. Together, the data suggest that
decreases (or increases) to carrying capacity of moose winter
range downstream from Talkeetna would have a significant
effect on moose available to hunters.
Predation:
Only one adult radio-marked moose was suspected to have been
killed by a predator. This moose may have been killed by a
hunter and the brown bear observed at the kill site may have
been feeding on carrion. Because a hunting camp was located
near to the kill site, I suspect that the latter scenario may
be the most likely cause of death.
56
Because neQnate and calf moose were not radio-marked, parallel
information on predation rates for those age categories is
lacking. However, evidence from other studies in nearby areas
(Ballard et al. 1980b), and other areas in Alaska (Franzmann
et al. 1980), indicate that brown and black bears,
respectively, can be significant predators on neonate moose.
Brown and black bears are common in many portions of the lower
Susitna River valley and probably are a significant mortality
factor for neonate moose. With-project actions that increase
the numbers of bears or displace additional bears into other
areas could secondarily impact moose subpopulations by
increasing rates of predation. Actions that decrease numbers
or densities of -bears would have opposite effects on moose
mortality :rates.
Predators and rates of
subpopulations within the
thoroughly in a subsequent
Subpopulation Narratives) .
predation
study area
section of
for various moose
are discussed more
this report (Moose
In some localities wolves feed primarily on moose (Ballard and
Spraker 1979 and Peterson .et al. 1984). In some situations
predation by wolves may limit expansion of moose subpopula-
tions (Gasaway et al. 1983). Wolves are uncommon in most
portions of'the study area. Wolves occur in areas north of
Talkeetna and probably account for a small percentage of moose
mortality in that area.
Winter Kill:
Moose carcasses were observed during aerial surveys in all
winters, 19-81-1985. Numbers of carcasses observed in each
winter (Figs. 33-36) roughly correlated with amount of
snowfall and the accumulative snowpack. The 1981-82 and
1984-85 \\Tinters were judged to be mild and severe,
respectively. The 1982-83 and 1983·-84 winters were inter-
mediate to the former winters but estimated to be more near
severe than mild. Five, 31, 8, and 50 moose carcasses were
observed on the -susi tna River floodplain in the winters of
1981-82, 1982-83, 1983-84, ~nd 1984-85, respectively. The
occurrence of moose carcasses in wintering areas as a winter
progresses indicates that the resident subpopulation has
exceeded carrying capacity of that winter range (primarily
density dependent mortality) and/or that the energy costs of
obtaining forage exceeds energy extracted from forage
(primarily density independent mortality) . In either case,
availability of winter browse was inadequate to support and
maintain moose under the given environmental conditions.
Data colle,cted in Susi tna River and adjacent floodplain areas
provided evidence that moose died in those habitats in the
57
winter of 1984-85. Within the latter area, magnitude of
mortality was found to vary between two areas differing in
geographic location and gross habitat type.
The percentage of calf moose and number of dead moose observed
during aerial surveys conducted on Moose, Kroto, and Alexander
Creeks and riparian areas adjacent to the Susitna River
floodplain were found to decrease and increase, respectively,
between late November and mid-April (Tables 14 and 15) . The
percentage of calves in the those herds decreased from 19 or
28 percent, in November, depending on area, to about 6 to 10
percent by mid-April.
Numbers of dead moose observed varied between 9 and 18
depending on location. Nine dead moose and 8 percent calve~
were observed on a similar moose survey conducted 10 April on
the Yentna River floodplain. Data collected in the three
previous milder winters indicated that moose herds typically
contained more than 16 percent calves (Modafferi 1983:36,
Table 14) . Appearance of moose carcasses and decreases in
calf composition through winter indicate that winter
conditions were severe and suggest that winter range was
inadequate for that level of moose standing crop.
Likewise, data collected from Susi tna River riparian areas
indicated that herd calf composition decreased from 20 or 40
percent in November-December, when adequate size samples were
obtained, to 11 or 2 to 3 · percent, depending on area, by
mid-April. During the latter time period, moose carcasses
were also observed in the two northern floodplain areas, but
no carcasses were observed in the more southern islanded areas
nea~ Cook Inlet. As for floodplains adjacent to the Susitna
River, appearance of moose carcasses and decreases in herd
calf composition indicate relatively inclement winter
conditions and suggest inadequate winter forage for moose
herds on the Susi tna River floodplain. Differences in herd
calf composition recorded between the two areas on the Susitna
River floodplain suggest that environmental conditions were
not as harsh near Cook Inlet and/or moose subpopulation levels
there were closer to range carrying capacity. The areas
nearer Cook Inlet characteristically have a shallower snowpack
than inland areas farther north. Strong northeast winds
typically displace fallen snow from the latter areas,
facilitate travel by moose, and expose low growing browse and
non-browse forage plants.
Seventy-nine percent of a sample of 24 moose carcasses
examined on Alexander Creek, Kroto Creek, and the Susi tna
River in winter 1984-85 were found to be calves. Age
composition of this sample indicates a very low potential
annual recruitment to the subpopulations involved. Expansion
58
of moose subpoopulations involved is probably precluded
because of: the low potential for recruitment. Expansion of
these moose subpopulations in 1985 was apparently limited by
effects of inclement winter conditions on forage and foraging
behavior.
Studies by Franzmann and Arneson (1976) demonstrated that
moose femur marrow fat content may be used as an indicator of
nutritive condition. They provided evidence indicating that
dead calf and adult moose with levels of femur marrow fat near
7.3 and 9.7 percent, respectively, died from inadequate
nutrition. They found percent marrow fat for moose dying from
accidental causes was determined to be 30.4 and 69.3 for
calves and adults, respectively. They indicated that dead
moose with marrow fat values below 10 percent dry weight
probably were winter-killed (died from malnutrition) .
Femur mari:ow fat content from a sample of moose found dead on
the Susi tna River and adjacent floodplains in late winter
1984-85 suggest that they died from undernourishment
(Table 16). Inadequate winter forage conditions probably
resulted in moose dying of malnutrition_ in the lower Susi tna
River valley during the 1984-85 winter. Apparently, some
moose subpopulations in the lower Susitna River valley were
temporally above range carrying capacity.
Defense of Life and Property:
Alaska state law allows humans to kill game animals in defense
of life and property. _Normally, defense of life and property
killings involve aggressive confrontations with bears.
However, female moose protecting calves and moose stressed by
inadequate~ forage and difficult foraging conditions (a deep
snowpack) in late winter can, and will, become very aggressive
when conf1~onting humans.
Because dense human populations are sympatric with moose
·winter range in the lower Susitna River valley, when inclement
winter weather conditions occur human/moose interactions are
common. · Under these circumstances, moose, and females with
calves particularly, become defensive and aggressive towards
humans. In winter 1984-85, over 40 moose were killed in
defense ojE life and property along the "railbelt" in the lower
Susitna River valley (ADF&G files) . An extremely deep
snowpack occurred in the area and moose were reluctant to
leave snowpacked trails and plowed roadways. One radio-marked
moose was killed in defense of life and property in the winter
of 1984-85. Apparently, this radio-marked moose acted
aggressive towards children and would not permit a property
owner access to several "out" buildings. I am certain many
more moose were killed under similar circumstances, but were
not repor·ted .
59
Other moose were known killed by sled-dog owners when
aggressive moose were confronted on remote training trails.
If hydroelectric development of the Susitna River
increased development and human population in
Susitna River valley, there will undoubtedly be an
the number of moose killed in defense of life and
severe winters.
Illegal Kill:
results in
the lower
increase in
property in
Illegal killing (poaching) of moose occurs in the lower
Susitna River valley. Moose are killed illegally in urban and
rural areas. One moose radio-marked near Anchorage was later
killed illegally (ADF&G files) • Recent disposal of remote
parcels of land by the State of Alaska has encouraged many
people to settle in rural areas. Moose meat commonly provides
sustenance for humans settling on remote land parcels. Moose
poaching is probably not an uncommon occurrence in remote
settlements.
One radio-marked. moose was relocated in the highway
right-of-way near Talkeetna. Two weeks later, the
radio-collar from this moose was relocated in the Talkeetna
land fill. I suspect this moose was killed illegally and its
remains and the radio-collar were subsequently deposited in
the.land fill.
If hydroelectic development increases human
remote areas, . I believe that the number of
illegally can be expected to increase.
Mitigation for Loss of Wildlife and/or Habitat
settlement in
moose killed
Because habitat for moose and other wildlife will be altered
and/or lost with hydroelectric development of the Susitna
River, mitigation to compensate for these losses is necessary.
Mitigation for loss of wildlife and habitat will, in part, be
achieved by measures that compensate for . losses through
enhancement and/or protection of moose winter range habitat on
designated (11 compensation11
) lands. Habitat enhancement will
involve utilizing various land management techniques to
increase moose carrying capacity by altering existing plant
communites to favor regrowth of early successional communities
that produce large quanti ties of high quality winter moose
browse. Habitat protection will involve preventing habitats
that naturally have high carrying capacity from being
disturbed or altered.
For habitat enhancement to be successful, target moose
subpopulations should be limited by carrying capacity of the
60
winter range. Therefore, before considering habitat
enhancement, it should be demonstrated that moose subpopula-
tions will respond to quantitative or qualitative improvements
in winter browse. Deficiencies in winter range quality and/or
quantity may be evidenced by moose mortality on wintering
areas.
Data gath~ered on the number of moose carcasses observed on
routine surveys, age composition of dead and live moose, and
femur marrow fat content of dead moose suggest that moose from
some subpopulations in the lower Susitna River valley were in
poor nutritive condition in winter and died on winter range.
In either case, when mitigating for with-project losses,
compensation should be directed at affected moose
subpopulations (for the benefit of moose) and/or near the
location of loss (for the benefit of resources users) . If
integrity of a moose subpopulat.ion is threatened by
hydroeleci:rical development, compensation should be directed
at that specific subpopulation or the next proximal
subpopulai:ion.
Identification of Potential Compensation Lands:
Moose Distribution and Abundance.
Moose distribution and abundance were criteria utilized to
identify location of moose winter range lands. The relative
importancE~ of different winter range lands was evaluated by
moose use. Moose use was estimated from densities of moose
observed in delineated areas by aerial survey sampling
technique~; (Appendix A-C) . Data from aerial surveys were used
to identify and rate relative importance of different moose
winter range lands in the lower Susitna River valley
(Appendix D and Table 17).
Fifty-eight percent of the moose observed on distribution
surveys occurred on 13 percent of the survey area. Ninety-one
percent of the moose observed occurred on 36 percent of the
land surveyed. No moose were observed on 29 percent of the
area surveyed. Over 60 percent of the area surveyed had less
than one moose/4.5 mi 2 and was considered poor quality winter
moose ran~:Je.
Twenty-ei~:Jht delineated areas · ( 6. 8 percent of the area
surveyed), contained 41 percent of the moose observed.
Calculated densities of moose for these areas ranged from 3.1
to 13.6 moose/mi 2 • These areas were considered to be good
moose winter range and to have potential as compensation
lands.
61
The 27 survey areas identified as compensation lands were
dispersed through the lower Susitna River valley (Fig. 37).
Most identified areas were associated with riparian or
floodplain habitats. The fact that eight areas were located
on the Susitna River floodplain reemphasizes its importance as
moose winter range in the lower Susitna River valley.
Nonfloodplain areas identified as compensation lands were
located in alpine habitat near the timberline ecotone on
Willow Mountain (sample unit Nos. 19 and 24, Appendix A) and
on glacial moraine of the Kahiltna Glacier (sample unit No.
343, Appendix B).
Another nonfloodplain moose wintering area not specifically
identified as a potential compensation land, but worthy of
special mention, is an alpine area (sample unit No. 329,
Appendix B) located on the southwestern slopes of Little
Peters Hills. This survey area contained 2.4 moose/mi 2 • The
area had burned by fire previously and has been recolonized by
birch vegetation.
Snowpack Depth.
Because large numbers of moose were consistently observed
wintering in specific areas of the lower Susitna River valley,
it does not necessarily follow that these areas are good
winter range. These areas may be adequate winter range during
an average wint~r but they may become undesirable in severe
winter conditions. Heavy snowfall·and a deep snowpack affect
availability of browse and movement of moose and decrease the
desirability of areas for moose in winter (Coady 1974) . It
would be futile to enhance habitat for moose in areas where
excessive snowfall would preclude a positive response in moose
carrying capacity. Areas where the snowpack characteris-
tically remains shallow through winter are ideal for moose
winter range.
Survey results indicated that snowpack depth varied from 25 to
225 em within the lower Susitna River valley in March 1985
(Fig. 38). Snow depth measurements between 110 and 150 ·em
were most common (Fig. 39). Eighty percent of the survey area
was estimated to have a snowpack exceeding 100 em and was
considered undesirable for moose (Fig.40). After grouping
locations with like snowpack depth measurements (Fig. 41), a
geographical pattern between snowpack depth and moose
distribution and mortality became apparent.
These data helped to explain moose distribution and mortality
patterns observed in the lower Susitna River watershed. Areas
that had relatively shallow snowpacks (Fig. 41) were used by
relatively large numbers of moose (Fig. 37) and exhibited
little winter mortality (Big Island-Bell Island, Figs. 33-36
62
and Table 14, and the Wasilla area) . Other areas vli th less
shallow s;nowpacks (Talkeetna Mount.ains foothills, Little
Peters Hills, and Kahiltna Glacier moraine) also had large
numbers oj: moose and also exhibited little moose mortality.
Some areas with intermediate snowpack depths (Susi tna River
corridor and Chunilna Hills) contained substantial numbers of
wintering moose and exhibited moose mortality (Table 15).
Geographical areas with deep snowpacks (Alexander Creek, Moose
Creek, Kroto Creek, the Yentna River, and most other locations
in the survey area) either had very low densities of moose or
exhibited substantial moose mortality (Table 14).
Data on snowpack depth, moose distribution, abundance, and
mortality in the lower Susitna River valley provided a basis
for evaluating locations for conducting mitigation.
Procedures for Conducting Mitigation on Compensation Lands
Replacement Lands:
Areas that sustain large numbers of healthy moose through
inclement winter conditions have a high innate carrying
capacity and are important in maintaining high subpopulation
levels. Protecting important moose habitat (lands with high
carrying capacity) .from alternative land management practices
can be considered a form of mitigation. Areas identified to
have a high winter carrying capacity are important to moose
subpopulations and should be considered in mitigation as
replacement {lands) for lands altered during hydroelectric
development.
Data on moose distribution, abundance and mortality, and
snowpack depth suggest that floodplain areas including and
downstrean[ from Bell Island, nonriparian areas between Wasilla
and the :Little Susi tna River, timberline ecotone areas of
Willow and Bald Mountains, and western slopes of the Little
Peters Hills should specifically be considered as replacement
lands (land areas with A and B snowpack designations,
Fig. 41). These areas exhibited relatively densities of moose
in winter" shallow snowpacks, and low winter kill levels.
Quantifying the gain in carrying capacity as a result of
habitat protection (i.e., over and above that which would have
occurred :i.n the absence of habitat protection) on replacement
lands is considerably more difficult than for assessing
compensation in carrying capacity on enhancement lands and is
beyond the scope of this study.
Enhancement Lands:
Lands that supported relatively high densities of wintering
moose, exhibited moose winter kill, and had snowpack depths
63
less than 120 em (land areas with C snowpack designations,
Fig. 41) should be considered for compensation in mitigation
through habitat enhancement.
Lands with E designation should not be considered for
enhancement. Effects of the deep snowpacks on these lands
would far outweigh any benefits to moose gained from
increasing winter browse.
Most lands with D designations are probably also unsuitable
for successful habitat enhancement programs. Some of these
lands with snowpack depths near 120 em (Moose Creek downstream
from Petersville Road and Kroto Creek downstream from its
confluence with Moose Creek) may be acceptable for
enhancement. However, the fact that substantial moose winter
kill occurred in the latter areas during consecutive winters
indicates that the carrying capacity was exceeded even in
relatively mild winters. Enhancement procedures would have a
higher probability of greater success (i.e., larger positive
gains in carrying capacity) in C designated snowpack depth
areas.
Most radio-marked moose consistently repeated annual movement
patterns to use traditional winter ranges. These data suggest
that a~eas selected for habitat enhancement should be located
in traditional migratory routes and near traditional moose
winter ranges to assure a high probability of success.
Locating enhanced areas near traditional winter ranges or in
traditional migratory routes will assure that migrating moose
will be exposed to improved winter habitats and minimize
divergence from traditional behavior patterns.
Enhanced habitats could be located away from traditional use
areas where snowpack depth is desirable. However, if newly
enhanced habitats were remote from traditional use areas, I
would expect that moose would be slow to learn of and utilize
them. I doubt if many moose would greatly alter traditional
behavior patterns to utilize newly created habitats. Most
probably, moose that would colonize enhanced areas that are
removed from traditional wintering areas would be moose that
were resident to the area or yearling moose that are actively
establishing traditional behavior patterns. Moose use of
newly created winter habitats remote from traditional winter
ranges would increase at a slower rate than for enhanced
habitats located near traditional ranges (Gasaway et al.
1980) . If other factors were equal and after carrying
capacity was attained, total numbers of moose using enhanced
habitats in both locations may be the same, but over a given
time period significantly more moose would have utilized the
area near traditional winter ranges.
64
Though benefits exist· from enhancing habitats in close
proximity ito traditional winter use areas, in those instances,
newly emerging second growth vegetation may be exposed to
excessive browsing before it becomes established. Overbrow-
sing may even prevent new second growth vegetation from
becoming established. I suspect that this may particularly be
a problem in areas where the snowpack is shallow. A rela-
tively deep snowpack may act to obscure newly growing plants
from moose browsing for several years. Several years of pro-
tection from browsing pressure will enable plants to become
more firmly established before being subjected to moose
browsing.
Other factors significant to selection of areas for
enhancemen·t and implementation of enhancement procedures have
been presented in detail elsewhere {Harza Ebasco, Susitna
Joint Venture 1984}.
Quantifying Mitigation Potential for Compensation Lands
With-project losses to wildlife and habitat will, in part, be
offset with increases in moose carrying capacity on
compensation lands. Improved moose carrying capacity will
eventually result in net increases in moose numbers and sub-
population sizes. Mitigation will be considered successful
when wi th-·project losses in wildlife carrying capacity are
·offset by gains in moose carrying capacity and increases in
moose numbers. Follow-up field studies will be necessary to
determine if mitigation is successful.
Replacement Lands:
Moose use {carrying capacity} was assessed for several areas
representative of potential replacement lands. Areas selected
represented alpine habitats {Table 18, Fig. 7, and
Appendix E), riparian habitats adjacent to the Susitna River
floodplain {Table 19, Fig. 4, and Table 14), and a Susitna
River riparian habitat (Table 20, Fig. 6). All areas selected
were used by relatively large numbers of moose for winter
range.
Data from alpine habitats, Bald Mountain Ridge and Willow
Mountain, indicate that these areas provided about 45,000 and
40,000 moose days use, respectively, during 196 days in the
winter of 1985-86. These areas supported about eight and
seven moose, respectively, per mi 2 of habitat for a 196-day
period. Numbers of moose using these alpine areas peaked
between November and January. ·
Data from riparian areas adjacent to the Susitna River
floodplain, Alexander, Kroto, and Moose Creeks, indicate that
65
these areas provided roughly 23,000, 17,000, and 16,000 moose
days use during the winter of 1984-85. These areas supported
about six, two, and four moose per mi2 of habitat for a
140-day period. Numbers of moose using these riparian areas
peaked during December, January, and February, respectively.
Moose use of these areas was relatively low in November.
Data from Bell Island, a Susitna River riparian area studied
for four years, indicate that moose use varied greatly
between years (Table 8) and correlated with snowpack depth and
winter weather conditions. In winter 1984-85, this area
provided about 11,000 moose days use, four times the use which
occurred in the winters of 1981-82 and 1983-84. In the winter
of 1984-85, the area provided winter range for about 15 moose
during a 139-day period.
Bell Island supported the greatest amount of moose winter use
per mi2 of habitat of any area studied. My calculations
indicate that Bell Island provided about 2,000 moose days use
during a 139-day period in the winter of 1984-85. These data
suggest that each mi 2 of habitat on Bell Island provided
winter range for about 14 moose. ·
For mitigation purposes, it may be said that protecting Bald
Mountain Ridge from alternative land uses could offset a
with-project loss in moose carrying capacity equivalent to
45,000 moose days use. Each square mile of habitat protected
on Bald Mountain could theoretically offset with-project
losses of about eight moose. Of course, these calculations
assume that alternative land . uses would eliminate all moose
carrying capacity on Bald Mountain Ridge, if the area were not
protected. However, in reality this assumption would most
likely be incorrect.
Perhaps from an economic standpoint, moose use per mi 2 of
habitat protected should be considered when selecting
replacement lands. Bell Island supported the largest amount
of moose use per mi 2 of habitat. During a 139-day period in
the winter of 1984-85, Bell Island provided about 2,000 moose
days use per mi 2 of habitat. Each square mile of habitat on
Bell Island had the capacity to support 15 moose through a
139-day winter period. Considering data obtained during the
winter of 1984-85, protection of habitat on Bell Island (15
moose per mi 2 ) would offset twice as much loss in moose winter
range carrying capacity as could be offset by protecting an
equal quantity of habitat on Bald Mountain Ridge.
Enhancement Lands:
To assess
moose use
the mitigation potential
(carrying capacity) was
66
of habitat
studied on
enhancement,
14 disclimax
habitat sites located adjacent to the Susitna River floodplain
(Table 20, Appendix F, and Fig 6). Carrying capacity
estimates averaged 4,500 and 4,300 moose days use,
respectively, for the Montana West and the Montana Middle
disclimax sites over three winter periods: 1982-83, 1983-84,
and 1984-·85 (Table 20). Maximum values of 6,200 and 3,900
moose days use, respectively, were calculated for those
respective sites in the winter of 1982-83. These higher
values may be attributed to the fact that significant snowfall
occurred at least a month earlier in the winter of 1982-83
than in t:he latter two winters. This early snowfall prompted
large num~ers of moose to use these sites earlier."
Data from the former disclimax si·tes suggest that habitat
enhanceme:nt on about a square mile of land similarly located
could be expected to provide 4,300-4,500 moose days use in an
average winter. These data indicate that application of
appropriate habitat management procedures (habitat enhancement
activity) to one mi 2 of mature forest habitat in the same area
could provide winter range with carrying capacity for 30-34
moose.
These da·ta indicate that disclimax sites (Montana· West and
Montana Middle) and application of appropriate habitat
manag'ement techniques may provide winter range with carrying
capacity for three times as; Inany moose as the best natural
site (Bell Island) studied. These data indicate that habitat
managem~nt {rather than habitat protection) may be the most
economical method for accomplishing compensation of
with-project losses in wildlife carrying capacity with
carrying capacity of moose winter range.
Avoidance~ of Bald Eagle Nest Sites.
Nests of bald eagles were conunonly observed incidental to
conducting moose surveys in the lower Susi tna River valley.
Federal law prohibits activities that might cause eagles to
desert t:radi tional nest sites. Eagles conunonly nest in
cottonwood trees in mature forest habitats located on
floodplains. Because habitat enhancement activities involves
altering and/or disturbing mature forests to encourage
regrowth of early successional plant com.rriunities, conflicts
with eagle nest trees or nesting activites may occur. Eagle
nests were conunonly observed throughout the lower Susitna
River valley (Fig. 42). Areas containing eagle nest sites
should not be considered for habitat enhancement unless more
specific field studies are conducted to more precisely
delineatE~ location of nests and to determine if enhancement
activities would follow federal law.
67
Potential Impact Mechanisms Incidental to With-Project
Alteration in River Hyrology
The following is an annotated list of with-project
hydrological mechanisms that I believe could impact moose
subpopulations downstream from Devil Canyon. Relative impacts
of these mechanisms will likely vary greatly between river
sections from the Devil Canyon dam site to Talkeetna, from
Talkeetna to Sunshine Bridge, from Sunshine Bridge to the
Yentna River, and from the Yentna River to Cook Inlet.
Some hydrological mechnisms may have relatively small impacts
on moose subpopulations but "insignificant" losses to a
subpopulation from a number of different sources may in total
result in a "significant" impact.
Assessments of the significance of any should be related to
the percent of the moose subpopulation affected. Impacts to
small numbers of moose may have profound effects on a small
moose subpopulations. Impacts to small numbers of moose in a
large subpopulation may in reality be insignificant.
I believe that
mechanisms could
Devil Canyon:
Flow Regimes:
the following with-project hydrological
impact moose populations downstream from
Moose use of floodplain habitats is greatest in winter
(October to April) for foraging and in spring (May to June)
for calving, foraging and/ or escape from predators. Altered
flow regimes (timing, depth, or flow rates) may impact moose
by directly or indirectly affecting species composition of
vegetation, availability of browse plants, access to food
sources, and refuge from predators. Strahan (1981) found that
establishment patterns for poplar and willow seedlings were
affected by altered flow regimes associated with flood control
and water resource development projects.
Proposed with-project (vs. pre-project) increases in winter
water levels and/or decreases in .spring water levels will
impact moose subpopulations downstream from Devil Canyon.
Extent of impacts will probably vary between the following
river sections: Zone I (Devil Canyon to Talkeetna) , Zone II
{Talkeetna to Sunshine) , Zone III (Sunshine to the Yentna
River, and Zone IV (Yentna River to Cook Inlet). Alterations
in timing of peak flows and maximum and minimum flow levels
are probably more important values to consider when evaluating
potential impacts of flow regimes than monthly averages for
those values. The current or rate of speed of water flows
during these time periods will also affect dynamics of the
floodplain.
68
Inundatiori of Habitats.
Ground wat.er tables, water levels, and soil oxygen content can
affect su:~vival of plant species differently and result in
plant communities with different species composition (Strahan
1981) and/or differences in seasonal timing of plant growth
and maturation processes (Harris et al. 1975). Timing and
duration of these hydrologic variables will influence their
level of impact. Water acts as a medium for plant seed
dispersal and affects where viable seeds are distributed and
the viability of seeds (Peltzman 1973). Together, these
hydrological factors along with· floodplain inundation will
affect quantity (browse availability) and quality (timing of
plant growth and maturation} of moose browse and species
composition of floodplain plant communities.
Water levels can also influence moose movements and foraging
along and across the floodplain.
Incidence of Open Water.
