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MOOSE MOVEMENTS AND HABITAT USE ALONG THE SUSITNA RIVER NEAR DEVIL'S CANYON
KENTON P. TAYLOR, Alaska Department of Fish and Game, Talkeetna, Alaska 99676
WARREN B. BALLARD, Alaska Department of Fish and Game, Glennallen, Alaska 99588
Abstract: From October 1976 through January 1979 a moose movements
and population study was conducted along the Susitna River in
southcentral Alaska to aid in assessing the potential impacts of
hydroelectric power development on moose (AZ.ees aZees gigas).
Twenty-two radio collars and 21 visual collars were placed on adult
cow moose during the study. Radio-collared moose were located on
467 occasions while visual-collared moose were observed 43 times.
Annual home ranges of moose are calculated and compared between
drainages and to those from other studies in North America.
Movement patterns, fidelity to summer and winter ranges and habitat
utilization are discussed. Areas of hiqh moose concentration are
identified. 'Pro9osed hydro-electric developments are described and
their potential impacts on moose are considered.
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The merits of utilizing the Susitna River to provide Anchorage and
Fairbanks, Alaska with hydro-electric power,. have been.the-subj.ect of:(&•
number of feasability studies since 1948.· Proposals have "riwged from a
two to twelve dam system. Most recently, the Devil's Canyon-Watana
Creek two dam system was selected by the U.S. Army Corps of Engineers as
the most viable of several alternatives.
The Susitna River drainage, located south of the Alaska Mountain
Range in south-central Alaska, has long been recognized as an extremely
rugged wilderness area of high esthetic appeal and as an important
habitat area to a variety of wildlife species (Ak. Dept. Fish & Game,
unpubl. data). Large numbers of moose (Alaes alaes) and caribou (Rangifer
t~ndus) have historically inhabited the Susitna River Basin. The
recent upsurge of interest in providing hydro-electric power by damming
the Susitna River has focused attention on the potential impact of this
action on wildlife. Although many species of animals could potentially
be influenced, studies to date have focused on ungulate populations,
primarily moose. The purpose of this report is to present our findings
on moose movements and habitat use in and adjacent to the proposed
impoundment areas and to discuss the potential impacts of the hydro-
electric projects.
DESCRIPTION OF PROPOSED HYDROELECTRIC PROJECTS
The Devil' s Canyon-Watana Creek two dam system would theoretically
provide 6.1 billion kilowatt hours of electrical power annually from a
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dependable capacity of 1,568 megawatts {Ak. Dist. Army Corps Engineers
1975). The Devi1's Canyon dam would be a concrete structure 193m high,
while the Watana dam would be a rock fill impoundment rising 247m above
the river bottom. A 103 km road from Chulitna to the Watana site,
including a 198 m bridge across the Susitna would be constructed for
transporting materials and personnel to the dam sites. 586 km of
transmission line corridors, 57-64 m wide, would be cut across the
mountains between Anchorage and Fairbanks. Warehouses, vehicle storage
buildings and permanent living quarters would be erected at the dam
sites. The total projected cost. of completing this project is 2.6
billion dollars (Ak. Dist. ArmY Corps Eng. 1977). The estimated annual
cost of operation for 100 years following compi'etion is 104 mill ion
dollars. Construction and maintenance of this system would constitute
the largest hydro-power project in North America (Gravel 1977).
Construction of both proposed dams would inundate 20,700 hectares
of the river valley, 132 km upstream to a point between the Tyone and
Oshetna Rivers (U.S. Fish and Wildl. Serv. 1975). Water levels of the
Devil's Canyon reservoir are expected to rc~ain almost constant, but may
fluctuate up to 55 m (op. cit.). The Watana reservoir is projected to
have seasonal fluctuations up to 78 m. Downstream flow is expected to
be maintained at a relatively constant rate between 230 and 280 cubic
meters per second (ems) eliminating the flooding action that presently
occurs each spring when downstream flows may be as high as 2,550 ems (Ak.
Dist. ArmY Corps Eng. 1975).
172
STUDY AREA
Moose were studied in that portion of the Susitna River Basin lying
between latitudes 60°30'-63°15' north and longitudes 146°30'-149° west
(Fig. 1). The landscape is primarily mountainous and ranges in elevation
from 300 to 1900 m. Semi-arid conditions dominate this area of the
basin. Temperatures are generally cool in the summer and overcast days
are common. Snowfall is usually moderate and ground accumulation seldom
exceeds one meter (U.S. Soil Cons. Ser. 1976-78). Prevailing winds are
--~ -
from the east and north. Strong winds along the river are common
during any season.