In winter, moose commonly use ice covered waterways as travel
~cutes. Wind action and periodic ice "glaciering" on
waterways act to decrease snowpack depth over river ice and
facilitate moose travel across and along floodplain areas.
This relatively unrestricted travel enables moose to utilize
available browse and does not discourage moose from
"wander inc;-" and "locating" other local, new, and preferred
food sources.
The extent of "open water" downstream from the Devil Canyon
darn site in winter will have a profound effect on moose
movements in that area. Theoretically, with-project, in
winter, open water will at least extend from the Devil Canyon
dam site to Talkeetna. Circumstantial evidence obtained from
studies in Canada suggests that open water in winter may be a
barrier to moose movements (Harper, pers. cornmun.). However,
Bonar (pers. cornmun.l" reported that in. British Columbia moose
regularly entered open water during winter. He believed that
open water in winter would not be a barrier to moose
movements.
Evidence obtained in this study indicates that open water in
combination with shore ice and/or ice shelving along the
margins can be detrimental to moose attempting to traverse
open water.
Moose from subpopulations east and west of the Susitna River
frequently cross the waterway to forage on opposing bankside
vegetation. The existence of open water in winter will
discourage or inhibit this behavior. Occurrence of ice
69
shelving or shore ice along the river margin will likely
result in mortality.
In spring 1 open water in waterways surrounding islands may
inhibit predators from frequenting those habitats and locating
and preying on neonatal moose. Low water levels in the
Susitna River during this season may make island habitats more
accessible to predators and increase predation on moose
calves.
The impacts of open water separating island habitats from the
mainland shore line in winter and decreased water levels
bridging island habitats to mainland shoreline in spring will,
in part, be influenced by the location and amount of island
habitat involved. Effects of these phenomena will vary
between moose subpopulations.
River Ice Regimes.
Ice jams which occur during spring breakup on the Susi tna
River result in flooding, scouring, diversion of main channel
water, bank erosion, and transportation of soil, debris, and
browse plants. All of these f~ctors can act to create,
eliminate 1 and/ or maintain early successional riparian plant
communities preferred by moose.
Since ice will not form in a stretch of the Susitna River
downstream from the Devil Canyon dam site, ice processes now
associated with fall freeze-up and spririg breakup will not
occur with-project.
Miller and Gunn (1980) reported that thin lake ice conditions
affected migratory movements of caribou and resulted in
mortality of caribou which attempted to cross.
The ability and desire of moose to negotiate open water in
winter may be affected by timing, occurrence, and extent of.
river ice and mainland and island shore ice shelving. Both
Harper (pers. comm.) and Bonar (per. comm.) mentioned that
thin-ice conditions frequently resulted in mortality of moose
and that in spring when ice becomes "rotten" moose avoid
crossing frozen waterways. Addi tiona! shoreline and island
habitat may be innundated if shore ice forms, dislodges daily,
and subsequently accumulates downstream in ice jams which, in
turn, restrict flow rates and act to rise water levels
upstream and flood adjacent habitats.
Some riparian habitats are impacted and changed annually by
ice processes associated with spring breakup. Scouring,
flooding, and other processes associated with ice dynamics
affect occurrence and availability of moose winter browse and
70
phenology and composition of vegetation on islands and
streambank.s. Absence of ice processes will tend to stabilize
riparian habitats utilized by moose and not perpetuate there
maintenance. Downstream from the Devil Canyon dam site where
formation of cover ice is initiated, ice jams may occur from
ice forming instream or shore ice dislodging daily. Ice jams
will cause! water levels to rise and result in backup flooding
in upstream areas. Backup flooding and residue ice formed
after flood waters release could be detrimental to moose
directly or indirectly through impacts to vegetation.
Backup flooding caused by ice jams in winter may leave a
coating of glare ice over the floodplain after jams release
and water levels subside. Glare ice may remain in these areas
until the next backup flood or until spring. Periodic backup
flooding could result in a thick layered build up of ice on
the floodplain. Ice cover on the floodplain can result in
mortality of moose. I documented moose mortality attributable
to glare ice cover on the floodplain.
Daily fluctuations in water levels in winter will leave a
glare ice cover over periodically innudated floodplain _areas.
Ice cover on the floodplain will result in moose mortality,
may affect moose use of these floodplain areas and may have
long term effects floodplain plant communi ties. Ic·e ···cover
formed in this manner may become layered and increase in
thickness each time the water subsides after a daily flooding.
River Waber Temperature Regimes.
Water temperature can affect all of the ice processes
discussed above. Water temperature can affect temperature of
subsurfac'e water and alter seasonal timing of plant growth.
Altered water temperature regimes may eventually affect
species composition of floodplain plant communities because of
variation in physiological tolerances between different plant
species. Phenology of moose spring forage plants and species
composition of floodplain communi ties preferred by moose may
be affected by altered water temperature regimes. If
parturition in moose is correlated with plant phenology (diet
quality) , changes in timing of plant development may affect
productivity of moose subpopulations that feed and calve on
the floodplain.
River Silt Loads.
Accumulation of silt in sections of the river forms bars that
may eventually become more stabilized and lead to the
formation of islands. Silt originates from melting headwater
glaciers and from erosion in nonglacial tributary streams.
Erosion and secondary deposition of silt already in the
mainstem system also contribute to island formation. Bars and
islands form the substrate for establishment of early
successional plant species. Presence or absence of silt in
the substrate and size of surface sediments may also determine
which plant species are able to colonize a particular site.
Alterations in water turbidity will affect transmission of
light in water column and may affect composition,
distribution, and/or abundance of aquatic plant species that
become established on the floodplain.
McBride and Strahan (1984) demonstrated that willows, the
preferred moose browse species, preferentially colonized sites
where surface sediment was small-sized (less than 0.2 em), and
poplars more readily became established on sites with
larger-sized surface sediments (0.2-1.0 em). Birch, less
preferred as moose browse, succeed the former species as the
sites become more stable and drier.
Plant species such as willows are adapted to periodic silting
and may outcompete other plant species in areas where silting
is common. Siltation may stimulate willows to root or shoot
side-sprouts. Prolific side-sprouting gre<?-tly increases
willow biomass and production.
Impoundments associated with hydroelectric development of the
Susitna River will greatly restrict or essentially eliminate
silt from the Susi tna River system between Devil Canyon and
Talkeetna. This will further decrease the silt load in the
Susitna River south of Talkeetna. Silt will be reintroduced
into the Susi tna River mainstem by the Chulitna River at
. Talkeetna. Farther downstream, other tributary streams will
contribute to the silt load.
Lack of silt
will affect
willows) , and
browse plants
in the mid-river section of the Susitna River
ecology of riparian vegetation (particularly
may affect competition between preferred moose
and less desirable species (alder) .
In the absence of a silt source, ex.isting islands formed of
silt and substrates permeated with silt may gradually erode
and be translocated to areas farther downstream. Silt islands
may fail to be reformed in the mainstem Susitna River
immediately downstream from the Devil Canyon impoundment. A
decrease of silt in the Susitna River system immediately
downstream from the Devil Canyon dam site with-project will
probably cause willows to be a less common component of the
floodplain plant communities in that area.
The projected with-project decrease in peak spring and summer
mainstem flows (vs. increased winter flows) will affect
present patterns of silt erosion, translocation, and
deposition.
72
Occurrence, Transportation and Disposition of Riverine Debris.
During peak spring flows, many floodplain trees are uprooted
and carried downstream. Uprooted trees eventually become
stranded in relatively shallow water on gravel or silt bars,
entangled in perennial log jams or are deposited as peak flows
decrease. In many cases, deposited vegetation initiate
additional silt deposition and lead to the formation of more
stable silt bars or islands. Logs, trees, and other debris,
etc. , frequently occur at the leading edge of silt
bars/islands on which willows and poplars subsequently become
established. Lack of peak flows will decrease occurrence and
transportation of debris and slow or preclude processes which
lead to formation of mainstem islands.
Newly formed log jams and islands divert mainstream currents.
When mainstream currents are diverted, erosion is redirected
to other substrates on the floodplain. Erosion then occurs in
different areas releasing additional tree debris and silt for
formation of new islands which in turn initiates erosion of
other substrates that may also contribute to formation of
additional islands farther downstream.
Uprooted or dislodged vegetation, particularly willows and
poplars ,.,hich moose prefer for browse, may subsequently become
established where they are deposited. Willows and poplars are
particularly adept at rerooting and growing when deposited on
suitable substrates. These plant species are important source
plants for colonizing and stablizing new silt bars or islands
as well as important moose forage plants.
Tree debris appears to be a important component for initiating
formation of silt bars or islands. Tree debris also appears
to be important for stabilizing and protecting the uptream
side of newly-formed silt bars or islands.
Altered flow regimes and decreased peak spring and summer
flows will probably affect creation and transportation of tree
debris o:r uprooting and transportation of browse plants.
Incidence of Fog.
In winte!r and summer, fog frequently forms above the Knik
River downstream from where effluent enters from a hydro-
electric project facility (Eklutna Hydroelectric project,
Eklutna, Alaska). Persistent winter fog can affect
microclimates and phenology of riparian vegetation and heat
balance of moose. Harper (pers. comrn.) believed that winter
fog formed from relatively warm discharge water may have
affected local distribution of moose in the Peace River region
of British Columbia. He speculated that moose may have moved
73
out of some locations because fog decreased incident solar
insulation and negatively affected moose energy budgets.
Because of warmer water temperatures and relatively cold air
temperatures (-40 degrees below zero C), fog will probably
form in winter over open water sections of the Susitna River
downstream from the Devil Canyon dam site. To my knowledge
many questions regarding the formation of fog (ice fog, icing
of vegetation, etc.) have yet to be addressed: how far from
·the river will fog occur? how far downstream from Devil
Canyon will fog form? how frequently will it form? how many
days in an average, cold and warm winter will fog form? how
many consecutive days will fog occur at any one time?
Presence of fog will affect solar radiation of moose and
vegetation on the floodplain. This may affect winter energy
budgets of moose and phenology of floodplain plants. The
occurrence of fog over the floodplain may ultimately affect
species composition of floodplain plant communities.
Dissolved Nutrient Regimes.
Glacial streams such as the Susitna River are generally
considered sterile. Waters in these streams are generally
very low in organic nutrients and minerals. When flood waters
inundate substrates adjacent to· the floodplain which are rich
in organics and minerals, the latter chemicals can become
dissolved and/ or suspended in floodwaters. Moist conditions
resulting from floodwaters can further hasten on site
decomposition of organic materials and release additional
nutrients and minerals from (and to) underlying substrates.
It appears likely that flood waters can increase fertility of
underlying local floodplain substrates and/or transport
nutrients to other· floodplain substrates areas downstream.
Peterson and Rolfe (1982) provided information indicating that
availability of nutrients in floodplain soils was influenced
by soil pH, which was in turnaffected by flooding.
Ai tered flow regimes and d.ecreased frequency and extent of
flood conditions may affect ferti~ity, nutrient turnover
rates, and overall productivity of floodplain habitats along
the· Susi tna River downstream from Devil Canyon. Number and
extent of spring and summer floods will be decreased
with-project.
Incidence of Salt Water Encroachment.
With-project flow rates and reduced water levels in the
Susitna River will enable salt water to encroach farther
upstream from Cook Inlet than presently occurs. Species
composition of plant communi ties will likely be altered in
74
areas where salt water infiltrates substrates or inundates the
floodplain.
Floodplain and island habitats near Cook Inlet support very
dense wint.er concentrations of moose. Increased encroachment
of salt 1water into the mouth of the Susitna River may
negatively affect survival of moose browse plants (willows and
populars) in this region and decrease the value of these
habitats to moose.
If increased substr~te salt
growth, existing islands may
erode away.
concentration precludes plant
lose stability and eventually
Alteration of Ecosystem.
Alterations in river hydrology may affect moose at secondary,
tertiary, and even quaternary levels if impacts are mediated
through a series of plants and/or animals as salmon, beaver,
bears, wolves, (etc.) and other moose subpopulations.
Potential Impact Mechanisms Not Related to With-Project
Alterations in River Hydrology:
Direct Alteration in Habitat.
Habitat altered or lost with development and construction of
temporary or permanent transmission line corridors, railroad
and highway vehicle rights-of-way, and project facilities will
impact moose subpopulations.
Increased Access.
Increased access to and within the area via transmission line
corridors, railroad and vehicle rights-of-way and year-round
open river water will impact moose sulbpopulations.
Human Encroachment.
Increased human use of the area by construction and
maintenance employees, tourists, hunters, and other
recreationists will impact moose subpopulations.
Altered Ecosystem.
Changes in aforementioned nonhydrological mechanisms
impact plant and animal populations which in turn may
secondary, tertiary, or quaternary effects on
subpopula1:ions.
75
will
have
moose
I.
I
Moose Subpopulation Narratives
Fourteen moose subpopulations were identified to utilize the
Susitna River floodplain between Devil Canyon and Cook Inlet.
Annual range for each identified moose subpopulation was
delineated (Table 21 and Fig. 43). Moose "subpopulations"
were primarily differentiated on the basis of movement
patterns, range use, and behavior or life history patterns
that appeared common for moose in a given geographic area.
The following narratives summarize knowledge about life
history, biology, environment, and management of moose
subpopulations accumulated during this study. Data provided
may be important to consider when assessing impacts or
prescribing mitigation for hydroelectric development of the
Susitna River.
Some information provided is circumstantial, some information
contained in these accounts was not substantiated by
scientific methodology, and other information presented is my
best assessement ~nd interpretation of the present situation.
Devil Canyon-Talkeetna:
The Area.
This 360-mi 2 area encompasses the watershed of the Susi tna
River from Talkeetna to Devil Canyon. It is not accessible by
the highway system or by highway vehicle. Access is afforded
by boat on the Susi tna River, the Alaska Railroad, and by
aircraft on an unimproved mail airstrip adjacent to the river
and railroad at Gold Creek. Several lakes and flat ground
topography in other locations are seasonally accessible by
£loat-, ski-, or wheel-equipped light aircraft. The area
provides opportunites for fishing, hunting, trapping, and
limited hiking and camping in the Curry Ridge Lookout area.
Some recreational activities are undertaken with professional
guides and commercial boat or air taxi operators. About a
quarter of the land area utilized by this moose subpopulation
occurs within the Denali State Park. Human settlement in the
area is limited to a scattering of recreational and year-round
remote homesites. Year-round residents probably rely heavily
on available wildlife resouces for sustenance.
The entire area is bisected longitudinally by the Susi tna
River. The Alaska Railroad right-of-way parallels the Susitna
River for 35 miles from Talkeetna to Gold Creek where the
railroad diverges westerly away from the river valley. The
river and the railroad rights-of-way may, at times, affect
movements and negatively impact moose that utilize habitats on
both sides of the valley.
76
In general, temperatures and snowfall in this 11 interior"
climatic area tend to be more extreme than for more southern
areas where climate is milder· and more maritime. However,
"winter 11 and 11 spring" come sooner to the former area. At
times, thl; snowpack is deeper on side slopes and valley
bottoms, where windblown snow is deposited, than on the alpine
ridges whlare windblown snow orginated. In spring, ground
vegetation may become prevalent sooner on higher south-facing
ridges than at lower elevations in the valley bottoms.
The Subpopulation.
I estimate that 375 moose presently winter in the Susitna
River watershed between Devil Canyon and Talkeetna. Short and
long-term subpopulation size can be -influenced by contemporary
land and wildlife management practices and annual weather
conditions. This subpopulation could be larger or smaller
under di:Eferent management programs or winter weather
c.ondi tions and may not presently be at carrying capacity of
the habi ta.t.
Data obtained from a radio-marked sample of moose indicate
that individuals from this subpopula·tion seldom range out of
the Susitna River watershed. Moose use of the Susitna River
floodplain and southeast facing mid-slope habitats located
northwest of the Susitna River were considerably greater than
use of ridge tops and northwest facing habitats on th~ south
side of the Susitna River.
Significant Movement Patterns.
Evidence obtained from radio-marked moose and aerial surveys
of unmarked moose substantiated several basic subpopulation
movement patterns.
Females in this subpopulation moved to and remained in
floodplain and island habitats of the Susitna River during May
and June (Modafferi 1984). Timing·of this movement, late May
to early June, correlated with parturition. Other studies
indicate ·that female moose may move to riparian and islanded
habitats during calving to avoid contact with predators
(Edwards 1983). · Moose are known to seek water as a defensive
behavior 'Nhen pursued by predators. It is also probable that
dams move to island and floodplain areas in spring to obtain
early grm•ling, nutritious, riparian forage for themselves and
their neonates. If the former contention is correct, preda-
tion must be {or was once) a significant mortality factor to
this subpopulation.
Moose of both
floodplain and
---·------··
sexes moved to
island habitats
77
and utilized Susitna River
during the winter period.
Timing, magnitude, and duration of this movement was
correlated with winter severity (occurrence, depth, and
persistence of the snow pack) . Moose apparently seek refuge
on the Susitna River floodplain from deeper snowpacks and
associated poor forage conditions on adjacent, predominantly
alder covered upland slopes. The windblown and frozen
riverbed and floodplain provide moose with preferred early
successional, low growing, browse species. Movements to and
from different food patches are less restricted by the
-shallower, wind compacted snow pack conditions on the
floodplain. Shallow sn,ow conditions probably also decrease
the vulnerability of moose to predation by wolves. Though a
shallow snow pack also occurred on exposed upper alpine slopes
and ridge tops, the scarcity of forage or excessive wind chill
may preclude moose use of those habitats.
Six, 10, 7, and 11: surveys conducted to quantify moose use of
the Susitna River floodplain in winter 1981-82, 1982-83,
1983-84, and 1984-85 revealed an average of 26, 78, 54, and
116 moose, respectively, for the highest three survey counts
within each winter. The greatest number of moose observed on
the floodplain in those winters was 36, 84, 8 8, and 132,
respectively. These data demonstrate that moose use of
floodplain wintering areas is highly variable and closely
related to winter weather conditions. Snowfall in 1984-85 was
reported to be the greatest in the last ten. years (U. S.
Department Agriculture 1985).
Moose which are attracted to and utilize the Susi tna River
floodplain in winter are vulnerable to mortality from drowning
by falling through thin ice and/or into open water and from
collisions with trains in the adjacent Alaska Railroad
right-of-way.
Moose collisions with trains increase dramatically with depth
and persistence of the snow pack in areas adjacent to the
railroad right-of-way. Inclement winter conditions cause
large numbers of moose, that are stressed physiologically, to
utilize the railroad rights-of-way and adjacent lowland
habitats for a longer period of time. An above average snow
pack in ~inter 1984-85 resulted in substantial moose mortality
from collisions with trains.
A 13-15 March 1985 moose survey revealed gatherings of 60+
moose southeast of Lane Creek above timberline on south facing
slopes (1,000-2,000 ft. elevation) in the Chunilna Creek
watershed and 40+ moose above timberline on south facing
slopes ( 1·, 700-2,300 ft. elevation) between the Chulitna and
Susitna Rivers north of Blair Lake. These concentrations
probably included moose from this and the respective adjacent
Chunilna Creek and Chulitna River (not included in this
78
report) subpopulations that moved to these alpine areas for
winter ran<ge.
Movements of radio-marked moose outside this general area were
recorded infrequently during the rut (September-November) and
calving (June-July) periods.
Noteworthy Behavior Patterns.
On winter surveys moose were commonly observed lying singly or
in small grroups, in the open, on the exposed, frozen riverbed
or floodplain. In most instances, moose appeared to be
exposing t:hemsel ves to solar radiation, probably for warmth.
Resting in the open probably also lessened the opportunity for
wolves to approach unnoticed.
Tracks in the snow indicated that moose commonly walked along
the margin of the floodplain seeking and utilizinq browse
offered by trees overhung from undercut river banks.
It was apparent that the windblown and hard-packed sne.w on the
floodplain provided considerably less resistance to moose
movements than the deeper, soft snow pack on adjacent upland
slopes where additional windblown snow secondarily
accumulated.
On several occasions, moose ~ere observed on sparsely-timbered
upland slopes bedded in the relatively snowfree area under a
spruce tree. These individuals were apparently seeking the
snowfree bedding area, avoiding wind and intense solar
radiation, and/ or seeking visual concealment from potential
predators.
On the we:st bank of the Susi tna River, upstream about 10 mi
from Talk1eetna, moose were commonly observed in open paper
birch/white spruce forest habitats digging ("cratering")
through snow. Subsequent field trips to that area during the
snowfree period revealed that overwintering basal stems and.
rhizomes of ferns had been heavily grazed by moose. Ferns are
utilized as winter forage by large numbers of moose in post
rut and wintering areas farther south in the western foothills
of the Talkeetna Mountains. Chemical analyses indicated that
fern fiddleheads, basal stems, and rhizomes appear to be a
relatively high quality winter food source (Modafferi 19 8 4,
p.lOO.).
Mortality ..
Predators and predation. Very dense black bear and moderately
dense brow·n bear populations occur in this area (Miller and
McAllister 1982). Black bears primarily utilize south-facing
79
slopes north and west of the Susi tna River. Black bears
usually frequent timber habitats, except in fall when they
seek ripening berries above timberline (Miller and McAllister
1982). Brown bears primarily occur above timberline. In
winter, wolf sign was frequently observed in this area. This
is the only area downstream from Devil Canyon where I observed
wolves. Packs of five wolves each were observed near the
Chulitna-Susitna Rivers confluence (January 1985) and in upper
Portage Creek (March 1985) . Wolf tracks were observed in snow
along the floodplain on two separate occassions in the Sherman
area, at the mouth of Portage Creek and near Gold Creek. In
two of the above ·instances, moose carcasses were obsevered
near the wolf tracks. I presume the moose had been killed by
wolves.
Though no radio-marked moose in this area were known to be
killed by predators, I presume brown and black bears prey on
neonatal calf moose in spring, and wolves and brown bears prey
on moose of all ages throughout the year. Though brown and
black bears may prey heavily on moose calves (Ballard et al.
1980b and Franzmann et al. 1980, respectively), I_ suspect that
black bear predation may predominate in this area because of
their greater abundance and more common use of riparian and
south facing, side-slope habitats frequented by moose.
Attempts to avoid vulnerable confrontations with predators
may, in part, account for moose use of island and floodplain
habitats in both spring and winter. Other studies have
documented influence of predators on moose movements (Ballard
et al. 1980a) and habitat use (Edwards 1983).
Other sources of mortality. Eight moose radio-marked in this
area were observed or reported dead during the study. Four
moose were killed during winter by collisions with freight or
passenger trains. One was killed in winter 1983 (March) and
three were killed in winter 1985 (one in January and two in
March) .
Death of one moose in April 1984 was classified as a "winter
kill." Winter kill is a "catch-all" category including many
winter-related mortality factors associated with inclement
winter weather conditions. The most prominent, proximate
mortality factor included in the winter-kill category is
starvation from inadequate nutrition. The moose found dead
was estimated to be 19 years old when captured in March 1982.
One male moose was killed by a local resident hunter during
the 1982 open hunting season~
Death of three moose was associated with the Susi tna River
itself. Presumably these individuals died from drowning while
80
.
trying to traverse the river. Circumstances at the site of
one death in March 1985 suggested that the moose fell through
an open lead in the ice on the snow-covered river. The moose
apparently never resurfaced and was located later that spring
in a side slough farther downstream. Another "river-related"
mortality occurred sometime prior to June in 1981. Circum-
stances suggested that this individual moose got caught
between breakup iceflows while crossing open water or fell
through thin ice or an ice jam while crossing "apparently"
solid river ice. Its carcass was discovered "silted in" on a
river bar in an area where "breakup" ice jams commonly form.
The third "river-related" moose mortality was discovered in
June 1982, floating near a log jam in a Susitna River
side-channel, shortly after spring peak flow levels. This
individual had previously been relocated on the adjacent bank
several w•eeks before. Perhaps the moose tried to cross the
river when flow rates were extreme and was swept into the log
jam where it subsequently drowned.
On 3 January 1985, while capturing moose on the Susitna River
floodplain about 10 mi upstream from Talkeetna, I observed two
dead moose, about 400 m apart, frozen into "rough" river ice.
Evidence at the site suggested that these moose attempted to
cross the river but fell through the soft ice cover and could
not get back out before succumbing to hypothermia or drowning.
At that time, there was about 1 m of snow cover over existing
river ice. This deep snowpack probably insulated preformed
river ice from cold ambient temperat:ures and resulted. in the
ice gradually melting/eroding away from ·beneath by warm
flowing 1water. In places, the ice was very thin or
nonexistent, and the river was essentially covered by a
floating, 1+ m soft mat of snow and slush-ice. Toward the
river banks where water was shallower and current less, river
ice was still firm and supported .humans. Evidence in the
snow/slush-ice indicated that after breaking through the
surface both moose had moved/swam around for about 400-500 m
making unsuccessful attempts at several locations to climb out
onto firmer shorebound ice. Both carcasses were located at
the interface of snow/slush river· ice and firm shorebound ice.
Similar conditions probably reoccur whenever a deep snow pack
blankets and insulates preformed river ice over fast moving,
deep channel water. These conditions are probably prevalent
in winters when large amounts of snowfall occur before rivers
become ad•~quately frozen.
Between 1 January and 27 March 1985, 65 moose were reported
killed by collisions with trains in the 45-mi stretch of
railroad right-of-way between Talkeetna and Chulitna Pass.
Inclement winter conditions persisted in this area through
mid-April 1985, and more moose undoubtedly were killed after
the 27 March period for which mortality data were available.
81
Moose kills per mile of track decreased from south to north~
23 moose were reported killed in the 9-mi stretch immediately
north of Talkeetna 1 whereas only eight were killed in the
14-mi stretch between Sherman and Chulitna Pass. The rate of
moose killed by trains probably decreases northward of
Talkeetna because of lower moose densities and because the
railroad right-of-way diverges from the river bottom,
spatially and altitudinally 1 in its course from Gold Creek to
Chulitna Pass. Both factors probably contributed to decrease
the probability of moose-train collisions.
In winter, periodic surveys were conducted on the Susitna
River floodplain to assess moose distribution and abundance
during 1981-85. Incidental to primary objectives of these
surveys 1 0 1 11 1 2 1 and 5 moose carcasses were observed in
winter 1981-82 1 1982-83, 1983-84 1 and 1984-85 1 respectively.
Death of these moose was attributed "winter kill" and probably
related to winter severity. Because frequency and timing of
surveys, field and weather conditions, and moose population
levels varied between years, caution must be exercised in
making annual comparisons with these data.
Concerns and Potential With-Project Conflicts.
In winter, the frozen Susitna River and floodplain provides
moose with high quality forage, a place to be exposed to solar
radiation, and to rest relatively protected from secretive
approaches by wolves, and a relatively snow-free corridor for
movement to and from dispersed and patchy food sources and
habitats on both sides of the valley bottom. If hydroelectric
development of the Susitna River prevents the river from
freezing over in winter, these values to moose will be altered
or lost altogether.
Moose forage on early successional plant species. In most
cases, ~vailability of these food sources is both
unpredictable and temporary. However, periodic perturbations
on the Susitna River floodplain caused by large variations in
flow regimes add periodicity and relative stability to early
successional plant communities preferred by moose in winter.
Specific locations of these plant communi ties may vary over
time, but the quantity of surface area involved may be
relatively stable during that same time period. Eliminating
or decreasing these hydraulic perturbations will reduce the
amount of habitat that is peridocially altered · and thereby
renewed and/or maintained in the early successional state.
Altering the variation and intensity of the perturbations will
decrease the quantity of high quality habitats and winter
browse for moose.
Because specifics on changes in ice and flow regimes,
calculations of amount and location of habitats affected (or
82
not affected) , and data for calculating and balancing amounts
and locations of browse lost and/or gained were produced by
other disciplines, proportional alterations in moose carrying
capacity cannot presently be estimated.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
timing of river ice or flow regimes. These alterations could
·result in mortality to moose directly or indirectly through
decreased carrying capacity of the habitat.
Any increase in access, human settlement or the human
population· in the area may affect this moose subpopulation
negatively by increasing numbers of moose killed legally
during opE~n hunting season, illegally during closed hunting
season and in defense of life and property; by decreasing or
altering habitats preferred by moose; or by increasing the
level of human disturbance.
Chunilna Creek:
The Area.
This 400-·mi:a area encompasses the Chunilna Creek ("Clear
Creek") wate~shed. The area is not accessible by the highway
or railroad systems. Seasonal access into the area is
provided by snowmachine; river boat from Talkeetna via the
Talkeetna River; all terrain vehicle from Curry via an
overland unimproved trail to a placer gold mining camp located
in the upper watershed; and ski-, float-or wheel-equipped
light aricraft. The area provides opportuniti~s for fishing,
hunting, and trapping. Some activities are undertaken with
professional guides and commercial boat or air taxi operators.
Chunilna Creek is a popular salmon fishing stream. Placer
gold mining camps, which are active during the ice-free
season, occur in the upper watershed.
Recreational homesi tes occur along the T.alkeetna River
downstream from its con.!luence with Chunilna Creek. State
landholdings in the area were recently opened to entry for
agricultural development and recreational homesites.
The Alaska Department of Natural Resources has recently
classified portions of this area as having a high potential
for livestock grazing. This particular area is located on the
south-facing alpine slopes north of Chunilna Creek. This same
area is utilized by substantial numbers of moose from the
post-rut period through winter.
Temperatures and snowfall in this "interior" area tend to be
more extreme than for more southern areas which are under
83
greater maritime influence. The snow pack on sides lopes and
in valley bottoms of this watershed is frequently deeper than
in alpine areas as windblown snow from exposed ridge tops is
deposited and accumulates in the latter lee areas.
The Subpopulation.
I estimate that about 3SO moose presently utilize the Chunilna
Creek watershed as winter range. This estimate is subjective
and extrapolated from data obtained on a distribution type
survey conducted 13-1S March 198S. Approximately, 1SO moose
were actually observed in the Chunilna Creek drainage on that
survey and roughly SO percent of the moose present may be
overlooked on this type of survey. An additional SO moose are
estimated to have moved downstream out of the watershed to
winter on the more extensive Talkeetna and Susitna River
floodplains.
Previous winter surveys on the Susitna River floodplain
revealed concentrations of moose near the confluence of the
Chulitna, Susitna and Talkeetna Rivers. I suspect that this
conglomeration of moose also included migrants from smaller
upstream tributary watersheds~ A small sample of moose was
captured and radio-marked on the Susitna River floodplain near
Talkeetna, in February 198S. One moose from that small sample
was relocated in early spring several miles up Chunilna Creek.
I estimate that about SO or so other moose from the Chunilna
Creek subpopulation probably also ·utilize Susitna River
floodplain habitats during severe winters.
The 13-1S March 198S distribution survey revealed more than 60
moose southeast of Lane Creek above timberline on south facing
slopes (1,000-2,000 ft. elevation) of the Chunilna Creek
watershed. Moose from this and/or the Devil Canyon-Talkeetna
subpopulation apparently utilize these alpine habitats as
winter range.
During the distribution survev, more than 70 moose were
observed on the Chunilna Cr;ek floodplain. Though this
riverbed is considerably smaller than that of the adjacent
Susitna River, it appeared to support more wintering moose in
1984-BS than the latter river bed. In this particular area,
the Chunilna Creek riverbed appears to have a higher propor-
tion of actively changing floodplain, where preferred moose
winter forage grows, than the adjacent Susi tna River. This
could, in part, account for the relatively high densities of
wintering moose observed on the narrower Chunilna Creek
floodplain.
Moose from this subpopulation which travel to and utilize
winter range on the Susitna River floodplain must traverse the
84
railroad right-of-way which parallels the east bank of the
Susitna River. While migrating and/or remaining in this area
moose are particularly vulnerable to collisions with trains.
Significant Movement Patterns.
Data on movements of this subpopulation are largely based on
circumstantial evidence. However, it seems probable that
behavior patterns of moose in this watershed mimic those of
the Talkeetna-Devil Canyon subpopulation in the adjacent
Susitna River watershed. Most moose which winter in the
Chunilna ·creek watershed are probably resident to the area
during other seasonal periods. In winter, some moose from the
Talkeetna-Devil Canyon subpopulat.ion may move from
northwest-facing slopes in the Susitna River valley to occupy
southeast-facing slopes in the Chunilna Creek watershed.
South-facing slopes are more exposed to solar radiation and
probably contain a shallower snow pack and more desirable
plant communities.
A portion of the Chunilna Creek moose subpopulation moves
downstream with inclement winter weather and increasing snow
pack depth.· It is probable that some moose which make this
downstream movement eventually end up on the Talkeetna and
Susitna River floodplains in late winter when the snow pack is
typically deepest. Timing, duration, and magnitude of this
movement is correlated with winter severity (depth and
persistence of snow cover) . Some individuals from this sub-
population probably utili·ze the Susitna floodplain every
winter re<;Jardless of weather conditions, whereas movements
into this area by other segments of the subpopulation are
probably more closely governed by prevailing winter weather.
Duration and magnitude of moose use of the Susitna River
floodplain by moose from this subpopulation would be greatest
during a winter characterized by large amounts of early
snowfall that forms a deep snow pack which persists well into
spring. I suspect that the 30 percent increase in moose
observed on the Susi tna River floodplain between Sunshine
Bridge and Devil Canyon in late winter 1984-85 (Table 6) was,
in large part, attributable to moose "funneling" into the
drainage from smaller, peripheral, tributary drainages as
Chunilna Creek.
Mortality.
Predators and predation. Dense black and brown bear
populations exist in the Chunilna Creek watershed. Density of
black bears is greatest in the timbered lower reaches of the
drainage and density of brown bears is greater near the alpine
portions of the watershed. Brown and smaller numbers of black
bears concentrate in this drainage in late summer to feed on
85
spawning salmon. Densities of wolves in this drainage may be
greater than those along the Susitna River because this
watershed is more remote (off the "beaten path") than the
latter. I presume that black and brown bears prey on moose
calves in spring and early summer and brown bears and wolves
prey on adult moose throughout the year. I do not know if
moose in this watershed utilize floodplain habitats during the
calving period as was documented for moose in the Susitna
River watershed. Islands on the Chunilna Creek floodplain may
not be attractive to parturient female moose because of their
r~latively small size. However, if availability of high
quality forage and not the lack of predators is the salient
factor responsible for · this behavior pattern, parturient
female moose in this subpopulation may utilize riparian
habitats along Chunilna Creek in late May and early June to
obtain phenologically early and nutritious plant species that
are present in the floodplain plant communities.
Other sources of mortality. One radio-marked moose that moved
from the Susitna River to the Chunilna Creek watershed in late
winter was found dead in early spring, three miles upstream
fro~ the Talkeetna River. Death of this individual was attri-
buted to the category "winter kill." Two other unmarked
"winter killed" moose were also observed near the mouth of
Chunilna Creek in early March 1985.
I presume that some moose killed by collisions with trains
immediately north of Talkeetna were emigrants from the
Chulitna Creek subpopulation utilizing or enroute to or from
winter range on the Susitna River floodplain.
Concerns and Potential With-Project Conflicts.
Because moose from this subpopulation move to and utilize the
Susitna River floodplain near Talkeetna in winter, alterations
in river ice or flow regimes or floodplain habitats of
Chunilna Creek or Susitna River in that area that result from
hydroelectric development of the Susitna River will affect
moose from this subpopulation.
Any increase in access, human settlement, or the human
population in the area may affect this moose subpopulation
negatively by increasing numbers of moose killed legally
during open hunting season, illegally during closed hunting
season, and in defense of life and property~ by decreasing or
altering preferred habitats, or by increasing the level of
human disturbance of moose.
Increases in train traffic on the railroad will result in
additional moose mortality from collisions with trains.
Construction of vehicle rights-of-way between this area and
86
··.-' ' .,
the Susi tna River will increase moose mortality from colli-
sions wi 1:h vehicles. Moose from this subpopulation will
primarily be exposed to these sources of mortality in winter
when utilizing or migrating to or from wintering areas along
the Susitna River floodplain.
Lower Talkeetna River-Iron Creek-Sheep River:
The Area.
This 800-mi 2 area is bounded on the west by the Susitna River
and includes watersheds of the Iron Creek, Sheep River, and
the Talkeetna River downstream from Praire Creek. The area is
seasonally accessible primarily by float-, ski-and
wheel-equipped light aircraft. The lower 10 mi of the
Talkeetna and Sheep River are accessible by boat. The western
part of the area contains the town of Talkeetna and its
satellite communities, the Alaska Railroad right-of-way and a
major highway spur road right-of-way into Talkeetna. The spur
road and railroad rights-of-way run parallel to each other and
the Susitna River. Substantial human settlement radiates
easterly from Talkeetna and the Susitna River over about 40
mi 2 • Recent state-sponsored land disposals in the area have
provided lands to the public for remote recreational homesites
and agricultural development. The area provides·. opportunities
for recreational fishing, hunting, and trapping. Limited
snowmachining and cross-country skiing occur in the Larsen
Lake and Bald Mountain areas. Some recreational activities
are undertaken with professional guides and commercial boat or
air taxi operators.
About 300 mi 2 of land area in this area rises above 3,500 ft.
in elevation. Since moose seldom utilize habitats above that
elevation, only about 500 mi 2 in the area should be considered
as usable moose habitat.
Human settlement in the area includes scattered homesites I
fledglingr ·agricultural developments, and rural town. and
residential developments in Talke!etna and its satellite
communities along the highway system. Year-round residents in
the area desire a "rural" lifestyle and "expect" that the
opportunity to live off available wildlife resources is a
necessary part of that lifestyle.
The railroad, highway spur road, agricultural developments,
and human settlements and associated activities may at times
affect movements of moose, preclude traditional use of
winterin9 areas and negatively impact moose using the area.
These conflicts become particularly evident during winter when
large numbers of moose immigrate to lowland areas near and on
the Susitna River floodplain.
87
In general, temperatures and snowfall in this "interior" area
tend to be more extreme than areas farther south which are
more under maritime influence.
The Talkeetna River watershed, upstream from its confluence
with Praire Creek, was not considered within the range of this
moose subpopulation for several reasons: (1) moose from there
would have to travel over 40 mi to utilize Susi tna River
floodplain winter range and no radio-marked individuals were
known to travel that far to winter on the Susitna River
floodplain; ( 2) because more than 140 moose were observed in
that upstream portion of the Talkeetna River during a
13-15 March 1985 distribution survey, it appeared that
numerous moose remained in or immigrated to that area for
winter range rather than travel to lower elevations and the
Susitna River floodplain; and (3) snow depth, an important
factor influencing moose use and selection of wintering areas,
appeared to be considerably less there than farther down-
stream. For these reasons, it appeared that this upstream
area provided adequate winter range for moose.
The Subpopulation.
One hundred sixty-six moose were observed in this area on the
distribution survey. Substantially more moose were probably
present in this area than were evidenced by the survey
because: ( 1) a large· proportion of the habitat. is forested
and the probability of observing moose on this type survey is
lower in forested habitat, and (2) search effort was greatly
reduced in settled areas along the railroad and highway
rights-of-way where substantial numbers of moose are known to
winter. Assuming that 50 percent of the moose present were
not observed on the distribution survey, that 100 moose are
added to compensate for those not observed in forested
habitat, and that another 75 moose are added to account for
moose ·in settled areas not surveyed, it was estimated that
about 500 moose occurred in the area that winter.
Most moose observed on the 13-15 March distribution survey
were scattered in floodplain habitats along major watersheds
or their tributary streams. Few· moose were observed on the
-Talkeetna River near Praire Creek and on the Sheep River
upstream from Rainbow Lake. Noteworthy numbers of moose were
observed near the headwaters of Iron Creek and on the
Talkeetna River upstream from Praire Creek.
The only nonfloodplain area where concentrations of moose were
observed was a southwest-facing slope ( 1, 500-2,500 ft.
elevation) about two mi west of Diana Lakes and immediately
north of Sheep River.
88
Significant Movement Patterns.
Since only one individual from a small sample ( 12) of moose
radio-marked near Talkeetna in February 1985 was later
relocated near the Sheep River floodplain five miles upstream
from the 'Talkeetna River and 15 mi from its capture site, I
suspect that a very small number of moose from these
watersheds migrate downstream to winter at lower elevations
and on the Susitna River floodplain.
Because large concentrations of moose were not observed near
the mouth of the Talkeetna River and fair numbers were
observed spread evenly along its downstream floodplain and in
the headwaters of it and Iron Creek, there was probably not a
major moose movement out of these watersheds to the Susi tna
River floodplain. However, large numbers of moose could have
emigrated from those watersheds but (1) wintered on disclimax
vegetativE~ sites (disturbed sites) which are readily available
near human settlements and along the railroad and highway
rights-of--way in and near Talkeetna or ( 2) bypassed the
Susitna River floodplain to winter on the Chulitna River
floodplain, which in that. area is more braided and probably
has greater carrying capacity than the adjacent Susitna River
floodplain.
Perhaps t:here once was a traditional movement from these
upland drainages to the Susitna River floodplain but moose may
have secondarily altered that behavior pattern to take
advantage of winter browse recently availab,le in disclirnax
seral plant communities associated with human settlement and
development along the railroad and highway rights-of-way. If
this scenario is correct, and those disclimax plant
communities become unavailable or undesirable in the future,
displaced moose would probably again seek traditional winter
range on the Susitna River floodplain:
Mortality.
Predators and predation. Though specific information on bear
population levels is lacking for this area, I suspect the area
supports dense black bear and moderately dense brown bear
populations. Black bears are probably closely associated with
forested habitats and brown bears probably occur more commonly
in the alpine and short shrub habitats. Bear population
levels and distribution suggest that predation by bears on
adult and calf moose may be substantial. Traditionally low
calf:cow moose ratios observed in this area on fall moose herd
composition surveys lend support to this contention (ADF&G
files) .
Wolves are reported to occur in the area. Upper watersheds in
this area are somewhat "remote" and local wolf populations
89
probably remain relatively unexploited by trappers or hunters.
For this reason I suspect that moose in this area are subject
to higher levels of wolf predation than are other moose
subpopulations in the lower Susitna River valley.
Other sources of mortality. When moose migrate from these
watersheds to winter in lowland areas near human settlements
along the highway and railroad rights-of-way and the Susitna
River floodplain, they are exposed to mortality from the
following sources: collisions with trains and highway
vehicles, defense of human life and property situations,
drowning by falling through thin ice and/or open water, and
injuries sustained by slipping and falling on glare ice on
major rivers. Though moose migrate to lowland areas to find
ameliorated winter conditions, severe winters may still result
in considerable mortality from inadequate nutrition. Moose
undertaking these weather related movements are very dependent
on obtaining adequate winter food sources in the lowland areas
for survival.
Mortality from hunting is relatively low in this area due to
limited access.
Noteworthy Behavior Patterns.
Moose that move from this area to lowland areas during
inclement winters likely share available winter ranges with
moose from several other subpopulations. This may be
particularly true for the area where. the Talkeetna 1 Sus i tna 1
.and Chulitna Rivers converge near Talkeetna. Moose
originating from subpopulations in each of those drainages
probably gather in this area and share a common winter range.
One radio-marked female moose captured on the Susi tna River
floodplain near Talkeetna in early February was soon after
relocated about 15 miles up the Talkeetna River watershed on
Sheep River; Evidence available suggests that this individual
migrates from the lowland area near Talkeetna in midwinter and
travels up the Talkeetna River watershed to spend the critical
late winter period near alpine habitats. This individual
followed a similar movement pattern for two consecutive years.
Snowfall in these upper drainages does not appear to be any
less than in lowland areas but wind action in alpine areas may
displace snow and result in a shallower snow pack and more
favorable foraging conditions. I do not know if this movement
pattern is common for large numbers of moose.
Concerns and Potential With Project Conflicts.
Because moose from this subpopulation must contend with trains
and vehicles in railroad and highway rights-of-way when moving
90
to and from wintering areas, any increase in train or vehicle
traffic will likely result in increased moose mortality.
Alterations in the carrying capacity
floodplair1 near Talkeetna will affect
area can sustain during winter.
of the
numbers
Susitna River
of moose the
Alterations in characteristics or seasonal timing of river ice
formation or flow regimes could result in moose mortality
directly or indirectly through decreased carrying capacity of
floodplain areas. This impact could be accentuated if
disturbed sites near human settlements and developments become
unavailable or altered in the future. ·
Moose mortality is likely to i·ncrease if access into and/ or
the human population within the area increases. Additional
mortality could result from moose killed legally during open
hunting season or illegally for sustenance during closed
hunting season, moose displaced from areas by human distur-
bances, and from alterations in habitats and decreased
carrying capacity caused by increased human activities.
Montana Creek-Sheep Creek-Kashwitna River:
The Area.
This 600-mi 2 area is bounded on the west by the Susitna River,
on the 13ast by the Talkeetna Mountains and includes the
watersheds of Montana Creek, Sheep Creek, and the Kashwi tna
River. 'l'he interior of the area is seasonally accessible by
all-terrain vehicle, snowmachine, and to a lesser extent
wheel-and ski-equipped light aircraft. Limited access is
also provided by float-equipped light aircraft. One
unimproved "four-wheel drive" road extends from the Parks
highway 1easterly about seven miles along the banks of ·the
South Fork of Montana Creek. The Alaska Railroad and the
Parks Hii:Jhway rights-of-way essentially parallel each other
and the Susitn~ River along th~ western boundary of the area.
Small human settlements and numerous parcels of land that had
previously been cleared for homesteads are scattered thoughout
a three-mile-wide band adjacent to those rights-of-way. In
many casE~s, ·homestead activities have been abandoned and land
previously cleared in that process has reverted to second
growth plant communi ties which are preferred by moose for
winter range. Similar, disclimax, seral vegetative
associations occur in rights-of-way maintained for the
railroad and highway and around human habitat ions where man
has disturbed natural plant communities.
Recent si:ate sponsored land disposal programs have resulted in
numerous fledgling agricultural developments and recreational
homesites in the northwest portion of the area.
91
·_. ._ --~ -~.. . ..,. , :
The area provides opportunities for fishing, hunting, and
trapping. Limited cross-country skiing occurs near Bald
Mountain and the North Fork of Montana Creek. In the last two
years, recreational snow.machining has become increasingly
popular in alpine habitats of the area. After a fresh
snowfall, it is not uncommon to see evidence of snow.machining
in watersheds of Sheep Creek, North Fork of Kashwitna River,
and all Montana Creek tributaries. If uncontrolled in the
future, disturbances from winter recreational activities may
displace, unduly stress, and/or otherwise conflict with moose
use of the area.
Increased summer/fall use of all-terrain vehicles throughout
the area has resulted in rutted trails and limited habitat
destruction in wetland areas. If vehicle use in alpine areas
increased greatly during late summer when moose begin to
concentrate in those habitats, conflicts with moose may be of
concern. Presently, these activities do not appear to impact
moose directly.
Prevailing winds in some alpine areas of the Talkeetna·
Mountains commonly displace fallen snow, lessen snow pack
depth and often expose ground vegetation. Moose prefer to
forage in areas with shallow snow and are known to concentrate
in these habitats in fall and early winter.
The Subpopulation.
Thirty-three, 74, 13, and 93 moose were observed in Montana
Creek, Sheep Creek, North Fork Kashwitna, and Kashwitna River
watersheds, respectively, on 15 March on a distribution surv~y
in the inclement 1984-85 winter. Significantly more moose
probably occurred in these areas but large tracts of forest
habitat in the survey area decreased observabili ty of moose
and survey intensity was greatly reduced near human
settlements to decrease disturbance of humans.
Survey_s in December 1985, in alpine habitats only, near Sheep
Creek and North Fork of the Kashwitna River in December 1985
revealed 126 and 129 moose, respectively.
Annual late fall/early winter moose population composition
surveys conducted by the Alaska Department of Fish and Game
indicate that 600-800 moose occurred in this area between 1968
and 1971 (ADF&G files}. About 400 moose were observed on
similar surveys conducted between 1978 and 1982. These data
may, in part, reflect variations in carrying capacity of the
habitat, but they also indicate what the habitat could support
under different environmental conditions or land managment
practicies. I estimate that 500-600 moose inhabited this area
in winter 1984-85.
92
Five moos~::! captured and radio-marked on the Susitna River
floodplain were periodically relocated in this area. Four of
the moose were captured in a 17 April 1980 sample and one
female was captured in a 10 March 1982 sample. One marked
male commonly ranged in middle to upper Sheep Creek from
spring through early fall. During late fall, he moved down to
the North Fork of the Kashwitna River. In late winter, this
individual typically moved downstream to an alpin.e area
between the Kashwi tna River North Fork and Sheep Creek. If
mild winter weather conditions prevailed, he remained in this
area until spring~ when he would return to higher elevations
in the Sheep Creek drainage to complete an annual circuit.
However, if the winter snowpack became deep, ·this individual
would depart the alpine habitat and move to disclimax,
disturbed sites in lowland areas near human settlements along
the Susitna River floodplain where he remained through winter,
before re1turning to upper Sheep Creek in April completing a
different annual circuit pattern.
One femal,e moose, which spent each winter above timberline
near middle Sheep Creek and Montana Creek South Fork, departed
those areas in mid~April and traveled about 30 miles southwest
across the Susitna River to a location near Lockwood Lake for
parturiticm. After calving, she traveled north to Trapper
Lake for sever~l weeks in June before returning to the par-
turition area where she remained until late September when she
again traversed the Susitna River and returned to the alpine
area near middle Sheep Creek. This individual apparently
"wintered" in alpine habitats near middle Sheep Creek and was
probably initially captured in a mid-April sample near the
Susitna River while in transit to her parturition area.
The other three radio-marked females wintered on or near the
Susitna River floodplain, went through parturition west of the
Susitna River and spent the remainder of the year in the low
to middle elevations of Sheep Creek-south fork Montana Creek.
Although accurate data are lacking there appear to be three
behaviorally different movement patterns within this moose
subpopulation: (1) a large portion of moose resident in early
winter remain near timberline through the winter; (2) an equal
portion o:E moose migrate from alpine habitats to winter on the
Susitna River floodplain and/or in disclimax habitats among
human SE!ttlements and near the railroad and highway
rights-of·-way; and ( 3) an unknown-sized portion of female
moose which migrate to lowland marshy habitats near or across
the Susitna River for parturition and do not return to alpine
habitats until early fall. Some moose from subpopulations
that typically winter near timberline seek refuge and forage
in lowland areas among human settleme:nts and along the Susi tna
River floodplain when the snow pack becomes deep in alpine
areas.
93
Significant Movement -Patterns.
Because large numbers of moose have been observed on the
Susi tna River floodplain near the mouth of Montana Creek,
Sheep Creek, and Kashwitna River, moose migrating from higher
elevations must "funnel down" through and from those drainages
enroute to winter range on the Susitna River floodplain.
Movements of radio-marked moose indicate that timing,
duration, and magnitude of migrations from higher elevations
to the Susi tna River floodplain are closely related to snow
pack depth. If the snow pack becomes deep early in winter
moose migrate early. Moose remain in lowland areas as long as
deep snows persist. Magnitude of the migratory movement is
positively correlated with persistence and spatial extent of
the deep snow pack. However, there is a small segment of this
subpopulation that remains near timberline throughout winter,
regardless of snow conditions. Of moose observed near timber-
line in early winter, some may eventually migrate to lowland
areas in response to deepening snow packs while others may
remain resident in alpine habitats regardless of snow pack
conditions.
Evidence obtained in November-December 1985 indicated that
moose congregate in alpine areas during late fall and early
winter (late October-December) . Few moose were observed in
these areas in early October. Either nonrutting moose moved
to these areas after the rut or rutting groups terminated
activities in these areas because by November large numbers of
moose were present. Incidental observations obtained in 1984
and 1985 indicated that considerably fewer moose were in these
alpine areas in mid-February of those years than were observed
in February 1986. Parallel observations indicated that large
numbers of moose had immigrated to lowland areas near human
settlements and the railroad and highway rights-of-way by
early February. This movement pattern may account for the
apparent inconsistencies in results of standard composition
surveys conducted in alpine areas in different seasonal
periods (ADF&G files}.. However, other evidence from
radio-marked individuals is contradictory, in that it
indicates that not all moose \'Thich occur in these lowland
wintering areas originate _from the Talkeetna Mountains. The
latter data indicate that many moose in these lowland winter
ranges have emigrated from areas west of the Susi tna River
floodplain.
Sex segregated groups of moose were observed in these alpine
areas in December. Groups solely or predominantly of males
were frequently observed at higher elevations in the head-
waters of major drainages above timberline in primarily
riparian shrub willow plant communi ties. This habitat was
94
noticeably different than that utilized by other moose. A
group of 25+ males was observed annually in the upper North
Fork of Kashwitna River. Smaller-sized male groups were also
observed annually in upper South Fork of Montana Creek. Even
when mixed among females, males still seemed to maintain
loosely knit groups. As winter progressed (and spring
approached) , these male groups seemed to drift to slightly
lower elevations (nearer to timberline), become less distinct,
and became more diluted by females.