Along the banks of the Susitna and its tributaries from the Maclaren
River to Devil Creek the dominant vegetative cover type is black spruce
(Piaea mariana) interspersed with muskeg bogs on the basin floor.
Occasional stands of cottonwood (PopuZus triahoaarpa) are found on
islands in the river. Understory vegetation in spruce forests includes
highbush cranberry (Vibernum eduZe), devil's club (Eahinopanax horridum),
blueberry (Vaaainium spp.), lowbush cranberry (Vaaainium vitis) and several
representatives of the rose and. grass families. Hardwoods such as aspen
(PopuZus t:r>emuZoides) and bit·ch (BetuZa papyPifezoa) are often found
interspersed among the spruce, predominantly on south-facing slopes.
White spruce (Piaea gZauaa) replaces the smaller stunted black spruce on
better drained soils. The forest understory above 800 m contains blueberry,
lowbush cranberry, Labrador Tea (Ledum spp.), fireweed (EpiZobium spp.),
crowberry (Empet:r>um nigrum) and several mosses and lichens.
0 30 km
MOOSE TS AREA
Figure 1. Devil's Canyon proposed hydroelectric project moose movement study area.
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Alder (Alnus spp.) is the predominant woody plant between timberline
and alpine tundra particularly along the headwaters of s:tlreams. Willow• ~
(salix spp.) exists throughout the study area but occurs most frequently
at timberline and riparian sites. Alpine tundra extends above the alder
zone to about 1200 m.
METHODS
A totai of 43 moose were captured during October 1976, March 1977,
and August 1978 along the Susitna River from its confluence with the
Maclaren River downstream to Devil Creek. They were darted with 23 to
29 mg of succinylcholine chloride from a Bell 206B Jet Ranger helicopter
employing standard techniques in use throughout Alaska {Franzmann et a1.
1974). All captured moose were marked with plastic flagging affixed
with metal ear tags. Twenty-two moose were fitted with radio collars
manufactured by AVM Instrument Company (Champaign, Illinois). Numbered
canvas collars were placed on 21 moose. Small {presumably yearling)
moose were generally avoided during the coilaring operation.
A first incisor was taken from the lower jaw of each moose for age
determination (Sergeant1!nCI Pimlott 1959). Blood and hair samples were
also taken to aid in assessing physiological condition using methods
described by Franzmann et al. (1975). Total body length and girth
measurements were taken when time permitted and general physical condition
was assessed according to criteria developed by Franzmann.:aru!Arneson
{1973). Cows captured in March were rectally palpated to determine
175
pregnancy (Greer and -Hawkins 1967). Results of pregnancy tests and
physical condition assessments were reported in Ballard and Taylor
(1978).
Radio tracking flights were made at least once a month 1n either a
Piper PA-18 Supercub or a Stol Cessna 180 equipped with two directional
Vagi antennas connnected to a portable receiver manufactured by AVM
Instrument Company. Tracking methods were similar to those described by
Mech (1974). During and for six weeks following parturition, flights
were increased to approximately every 3 to 5 days to assess productivity
and survival of calves. Radio locations, vegetation type and miscellaneous
notes were recorded for each observation. Locations were mapped on U.S.
Geological Survey topographical maps (scale 1:250,000). Range sizes
were computed by including the total area within the outermost observation
points for a given moose. Dominant vegetation at each moose observation
was classified in one of nine groups: open spruce (trees with average
space of 6 or more meters apart}, medium spruce (trees with average
space 3-5 meters apart), dense spruce (trees less than 3 meters apart},
spruce/hardwood (spruce mixed with aspen, ~irch -or cottonwood), alder,
alpine tundra, upland willow, riparian willow and marsh.
RESULTS
Four hundred sixty-seven observations of radio-collared moose were
recorded during this study. Visual collars were observed on 43 occasions.
Movement behavior ranged from sedentary to migrations in excess of 150 km.
176
Some individual radio-collared animals ranged as far as 70 km north,
150 km east and 100 km south of the. capture locations. Little migratory
behavior was noted in the western portion of the study area. · Extensive
seasonal migrations were most evident in those moose radio-collared east
of Jay Creek (Figure 2). Long migrations from. summer range along the
Maclaren River and Clearwater Creek to wintering areas near the mouth of
the Oshetna River· and along the Tyone River were repeated annually, Some
interchange from Butte Creek to Watana Creek and from Jay Creek to Coal
Creek was also evident. Migrations from lower Butte Creek to the mouth
of the Tyone River occurred during two of the three winters of this study
when snow depths were greatest (U.S. Soil Cons. Service 1976-lg78).