The rail:road, highway, agricultural developments, human
settlement:s, and associated human activities may at times
affect moose movements or preclude moose traditional use of
wintering areas and negatively impact moose subpopulations
involved. These conflicts become particularly evident when
moose seek lowland areas and the Susitna River floodplain for
winter range.
Mortality.
Predators and predation. Wolves, brown bears, and black bears
occur in this area. There are reports of wolf sightings in
the area but their occurrence must be rare as I have yet to
observe wolves or their sign. Impact of wolves on moose is
probably negligible. Brown bears are primarily distributed in
areas near and above timberline. A brown bear was observed on
the-carcass of a radio-marked moose. I am uncertain whether
the moose was carrion from a hunter kill or killed by the
bear. Black bears are distributed throughout the area, but
probably primarily occur in forested areas near and below
timberlin1:. I presume that brown and black bears prey on upon
neonatal moose calves as many radio~marked moose utilized
habitats immediately below timberline during parturition. I
suspect black bears also freque~t these habitats during the
same time period to forage and/or prey on moose calves.
Coyotes are common throughout the area and may harass moose
calves and may prey on them if the situation arises.
Other sources of mortality. Moose from this subpopulation .
that move to lowland areas near human settlements, the
railroad and highway rights-of-way, and the Susitna River
floodplain for winter range, are exposed to mortality from
humans in defense of life and property, from collisions with
trains and vehicles, respectively; from drowning by falling
through t:hin ice and/or into open water; and from injuries
sustained from slipping and falling on glare ice. Moose that
traverse the Susitna River during ice-free periods are also
exposed to drowning when crossing open water.
Though access into this area is difficult, numbers of hunters
and hunting effort is great and large numbers of moose are
killed by hunters during the open hunting season.
95
Because substantial numbers
desire a subsistence-type
moose are killed illegally
human sustenance.
of humans live in remote areas and
life style, I believe that some
{during closed hunting season) for
Points of Concern and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
timing of river ice or flow regimes which could result in
mortality directly or indirectly through decreased carrying
capacity of the habitat.
Any increase in access, human settlement, or the human
population in the area will negatively impact this moose
subpopulation by increasing numbers of moose killed legally
during open hunting season, illegally during closed hunting
season, and in defense of life and property: by decreasing or
altering preferred habitats, or by increasing the level of
human disturbance to moose.
Willow Mountain-Bald Mountain Ridge:
The Area.
This 650-mi 2 area is bounded on the west by the Susitna River
and encompasses watersheds of Little Willow Creek, Iron Creek,
Peters Creek, Furches Creek, Willow Creek, Deception Creek,
and northern tributary drainages of the Little Susitna River
upstream from the Parks Highway. · Rural towns of Kashwi tna and
Willow occur in the area. Rural communities of Houston,
Wasilla, and Palmer are within 15 miles and the metropolitan
areas of Eagle River and Anchorage which contain over a
quarter million people are less than 60 miles away. This area
is the "outdoor playground" for inhabitants of those rural
communities and metropolitan areas.
The area is seasonally accessible by ski~, wheel-, and
float-equipped light aircraft; all-terrain vehicle (ATV) ;
highway vehicle and snow machine. Several commonly used ATV
trails originate from the Parks Highway and Willow~Hatcher
Pass Road and provide terrestrial access into alpine habitats.
The Willow-Hatcher Pass Road bisects the lower one-third of
the area in an east-west direction. The western portion of
the area contains the Alaska Railroad and Parks Highway
rights-of-way which essentially parallel each other about one
mile east of the Susitna River. Numerous small settlements,
and the towns of Willow and Houston, occur in a five-mile-wide
band along those rights-of-way. Within this band of land are
numerous parcels that had been cleared for homesteads. In
many cases, homesteading and land clearing activities were
96
..
subsequently abandoned and land cleared in that process
reverted to second growth plant communities preferred by moose
for winter range. Similar disclimax plant communi ties occur
in rights-·of-way maintained for the railroad and the highway
and througrhout settled areas where man has disturbed natural
plant communities.
Active gold mining operations occur in the area along the
Willow Creek drainage.
Several areas adjacent to Bald Mountain Ridge are presently
leased from the state of Alaska for grazing livestock.
A land use management plan is being formulated for the Hatcher
Pass Area by the Alaska Department of Natural Resources. This
plan addresses an array of land uses including mining,
livestock grazing, snowmachining, skiing, wildlife viewing,
habitat preservation, forestry, and important alpine habitat
moose winter concentration areas.
The railroad and highway rights-of-way and settlements and
associated human activities, may negatively impact moose using
the area by affecting movements or precluding· use of tradi-
tional areas. Conflicts are evident when moose utilize
lowland areas ·and the Susitna River floodplain for winter··
range. Impac.ts. become of particular concern, when above-
average snowpacks occur at higher elevations and large numbers
of moose move to lowland areas.
The area provides opportunites for fishing, hunting and
trapping. In the past several years, seasonal use of all
terrain ve~hicles and snowmachines has increased tremendously
in alpine areas of Bald Mountain Ridge and Willow Mountain.
Limited cross-country skiing also occurs in alpine areas. If
uncontrolled in the future, disturbances from these human
activities may conflict with moose use of alpine areas when
moose concentrate there during the post-rut and \'Tinter
periods. Extensive use of all terrain vehicles throughout the
area during snow-free seasons has resulted in rutted trails
and limi t:ed habitat destruction in alpine and wetland
habitats.
Prevailing· winds in the western foothills of the Talkeetna
Mountains commonly displace fallen snow from exposed alpine
slopes, lessen the snow pack and low-growing vegetation.
Solar radiation on south-facing slopes also helps to melt snow
and frequ1:ntly exposes low-growing vegetation at unseasonal
times. Since moose prefer to forage in areas with shallow
snow, . high densities of moose occur in these habitats in
winter.
97
Ferns (Dryopteris sp.) are a conunon component of alpine
habitat plant communities in this area. Moose are commonly
observed digging ("cratering") through the snow pack to feed
on fern rhizomes. Ferns have been identified as a relatively
high quality forage plant for moose wintering in the area.
It has been said that this area contains some very high
quality moose wintering areas and at one time the area may
have supported the densest winter concentrations of moose in
the state (Chatelain 1951).
The Subpopulation.
Moose frequenting Willow Mountain and Bald Mountain Ridge in
winter probably do not commonly intermix .between those
respective mountains and may actually represent two distinct
subpopulations. However, because moose from both geographical
areas appear to exhibit parallel behavior patterns, they will
be treated as a common subpopulation in this report.
Late fall herd composition surveys conducted in the mid-1960s
and early 1970s indicated that over 1,000 moose occurred in
the area at that time (ADF&G files) .
A distribution and abundance survey in November of-1985 in
alpipe _habitats alone revealed over 275 and 300 moose,
respectively, on Willow Mountain and Bald Mountain Ridge
during the relatively mild 1985-86 winter.
Relatively low subpopulation levels that presently exist in
the area perhaps reflect effects of several harsh winters
and/or present land management practices and policies rather
than potential carrying capacity of the habitat. Different
land managment practices and several mild winters could
perhaps result in significantly higher subpopulation levels.
I would estimate that about 600-700 moose presently winter in
this area. These moose are concentrated on Willow Mountain,
Bald Mountain Ridge and in disclimax habitats near human
settlements and along railroad and highway rights-of-way.
Significant Movement Patterns.
Though no moose captured and radio-marked on the Susitna River
floodplain were later relocated in alpine habitats of this
area, I believe small numbers of moose from this subpopulation
commonly utilize and/or traverse Susitna River floodplain
habitats in winter or during other seasonal periods. I
believe that timing of sampling and weather conditions prior
to sampling may have prevented the latter moose subpopulations
from entering samples obtained on the Susitna River floodplain
98
in winter. There is little reason to suspect that
subpopulait:ion behavior in this area differs from that of
adjacent, northern subpopulations where moose captured on the
Susitna River floodplain were subsequently relocated in alpine
areas of the Talkeetna Mountains. Some moose from lowland
areas probably move to alpine winter range on Willow Mountain
and Bald Mountain Ridge. Timing, extent, and magnitude of
this seasonal movement may be affected by winter weather
condi tion:s. I suspect that some females from this subpopu-
lation utilize lowland and riparian areas in spring when they
seek particular habitat types during parturition. Some of the
latter female moose may also winter in the alpine areas.
Annual range of other moose in these subpopulations is
probably limited to higher elevations encompassed entirely
within the described boundaries.
Sex-segregated groups of moose were observed in this area in
December. Groups solely or predominantly of males (up to 30)
were frequently observed in alpine habitats at slightly higher
elevations than most other moose.
Mortality.
Predators and predation. Black bears, brown bears and wolves
are reported to occur in the area but I believe that densities
of predators in this area are considerably less than in more
northern areas. Basically, I believe that predation on moose
subpopulations in the western foothills of · the Talkeetna
becomes increasingly more important as a population-regulating
factor as one moves from south to north. It is believed that
this is the result of decreased exploitation rates by trappers
and hunters, but I also believe that subtle habitat factors,
human disturbance, and habitation and availability of
alternate prey are influential factors. However, approximately
12 brown bears were reportedly observed in Peters and Purches
Creek watersheds in spring of 1985. The very late phenology
in sprin~r 1985 may, in part, account for this "apparently"
atypical occurrence.
In the spring of 1986, I frequently observed black bears while
relocating radio-marked moose on the southeast slope of Bald
Mountain Ridge. Since numerous moose were also in this area
and these observations were made about the time of parturi-
tion, I suspect black bears had the opportunity to prey on
neonatal moose calves.
In spite of these two observations, I believe that predators
are not a major factor influencing the level of this
subpopula.tion.
Other sources of mortality. In wint~er 1984-85, 80 moose from
this subpopulation were reported killed by collisions with
99
trains in the railroad right-of-way between Houston and the
Kashwitna River.
In winter 1982-83 and 1983-84, 182 and 77 moose were reported ~
killed by collisions with vehicles in highway rights-of-way in
Game Management Subunits (GMS) 14A and 14B, respectively.
Because subpopulation delineations and GMS boundaries differ,
direct quantitative allocations of moose mortality to this
particular subpopulation are not possible.
In the winter of 1984-85, it was estimated that 40 moose in
GMS 14B were killed by humans in defense of life and property
(ADF&G files) . When a deep snow pack persists for long
period, moose are stressed and become aggressive when
confronted by humans. Stressed and aggressive moose interfere
with activities of humans and are eventually killed to resolve
local conflicts.
Mortality of moose from collisions with trains and vehicles
and defense of life and property is correlated with winter
weather conditions. Moose mortality from these causes
increases tremendously in relation to depth and persistence of
'the snow pack locally and in the surrounding uplands.
Mortality from these sources can have a significant impact on
this subpopulation in a severe winter when over 300 moose may
be affected.
Since moose from this subpopulation traverse the Susitna River
when moving to and from winter and calving ranges, I suspect
that some mortality results from drowning by falling through
thin ice and/or into open water and from injuries sustained by
slipping and falling on glare ice.
Proximity to large human populations and good access through
the area contribute to a relatively high hunter kill of moose
during the open hunting season. ·
Because of the large number of human inhabitants in relatively
remote areas, I believe that some moose are killed illegally,
out of season, by humans for food.
Concerns and Potential With-Project Conflicts.
Since moose from this subpopulation must contend with trains
and vehicles in those respective rights-of-way when moving to
and from wintering and calving areas, any increase in traffic
in those rights-of-way will result in increased mortality to
that subpopulation. Levels of moose mortality will be
elevated greatly if peak traffic flows correlate with moose
migratory and behavior patterns.
100
_~.-.. -. .--~--.' . : ' t·· .
With-project alterations in composition and/or distribution of
plant species on the Susitna River floodplain may affect the
carrying capacity of the area for wintering moose.
With-project alterations in timing, levels, and
characteristics of river hydraulics (flow rates, peak stages,
ice regimes, etc.) of the Susitna River may affect mortality
rates for moose that traverse the riverbed to utilize ranges
on both sides.
Hunting effort and mortality from hunting to this moose
subpopulation will likely increase if hydroelectric
development of the Susitna River increases the local human
populations or access into the area.
Little Susitna River:
The Area.
This 500-mi 2 area is bounded on the west by the Susitna River
and encompasses watersheds of the lower Little Susitna River
(excluding Bald Mountain Ridge tributaries) , Fish Creek and
Rolly Creek.
The area contains relatively larg·e rural/suburban human
settlements at Wasilla, Big Lake, Houston, and along the Parks
Highway and includes their associated infrastructure of roads,
residentia.l dweilings, and commercial developments. A
substantial rural human population occurs in outlying and more
remote are!as. Large parcels of land in the south, which were
once black spruce and muskeg and mixed mature paper birch and
white spruce forests, have recently been cleared as part of a
fledgling, state sponsored, agricultural industry. The Alaska
Railroad, Parks Highway, and a network of paved and unpaved
vehicular roads occur throughout the central portion of the
area. The area lacks alpine habitats and is dominated by
lowland habitat types with elevational extremes varying from
sea level to about 400 m. Numerous lakes, muskegs and black
spruce bo.gs occur in the west where human habitation is
negligible!.
Along the railroad and highway rights-of-way and near most
human sett:lements, previously disturbed natural vegetation has
reverted t:o second growth plant communi ties that are preferred
by moose for winter browse. Overall, the area appears as a
mosaic of lowland habitat types interspersed with rural
developments and disclimax second growth plant communities on
sites where human disturbances altered natural plant
communi tie~s. Large numbers of moose presently utilize browse
available on these disclimax disturbed sites in winter.
101
Much of the eastern and central portion of
accessible by a network paved or unpaved roads.
western portion is seasonally limited to
all-terrain vehicle, river boat and ski-,
wheel-equipped light aircraft.
the area is
Access to the
snowmachine,
float-, or
The trains, vehicles, human settlements and associated human
activities, may negatively impact moose by affecting their
migratory movements or precluding traditional use of
particular areas. Conflicts between humans and moose are
evident in winter when moose seek second growth browse in
lowland areas near railroad and highway rights-of-way and
human settlements. Magnitude of conflicts are of particular
concern when an above-average snow pack occurs in adjacent
areas and very large numbers of moose seek refuge from the
deep snow pack in lowland areas where the snow packs are
shallow and forage is plentiful on disclimax, second growth
disturbed sites.
The area provides opportunities for cross-country skiing,
hiking, boating, camping, fishing, hunting and trapping.
Human participation in these activities decreases westerly
away from access routes· and population centers.
In all winters, prevailing north and northeasterly winds from
the Matanuska and Knik River valleys commonly displace fallen
snow, lessen the snowpack and expose low-growing vegetation in
most of these lowland areas. Since moose prefer areas with
shallow snow cover, these lowland habitats remain attractive
to moose even in winters when most other areas have very deep
snowpacks. Because of consistently shallow snowpacks and
readily available high quality winter forage, this area
supports a very large and productive moose subpopulation and
provides an attractive winter range for moose from adjactent
areas and subpopulations. For these reasons, winter survival
rates for moose, particularly calves, which utilize this
wintering area, are probably significantly higher than for
most subpopulations elsewhere in the state. The coincident
a:qundance and ava·ilabili ty of high quality winter browse and
lack of deep persistent snowcover enable the area to support
extremely large numbers of moose through the winter period.
A ma]or portion of moose winter browse available in this area
resulted from past and present disturbances to natural
(sometimes climax) plant communities by human activities. I
believe that the availability of these food sources have
caused an increase in the resident moose subpopulation and
secondarily attracted (or encouraged the establishment of
different movement patterns) moose from neighboring
subpopulations which previously wintered in other adjacent
areas such as the Susitna River floodplain.
102
In this area, ice on Susitna River is frequently blown free of
snowcover and polished to a glare surface. Moose are known to
have died as a result of injuries sustained from slipping and
falling while negotiating glare ice conditions in this area.
The Subpopulation.
The typically light and shallow· windblown snow cover in this
area frequently precludes accurate surveys and information on
moose subpopulation distribution and abundance in this area is
piecemeal. Though available data suggest that small numbers
of moose are· resident in this lowland area, very large numbers
of moose are observed in portions of the area · in winter.
Whether these local concentrations of moose result from a
redistribution of the resident subpopulation or an immigration
from adjacent subpopulations. is presently unknown. I suspect
the latter possibility is the predominant factor.
Density for the resident moose subpopulation probably averages
slightly less than 1 per mi2.
Significant Movement Patterns.
Data presently available from several moose radio-marked on
the Susitna River in winter, indicate that some moose from
this subpopulation make seasonal movements from that area to
near Pittman and Wasil.la, the Little Susitna River or, the Big
Lake area in early winter, late winter and during parturition,
respectively.
Because this area provides a winter range with shallow snow
cover and readily available high quality winter browse, many
resident moose probably redistribute within the area rather
than move to the Susitna River floodplain for winter range.
It is very likely that moose from neighboring subpopulations
immigrate to this area in winter.
Data gathered in the 1960s, from a sample of visual-marked
moose, suggested that about 15% of the moose captured in
winter nE~ar Willow, Pittman, Wasilla, or Palmer, utilized
areas east of the Matanuska River and that another 15% later
utilized areas west of the Susitna River (ADF&G files). Most
moose making the shorter movement (generally less than 15 mi)
across the Matanuska River were females, whereas mostly male
moose were found to make the longer movement (over 50 mi)
across the Susitna River.
Apparently, moose movements into and within this area occur
during different seasons,. result from a combination of
reasons, and involve several different subpopulations.
103
In winter, moose prefer early successional stages of
vegetation for browse. Because many of these plant
communi ties are seral in nature, one must be cautious when
using "historical" data to characterize contemporary patterns
of movement and habitat use. As early seral habitats are
replaced by more climax vegetative communities, carrying
capacity and numbers of moose using them will typically
decrease. Moose displaced by a gradual decrease in carrying
capacity or an abrupt and complete loss in carrying capacity
will only gradually alter movement patterns to utilize newly
available and/or more productive seral communities available
at different locations. Movement patterns for subpopulations
of moose documented in the 1970s may not ·be appropriate for
subpopulations inhabiting the same area in the 1980s.
Mortality.
Predators and predation. Brown bears frequent the Little
Susitna River when spawning salmon are available. But because
of the relatively high density of human habitation in the area
numbers of wolves and brown bears are low. Predation from
.brown bears and wolves on this moose subpopulation is probably
very low. Black bears occur commonly in the east and west
portions of the area. Numbers of black bears in the central
portion are probably considerably lower because of denser
human habitation. Black bear predation may be a significant
mortality factor for neonatal moose calves in the western
portion of the area where wet marshy habitats probably attract
parturient females for calving and black bears for foraging on
early spring herbaceous vegetation •
..;..O....;t...;.,h:-e...;r;;..._....;s;,.;o;...,u;;-r;;;.,c=--e...;s~o~f-m_o..;..;;:;r....;t..;..a_l.;;.l..;;.. t~y . Co 11 is i ens of moose with trains
and vehicles in the railroad and highway rights-of-way,
respectively, are a significant source of mortality to t_his
subpopulation in the winter.
Moose from this subpopulation that move ·to the Susitna River
floodplain for winter range or calving, are exposed to
seasonal mortality from drowning by falling through thin ice
and/or into open water and from injuries sustained by falling
on glare ice.
Due to relatively easy access and the proximity to large human
populations, a substantial hunting effort occurs in the area
and results in a large moose kill.
Concerns and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect
moose utilizing these areas by altering characteristics or
seasonal timing or river ice or flow regimes or by increasing
the human related activities in the area.
104
With-project alteration in timing, levels, and characteristics
of hydraulics (flow rates, peak stages, ice regimes, etc.) of
the Susi tna River may affect mortality rates for moose that
utilize and/or traverse these floodplain areas enroute to
seasonal ranges on opposite sides.
With-project alterations in phenology, composition and/or
distribution of plant species on the Susitna River floodplain
may affect: the carrying capacity of the area to support
wintering moose.
Moose from this subpopulation which must cross the railroad or
highway rights-of-way to access seasonal ranges will be
exposed to mortality from collisions with trains or vehicles,
respectively. Any increase in traffic in those rights-of-way
will increase moose mortality. Seasonal increases in traffic
that correlate with moose movements or behaviors will increase
mortality .3.bove that level.
Hunting effort and moose mortality from hunting will likely
increase if the local human population or access into the area
increases as a result of hydroelec-tric development. Decreases
in predation rates and increases in moose net productivity
levels may be expected with-project if increases in human
populations and access in the area resulted in increased
hunting, t,rapping, and human disturbances of predators which
negatively affected local predator population levels.
Little Susitna River Flats-Susitna River:
The Area.
This 100-mi 2 area is located along the north shore of Cook
Inlet, extends from the mouth of the Susitna River to east of
the mouth of the Little Susitna River and includes the tidal
salt flats of Cook Inlet.
Except for several streamside seasonal commercial fishing
set-net site outbuildings an~ scattered duck hunting shacks,
the area contains little human development. Seasonal access
to the area is provided by ski-, float-and wheel-equipped
light aircraft; snowmachine; all-terrain vehicle; and boat via
Cook Inle·t and the Susitna and Little Susitna Rivers. The
area is dominated by lowland bog habitat types interspersed
with "iSlands" of sparse black spruce and mature paper
birch/white spruce forest. Some habitat types present in the
area are commonly used by female moose during parturition.
Elevations in the area seldom rise above 100 m. The area
provides opportunities for fishing, hunting, trapping and
snowmachining.
105
Prevailing north and northeasterly winds from the Matanuska
and Knik River valleys commonly displace fallen snow, lessen
the snow pack and expose low-growing vegetation in most of
this lowland area. Tidal action in Cook Inlet melts and
erodes the snow pack from the tidal flats and exposes
low-growing vegetation. Since moose prefer areas with shallow
snowcover, these lowland and tidal areas are utilized by moose
in winter and become particularly attractive to moose when
deep snow packs ocur in adjacent areas.
In winter, moose from the Little Susitna River subpopulation
may travel through this area when moving to winter range on
the tidal flats winter range along Cook Inlet.
The Subpopulation.
Because the typically light snow cover precludes accurate
surveys, information on distribution and abundance of this
moose subpopulation is piecemeal. Probably only very small
numbers of moose are resident to this area.
One female moose radio-marked near the Susitna River
floodplain subsequently ranged annually over only 6 mi 2 within
this area. On occasions, up to 25 moose have been observed in
winter, shortly after daybreak, feeding on the salt flat areas
adjacent to the north shore of Cook Inlet._ In the spring, up
to 15 moose have been observed feeding in wet, m~rshy habitats
and ponds iocated near the Susitna River. In winter, up to 15
moose have also been. observed feeding in this same area and
along adjacent minor drainages into the Susitna River. It is
unknown whether moose involved in these local concentrations
are resident within the area or are from neighboring
subpopulations. A large proportion of the resident moose
subpopulation probably utilize winter range on the Susitna
River floodplain. Densities of moose within this area
probably do not exceed 0.5 moose per mi 2 •
Significant Movement Patterns.
I suspect that this moose subpopulation is largely sedentary.
Major short distance seasonal movements. occur, in winter, to
the Susitna River floodplain or to the tidal flats along Cook
Inlet and in spring, to wet, marshy habitats between the
Susitna River and Figure Eight Lake.
Mortality.
Predators and predation. Wolves are rare in the area and
brown bears may occasionally travel through it. Black bears
occur at low densities throughout the area. Black and brown
bears likely prey on neonatal moose calves as habitats
106
.,_;' . ·,: .· .. • ·• _,i ••• •
frequented by parturient
interspersed with islands
throughout the area.
female moose (marshy habitats,
of sparse black spruce) occur
01:her sources of mortality. Moose which winter on the Susi tna
River floodplain would be exposed to mortality from drowning
by falling through thin ice and/or into open water and from
injuries sustained by slipping and falling on glare ice.
Though near a large human population, restricted access into
the area probably results in only a small amount of hunting
effort and hunting related moose mortality.
Concerns and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
timing of river ice or flow regimes. These impacts could
result in mortality directly, or indirectly through decreased
carrying capacity of the habitat or by increasing access or
the human population in the area which could, in turn,
increase the number of.moose killed by hunters.
Increased human settlement and access into the area could
dl:pressed predator levels by increasing the numbers killed by
trappers and hunters or degrading habitat quality by
increasing the level of human disturbance. If this.occurred,
there would be a corresponding decrease in mortality from
predators and an increase in net productivity of the
subpopulation.
Beluga River-Susitna River:
The Area.
This 50-mi 2 area occurs along the north coast of Cook Inlet,
extends from the mouth of the Susitna River to the mouth of
the Beluga River and includes the lower sections of Ivan,
Lewis and Theodore Rivers and the adjacent tidal salt flats of
Cook Inlet.
Other than riverside seasonal commercial fishing site out
buildings and scattered duck hunting shacks, the area contains
little human development. Seasonal access to the area is
provided by ski-, float-, and wheel-equipped light aircraft;
snowmachine; all-terrain vehicle; and boat via the Susitna
River or Cook Inlet. The area mainly contains lowland marshy,
muskeg type habitats interspersed with "island forests" of
sparse black spruce and mature paper birch/white spruce. The
sparse black spruce forest present in this area are commonly
used by female moose during parturition. Elevations within
107
the area rarely exceed 100 m. The area provides opportunities
for hunting, fishing and trapping.
Prevailing northeasterly winds from the Matanuska and Knik
River _valleys and northerly winds from the Susitna valley
commonly displace fallen snow, lessen snowpack depth and
expose low-growing vegetation throughout most of this lowland
area. High waters from tidal action of Cook Inlet frequently
erode and melt the snowpack from the tidal flats and expose
low-growing vegetation. Since moose prefer to winter where
snowpacks are shallow, these lowland areas are commonly
utilized by moose for winter range. These habitats become
particularly attractive to moose in winters when deep
snowpacks occur in adjacent areas.
The Subpopulation.
Because the typically light and patchy snow cover precludes
accurate surveys, information on moose subpopulation
distribution and abundance in this area is piecemeal.
Probably only very small numbers of moose are resident to this
area. A high. proportion of the resident moose subpopulation
probably travel to and utilize winter range on the Susitna
River floodplain. In winter, moose from other subpopulations
probably travel through this area when moving to winter range
on the Susitna River floodplain. In spring, female moose from
adjacent subpopulations probably move into the area to utilize
muskeg habitat during parturition. Density of the resident
subpopulation is probably less than 0.5 moose per sq mi.
Significant Movement Patterns.
Though no radio-marked moose remained entirely within this
area, I believe that contains a small number of resident
moose. Seasonal movements of this subpopulation would likely
be to the Susitna River floodplain or the tidal flats along
Cook Inlet for winter range and to the open marshy muskeg
habitats in spring for parturition.
Mortality.
Predators and predation. Wolves rarely occur in the area.
Brown bears probably occasionally pass through the area.
Black bears probably frequent the small bands of forest that
occur in the area. Use of the area by black bears is probably
greatest during spring when the area is also utilized by
parturient female moose. Occurrence of moose and black bears
in the same habitat probably results in limited black bear
predation on neonatal moose calves.
108
O·ther sources of mortality. Moose from this subpopulation
that move to the Susitna River floodplain for winter range are
exposed to seasonal mortality from drowning by falling through
thin ice and/or into open water or from injuries sustained by
slipping and falling on glare ice.
Though the area is near a large human population, low
densities of resident moose and poor access probably
discourage efforts by hunters and lead to a low hunter moose
kill.
Concern and Potential With-project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
timing of river ice or flow regimes. These impacts could
result in mortality directly or indirectly "through decreased
carrying capacity in the habitat or by increasing access or
human population in the area which could in turn increase
human disturbance or the number of moose killed by hunters.
Increased human settlement and access in the area could
negatively impact predator populations by increasing numbers
killed by trappers and/or hunters and by increasing the level
of human disturbance. If this occurred, there would be a
decrease in moose mortality from predators and a corresponding
increase in net moose productivity.
Mount Susitna-Little Mt. Susitna:
'l'he Area.
This 650-mi 2 area erncompasses the upper watersheds of Beluga,
Theodore, Lewis, and Ivan Rivers; watersheds on Little Mt.
Susi tna, Mount Susi tna and Trail Ridge and lower Alexander
Creek. Topography and habitats in the area range from flat
TJiet marshy habitats only slightly above sea level, to lowland
floodplain habitats along the lower Yentna River and Alexander
Creek, to alpine habitats at elevations above 3,000 and 4,000
jEt. on Little Mt. Susi tna and Mount Susi tna 1 respectively 1
and to wet, marshy habitats above 800 ft~ elevation near Drill
Creek and upper Theodore River.
'rhe area is seasonally accessible by wheel-, float-and ski-
equipped light aircraft; snowmachine and all-terrain vehicle.
A major strip coal mining operation is centered in the upper
Lone Creek watershed.
109
Some activities in the area are undertaken with professional
guides and commercial air taxi operators. Hunting and fishing
field camps are sparsely scattered throughout the area.
Very heavy snowfall and deep snowpacks are not uncommon in the
upper elevations of this area.
The Subpopulation.
Behavior of this moose subpopulation is strongly influenced by
snowpack depth and winter weather conditions. When a
snowpacks are deep· in upper elevations of the area, large
numbers of resident moose emigrate to winter ranges at lower
elevations on Alexander Creek, the Yentna River and the
Susitna River floodplains.
Six moose radio-marked on the Susitna River floodplain in late
winter, later redistributed off the floodplain within portions
of this area. Nonwinter ranges for these individuals centered
near Beluga River, Drill Creek, Theodore River, Talchuli tna
River, Mount Susitna and Trail Ridge. Timing, magnitude and
duration of moose use of Susitna River floodplain winter range
in this area is closely associated with occurrence and extent
of snowfall and snowpack depth. This ·moose subpopulation
probably contributes greatly to the dramatic fluctuations in
numbers of moose wint~ring on the Susi tna River floodplain
downstream from the Yentna River.
Information obtained in winter 1982-83, indicated that moose
subpopulations in this area promptly, responded to a decrease
in the snowpack, as well as increasing snowpack depths.
Following a heavy snowfall in late October, early November and
through December a major immigration of moose onto the Susitna
River floodplain occurred from Bell Island to Cook Inlet.
During that time period, numbers of moose observed in that
section of the Susitna River floodplain increased from about
100 to 260. By early December over 120 moose were observed on
Bell Island alone and 412 were present on the Susitna River
floodplain· downstream from the Yentna River. Ameliorating
weather conditions, redistribtuion and settling of the deep
snowpack was followed by a significant decrease in numbers of
moose observed on the floodplain~ By early February, when the
snowpack is normally deepest and moose use of the floodplain
typically greatest, numbers of moose observed in that same
area had decreased to 206. I presume the decrease in numbers
of moose was due to an emigration of moose back to alternate
winter ranges off the floodplain. These data suggest that
more than 300. moose from this subpopulation may migrate to the
Susitna River during inclement winter conditions.
110
In addition to the Susitna River floodplain, some moose from
this subpopulation probably winter on the floodplains of
Sucker and Alexander Creeks and the Yentna River. Large
numbers of moose have been observed on these drainages in
previous winters. Though, these later floodplains may provide
some refuge from an excessive snowpack, I believe that in all
winters, they normally have a deeper snowpack than the Susitna
River floodplain. The Susitna River floodplain also differs
from the former areas in that it is more open and exposed to
prevailing northerly and northeasterly winds which typically
redistribute and compact fallen snow so effectively that the
snowpack seldom completely covers low-growing vegetation for
periods longer than a week. Very few "winter killed" moose
were observed in this section Susi tna River floodplain in
1984-85, when about 30 dead moose were observed on Alexander
C:reek.
Since relatively "favorable" winter conditions prevail in this
area even in harsh winters, winter mortality of moose,
particularly calves, in this area is exceptionally low even
when compared to other low elevation winter ranges in the
Susitna River basin.
Information obtained from several radio-marked female moose
suggested that female moose in the area may utilized wet,
marshy, lowland muskeg habitats during parturition.
Concentrations of moose were observed on the southern slopes
of Mount Susitna in October, a time period when rutting
activity normally occurs. Apparently, moose from this
subpopulation utilize this portion of the area for rutting
behavior.
Significant Movement Patterns.
In winter, a portion of this moose subpopulation moves to
lowland .ranges. Timing, duration and magnitude of this
movement is correlated with snowpack depth and severity of
winter weather conditions. In winters when snowpacks become
deep, a large proportion of this moose subpopulation
immigrates to wintering areas at lower elevations along the
Yentna River, Alexander Creek and the Susitna River floodplain
downstream from the Yentna River. This movement pattern
results in extremely high densities of moose on the Susitna
River floodplain.
One radio-marked female moose in this subpopulation was found
to travel over 25 miles to winter on the Susitna River
floodplain. One radio-marked male.moose which also winter on
the Susitna River floodplain traveled about 25 mi to the
Denslow Lake area, during the rut period. These individuals
111
made similar movements in several consecutive years. Some
female moose from this subpopulation move to wet, marshy
muskeg habitats at lower elevations along the Susitna River
floodplain during parturition. Similar type habitats occur
west of the Susitna Mountains at higher elevations near the
upper Talchuli tna River. I presume some females from this
subpopulation move to and utilize calving habitats at these
higher elevations in years when snowpacks are shallow.
Mortality.
Predators and predation. Wolves, brown bears and black bears
occur in the area. Observations of wolves or wolf sign are
frequently reported for the upper Sucker Creek and Wolf Lake
areas west of the Susitna Mountains. Because of human
activities in lowland areas along the Susitna River, I suspect
that wolves normally remain at higher eleveations and seldom
visit the Susitna River floodplain. Brown bears occur
scattered throughout the area but are probably more common at
higher elevations away from human disturbances. Black bears
are common at all elevations throughout the area. Because of
their tolerance for humans, black bears occur commonly in
lowland areas and .along the Susitna River floodplain. I
presume that black and brown bears frequent muskeg habitats in
spring to prey on neonatal moose calves. I suspect brown
bears prey on adult moose in spring and through summer when
deep· snowpacks and relations with calves increase their
vulnerability.
Other sources of mortality. Moose from this subpopulation
that utilize the Susitna River floodplain are seasonally
exposed to mortality from drowning by falling through thin ice
and/or into open water and from injuries sustained from
slipping and falling on glare ice. In winter 1982-83, several
marked moose in this area died of injuries sustained from
slipping on glare ice. Circumstantial evidence indicated that
several unmarked moose also died from similar causes. This
source of mortality is probably most common in this section of
the floodplain because of very wide ice-covered river channels
and strong winds which remove snow cover and expose and polish
extensive areas of glare ice.
This subpopulation is exposed to moderate levels of mortality
from hunters. I suspect that additional moose mortality
results from illegal hunting for sustenance by year-round
residents after the open hunting season closes.
Concerns and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
112
timing of river ice or flow regimes. These impacts could
result in mortality directly or indirectly through decreased
carrying capacity of the habitat and/or by increasing human
access or the human population in the area which could in turn
:Lncrease the level of human disturbance or the number of moose
killed by hunters.
Increased human settlement and access into the area could
negatively impact predator populations by increasing the level
of human disturbance and by increasing numbers killed by
trappers and/or hunters. If this occurred, there would be a
corresponding decrease in mortality from predators ~nd an
increase in net moose productivity.
Big Island-Bell Island (floodplain):
The Area.
This 80-mi 2 area encompasses 12 miles of the Susitna River
floodplain and adjacent habitat immediately upstream from Cook
Inlet. The area is composed mainly of five large, low relief
islands on the Susitna River floodplain. The islands range in
size from about 1 to 6· mi 2 • The area includes about 1 mi 2 of
land which parallels this section of the floodplain.
The area is bisected by a buried natural gas pipeline and
overh~ad electrical transmission lines. A roughly-maintained,
maintenance road paralleling these facilities provides
seasonal access to the area by snowmachine, all-terrain
vehicle and four-wheel drive highway vehicle. The area is
also accessible seasonably by boat from the Susitna River and
Cook Inlet or by float-, ski-and wheel-equipped light
aircraft.
Permanent human habitation, in the area, is limited to small
rural settlements along lower Alexander Creek. Several duck
hl.J.nting shacks and commercial fishing cabins occur in the
area. The area provides opportunities for recreational
snowmachfning, hunting, fishing, trapping, and boating.
Prevailing northerly winds and northeasterly winds from the
Matanuska and Knik River valleys commonly displace fallen
snow, lessen the snowpack and expose ground vegetation in most
of this lowland area. In winter, high water and tidal action
of Cook Inlet frequently melt and erode the snow pack from the
tidal flats and island margins and expose low-growing
vegetation. Because moose prefer areas with shallow or no
snow cover, this floodplain area is particularly attractive to
migratory moose subpopulations in winters when deep snowpacks
occur in adjacent areas. In winters of heavy snowfall, this
area provides the most favorable winter range available to
113
moose subpopulations from the west and southwest. Numbers of
moose utilizing the area may increase by 4-5 times in winters
with deep and persistent snowpacks.
These islands are apparently varied and large enough to
sustain small numbers of moose year-round. The island
habitats are a mosaic of wet meadows, open shrub grasslands
and mature mixed deciduous/conifer forests. Willow and poplar
browse is abundant along island perimeters and on sandbars
where river hydraulics and flood action maintain early
successional plant communities.
The Subpopulation.
Because the typically light snow cover precludes accurate
surveys, information on moose· subpopulation distribution and
abundance in this area is piecemeal.
Small numbers of moose are resident within this large islanded
area of the Susitna River floodplain. Density for the
resident moose subpopulation is probably about 1 moose per
mi 2 • One female moose, radio-marked in an adjacent are.a near
Figure Eight .Lake seldom ranged more than 2 .mi from its
capture site. A radio-marked male, seldom left Bell Island,
and over a three-year period ranged within a 30-mi 2 area. I
believe the behavior patterns exhibited by these individuals
are characteristic of the resident moose subopopulation.
In winter, the resident moose subpopulation shares these
island and floodplain habitats with subpopulations from
adjacent areas. In severe winters, densities of 10-20 moose
per mi 2 are neither unrealistic nor uncommon for portions of
the area.
Perhaps some of the moose observed in spring utilizing the
wet, muskeg habitats adjacent to the Susitna River floodplain
orginate from this subpopulation.
Significant Movement Patterns.
The resident moose subpopulation is largely sedentary. The
only major seasonal movements for this subpopulation are
probably to wet, marshy muskeg areas adjacent to the
floodplain in early spring and spring to forage and calve,
respectively, or to particularly good foraging areas on the
islands themselves in winter.
Mortality.
Predators and predation. Wolves are probably absent from this
area. Because of the proximity of the area to Mt. Susitna,
114
brown bears are probably not uncommon. Black bears are common
throughout the area. I suspect that brown and black bears
both prey on neonatal moose calves. Brown bears probably also
prey on adult moose in early spring and summer when deep
snowpacks or presence of neonate calves, respectively,
incre.ase their vulnerability.
Coyotes are commonly observed in the area. I would not be
surprised if coyotes did not harass and/or occasionally prey
on neonatal moose calves.
Other sources of mortality. Moose which winter on the Susitna
River floodplain would be exposed to mortality from drowning
by falling through thin river ice and/or into open water and
from injuries sustained by slipping and falling on glare ice.
Good access to the area by river boat and float-or
wheel-equipped light aircraft contribute to substantial
hunting effort and moderate hunting related mortality.
Concerns and Potential with-Project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
timing of river ice or flow regimes. These impacts could
result in mortality directly or indirectly through decreased
carrying capacity or by increasing access or the human
population in· the area which in turn could increase the level
of human disturbance and/or number of moose killed by hunters.
Increased human settlement and access into the area could
negatively impact predator populations by increasing numbers
killed by trappers and/or hunters and by increasing the level
of human disturbance. If this occurred, there would be a
corresponding decrease in mortality from predators and an
increase in net moose productivity.
Kroto Creek-Moose Creek:
~rhe Area.
This 700-mi 2 area is located west of the Susitna River and is
bounded by the Yentna River, Peters Creek, Little Peters Hills
and the Sunshine Bridge on the Susitna River.
The area is seasonally accessible by highway vehicle along its
northern border, all-terrain vehicle, river boat, snow
machine, float-, ski-and wheel-equipped light aircraft and
off-road vehicles via the Oilwell and Moose Creek Roads.
Human habitation ranges from solitary homesteads, recreational
homesites and recreational cabins on many lakes scattered
115
throughout the area, to clusters of rural homesites and
recreational cabins along the unmaintained Oilwell and Moose
Creek Roads which extend south 15 and 10 mi from the
Petersville Road to the Amber Lake area and from the Moose
Creek Road to Gate Creek, respectively.
Numerous state-sponsored land disposals have occurred and are
proposed within this area. The most recent land disposal was
along the eastern banks of the lower Yentna River.
Matunuska-Susitna Borough state forest land occurs in the
Chijuk Creek area. This land area is unique 1n that it
encompasses the most extensive mature paper birch/white spruce
forest in the lower Susitna River valley.
The area is generally characterized by marshy lowland meadows
interspersed with "islands" of open black spruce and paper
birch/white spruce forests.
The area provides opportunities for recreational fishing,
trapping, hunting, boating, camping and sled-dog mushing. The
area .is not exposed to strong winter winds and fallen snow
remains undisturbed and accumulates to considerably deeper
depths than in areas farther south that are exposed to strong
northerly and northeasterly-winds. Within the area, snowfall
and the snowpack both generally increase westerly a\<1ay from
the Susitna River.
Riparian habitats along Kroto and Moose Creeks and the Susitna
River floodplain and a previously burned area on the
southwestern slopes of Little Peters Hills provide winter
range for substantial numbers of moose.
Wet, marshy habitats interspersed with "islands" sparse black
spruce and mature paper birch/white spruce forests are
commonly utilized by female moose from this and adjacent moose
subpopulations during parturition. These "calving" habitats
are essentially devoid of moose during winter.
The Subpopulation.
About 2,500 moose are presently estimated _to be in this
subpopulation. Short-and long-term size of this
subpopulation is strongly influenced by winter weather
conditions. Fluctuations of plus or minus 60-70% about that
population level are probably realistic.
Data obtained from radio-marked moose and winter aerial
surveys indicate that a large portion of moose from this
subpopulation move to floodplain habitats along the Susitna
River, riparian habitats along Kroto and Moose Creeks, and
116
disclimax sites· along Parks Highway and Alaska Railroad
rights-of-way for winter range. Some moose from this
subpopulation utilize the Susitna River floodplain as winter
range in all winters but timing, magnitude and duration 9f
this migratory movement is closely associated with winter
\~eather and snowpack depth. A large portion of the moose
w·hich winter on the Susi tna River floodplain originate from
this subpopulation. About 400-500 moose from this
subpopulation wintered for varying periods of time in riparian
habitats along Kroto and Moose Creeks in winter 1984-85.
Roughly, 40 to 65 moose wintered opposite Goose Creek on an
abandoned homestead adjacent to the western bank of the
Susitna River between October and March, 1982-85.
:Since moose radio-marked on the Susitna River . floodplain in
winter were not found to range farther west than the Yentna
River, I presume the Yentna River to be the western range
boundary for this subpopulation. Because snow conditions
normally worsen to the west, I assume that as the winter
snowpacks deepen moose from this subpopulation normally move
easterly to obtain relief from excessively deep snowpacks.
'rhis migratory movement brings moose to wintering areas along
Kroto and Moose Creeks and the Susitna River floodplain.
Significant Movement Patterns.
Because of deeper snowpacks and a scarcity of adequate
'Wintering areas, moose from this subpopulation migrate in an
easterly direction as winter progresses. Timing, magnitude
and duration of this movement is closely correlated with
snowpack depth. Moose appear to utilize wintering areas along
Kroto Creek early in winter and move on toward Moose Creek and
the Susitna River floodplain as winter progresses and/or snow
conditions become worse.
Female moose were commonly observed in the wet, marshy
habitats interspersed w-ith "islands" of sparse black spruce
and paper birch/white spruce forests during parturition. I
suspect movement to these areas is for more favorable foraging
habitat or away from habitats more commonly frequented by
predators. Movements to these habitats involve moose from
this subpopulation as well as moose from adjacent
subpopulations.
Mortality.
Predators and predation. Wolves, black bears and brown bears
occur in the area. Wolves occur more commonly in the western
and northern portions of the area. Wolf sign has been
observed along the Moose and Kroto Creek drainages in winter.
117
Brown and black bears are distributed throughout the area.
Densities of black bears are considerably greater than for
brown bears.
I presume that black bears prey on neonatal moose calves as
habitat use overlaps between the two species in spring when
parturient female moose seek stands of sparse black spruce in
wet muskeg habitats. Because of relatively high black bear
densities their predation on moose calves may be a significant
mortality factor. Brown bears probably also prey on neonatal
moose calves in spring, as well as adults during other
seasonal periods. But, because of relatively low densities,
the contribution of brown bear predation to moose mortality is
probably not as significant as that of black bears.
Coyotes occur commonly throughout the area and may
occasionally harrass and/or prey on neonatal moose calves.
Other sources of mortality. Moose from this subpopulation
that move to the Susitna River floodplain for winter range are
exposed to seasonal mortality from drowning by.falling through
thin ice and/or into open water and from injuries sustained by
slipping and falling on glare ice.
Because the area is near a large human population center and
is relatively accessible during the open hunting season,
hunting· related mortality can be a _significant mortality.
In winter, some moose from this subpopulation cross the
Susitna River to utilize disclimax habitats near human
settlements and railroad and highway rights-of~way. Mortality
from collisions with trains and highway vehicles can be a
significant mortality factor. Because this subpopulation
winters among human settlements it is not uncommon for moose
to be killed in defense of life and property. These mortality
factors. become of particular significance during in winters
when deep snowpacks persist for long periods.
Large numbers of humans live in remote portions of this area.
Many individuals living in remote areas depend heavily on
wildlife resources for sustenance. Though there is a special
"subsistance" open hunting season in the area to accommodate
use of moose by rural inhabitants, I believe there is still a
significant illegal kill of moose in the winter for use as
human food.
Indirect loss of moose in this subpopulation may occur when
land use patterns are altered and carrying capacity of the
habitat for moose is decreased. This situation may occur when
large state-sponsored land disposals result in moose habitat
being changed into homesites or agricultural developments.
118
Concerns and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
timing of river ice formation or flow regimes. These impacts
could result in mortality directly or indirectly through
decreased carrying capacity or by increasing access or the
human population in the area which could in turn increase the
number of moose killed by hunters.
Increases in the human population and access into the area
could negatively affect predator populations by increasing
numbers killed by trappers and/or hunters and by increasing
the level of human disturbance. If this occurred, there would
be a decrease in mortality from predators and a net increase
in moose productivity.
Delta Islands-Caswell Islands (floodplain):
The Area.
This area encompasses about 100 mi 2 uf open river water, large
islands, floodplain and paralleling adjacent uplands of the
Susi tna River between the mouth of Kroto Creek and Sheep
Creek.
This area is season-ally accessible by all-terrain vehicle,
river boat, snow machine, float-, ski-and wheel-equipped
light ·aircraft. Human habitation is limited to recreational
cabins along the banks of the Susitna River and major
tributary streams.
Riparian poplar forests were commercially logged on
islands in the past. Grass, shrubs and second growth
and poplar stands now dominate these disturbed sites.
logging bperations have recently been initiated on
floodplain islands.
some
birch
New
other
The area provides opportunities for recreational
exceptional salmon fishing, trapping, boating,
sled-dog mushing, and cross-country skiing.
-hunting,
camping,
This area does not appear to be northerly or northeasterly
winds from. Susitna River valley or the Matanuska and Knik
River valleys, respectively, as more southern floodplain
areas. In the absence of strong winter winds, fallen snow in
this area remains relatively undisturbed and snowpacks
accumulate to considerably deeper levels compared to more
southerly floodplain areas which are exposed to valley winds.
This area generally seems to receive larger amounts of
snowfall than areas to the south and snowpacks within the area
119
appear to decrease from south to north. In general, winter
conditions in this area are more favorable for moose than
conditions to the west but less favorable than winter
conditions to the south.
River islands in this area apparently are large enough and
contain habitats types essential for sustaining small numbers
of resident moose year-round. River hydraulic action
maintains early successional open shrub plant communites and
higher relief islands provide stability for open and closed
canopy forest communities.
Though some islands in the Delta Island complex are as large
as those in the Big/Bell Island area, habitats in the former
area are denser, more mature, closed canopy forests which
lack many of the seral plant communities preferred by moose.
During particular seasonal periods, moose from other
subpopulations travervse and/or · share these floodplain
habitats with the resident subpopulation. In winter, moose
from subpopulations east and west migrate to and winter on
this section of the Susitria River floodplain. Depending on
severity of winter conditions, numbers of moose in the area
may increase by five to tenfold. Field data gathered indicate
that large numbers of moose from westerly subpopulations
problably utilize the floodplain in most all winters. In
severe winters, substantially larger numbers of moose from
those westerly subpopulations and additional moose from
easterly subpopulations migrate to and use habitats on this
section of floodplain. Some moose from westerly
subpopulations traverse the floodplain area to utilize
disclimax (disturbed sites) habitats near human settlements
and highway and railroad rights-of-way. Smaller numbers of
moose from westerly subpopulations are known to migrate
completely through this area en route to alpine wintering
areas in the western foothills of the Talkeetna Mountains.
Immediately prior to parturition, some female moose from
subpopulations east of the Susitna River traverse the
floodplain when migrating to lowland muskeg calving areas west
of the Susitna River.
The Subpopulation.
About 50 moose are probably resident to this area and range
almost entirely on this section of the Susitna River
floodplain. These resident moose may ocasionally make forrays,
short in distance and time, to adjacent uplands which parallel
the floodplain.
Field data obtained from early winter floodplain surveys and
observations from several radio-marked moose which seldom
120
r· .·
moved far off the floodplain in this area during a five-year
period, provide biological evidence in support the former
contentions.
Size and existence of this moose subpopulation is largely
determined by the presence and maintenance· of the mosaic of
habitat types on the floodplain. Size and/or behavior
patterns of this moose subpopulation would likely be altered
if the proportions of seral and climax plant communities were
changed.
Two radio-marked female moose, relocated over a four-year
period only rarely departed floodplain habitats. Another
radio-marked female, observed over a similar time period, only
infrequently utilized habitats immediately adjacent to the
floodplain.
Significant Movement Patterns.
Moose in this small resident subpopulation are quite
sedentary. Subpopulations, from the east and west, travel
distances up to 25 mi to winter on this section of the
floodplain. Numbers of moose wintering in this area are
correlated with winter severity. Moose from some
subpopulations move through. the area in spring and winter en
route to other wintering and calving areas. Some moose from
this subpopulation may move to disclirnax habitats, east of the
floodplain and near human settelements and highway and
railroad rights-of-way for winter range.
Mortality.
Predators and predation. Brown bears probably rarely occur in
the area. Wolves may occasionaly occur in the area in winter.
Black bears and coyotes occur commonly throughout the area.
Black bears probably prey on neonatal moose calves in wet
muskeg habitats used by parturient females. Coyotes may
harass and/or alio prey on neonatal moose calves.
Other sources of mortality. Moose utilizing this area are
seasonally exposed to mortality from drowning by falling
through thin ice and/or into open water and from injury by
slipping and falling on glare ice. Moose that winter along
highway and railroad rights-of-way and human settlements may
be killed by collisions with vehicles and trains or by humans
in defense of life and property.
Concerns and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by increasing train and vehicle traffic in
121
the railroad and highway rights-of-way, by altering
characteristics or seasonal timing of river ice or flow
regimes which could result in mortality directly or indirectly
by decreasing habitat carrying capacity, by increasing access
or the human population in the .area which could in turn
increase the number of moose killed legally or illegally by
humans.
Little Peters Hills-Petersville:
The Area.
This 350-mi 2 area extends from the Susitna River westerly to
Petersville and the Little Peters Hills. East, north and
south boundaries of the area are the Mouth of Whiskers Creek
on the Susitna River north of Talkeetna and the Sunshine
·Bridge, respectively. The area emcompasses the upper
watersheds of Peters, Kroto and Trapper Creeks and the
terminus of the Chulitna River.
The area is seasonally accessible by riverboat from the
Susitna and Chulitna Rivers~ by vehicle from the Parks Highway
near the eastern boundary, the Petersville/Trapper Creek Road
which bisects the area into north/south halves and the Oilwell
Road which extends south from the Petersville Road and by
float-, ski-and wheel-equipped light aircraft, snowrnachine,
and all-terrain vehicles at other locations.
The area provides opportunity for fishing, hunting, trapping,
camping and sled-dog mushing. The area is served by
commercial air taxi operators and professional guides.
Human habitation ranges from roadside developments, residences
and homesteads along the Parks Highway and the
Petersville/Trapper Creek Road and clusters of rural
settlements and recreational cabins and homesites along the
unmainta~ned Oilwell and Moose Creek Roads. Many small
seasonal placer mining operations occur along streams near the
Dutch/Peters Hills.
Numerous state sponsored land disposals have occurred and are
planned within the area along the Oilwell and Petersville
Roads.
The area is characterized by marshy lowland meadows
interspersed with "islands" sparse balck spruce and mature
paper birch/white spruce forests. These lowland areas grade
up elevationally to alpine habitats in the northwest.
122
. ~·
~--
"
The area receives very large amounts of
Dutch/Peters Hills. Generally, winter
increase westerly from the Susitna River.
snowfall
snowpack
in the
depths
Riparian habitats along Moose Creek and floodplain habitats on
the Susitna and chulitna Rivers provide winter range for large
numbers of moose.
The Subpopulation.
About 500 moose are presently estimated to be in this
subpopulation. Short-· and long-term size of this
subpopulation is strongly influenced by snowpack depth and
winter weather conditions. Fluctuations plus or minus 60-70%
about that population level are probably not unrealistic.
Data obtained from radio-marked moose and winter aerial moose
surveys indicate that a large portion of moose from this
subpopulation move to riparian and floodplain habitats along
Moose Creek and the Susitna and Chulitna Rivers, respectively.
Ptn unknown portion of this subpopulation may winter on the
western slopes of Little Peters Hills or on the Kahiltna
Glacier forelands where large numbers of moose have been
observed in winter. A small number of moose from this
subpopulation may travel across the Susitna River to winter on
disclmax habitats along the railroad and highway rights-of-way
and near human settlements in the Talkeetna area.
Significant Movement Patterns.
In winter, moose from this subpopulation gather along Peters
Creek near the Little Peters Hills, on the south-and
west-facing slopes of Little Peters Hills, along Moose Creek
south of the Petersville Road, on disclimax sites near the
town of Trapper Creek, and on the floodplains of the Susitna
and Chulitna Rivers. The latter five locations are the most
heavily used winter ranges in the area.
I~arge portions i~ the interior of this area are essentially
devoid of moose in winter. Data collected during winter
1984-85, suggested that as the snowpack depth increases moose
may move from the interior of the area {Kroto and Moose
Creeks) easterly to winter on disclimax sites near the town of
Trapper Creek and on floodplains of the Susitna and Chulitna
Rivers. .
In winter, a small number of moose may traverse the Chulitna
and Susitna River floodplain to utilize disclimax habitats
along highway and railroad rights-of-way and around human ·
settlements near Talkeetna.
123
I suspect that in spring female moose depart winter ranges and
move to wet, marshy muskeg areas during parturition.
Mortality.
Predators and predation. Wolves, brown bears and black bears
occur in the area. A pack of 5 wolves were observed near
Talkeetna in winter 1983-84 and wolf sign was frequently
observed in the western portions of the area. I suspect that
wolf predation could be a significant mortality factor in this
area. Moose may be particularly vulnerable to wolf predation
in relatively s·evere winters when large numbers of moose
concentrate on open floodplains.
Density of brown bears probably increases in westerly portions
of the area. Brown bears probably prey on adult moose in
early spring when snowpacks are deep, neonate shortly after
parturition and adult moose during summer when they are
protective of neonate calves. Black bears are distributed
throughout the area and probably are a significant predator on
neonatal moose calves shortly after parturition ..
Coyotes occur commonly along open floodplains in eastern
portions of the area. Though not documented, I believe that
coyotes may harass neonatal moose calves and occassionally
prey on them if the opportunity arised.
Other sources of mortality. Moose which winter on the Susitna
and Chulitna River floodplains would be exposed to seasonal
mortality from drowning by falling through thin ice and/ or
into open water and from injuries sustained by slipping and
falling on glare ice.
Because interior portions of this area may receive large
amounts of snowfall, winter kill can be a significant
mortality factor. Winter kill mortality is particularly
significant in winters when deep snowpacks persist in·to early
spring. Winter kill typically affects a disproportionate
number of calf and yearling moose.
Moose which travel across the Susitna and Chulitna River
floodplains to winter in disclimax sites near human
settlements and along highway and railroad rights-of-way are
exposed to mortality from collisions with trains and vehicles
and from humans defending life and property. These sources of
mortality are particularly important during severe winters
when large. numbers of moose utilize these areas.
Good access into the interior of this area contributes to a
relatively high kill of moose during the open hunting season.
124
Because of the large number of seasonal and year-round human
inhabitants in remote portions of the area, I believe that
substantial numbers of moose are killed illegally in winter
for human consumption. As human populations in remote areas
increases the illegal kill of moose can be expected to
increase.
Increased human habitation in remote portions of the area can
have positive effects on local moose populations, if predator
populations are decreased by trapping and/or hunting or human
disturbances.
Concerns and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect this
moose subpopulation by altering characteristics or seasonal
timing of river ice or flow regimes or by increasing human
activities or habitat ion in the area. These impacts could
result in moose mortality directly or indirectly by decreasing
habitat carrying capacity or by increasing access or the human
population in the area which could in turn could increase
levels of mortality related to human activities (hunter kill,
illegal kill, defense of life and property kill, kill by
collisions ·with trains or vehicles). ·
Increased human settlement and access into the area could
negatively impact predator populations by increasing numbers
by trappers and/or hunters and by increasing the level of
human disturbance. If this occurred, there would be a
decrease in mortality from predators and an increase net moose
productivity.
Remainder of Susitna River Floodplain:
The Area.
This area includes all remaining portions of the Susitna River
floodplain that: (1) have not been identified as being
utilized by any particular moose subpopulations; and (2) are
communally utilized in winter by several subpopulations from
adjacent areas. More specifically, this area includes a
60-mi 2 portion of the Susi tna River floodplain between Bell
Island and the Delta Islands and a 100-mi 2 portion of the
floodplain between the Caswell Islands and Whiskers Creek.
These floodplain areas are seasonally accessible by
all-terrain vehicle, river boat, sled-dog, snowmachine,
float-, ski-and wheel-equipped light aircraft. Human
habitation in the area is primarily limited to seasonal
recreational cabins along the banks of the Susitna River.
125
The areas provide opportunities for
fishing, trapping, boating, camping,
cross-country skiing.
recreational hunting,
sled-dog mushing and
The areas encompasses a variety of floodplain plant
communi ties, which include: river bars colonized by sedges
and equisetum, alder and willow shrub communities, open early
seral poplar and adler forests, open and closed canopy mixed
deciduous/ conifer forests, and closed canopy cottonwood
forests. Though these plant communi ties may be similar to
those in other sections of the floodplain, I suspect that the
habitats and islands are not extensive enough to support
resident moose subpopulations.
Islands, habitats and plant communities formed on the
floodplain are largely the result of seasonal river flow and
ice dynamics that initiate flooding; ice and debris scouring;
erosion and deposition of soil; uprooting, translocation and
deposition of debris and vegetation; disolving and
translocation of minerals and organic compounds which, in
turn, act to: (1) preclude development of climax plant
communi ties, and ( 2) maintain portions of the floodplain in
early seral shrub communi ties preferred by moose for winter
r~nge. These seral habitats attract and provide winter range
for large numbers of moose from adjacent migratory
subpopulations.
Since the floodplain is relatively open and exposed to
sunlight and wind, its snowpack tends to settle, become
crusted and/or be.redistributed in a manner more favorable to
moose for obtaining forage and for moving from one food source
to another than snowpacks in surrounding forested or
non-floodplain areas. At times, moose appear to prefer to
rest in open areas on the floodplain exposed to the sun and
incident solar radiation.
Timing, duration and magnitude of moose use of floodplain
winter range are correlated with snowpack depth in surrounding
areas. Moose use of floodplain winter range increases greatly
when deep snmvpacks occur in adjacent areas.
The Subpopulation.
Moose utilizing these floodplain areas originate from numerous
different migratory subpopulations resident to adjacent
non-floodplain areas. Data obtained from radio-marked
individuals indicate that some moose migrate over 25 miles to
utilize these floodplain winter ranges.
Data obtained from radio-marked moose indicate that indivduals
which utilize floodplain areas are also known to frequent
126
nearby disclimax habitats located among human settlements and
along railroad and highway rights-of-way. If these disclimax
sites became unavailable, moose from many subpopulations would
become more dependent on floodplain areas for winter forage.
Similarly, as food sources on the floodplain become exausted,
some moose probably opt to spend more time foraging off the
floodplain in nearby disclimax habitats.
In several consecutive years, three radio-marked female moose
moved to and utilized these floodplain areas during
parturition.
Significant Movement Patterns.
Large numbers of moose from subpopulations in adjacent
nonfloodplain areas immigrate from distances over 25 miles to
winter on these floodplain areas. Timing, duration and
magnitude of use of these areas are correlated with snowpack
depth in adjacent areas.
A small number of female moose from subpopulations in adjacent
areas migrated to utilize these floodplain areas . during
parturition.
Moose from adjacent subpopulations that utilize areas on
opposite sides of the floodplain traverse this area en route
to other seasonal ranges.
Mortality.
Predators and predation. Wolves and brown bears probably
occur infrequently in these areas. Black bears are commonly
distributed throughout both areas. Black bears probably prey
on neonatal moose calves. Because of the relatively high
density of black bears in these floodplain areas, I suspect
black bear predation on moose neonates may be a significant
. mortality factor for moose which use the area during
·partur~tion. Coyotes occur commonly in these floodplain areas
and may harass and prey of neonatal moose calves if the
situation arises.
Other sources of mortality. Moose which utilize these areas
or travel through them are seasonally exposed to mortality
from drowning by falling through thin ice and/or into open
water and from injury by slipping and falling on glare ice.
Moose that move through or off the floodplain area to forage
on disclimax distrubed sites among human settlements or along
railroad or highway rights-of-way may be killed by collisions
with trains or vehicles or by humans. in defense of life and
property.
127
·---------·----~. ---~~~-~-·--
Concerns and Potential With-Project Conflicts.
Hydroelectric development of the Susitna River may affect
moose utilizing these floodplain areas by altering
characteristics or seasonal timing of river ice or flow
regimes or by increasing the human related activities in the
area.
With-project alteration in timing, levels and characteristics
of hydraulics (flow rates, peak stages, ice regimes, etc.) of
the Susi tna River may affect mortality rates for moose that
utilize and/or traverse these floodplain areas en route to
seasonal ranges on opposing sides.
Moose from subpopulations east of the floodplain which utilize
these areas are confronted with trains and vehicles, in those
respective right-of-ways, when traveling to and from wintering
and calving areas. Moose from subpopulations west of the
floodplain which also frequent disclimax habitats east of the
floodplain will likewise be exposed to mortality from
collisions with trains and· vehicles. Any corresponding
increase in traffic in those rights-of-way will result in
increased moose mortality. Mortality rates· will increase
significantly if increases in traffic correlates with moose
diurnal and seasonal behavior patterns.
Alterations in phenology, composition and/or distribution of
plant communities on the Susitna River floodplain may affect
the carrying capacity of the area to support wintering moose.
Hunting effort and moose mortality from hunting will likely
increase, if hydroelectric development of the Susi tna River
increases local human populations or access into the area.
Increased human settlement and access into the area could
negatively impact predator populations by increasing numbers
killed by trappers and/or hunters and by incresing the level
of human disturbance. If this occurred, here would be a.
corresponding decrease in mortality from predators and a net
increase in moose productivity.
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----···----~-----
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131
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PERSONAL COMMUNICATIONS
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Jackson Hole, Wyoming.
133
NORTH
Appendix A easte • Identification
rn p 0 rtlon of the
number and location f
stratification or sample survey M • arch 1985.
units Included 1 n the
----~134
NORTH
Scale 1:650000
0
Ap;pendlx 8. Identification number and location for sample units Included In
thtt western portion of the moose stratification survey, ~arch 1985.
135
Appendix C. Number and density of moose and moose tracks observed in
different size sample units during a stratification
survey in the lower Susitna River valley watershed, 13-15
and 18 March, 1985.
SamEle unit Number D . 1 ens1.tz
Number Area (sq mi) Moose Tracks Moose Tracks
1 14~5 38 5 2.6 0.3
2 12.5 44 22 3.5 1.8
3 11.6 5 2 0.4 0.2
4 14.9 1 3 0. 1 0.2
5 10.8 7 1 0.7 0.1
6 11.4 12 9 1.1 0.8
7 12.9 1 11 0.1 0.9
8 15.0 0 4 0.0 0.3
9 17. 1 4 2 0.2 0. 1
10 15.3 13 20 0.8 1.3
11 11.4 10 10 0.9 0.9
12 14.0 16 1 1.1 0.1
13 9.9 7 9 0.7 0.9
14 11.4 6 4 0.5 0.3
15 12.5 4 16 0.3 1.3
16 6.7 16 3 2.4 0.4
17 10.0 7 9 0.7 0.9
18 17.3 7 0 0.4 0.0
19 8.4 27 0 3.2 0.0
20 10.7 1 6 0.1 0.6
21 10.8 0 1 0.0 0.1
22 14.5 1 2 0. 1 0.1
23 10.6 13 6 1.2 0.6
24 9.4 34 5 3.6 0.5
25 7.0 1 13 0. 1 1.9
26 13.8 2 17 0.1 1.2
27 16.6 13 10 0.8 0.6
28 14.7 5 3 0.3 0.2
29 7. 1 0 7 o.o -o. 1
30 10.9 0 3 o.o 0.3
31 14.4 13 10 0.9 0.7
32 12.0 0 7 o.o 0.6
33 10.7 8 9 0.7 0.8
34 12.5 0 3 0.0 0.2
35 13.4 9 6 0.7 0.4
36 15.8 14 11 0.9 0.7
37 17.0 26 13 1.5 0.8
38 13.0 5 12 0.4 0.9
39 9.5 10 5 1.1 0.5
40 15.7 38 13 2.4 . 0.8
41 9.9 0 8 0.0 0.8
42 10.2 12 24 1.2 2.4
136
Appendix C. (cont'd)
Sam:ele unit Number Density
Number Area (sq mi) Moose Tracks Moose Tracks
43 12.0 14 15 1.2 1.3
44 15.2 11 31 0.7 2.0
45 18.8 0 3 0.0 0.2
46 9.1 0 6 0.0 0.7
47 10.7 15 17 1.4 1.6
48 10.8 22 12 2.0 1.1
49 13.7 15 1 1.1 0.1
50 2. 1 0 6 0.0 2.8
51 1.6 4 1 2.5 0.6
52 8.5 0 15 0.0 1.8
53 14.2 0 2 0.0 0.1
54 11.8 4 8 0.3 0.7
55 7.1 2 1 0.3 0.1
56 6. 1 3 0 0.5 o.o
57 6.6 4 3 0.6 0.5
58 15.5 0 4 0.0 0.3
59 8.3 4 10 0.5 1.2
60 5.5 1 0 0.2 o.o
61 8.0 1 4 0.1 0.5
62 16.3 0 0 o.o o.o
63 9.4 0 0 0.0 o.o
64 14.5 2 5 0. 1 0.3
65 8.7 1 1 0. 1 0.1
66 15.5 3 8 0.2 0.5
67 16.9 11 15 0.7 0.9
68 16.1 12 16 0.7 1.0
69 9.5 2 0 0.2 o.o
70 2.5 3 14 1.2 5.5
71 7.7 0 2 0.0 0.3
72 6.7 0 7 0.0 1.0
73 1.4 5 " 3.5 1.4 ...
74 11.2 0 0 0.0 o.o
75 13.0 2 0 0.2 0.0
76 13.3 1 3 0.1 0.2
77 14.9 7 4 0.5 0.3
78 12.2 2 3 0.2 0.2
79 7.3 0 3 0.0 0.4
80 6.7 0 1 0.0 0.1
81 19.2 0 2 0.0 0.1
82 11.8 0 3 0.0 0.3
83 12.7 0 2 0.0 0.2
84 13.0 7 9 0.5 0.7
85 8.1 2 15 0.2 1.9
86 12. 1 25 10 2. 1 0.8
87 7.5 0 3 0.0 0.4
88 12.3 11 6 0.9 0.5
89 11.0 0 1 0.0 0. 1
137
Appendix C. (cont'd)
Sam:ele unit Number Densitz
Number Area (sq mi) Moose Tracks Moose Tracks
90 3.5 7 9 2.0 2.6
91 13.4 1 3 0.1 0.2
92 9.2 18 1 2.0 0.1
93 4.3 15 8 3.5 1.9
94 6.3 10 10 1.6 1.6
95 13 0 5 29 10 2.1 0.7
96 16.4 14 13 0.9 0.8
97 13.5 52 8 3.9 0.6
98 10.7 20 13 1.9 1.2
99 3.5 0 0 0.0 o.o
100 11.3 13 4 1.1 0.4
101 5.2 8 11 1.5 2.1
102 11.8 30 8 2.5 0.7
103 11. 6 1 20 0.1 1.7
104 9.2 5 17 0.5 1.9
105 13. 7 3 6 0.2 0.4
106 12.2 0 0 o.o o.o
107 4.1 10 10 2.4 2.4
108 8.6 5 4 0.6 0.5 ~
109 3.2 8 0 2.5 0.0
110 13.5 0 2 0.0 0.1
111 15.6 6 1 0.4 0.1
112 3.2 10 0 3.2 0.0
113 20.3 3 6 0. 1 0.3
114 9.7 4_ 8 0.4 0.8
115 13 0 5 4 4 0,3 0.3
116 10.4 7 0 0.7 0.0
117 14.5 1 0 0 0 1 o.o
118 13.8 0 0 0.0 0.0
119 15.4 1 1 0. 1 0.1
120 15.1 3 0 0.2 o.o
121 12.2 0 3 0.0 0.2
122 10.2 3 1 0.3 0.1
123 3.6 47 4 12.9 1.1
124 6.8 1 2 0.1 0.3
125 5.3 0 0 0.0 0.0
126 7.6 5 0 0.7 o.o
127 12.9 4 5 0.3 0.4
128 2.8 4 1 1.4 0.4
129 10.2 1 2 0 0 1 0.2
130 4.6 16 2 3.5 0.4
131 10.3 7 5 0.7 0.5
132 3.5 10 3 2.9 0.9
133 4.9 1 0 0.2 0.0
134 10.4 0 0 0.0 o.o
135 11.2 2 1 0.2 0. l
136 9 0 l l 1 0 .l 0.1
138
Appendix C. (cont'd)
SamEle unit Number Densit:z::
Number Area (sq mi) Moose Tracks Moose Tracks
137 16.8 13 2 0.8 0.1
138 11.7 7 1 0.6 0.1
139 6.6 3 0 0.5 o.o
140 9.2 22 0 2.4 0.0
141 20.4 39 1 1.9 0.0
142 8.4 0 2 o.o 0.2
143 6.5 0 3 o.o 0.5
144 3. 1 8 8 2.6 2.6
145 10. 1 0 10 0.0 1.0
146 10.1 28 14 2.8 1.4
147 9.9 1 1 0.1 0.1
148 14. 1 21 2 1.5 0.1
149 9.6 1 3 0. 1 0.3
150 11.3 1 3 0. 1 0.3
151 6.0 8 8 1.3 1.3
152 12.4 0 6 o.o 0.5
153 11.8 0 2 0.0 0.2
154 11.2 3 3. 0.3 0.3
155 2.8 3 4 1.1 1.4
156 16.2 1 9 0.1 0.6
157 4.0 0 7 o.o 1.8
158 9.0 4 2 0.4 0.2
159 6.6 0 0 0.0 0.0
160 10.8 5· 14 0.5 1.3
161 6.5 1 3 o.z 0.5
162 14.5 27 6 1.9 0.4
163 5.9 2 0 0.3 0.0
164 4.4 11 2 2.5 0.5
165 8.4 8 2 1.0 0.2
166 8.7 0 2 0.0 0.2
167 10.0 1 1 0.1 0.1
168 7.6 8 3 1.1 0.4
169 7.3 0 4 o.o 0.5
170 9.0 7 8 0.8 0.9
171 4.1 5 1 1.2 0.2
172 15.1 12 0 0.8 0.0
173 16.1 2 10 0.1 0.6
174 12.8 0 4 0.0 0.3
175 7.2 14 8 1.9 1.1
176 13.3 2 3 0.2 0.2
177 13.8 1 3 0. 1 0.2
178 5.0 19 3 3.8 0.6
179 8.0 3 4 0.4 0.5
180 15.9 4 9 0.3 0.6
181 10.3 0 0 0.0 0.0
182 12.5 0 2 0.0 0.2
183 12.7 4 1 0.3 0. 1
139
Appendix c. (cont'd)
SamEle unit Number Densitl:
Number Area (sq mi) Moose Tracks Moose Tracks •
184 9.9 0 5 o.o 0.5
185 8.6 0 4 o.o 0.5
186 6.9 0 5 o.o 0.7
187 7.5 4 13 0.5 1.7
188 14.3 15 9 1.0 0.6
189 9.4 0 0 o.o o.o
190 12.0 15 2 1.3 0.2
191 9.7 2 0 0.2 0.0
192 9.8 2 2 0.2 0.2
193 5.5 0 0 0.0 o.o
194 8.9 4 1 0.4 0.1
195 7.5 1 2 0.1 0.3
196 4.7 3 1 0.6 0.2
197 6.3 0 1 o.o 0.2
198 4.5 0 1 o.o 0.2
199 3.9 15 6 3.8 1.5
200 9.0 1 0 0. 1 0.0
201 6.5 0 3 0.0 0.5
202 13.6 2 0 0. 1 0.0 ~
203 2.8 7 6 2.5 2.1
204 10.8 5 2 0.5 0.2
205 9.8 0 0 o.o o-~ o
206 7.2 0 1 0.0 0.1
207 5 .. 5 5 2 0.9 0.4
208 7. 1 97 3 13.6 0.4
209 6.7 29 0 4.3 o.o
210 6.9 45 0 6.5 0.0
211 23.3 49 2 2.1 0.1
212 16.1 47 6 2.9 0.4
213 16.3 41 1 2.5 0.1
214 16.4 16 3 1.0 0.2
215 14.6 7 6 0.5 0.4
216 18.7 74 1 4.0 0.1
217 12.4 38 1 3.1 0. 1
218 8.6 12 4 1.4 0.5
219 13.9 1 1 0. 1 0. 1
220 14.8 99 1 6.7 0. 1
221 19. 1 3 1 0.2 0.1
222 14. 1 49 1 3.5 0.1
223 9.6 8 4 0.8 0.4
224 13.6 19 6 1.4 0.4 .,
225 17.5 1 2 0.1 0.1
226 10.6 38 0 3.6 0.0
227 9.8 1 1 0. 1 0.1
228 18.7 1 1 0.1 0.1
229 8.3 44 1 5.3 0.1
230 15.9 0 2 0.0 0.2
231 14.7 3 2 0.2 0.1
140
Appendix C. (cont'd)
SamEle unit Number Densitl
Number Area (sq mi) Moose Tracks. Moose Tracks
232 12.2 0 5 o.o 0.4
233 13.8 5 5 0.4 0.4
234 15.7 0 0 0.0 0.0
235 15.4 2 0 0.1 0.0
236 22.7 1 2 0.0 0.1
237 14.8 20 4 1.4 0.3
238 13.4 14 4 1.0 0.3
239 15.2 0 0 0.0 0.0
240 19.4 18 7 0.9 0.4
241 16.2 2 5 0.1 0.3
242 17.6 0 0 0.0 0.0
243 16.2 0 3 o.o 0.2
244 13.3 0 1 o.o 0. 1
245 14.0 24 20 1.7 1.4
246 20.6 1 4 o.o 0.2
247 16.0 12 1 0.7 0. 1
248 16.2 3 7 0.2 0.4
249 16.2 25 1 1.5 0.1
250 14.1 25 1 1.8 0.1
251 19.2 0 3 o.o 0.2
252 19.1 1 5 0.1 0.3
253 12.6 7 4 0.6 0.3
254 17.8 0 5 o.o 0.3
255 19.2 0 0 0.0 o.o
256 14.3 0 2 0.0 0.1
257 15. 1 61 1 4.1 0.1
258 15.3 0 4 o.o 0.3
259 18.9 0 0 0.0 o.o
260 14.1 5 12 0.4 0.9
261 13.3 0 1 o.o 0.1
262 19.4 1 2 0.1 0.1
263 13.1 0 0 0.0 o.o
264 12.2 1 10 0. 1 0.8
265 15.7 21 13 1.3 0.8
266 15.3 19 21 1.2 1.4
267 15.5 0 4 0.0 0.3
268 15.4 0 0 0.0 0.0
269 17.4 45 3 2.6 0.2
270 11.5 71 1 6.2 0.1
271 14.6 0 2 o.o 0.1
272 17.7 1 4 0.1 0.2
273 13. 1 98 0 7.5 0.0
274 18.3 0 0 o.o o.o
275 16.6 2 3 0. 1 0.2
2 76 12.0 5 4 0.4 0.3
277 14.0 0 0 0.0 o.o
278 15.7 2 1 0.1 0.1
279 15.4 0 2 o.o 0.1
141
Appendix C. (cont'd)
SamEle unit Number Densitz
Number Area (sq mi) Moose Tracks Moose Tracks
280 16.3 0 1 o.o 0. 1 ..
281 16.1 0 0 0.0 o.o
282 13. 1 1 6 0.1 0.5
283 15.0 0 4 0.0 0.3
284 15.7 0 4 o.o 0.3
285 15.7 2 6 0.1 0.4
286 16.1 ' 0 2 o.o 0.1
287 11.3 1 1 0. 1 0. 1
288 18.7 5 5 0.3 0.3
289 14.4 53 0 3.7 o.o
290 16.0 0 3 0.0 0.2
291 14.6 26 1 1.8 0. 1
292 17.6 17 1 1.0 0. 1
293 15.5 0 7 0.0 0.5
294 13.9 0 3 0.0 0.2
295 15. 1 0 0 o.o o.o
296 16.7 1 6 0.1 0.4
297 11. 1 1 4 0.1 0.4
298 11.4 1 5 0.1 0.4
299 14.0 22 12 1.6 0.9
300 15.5 5 19 0.3 1.2
301 13.0 3 3 0.2 0.2
302 13.0 9 2 0.7 0.2
303 10.8 0 0 o.o o.o
304 11.5 2 2 0.2 0.2
305 13.8 17 10 1.2 0.7
306 15.4 75 6 4.9 0.4
307 14.4 7 9 0.5 0.6
308 14.1 40 2 2.8 0.1
309 11.6 1 2 0.1 0.2
310 10.5 0 1 o.o 0.1
311 14.1 0 1 0.0 0.1
312 15.0 32 1 2 .·1 0.1
313 12.6 0 8 0.0 0:6
314 15.8 1 1 0.1 0.1
315 19.4 0 5 0.0 0.3
316 19.9 7 11 0.4 0.6
317 19.0 11 10 0.6 o.s
318 14.5 41 1 2.8 0.1
319 12.2 57 5 4. 7 0.1
320 13.5 6 11 0.4 0.8
321 14.4 24 5 1.7 0.3
322 14.2 1 3 0.1 0.2
323 12.9 11 7 0.9 0.5
324 9.5 0 0 0.0 0.0
325 15.0 0 5 0.0 0.3
326 15.4 1 4 0. 1 0.3
327 14.3 7 7 0.5 o.s
142
Appendix C. (cont'd)
Samele unit Number Densiti:
Number Area (sq mi) Moose Tracks Moose Tracks
328 16.8 7 14 0.4 0.8
329 15.2 36 3 2.4 0.2
330 15.7 1 10 0.1 0.6
331 12.8 6 4 0.5 0.3
332 17.2 7 13 0.4 0.8
333 10.5 1 2 0.1 0.2
334 12.6 3 6 0.2 0.5
335 18.6 15 0 0~8 o.o
336 17.4 7 1 0.4 0.1
337 15.7 0 0 0.0 o.o
338 12.0 8 13 0.7 1.1
339 14.0 19 27 1.4 1.9
340 12.3 0 6 o.o 0.5
341 21.5 68 0 3.2 o.o
342 13.8 25 3 1.8 0.2
343 11.2 112 2 10.0 0.2
344 15.7 20 9 1.3 0.6
345 8.5 7 5 0.8 0.6
346 3.8 0 0 o.o 0.0
347 13.7 0 0 o.o o.o
348 14.5 0 0 0.0 0.0
" 349 1.7 0 0 o.o o.o
350 3.4 0 0 o.o 0.0
351 5.8 0 0 0.0 0.0
352 12.4 0 0 0.0 o.o
353 25.4 0 0 0.0 o.o
Total 4252 3440
1 Density of moose and tracks = No. moose and tracks
divided by area (sq mi) of sample unit, respectively.
143
I-'
""' ""'
Al'PENDIX D
Frequency distribution of moose density classes for numbers of moose observed in various size
sample units on a stratification survey in the lower Susitna River valley watershed 13-15 and
18 March 1985.
Percent Accumulative
DensifY No. Total Total % Total
class units Moose Area (mi 2 ) Moose Area Moose Area
13.1 + 1 97 7 2.8 0.2 2.8 0.2
12.1 -13.0 1 47 4 1.4 0.1 4.2 0.3
11.1 -12.0 0 0 0 0.0 0.0 4.2 0.3
10.1-11.0 0 0 0 o.o o.o 4.2 0.3
9.1 -10.0 1 112 11 3.5 0.3 7.7 0.6
8.1-9.0 0 0 0 0.0 0.0 7.7 0.6
7.1 -8.0 1 98 13 2.8 0.3 10.5 0.9
6.1 -7.0 3 215 33 6.3 0.8 16.8 1.7
5.1 -6.0 1 44 8 1.3 0.2 18.1 1.9
4.1 -5.0 4 222 49 6.5 1.2 24.6 3.1
3. 1 -4.0 16 557 158 16.2 3.7 40.8 6.8
2.1 -3.0 23 615 248 17.9 5.8 58.7 12.6
1.6 2.0 18 383 220 11.1 5.2 69.8 17.8
1.1 -1.5 24 313 253 9.1 6.0 78.9 23.8
0.6 -1.0 41 411 523 11.9 12.3 90.8 36.1
0.1 -0.5 116 324 1,479 9.4 34.8 100.2 71.1
o.o 96 2 1,168 o.o 27.5 100.2 98.7
0.0 7" 0 77 0.0 1.2 100.2 99.9
Total 353 3,440 4,252 100.2 99.6 100.1 99.9
1 Density class = number of moose observed in sample unit divided by area (sq mi) of sample unit.
Seven sample units (77 sq mi) in density class 0.0 were comprised of habitat above 3,500 ft., an
elevation above which moose are seldom observed.
Appendix E. Numbers of moose observed on periodic surveys in two
alpine areas of the western foothills of the Talkeetna
Mountains, Alaska, 1985-87.
1985-86 1986-87
Area 4 17 8 18 3 23 31 17 26 24 15
Oct Oct Nov Nov Dec Feb Mar Apr Nov Dec Jan
Bald Mtn 1 37 109 264 302 260 275 191 40 408 120 47
Willow Mtn 5 148 265 268 313 164 121 59 492 43 15
1 Approximately 26 and 39 mi 2 of moose habitat were surveyed
on Bald and Willow Mountain, respectively.
+
145
Appendix F. Numbers of moose observed on sites in the lower Susitna
River valley where natural vegetation has been altered by
activities of man, 1981-85.
Site 1
Winter Date MW MN MM TW KL MS ME GC we KB cw CE KE TC
1981-82 2 Dec 41
10 Dec 8 0 23 4 17
14 Dec 28
28 Dec 25 11 7
6 Feb 1 9 4 4
1 Mar 24 1 2 1 1 6
24 Mar 6 0 4 1 6 0
12 Apr 4 0 0 0 1 1
1982-83 29 Oct 13 0 0
6 Nov 22 0 2 4 3
10 Nov 14
18 Nov 68 0 11 8 3
2 Dec 67 1 45 16 23
6 Dec 56 3 47 21
20 Dec 8 21
21 Dec 36 -42 25 19
.,
22 Dec 41 42 10
5 Jan 28 6 41 9 22 ..
20 Jan 21 0 59 36 5
24 Jan 48 0 63 14 29 13
7 Feb 14 11
9 Feb 57 0 7 27
22 Feb 8 2
23 Feb 30 2 16 6
7 Mar 7
8 Mar 43 3 22 8 2
20 Mar 7
22 Mar 17 -43 17
23 Mar 21 45 10 16
30 Mar 8 1 -
8 Apr 2 6 1 1
1983-84 17 Nov 6 0 4 4 11 0 1 0 0 3
18 Nov 0 0 0
25 Nov 22
29 Nov 45 0 5 0 3 0 3 0 3 2 0 0
9 Dec 32 0 5 9 14 2 10 0 7 2 0 3 5
16 Dec 47 0 7 11 7 2 6 0 5 0 0 3
24 Dec 72 0 5 18 3 0 7 0 2 2 2 0 1
30 Dec 49 0 0 1 0 0
3 Jan 23 5 1
5 Jan 73 0 12 14 8 0 12 6 1 2 4 3 2
13 Jan 29 1 18 14 4 5 0 2 2 4 2 2 0
146
··.-.. ·: -··
Appendix F. (cont'd)
s· 1 ~te
Winter Date MW MN MM TW KL MS ME GC we KB cw CE KE TC
~
1983-84 17 Jan 4 21 13 3 4 4 6 1 6 6 5 1
19 Jan 31 2 16 10 2 2 4 8 4 6 6 2 1
27 Jan 49 4 25 5 16 6 7 22 8 15 7 4 2
8 Feb 48 5 38 8 6 12 3 12 1 40 23 6 2
20 Feb 49 6 26 21 8 25 3 21 1 27 22 9 1
28 Feb 42 7 59 26 14 12 6 4 0 31 18 0 2
5 Mar 19 0 43 10 16 5 0 4 2 33 34 2 0
8 Mar 17 1 37 3 9. 6 1 4 2 28 34 2 0
15 Mar 3 0 38 3 8 6 0 1 5 16 16 0 0
29 Mar 4 0 27 1 21 3 0 0 5 6 3 0 0
1984-85 27 Nov so 0 0 0 6 0 0 0 0 0 0 ' 3 3
10 Dec 25 0 0 5 0 0 0 0
11 Dec 7 3 0 0 2 2
24 Dec 46 0 5 10 9 1 5 1 0 0 2. 0 0 0
28 Dec 43 1 0 5 0 2 0 3 1 2 0 0
7 Jan 51 2 17 27 4 5 0 7 1 3 0 0 3 3
18 Jan 48 4 22 11 6 9 5 2 6 2 0 2 2
19 Jan 2
29 Jan 24 4 37 17 5 18 2 7 0 11 7 0 3 3
11 Feb 29 1 35 6 12 2 16 0 18 22 7 4 4
13 Feb 43 7 51 18 13 11 6 11 0 22 22 8 5 5
22 Feb 35 16 37 12 4 1 4 3 2 27 25 6 0 0
1 Mar 17 8 1 32 43 13 1 1
2 Mar 40 3 39 6 6 11
9 Mar 34 4 24 20 6 1 0 3 6 21 so 6 1 1
16 Mar 20 4 33 8 1 0 8 4 20 46 2 0 0
21 Mar 18 0 39 20 2 0 0 7 2 18 40 4 2 2
5 Apr 12 0 39 11 1 4 0 1 1 13 29 1 0 0
16 Apr 10 0 so 16 0 2 0 2 3 7 2 3 0 0
1 - =
Site not surveyed on that day. ~~ =Montana west, MN = Montana
north, MM =Montana middle, TW =Talkeetna west, KL = Kashwitna
Lake, MS • Montana south, ME = Montana east, GC = Goose Creek,
WC • Willow Creek, KB = Kashwitna bluffs, CW= Chandalar west,
CE • Chandalar east, KE = Kashwitna east, and TC = Talkeetna cutoff.
Sites ME, GC, WC, KB, CW, CE, and KE were only surveyed during
1983-85. Site TC was only surveyed during 1984-85.
147
Table 1. Physical and geographical characteristics for selected zones along the Susitna River from Devil Canyon dam site to Cook Inlet, Alaska.
Approximate
Geographical distance Elevational Grade Prominent Contribution1to
Zone boundaries (km) change m/km tributaries total flow
Devil Canyon Susitna River
to Talkeetna 80 300 to 105 2.5 Indian River 20
II Talkeetna to Chulitna River
Montana Creek 30 105 to 76 1.0 Talkeetna River 20
Ill Montana Creek Montana Creek, Sheep Creek, Kashwitna River, Little
to Yentna River 65 76 to 15 0.9 Willow Creek, Willow Creek, Deshka River 10
IV Ventna River to
I-' Cook Inlet 40 15 to sea level 0.4 Ventna River 40
""" 00
Data obtained from Alaska Power Authority Public Participation Office Newsletter. November 1980. "The Susitna Hydro Studies," 8pp.
Table 2. Vegetative characteristics for general habitat types which occur in the Susitna River watershed from Devil Canyon to Cook Inlet.
Alaska.
Map ID
No.
2
3
4
5
6
7
8
1 Habitat type
(elevation m)
Moist alpine tundra/riparian complex
(600-1500)
Open spruce/birch forest
( 150-600)
Open, low growing spruce forest
(30-300)
~1ixed seral complex
(30-180)
Closed spruce/birch forest
(180-600)
Wet, moderately open spruce/birch forest
(6-300)
Dry alpine tundra
( 60-130)
Wet tundra
(0-130)
For more detailed descriptions, see Viereck and Little (1972).
Vegetation characteristics
Low growing heath species, dwarf birches and willows on ridge tops; slopes
densely covered with alder; spruce/birch forests at lower elevations, with
cottonwood, alder, and wUlow occurdng along stream margins.
Predominantly dense spruce/birch forests, occasional shallow bog pond, wet
tundra vegetation occurring around pond margins and in openings.
Poorly drained wet sites, dominated by black spruce, heath shrubs; sedges.
grasses, and sphagnum mosses; numerous slightly higher, dry "islands"'of
spruce/birch forest distributed between wet sites.
Mixture of variously disturbed sites with seral species; open low growing
spruce forests; and open spruce/birch forests.
Dense to moderately dense spruce/birch forests, intermixed with occasional
open low growing spruce forests.
Wet moderately open spruce/birch forests, interspersed with numerous
shallow bog ponds and open low growing spruce forests.
Dense spruce/birch forests, at elevations below 1000 m, low growing
eracaceous shrubs, grasses. sedges, crowberry, and moutnain avens at
higher elevations.
Numerous shallow bog lakes, vegetation predominantly sedges. cottongrass,
shrub willows and birches, cranberry, blueberry, sweetgale, and Labrador
tea.
1--'
lJl
0
Table 3. Total precipitation and snowfall for various locations in geographic zones along the Susitna River downstream from the prospective
Devil Canyon dam site,
Geographic Elevation
Zone Station Location (m) Inclusive dates
Chulitna River Lodge 381 1971-76
Chulitna Highway Camp 152 1973-79
Susitna Meadows 274 1970-75
II Talkeetna Airport 105 . 1941-801 Bald Mountain Lake 654 NA
Ill Caswell 88 1949-57
White's Crossing, Will ow 82
Willow Airstrip 61 1964-81
IV Anchorage Airport 35 1943-81
Goose Bay 30 1969-76
1 Data not available. 2 Data obtained from U.S. weather service, meterological summary reports. 3 U.S. Department of Agriculture, Soil Conservation Service snow surveys.
Total Greatest depth
precipitation on ground for
Annual mean Annual mean any month
(em, years) (em) (years)
62 2 434 191
66 513 163
109 NA 203 3
71 272 132 (1967-80)
NA 142 2
64 351 183
61 (1963-75) NA 1553(1970-76)
NA NA 130
38 178 79 (1963-81)
36 NA NA
Table 4. Mean daily maximum. monthly mean, and mean daily minimum temperatures (oC) for Anchorage (1953-80) and Talkeetna (1940-80),
Alaska.
Location Value Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Anchorage
Daily maximum - 7 - 3
-1 7 13 17 19 18 13 6 - 2 - 6
Monthly mean -11 - 8 -4 2 8 13 14 13 9 2 -6 -11
Daily Minimum -16 -13 -9 -3 3 8 10 9 4 -2 -10 -15
Talkeetna
Daily maximum -7 - 3 1 7 13 19 20 18 13 5 -3 - 8
Monthly mean -13 - 9 -7 7 13 16 13 8 0 -8 -13
Daily Minimum -18 -15 14 -6 7 9 7 3 -4 13 -18
t-'
U1
t-'
_Table 5. Inclusive calendar dates for significant life history events for moose subpopulations
along the Susitna River from Devil Canyon to Cook Inlet, Alaska.
Range or transitory interval Relevance to life history
Winter range Males recondition from breeding.
Sring transitory interval
Calving range
Summer transitory interval
Summer range
Autumn transitory interval
Breeding range
Post breeding transitory
interval
Pregnant females nurture fetus and prepare
for parturition.
First winter for calves.
Females bear young.
Growth of new born young. Females recondition
from parturition and lactation. Males begin
antler growth.
Males establish breeding units.
Sexes breed.
Location of breeding perhaps critical for
denoting subpopulation units.
152
Calendar dates
1 January
thru
28 February
10 May
thru
17 June
July
thru
31 August
14 September
thru
31 October
. --~'---' -_ ______:_ __ ·_· -----'--------
Table 6. Numbers of moose observed on periodic censuses of floodplain
habitat along four zones on the Susitna River between Devil
Canyon and Cook Inlet, Alaska 1981-85.
Winter
period
1981-82
Census date
9 and 10 Dec
28 Dec and 4 Jan
2 and 6 Feb
1 and 2 Mar
23 and 24 Mar
12 Apr
I
36
18
8
7
25
7
1982-83 29 Oct and 6 Nov 14
10 and 18 Nov 57
. 1, 2 and 6 Dec 76
20-22 Dec 76
5 and 6 Jan 84
20 and 24 Jan 56
7 and 9 Feb 26
22 and 23 Feb 27
7 and 8 Mar 32
22 and 23 Mar 17
7, 8, and 13 Apr 4
1983-84 17 and 18 Nov 21
1984-85
9, 14, and 16 Dec 34
29, 30, Dec and 5 Jan
13, 17, and 19 Jan· 27
3, 8, and 9 Feb 88
21, 28 Feb, and 1 Mar 41
15 Mar 15
27 Nov
10 Dec
24 Dec
7 Jan
18 Jan
29 Jan
13 Feb
2 Mar
21 Mar
5 Apr
17 Apr
7
10
36
111
132
105
42
47
47
61
32
River zone
II III IV
16
19
5
17
25
18
4
28
46
86
94
62
44
65
62
55
30
15
14
41
43
107
50
1
8
13
75
96
82
60
43
53
50
37
147
191
134
236
166
57
60
232
292
460
345
329
251
269
260
277
130
96
103
144
159
286
325
123
96
92
107
41
89
159
412
312
206
212
190
112
127
129
290
304
403
Total
322
324
239
369
257
82
171
476
826 '
934
523
447
527
573
544
349
276
132
278
314
529
785
819
15
8
18
49
186
228
165
85
100
97
111
69
1 Zones I-IV ~ Devil Canyon to Talkeetna, Talkeetna to Montana
Creek, (Talkeetna to Sunshine Bridge in 1984-85) Montana Creek to
Yentna River and Yentna River to Cook Inlet, respectively.
- = zone not censused because of inad~quate snow cover or
inclement flying conditions and --= zone not censused that year.
153
Table 7. Winter density of moose in 4 zones along the Susitna River
floodplain between Devil Canyon and Cook Inlet, Alaska
1981-85.
1 Zone
I
.II
III
IV
1
2
3
4
Habitat area 2 (km)
Aquatic Terrestrial
No. 3 moose Survey date Density 4
28 31 132 6 Jan 1983 4
23 21 107 9 Feb 1984 5
65 104 460 21 Dec 1982 4
65 29 412 1 Nov 1982 14
Zone I-IV = Devil Canyon to Talkeetna, Talkeetna to Montana
Creek, Montana Creek to Yentna River, Yentna River to Cook
Inlet, respectively.
Area of terrestrial and aquatic habitat estimated from 1:63,360
scale USGS topographic maps.
Maximum number of moose observed in zone during study.
Density = No. moose/area terrestrial habitat.
154
Table 8. Density of moose observed in floodplain and large island
habitats on the Susitna River floodplain between Hontana
Creek and Cook Inlet, Alaska, 1981-85.
Calculated density
Habitat 1 Area S . 2
~ze 1981-82 1982-83 1983-84 1984-85
Floodplain
Kashwitna
Caswell
14.5 (5.5)
15.5 (10.5)
1.9
2.7
2.7
3.9
0.8
2.2
2.4
3.9
Large Islands
1
2
3
Beaver
Alexander
Bell
Delta
9.0
10.5
13.0
21.0
(9.0)
(10. 5)
(13.0)
(18.0)
2.4
2.8
3.2
0.8
3.0
7.6
9.2
1.3
3.6
5.1
6.6
1.0
Locations of sample areas are illustrated in Fig. 5.
3.6
4.9
8.9
1.4
Size. expressed in Km 2 re·presents surface area surveyed as
estimated from 1:63,360 scale USGS topographic maps. Number in
parentheses represents terrestrial habitat included in area
surveyed.
Densities were calculated by dividing greatest number of moose
observed in each area by its surface area.
155
Table 9. Fate for 55 female and 22 male moose captured and radio-
marked along the Susitna River floodplain downstream from
Devil Canyon, Alaska, 1980-86.
Sex
Female
Male
Fate
Transmitter shed
Alive
Dead
Winter kill
Accidents
Collision with train
Suspected drowning
Injury from slipping on ice
Hunting related
Defense of life and property
Capture related
Total
Transmitter shed
Transmitter failure
Alive
Dead
Hunting related
Killed by hunter
Suspected bullet wound
Winter kill
Accidents
Collisions with trains
Capture related
Suspected poaching
Total
156
No. moose
4
30
21
5
10
5
3
2
3
1
2
55
3
1
1
17
10
9
1
2
2
2
2
1
22
Table 10. Numbers of moose killed by trains in the Alaska Railroad
right-of-way between Seward and Fairbanks during winter
(October through April) and summer (May through September)
seasonal periods. 1963-86.
Seasonal 12eriod
Year Summer Winter Total
1.963-64 45 45
1964-65 7 37 44
1.965-66 4 34 38
1.966-67 5 49 54
1967-68 2 30 32
1968-69 2 9 11
1969-70 2 7 9
1970-71 3 149 152
1.971-72 2 87 89
1972-73 5 23 28
1973-74 2 16 18
1974-75 1 69 70
1975-76 7 30 37
1976-77 4 23 27
1977-78 9 14' 23
1978-79 2 162 16.4
1.979-80 1 52 53
1980-81 4 16 20
1981-82 9 37 46
1982-83 18 130 148
1.983-84 8 57 65
1984-85 7 375 382
1.985-86 20 15 35
157
Table 11. Annual total, monthly percent, monthly totals for four
annual periods and average period percent (average for
percents of four annual periods) of moose killed by trains
in the Alaska Railroad right-of-way between Seward and
Fairbanks, 1963-86.
Month
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Har
Apr
Total
Annual Monthly
total percent
30 2
24 2
18 1
25 2
32 2
22 1
54 3
174 11
296 19
416 26
411 26
85 5
1587 100
Annual period
Average
1970-71 1978-79 1982-83 1984-85 pe~cent
0 0 4 1 1
0 1 3 1 1
0 0 5 0 1
0 1 3 3 1
3 0 3 2 1
2 0 3 0 '1
0 1 22 1 4
14 59 22 4 15
59 37 34 40 24
55 42 32 104 28
19 14 14 201 21
0 9 3 25 4
152 164 148 382 102
158
Table 12 .. Location, number and average percent (mean of percents
for each of three winter periods) of moose killed by trains
·in the Alaska Railroad right-of-way between Seward and
Fairbanks during winter (October through April) 1978-79,
1982-83 and 1984-85.
Alaska RR Winter Eeriod Average
Milepost Hi Station 1978-79 1982-83 1984-85 percent
000-109 0 Seward 6 7 15 4
110-149 114 Anchorage 4 5 5 2
150-154 151 Matanuska 2 0 0 0
155-159 160 Wasilla 2 2 0 1
160-164 1 0 0 0
165-169 167 Pittman 4 6 5 3
170-174 2 4 7 2
175-179. 175 Houston 4 4 5 2
180-184 2 1 10 2
185-189 186 Willow 13 2 16 5
190-194 194 Kashwitna ---6 1 28 4
195-199 25 13 46 12
200-204 202 Caswell ---19 ---6 24 8
205-209 209 Montana 11 4 23 5
210-214 ---12 ---· 3 26 5
215-219 215 Sunshine 20 4 24 7
220-224 8 4 19 4
225-229 227 Talkeetna 4 4 9 2
230-234 1 2 21 3
235-239 236 Chase 1 4 8 2
240-244 1 3 23 3
245-249 249 Curry 1 1 3 1
250-254 1 6 12 3
255-259 258 Sherman 4 6 2 3
260-264 263 Gold Creek ---0 2 4 1
265-269 268 Canyon 1 2 7 2
270-274 273 Chulitna 0 ---10 0 ---3
275-279 0 0 4 0
280-284 281 Hurricane 0 0 0 0
285-289 289 Honolulu 0 1 0 0
290-294 1 0 0 0
295-314 297 Broad Pass 2 0 0 0
315-319 0 0 5 0
320-324 320 Cantwell 3 4 10 3
325-329 327 Windy 0 5 4 2
330-374 359 Healy 0 4 0 1
375-449 412 Nenana 1 8 10 3
450-470 470 Fairbanks 0 2 0 1
Total 162 130 375 99
159
Table 13.
1 Year
1970-71
1971-72
1972-73
1973-74
1974-75
1975-76
1976-77
1977-78
1978-79
1979-80
1980-81
1981-82
1982-83
1983-84
1984-85
1985-86
Numbers of moose reported killed by collisions with
vehicles on highway rights-of-way in Game Management
Subunits 14A and B, 1970-1986.
Game Management Subunit 2
14A 14B
99
109
36
33
40
34
80
79
108
29
13
72
182
94
51
24
10
7
3
6
5
6
7
5
41
15
10
15
22
39
77
5
1 Calendar dates for years are from 1 July to 30 June.
2 Numbers of moose listed as killed are numbers actually reported
to the Alaska Department of Public Safety. Many moose hit and
killed by vehicles may not be reported. Other moose may be hit
and die later undetected.
160
Table 14. Live moose (M), dead moose (D) and percent calf moose
(%C) observed in riparian areas adjacent to the Susitna
River floodplain in winter 1984-85.
Moose Creek Kroto Creek Alexander Creek 1 M %C D M %C D M %C D Date
29 Nov 1984 32 28 0 142 18 0 53 26 0
12 Dec 1984 81 25 0 254 19 o· 110 23 0
28 Dec 1984 105 30 0 177 18 0 119 12 0
11 Jan 1985 138 12 0 176 17 0 246 21 0
7 Feb 1985 147 16 0 144 12 1 201 14 2
20 Feb 1985 181 10 1 151 11 4 162 9 3
5 Mar 1985 169 8 0 90 9 4 212 12 0
9 Mar 1985 158 9 2 64 5 2 188 10 1
20 Mar 1985 117 9 3 . 37 3 1 156 8 3
28 Har 1985 70 1 13 29 2 0 142 7 6
4 Apr 1985 67 7 10 19 5 9 160 6 9
16 Apr 1985 44 7 18 12 10 6 135 8 6
1 A survey on the Yentna River floodplain from the Susitna River
to Skwentna revealed 144 live moose, 8 percent calves and 9 dead
moose.
161
Table 15. Live moose ( LM), dead moose (DM) and percent calf moose
Date
28
11
28
8
11
16
4-5
17
1
(%C) observed on large island and floodplain areas of the
Susitna River in winter 1984-85.
Location
Beaver Alexander Kashwitna Caswell
Island! Island flood:elain flood:elain
LM %C DM LM %C DM LM %C DM LM %C DM
Nov 8 0 0 4 25 0 10 30 0 7 43 0
Dec 5 0 0 5 40 0 9 22 0 12 33 0
Dec 26 27 0 22 27 0
Jan 14 7 0 16 27 0 27 26 0 33 24 0
Feb 9 0 0 43 21 0 25 20 0 42 21 0
Mar 39 18 0 51 26 0 31 10 0 31 3 1'
Apr 15 13 0 36 19 0 35 9 0 52 10 3
Apr 13 8 0 35 11 0 29 3 4 59 2 5
DM = numbers of dead moose observed on each survey;· it does not
represent an accumulative total of dead moose. Snow cover may
act to conceal or expose moose carcasses.
162
Table 16. Femur bone marrow fat content (percent fat in marrow) for
moose found dead on the study area in winter.
Moose as;e
Collection date .Cal£ Adult
10 April 1983 5.51
27 March 1985 11.0 10.5
6.9
23 April 1985 12.5 60.02
1
2
11.0 10.2
9.8 10.1
9.5 9.2
8.9 8.2
7.9
7.8
7.6
7.4
7.3
Marrow fat determined by percentage loss of water on drying
(Neiland 1970).
Marrow cavity of bone for this sample was 95-90% filled. Marrow
fat was not solid, it was a thick-pasty consistency and pink in
color.
163
Table 17. Numbers and densities for moose observed during a late
winter distribution survey conducted in the lower Susitna
-River Valley, Alaska, 25-28 March 1985.
Densiti Percent Accumulative
class SamEle unit No. total 2ercent total
(moose/mi 2 ) No. Size (mi 2 ) moose moose area moose area
13.0 -4.1 12 126 835 24 3 24 3
4.0 -2.1 39 406 1172 34 10 58 13
2.0 -0.6 83 996 1137 33 23 91 •36
0.5 -0.1 116 1479 324 9 35 100 71
o.o 103 1245 0 0 29 100 100
Total 353 4252 3440 100 100 100 1-00
1 Density class = No. moose observed in sample unit divided by
size (mi 2 ) of sample unit. Seven sample units (77 mi 2 ) in
density class 0.0 were comprised of habitat above 3,500 ft.
elevation; an ele~ation above which not considered moose habitat:
164
Table 18. Moose use (moose-days, monthly, and accumulative) of two
alpine areas in the western foothills of the Talkeetna
Mountains calculated from 8 periodic aerial surveys
conducted between 4 October and 17 April, 1985-86.
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Total
1
Accum Bald Mtn Rid~e 1 Willow Mtn
days Monthly Accum Monthly Accum
28 3401 3401 3787 3787
58 8451 11852 8234 12021
89 8060 19912 9703 21724
120 8285 28197 7468 29192
148 7700 35897 4592 33784
179 7181 43078 4396 38180
196 2079 45157 1499 39679
196 45157 39679
Approximately 28 and 30 mi 2 of habitat were surveyed on Bald Mtn
Ridge and Willow Mountain, respectively. To estimate numbers of
moose using an area during intervals betwee·n consecutive surveys,
the mid point between surveys was determined and numbers observed
on, respective, previous and subsequent surveys were assumed to
occupy areas prior to and after that date.
165
Table 19. Moose use (monthly and accumulative monthly moose-days) of
riparian areas adjacent to the Susitna River calculated
from periodic aerial surveys conducted between 29 November
and 16 April, 1984-85.
Month
Nov
Dec
Jan
Feb
Mar
Apr
Accum
days
3
34
65
93
124
140
Alexander Creek1
Monthly Accum
106 106
3590 3696.
6930 10626
5143 15769
5335 21104
2398 23502
Kroto Creek
Monthly Accum
284 284
6390 6674
4707 11381
4015 15396
1635 17031
259 17290
Moose Creek
Monthly Accum
64
2554
4242
4602
3921
923
64
2618
6860
11462
15383
16306
140 23502 17290 Total 16306
1 Approximately, 20, 50 and 25 miles of river drainage were
surveyed on Alexander, Kroto and Moose Creeks, respectively. To
estimate numbers of moose using an area during intervals between
consecutive surveys, the mid point between surveys was determined
and numbers of moose observed on, respective, previous and
subsequent surveys were assumed to occupy areas prior to and
after that date.
166
Table 20. Moose use (monthly and accumulative total moose-days) of
areas adjacent to and on the Susitna River floodplain
calculated from periodic aerial surveys in winter,
1981-1985.
Date
1981-82
Dec
Jan
Feb
Mar
Apr
1982-83
Oct
Nov
Dec
Jan
Feb
Mar
Apr
1983-84
Nov
Dec
Jan
Feb
Mar
1984-85
Nov
Dec
Jan
Feb
Mar
Apr
1 Bell Island Montana West
Accum
days
20
51
79
100
3
33
64
95
123
130
18
51
72
3
34
65
91
122
139
Moose use Accum
Month Accum days
1553
1040
908
495
27
1826
3552
2104
1120
245
277
1491
1346
42
1258
2803
3220
2560
859
1553
2593
3501
3996
27
1853
5405
7·509
8629
8874
277
1768
3114
42
1300
4103
7323
9883
10742
30
61
89
120
132
3
33
64
95
123
154
162
14
45
56
85
114
3
34
65
93
124
140
Moose use
Month Accum
704 704
772 14 76
6 72 2148
402 25~0
52 2602
39
1498
1408
1129
1259
919
16
305
1485
1269
1330
307
200
1339
1321
911
744
192
39
1537
2945
4074
5333
6252
6268
305
1790
3059
4389
4696
200
1539
2860
3771
4515
4707
Montana Middle
Accum Moose use
days Month Accum
25
56
87
ll5
146
153
14
45
76
105
134
4
35
66
94
125
141
275
1328
965
309
1002
42
60
133
556
897
1045
0
95
732
1105
1068
690
27 5
1603
2568
2877
3879
3921
60
193
749
1646
2691
0
95
827
1932
3000
3690
1 Approximately 5, 1, and 0.8 mi 2 of habitat were surveyed surveyed
on Bell Island, Montana West, and Montana Middle areas,
respectively. To estimate numbers of moose using an area during
intervals between consecutive surveys, the mid point between
surveys was determined and numbers observed on, respective,
previous and subsequent surveys were assumed to occupy areas
prior to and after that date.
167
Table 21. Estimates of annual range size for moose subpopulations
identified to utilize habitat on the Susitna River
floodplain.
Subpopulation
1 -Devil Canyon-Talkeetna
2 -Chunilna Creek
3 -Lower Talkeetna River-Sheep River
4 -Montana Creek-Sheep Creek-Kashwitna River
5 -Willow Mountain-Bald Mountain Ridge
6 -Little Susi'tna River
7 -Little Susitna River Flats-Susitna River
8 Beluga River-Susinta River
9 -Mount Susitna-Little Mt. Susitna
10 -Big Island-Bell Island (floodplain)
11 Kroto Creek-Moose Creek
12 -Delta Islands-Caswell Islands (floodplain)
13 -Little Peters Hills-Petersville
14 -Remainder of Susitna River floodplain
168
Annual range
size (sq mi)
360
400
800
600
650
500
100
so
650
80
700
100
350
0 si==o:i..lllli:::==::IOii--=~zc•
NOimt
-tJ
A Bla· leland
0
"'
a Bell leland ~.o:§ C Mount Sualtna _
D Little Mount Sualtna
E Lower Beluga Lake tJ\'>Jf..P.)/--....,. _
F Beluga Mountain r Y , y ~ Gf{.
G Y en I o HIU a ~~ -:;..--' ; ~ ~r.G~
H Amber Lake ~"'"<. j /l q,~
1 Trapper Lake G'f. ~~ ,' T L---__
J Delta Iaiande, _..,. l. IV£ R
K A•dahlrt Lake ~~ • R
L Devil Canyon ~ .' M
Dant Site \,..
~Gold Creelc ,..--~·
~.$'... } ~~ I i
\ p.l¢1 (
\ \\ ;.(
41 (
-9o •t:~
COOK INLET
Figure 1. Map ehowlno location of the atudy area In Alaalca with 11amea llated tor
rl'lera. lakea and other prominent landacape teaturaa.
169
t
NORTH
K m.
50
~iiiiiiiiiil!!!!!!liiiiiiiiil!!!!!!liiiiiiiiiil!!!!!!!liiiiiiiiil!!!!!iiiiiiiiii
Scale 1:Q15000
0
Fig. 2. Location of riparian areaa and aubsectlons of the Susltna River floodplain
(J:-B:)where moose surveys were conducted (A=Aiexander Creek, B=Yentna R1ver,
C=Kroto Creek and D=Moose Creek).
170
0 I
10
NORTH
I
0
l
~0 lull
VEGETATIVE TYPES
1. Moist alpine tundra/
riparian complex
2. Open spruce/birch
fore at
3. Open, low growln~
spruce forest
""· Mixed seral complex
5. Closed spruce/birch
complex
e. Wet, moderately open
spruce/birch forest
7. Dry alpine tundra
8. Wet tundra
Fig. 3. Idealized habitat map showing the distribution of vegetative types which occur
In the Sualtna River watershed between Devita Canyon and Cook Inlet.
171
·~
168 ~
WEATHER STATIONS·
® Chulitna River Lodge
tl) Suattna rnoadowa
C ChuUtna highway cantil
C Bald Mountain Lake
~ Caawoll
~ Wblto'a Croaalng
G Willow alratrlll
® Gooao Bay
.,
I
\
I
L / '·_r-
Fig. 4. Mall of study aroa ahowlng locatlona of GaMo ManagoMoftt Sullut~lta (1aE. 14A.
148. 18A af!d 188). at a to and Htlonal parka · aa~ weatllor stations (A~).
172
',
\ •
----··
L
(
\
'--
' ..
' ____ ... _ ------.
__ ,..·
/
/
------
... .... __
/ ----.....
--------·
. ...,.... .... __ -...... -
. ___ _
.. ----
--:::::--..
Fl g u r e 5. LocatIon of f I o o d pI a In and I s Ian de d a r e as a Ion g the
Susltna River, Alaska, where densities and calf composition
were determined for wintering moose, 1981-83.
(A= Caswell floodplain, B = Kashwltna floodplain, C =Delta Island,
D =Bell Island, E =Alexander Island, F = Beaver Island)
173
( -r ,..
Figure 6. Location of sites adjacent to the Susitna River, Alaska, where climax
vegetation has been altered by man and numbers of moose were counted periodically
during the winter, 1981-84. (A= Talkeetna West, B =Montana West, C = Montana East,
D = Montana North, E =Montana Middle, F = Montana South, G =Goose Creek, H = Chandalar
East and West, I = Kashwitna Bluff, J = Kashwitna Lake, K = Kashwitna East and l = Willow Creek)
174
NORTH
Scale 1:915000
0
'Flg. 7. Location of alpine areas where moose use (moose days) was calculated for winter
1985-88. (A =Bald Mountain Ridge and 8 =Willow Mountain).
175
NORTH
1: 1000000
0 50 Km.
Fig. s. Areaa aurveyed for mooae dlatrlbutlon and anowpack depth In the lower
Sualtna River valley, March 1985. ( ) Snowpack depth, ( D> Moose
dlatrlbutlon.
176
NORTH
Scale 1:815000
0 -------_ __.. __ _
cooK INLET
Fig. 9. Locations where mooae were captured and radl~marked In 5 different annual samples.
(.=April 1980, e = March 1981, A= February 1982, 0 = February 1984, and
C =February 1985),
177
I
100
50
.. ·~ ~~ ~ .. .~t
.. ~· ~~:e ~~ ~ ' i( ~ ~~~ ' .!:: ~ -:~ R l~t
"'"
1984 85
0 I I l I I
100 ..
50 .. ~ 1983 84
w en
0
0 0
~
~ ~
ll4X
I I -. I I I I I
LL 100 0 ...
a: w
m 50
:::!
::l z
0
~-~ .. ~·~
~~
I I I I
1982 83
100 ...
1981 82
50 -
0
~~ ~ ~
EARLY' LATE IEARLY' LATE EARLY LATI=,IEAALYTLATE IEARLYI LATE IEARLYI LATE IEAALY' LATE
OCTOBER NOVEM8ER DECEM8ER JANUARY FEBRUARY MARCH APRIL
Fig. 10. Numbers of moose observed during periodic censuses of floodplain habitat between Devil Canyon
and Talkeetna (Zone 1 ), Alaska, 1981 85.
z
0 co en ,-....
< .-i
w en
a: w .... z
~
-----....../:
--'-.;' ------/
Fig. 11. Ann••• ••rlatlon In cll•trlbutlon of !Woo•• ratlllo-•arkod on tho •••Jtna
Rl••r flootllplaln tll•rl•t Doco~~tltor In 1ee1-e2, 1eez-ea, 1eea-e4, anc:l 1•••-ee.
179
t
NORTH
\.-.
'·
'·
. -"
I
1..
JAN
...,_
}
' \
I
I
' -
-~
I
' '
(
'
.,
_.
I •
.,.-,-
/~~ ..
I 't
'I
.---.
•
FEB
Fig. 12. Late winter dhtrlbutlon of moo•• radio-marked alont the 8ualtn• River floodplain
and relocated from 1980-86.
_1._. ___
0
00
.-;
.. _ ........ -...
NORTH
. -,
'-
Scale 1:887000
0
K m ; ..
50
1!!5ii~~!!5iiiiiiiii!!!!!!!5iiiiiiiiil!!!!!5iiiiiiiil
/ ---
Fig. 13. Poly;on encompassing 3852 relocation points tor 51 female and
18 male mooae captured and radio-marked along the Suaitna River
floodplain b•tween Devil Canyon and Cook Inlet, Alaska, 1980-85.
( 1 n c: 1 u sl v • a" • a = 8938 S Qua r • K II om • t e r s).
181
S c a I e
0
t
NORTH
1:887000
·-
I
)
'·.l
1..,
----··
(..:---.. ----
/
.· .
T T
+
Fig. 1•. Relocation points (3852) for 51 female moose radio-marked
along the Sualtna River floodplain between Devil Canyon and Cook
Inlet, Alaska, 1980-1985.
182
t
NORTH
'-,
Scale 1:887000
0
+
+. ...
'--....,
)
K m.
50
'--
:: ~ +
\, ' --~·
~·
·--_ _.1_,_ -------
-----
Fig. 15. Relocation point• (148) tor 18 Male 11t001e radlo-lftarked
along the Sualtna River floodplain between Devil Canyon and
Cook Inlet, Alaaka, 1980-85.
183
Scale
0
1
NORTH
1:887000
-----
'-
K m.
50 ------
+ +
+~..,. •
*
-----.. __ ,r,.. J ..., . ~ -,
v
',
+<
·.·,
p·--~·
-~
--___ L --
"" f ~ .. ·
~-,
I /
;'t
~',
I ":,
* ... .
+
+.
J' ,. .• -,-!'_
·'
r-....
\ '
+
.. ::
Fig. 1e. Locations where female moose radio-marked on the Susltna River
floodplain In winter were relocated durlnt the calving p.erlod (May-June).
184
Scale
0
t
NORTH
' '
1:887000
+
·-
+
'-. ·--
45 K m.
. ~ ,'-.
~+-.. ,,. -.· ....
\i .... -·:..:...-
,'-~·~· ... ' ' . __ -_ ...
,. .. -.. ~-
,/-,---
_,/'·-·
--;:'
/.. _,..
+
\
~----... _____ :;:..._:.._.-~------
~ ......
_...; (
-----~-...
··-:·-.
Fla. 17. Locations where male moo•• radio-marked along the Susltna River
floodplain were relocated during September (open hunting season).
1181 -15.
185
t
NORTH
'-,
S c a I e
0
1:887000
+
+ ... +
---
'-.
-
+ +
+ * +
"' '"'•
_,-, -\
-----......
"
·,
I -_.;
'.
+*~
+ •. . ~ .... _-'!' r.
'~~-~
.,,
'~ "' ... +
" . ~
,'\ .. :;'\
-~-~·,t:\.
: +' + / +• ' .... ';. .... +;'( ..
i·
)
\~
\.·
~
' (
(
~ \ ( ~--~----....._:::.__..._,~-,
--.
~.,k; .-·--.---~, ---J•;e Talkeetna
-)-
{7 ' '
+ .t±... ""+ __ ,-F: ----+ .-' -~ ---+---------
.... .• I
....... -
\
+ w ...
.... -.'
'114:++
-~---~~~~ ..
_____ .r----
;
•" +
\. _ .... -'=':..-_ . ..--..,
Fig. 18. Location• where male and female moose radio-marked on the Susltna
River floodplain In winter were relocated during the aummer period
(July-15 August), 1980-85.
186
25-
20-
10-
5-
10-
20-
25-
30-
20
COOK INLET TO TALKEETNA
No. moote providing data 58
No. moote Involved In cro11lngt 40
No. crot•lngt 187
TALKEETNA TO DEVILS CANYON
No. moose providing data 14
No. moose Involved In crossings 10
No. cro1slnga 68
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT teN 1EC
Flg.19. Frequency and 118880nal timing of Sulltna River crossings by moose radl~marked In 2 areas
between Owll Canyon and Cook Inlet and relocated between 1980-65. (Numbers-percent of observations
In respective area category).
187
Scale 1:915000
0
t
NORTH
73
r v· T a I k e e t n a
\ 26
50 Km.
,J
(
Fig. 20. Spatial relationship of radio-marked moose annual ranges with the Susitna
River floodplain.
188
Scale 1:915000
0
t
NORTH
59
/
42 --
68¥
/
!'
I
I
100
Fig. 21. Spatial relationship of radio-marked moose annual ranges with the Susltna
River floodplain <-=male moose).
189
t
NORTH
Scale 1:915000
0 50
f)• Talkeetna
,J 711
FIg. 2 2 • Spa tlal r • Ia t1 o n a h I p o f r a d I o-m a r k • d m o o 1 • a n n u a I r a n g e a w I t h t h e S u s I t n a
R 1v • r floodplain (underline= male moose).
190
t
NORTH
Scale 1:915000
0 50 Km.
FIQ.23. Polygona enclosing relocation points for radio-marked moose which exhibited
groaaly different pa t_terna of aeaaonal range uae.
191
~ ····..,;;
t
NORTH
Flg.24. Variation In spatial relationships of seasonal ranges for moose radio-marked
on the Susltna River floodplain (undernne=male moose).
192
. .... . . . · ... .-. ,, . '. ·. ; ~ . . ..
t
NORTH
Scale 1:915000
0
93
22
5.0
F I 0 • 2 5. P o I y o o n a • n c I o 1 I n g r • I o c a t I on p o I n t a f o r r a d I o-m a r k • d m o o s e w h I c h r a n g e d
over relatively large areas (underline =male moose).
193
NORTH
Scale 1:V15000
0 --·---------
Fig. 2e. Polygon• encompasalng annual rangea for radio-marked moose which
exhibited relatively little •between year• variation In movement patterns.
<·-·-·> 1980-81, (-) 1981-82, (--} 1982-83, (----) 1983-8<4, <······> 1984-85.
..
NORTH
Scale 1:916000
0 ---------_. --·--
Cook In I et
Fig. 27. Polygons encompa •sing annual ranges for radio-marked moose which
exlhlblted noteworthy •between year• variation In movement patterna.B-·-·-) 1980-81,
<-> 1981-82, (-) 1982-83, (----) 1983-1-4, ( ...... ) 198-4-86 (underline=male moose)]
195
t
NORTH
Scale 1:915000
0
----~,-------------------------------------------------------.. Fig. 28. Polygona enclosing relocation polnta for radio-marked moose w hlch ex hlbited
an •erratic• movement (underline =male moose).
196
•
ProxlmltJ to
floodplain (ml)
IIJOnd 15
mile.
5-11 mllll
S-5 mllea
0-3 miles
On floodplain
Month
No. oba.
No. mooae
DOWNSTREAM JI'EMAL!I
Peroe11t et ••••"''
ob1ervatleft1
100
71
so
25
0
J F M A .. J J A s 0 N D
1.7 188 211 351 .10 311 127 213 208 151 107 175
•• 103 12. 122 121 121 70 •• 88 90
Fit~. 29. Monthly variation In proximity to the Sualtna River floodplain for
f•n,ale moos• radio-marked In winter aloni the floodplain between Talkeetna
and Cook Inlet and rllocated periodically from AprH 1980 through July 1985.
(No. mooae aummed over years)
197
Proximity te
floodplala (MI)
Beyond 15
IIIII•.
0-3 miles--
On floodplain
Month
No. of obe.
J F
41 53
DOWNSTREAM MALES
Percent ef •o•tttlr
eltaerwatleaa
75
50
25
0
M A W J J A S 0 N D
1s 104 aa ta 48 7t et 41 38 38
No. moose 2 1 29 34 34 32 33 23 21J 28 22 22 22
FIg. 30. Month I y varIatIon In proxImIty to the S u al t n a RIver f I o o d pI a In tor
male moose radio-marked on the floodplain between Talkeetna and Cook
I n I e t a n d r e I o c a t e d p e r I o d I c a I I y f r o m A p r I I 1 t 8 0 t .h r o u g h J u I y 1 9 8 5 • ( N o .
m o o a • 1 u m m e d o v • r y • a r a·).
198
-.
"
UPSTREAM MALES AND FEMALES
Proximity to
llloodplaln (ml)
1-3 miles-
0-1 mile---
On floodplain
Month
No. of o b a.
No. m ooae
J
85
40
F M A M
75 1oe 12e 134
37 47 43 43
Fig. 31. Monthly variation In proximity to
m 111• and female moo•• radio-marked In
J J A
138 50 ao
42 23 32
the Sualtna
winter along
Percent of monthly
obaervatlona
75
50
25
0
s 0 N D
91 48 52 64
32 3 1 31 31
RIver floodplain for
the floodplain between
Talkeetna and Devils Canyon and relocated periodically from April 1980
through July 1985. (No. moose summed 011er years).
199
....
f
NOATH
238.0-}
11
~.~_,;;,;_;,~.;..;;...---225.0-
2a
14
Total 118
WINTER PERIOO
1178-71 1182-U 1184-&1
I 34 13
• I
sa 33 151
25 5 eo
13 22
141 92 325
Fig. 32. Dlatrlbutlon and number of mooae killed by tralna In the Alaska Railroad CARR)
right-of-way between mllepoat 180.0 (near Waallla) and 278.0 (near Chulitna Pass) during winter
(October-April) 1978-78, 1982-83 and 1984-65.
200
" t
NORTH
Scale 1:915000
0
K 111.
so
C 0 0 K I N L E T
Fl;. 33. Locations of moose carcasses observed during aerial surveys In
winter 1981-82 (Susltna Rlver=S).
201
t
NORTH
Scale 1:815000
0 ----------
C 0 0 K
Fig. 34. Locations of mooae care••••• obaerved during aerial surveys In
winter 1982-83 (Sualtna Rlver=31).
/.02
t
NORTH
Scale 1:915000
0
I
K m. ,JO
C 0 0 K I N L E T
Fig. 35. Location• of moose carcasaea observed during aerial surveys in winter
1983-84 (Kroto Creek=13, Moose Creek=O, Sualtna Rlver=8).
203
t
NORTH
Scale 1:915000
0
K m.
50
C 0 0 K I N L E T
Fig, 38. locatlona of mooae carcaaaea observed during aerial surveys conducted
In winter 1984-85 (Alexander Creek=17, Yentna Rlver=9. Kroto Creek=18,
M o o a • C r • e k = 3 1 , S u al t n a R I v e r =50) •
?04
... 1 , ... er It:,-
I
NORTH
gcale 1:1000000
F1g. 3 7. Locations of . I onoo lhat one .
or mitigation with m ompass lands with . •..•. . .......... . and/or replac ement potential
t
NORTH
.,2 ~~~ -
~ /10
JS:J. -I'H /00
1'1
J-0 ~10
160 /6S
IYS
l./2.
~2.5 !55
Scale 1:V15000
0
IS 111 /'IS L-
!J.I.
!.1i :Z.0'-
11.!
50 Km.
15'
Fig. 38. Snow depth (em.) meaaurement• recorded" In lower Suiltna River valley,
Mar.ch, 1985.
'206
~·-.' . ~ .
22-
20-
11-
.,
z 18-
0
... 14-
o(
>
a: 12-
w
Gf)
Ill
0 10-
~
0 1-
.
0
z e-
4-
2-
I
20 40 eo 140 180 180 200 240
S N 0 W D E P T H
F 1 g • 3 9. H I • t c 0 r a m o f a n o w d • P t h m • a • u r • m • n t a ( c m , ::!!: t a b I • I n t e r v a I ) r e c o r d e d
In lower Sualtna River valley, 24-27 March 1985 (n = 138).
207
RELAVANCE TO MOOSE (dept", percent • In oatetory)
--
>
()
z
IU
~
0
w
a: ...
IU
>
~
c _,
~
100-
eo-
eo-
40-
2 20-
~
<J.
()
c
o-
Mowe~~tonta unaltoc,tod ( 50 ••· 4'1)
Mowenunta IMpeded (10-70 c•. 4~)
Movement• aevorely reatrlctod, critical for
calvea, cheat "eight 71 c• (70-10 eM, 7'1)
Critical for adulta, cheat hol_ght
Mortality Inevitable
( 100 Cfll, IO'AI)
20 40 80 80 100 180
S N 0 W 0 E P T H
240
F I g. 40. A c c u m u I a t I v e f r e q u e n c y d I • t rIb u t I o n f o r • n o w de p t h m e a s u r e m e n t s
(em. ~table Interval) recorded In lower Sualtna AIYer 'lAIIey,
24-27 March 1885 (n= 138).
208
..
t
NORTH
Scale 1:i15000
0
C 0 0 K
Flg. 41. Geographical areaa In the lower Sualtna River valley where snow depths of
llllllii 70 em. (A),=-70 ~ 100 cm.(B),=-100:=::120cm.(C),=-120::=!i1SIS cm.(O) or =-155 ~212 cm.(E)
were recorded on 24-28 March 1986.
209
NORTH
Scale 1:815000
0
C 0 0 K I N L E T
Fig. 42. Location of eagle neat a In the lower Sualtna River valley.
210
1
NORTH
Scale 1;915000
0
Fig. _.3. Delineation of annual ranges for 13 hypothetical moose
a u b p o p u I a t I o n 1 I d e n t I f I e d t o. u a e t h e S u 1 I t n a R I v e r f I o o d P I a i n . { S h a d e d
a r • a a I n d I c a t e r a n g e u t I I I z • d b y m o r e t h a n o n e a u b p o p u I a t I o n ).
211