Radio-collared moose crossed the Susitna River a minimum of 27 times, 20 (74%)
of which were in the vicinity of the proposed impoundment areas. Eleven
(50%) crossed the river at least once. No moose were actually observed
crossing the river during radio monitoring flights, but it could be
inferred from the data that most crossings took place downstream from
the mouth of Fog Creek and upstream from the mouth of Jay Creek. Most
river crossings were associated with seasonal migratory movements. Once
moose reached their destinations they tended to remain there throughout
the season and did not wander back and forth across the river. During
the winter, however, numerous tracks along and across the river were recorded,
indicating that moose wintering along the riverbanks nioved freely back and
forth as long as the river remained frozen.
Total ranges occupied by radio-collared moose varied from 43 km2 to
1104 km2 in size (Table 1). Most were substantially larger than those
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Tablel. Number of observations, range sizes, distance between summer and winter ranges and minimum
number of river crossings of radio-c ollared moose along the Susitna River.
Sumner (1978) Total Distance Between Minimum No.
Moose rlumber of Range 2Size Range 2Size Summer and Winter River
Number Observations tkm l (km l Ranges (km) Crossings
1 24 13 43 None 0
2 25 26 113 11 5
3 22 14 88 None 1
4 2
5 1
6 6 47 0
7 7 63 0
8 28 16 277 None 2
9 23 69 None 0
10 15 90 None 1***
11 22 92 None 0
12 26 10 74 None 2
13 25 40 66 None 0 ....,
14 4 0 00
15 5 119 172* 0
16 42 29 188 None 0
17·' 27 29 76**· None 1
18 23 319 602 24 4
19 40 29 727 40 4
20 42 55 698 52 2
21 28 16 1104 90 2
22 ..1Q. ...._g 1030 .....iL .J.
TOTAL X=55.7 x=295.7 27
* Small sample size of observations
** Atypical emigration of approximately 170 km during fall not included in computation
*** Moose observed on island
179
found by Didrickson and Taylor (unpublished data) in the Peters Hills,
approximately 80 km southwest of the Susitna study area. Substantially-
smaller ranges were occupied in the rugged terrain between Devil's
Canyon and Jay Creek than to the east where the terrain becomes more
open and level. All sedentary radio-collared moose inhabited the area
west of Jay Creek.
Summer range sizes varied .from 10 km2 to 319 km2 in 1978. These ranges
_were substantially larger than those found by LeResche (1974) _who
concluded that home range seldom exceeds 5-10 km2 during a given season.
Fidelity to summer range was greater than to winter range. Of 14 radio-
collared moose alive through 1978, 10 utilized the same ranges during
summer 1978 as they inhabited .in summer·l977. Six of the 14 utilized
the same winter range in both years. Aithough the number of winter
observations in any given year was insufficient to-accurately determine
winter range sizes, moose appeared to be much less mobile during the
winter months. They were generally found in spruce dominated habitats
and at lower elevations than in the-summer. Two radio-collared moose in
the Watana Creek drainage, however, habitually wintered above timberline
along the south-facing windblown slopes in willow/alder habitat.
Habitat types utilized by collared moose were noted during radio
tracking flights and observations were categorized into 9 groups (Table 2).
Most (70%) .collared moose observations were made in spruce dominated
habitats, usually in spruce of low to moderate density, interspersed
with willows or scrub birch. Fifteen of 20 calves born to radio-collarea
cows were first observed in spruce dominated habitats; three were found
180
in the willow/alder community and two were first noted in marsh areas.
Willow/alder habitats at and above timberline Were utilized mostly
during the rut. Moose remained in these locations until late in the
fall when snow depths approached one meter, at which time they migrated
to their wintering areas.
The seasonal distribution and relative abundance of moose in_ the
study area was determined during radio monitoring flights by recording
unmarked moose observed in association with radio-collared moose, groups
of moose seen incidentallY and areas showing signs of extensive utilization
by moose. Highest densities were noted throughout the year between
Watana and Jay Creeks at elevations from 650 m to 850 m (Figure 2). A
major portion of this habitat lies within the area that would be flooded
by the proposed Watana reservoir. Winter concentrations of moose were
observed along the lower Tyone River west to the mouth of Goose Creek
and along the hillsides from Fog Creek to Stephan lake. Concentrations
were observed on the south side of the Maclaren River during spring and
summer and along the Susitna River from the mouth of Coal Creek to the
mouth of the Oshetna River during the breeding season. Few moose were
noted during any season on the north side of the river between Devil
Creek and Deadman Creek.
DISCUSSION AND. CONCLUSIONS
Hydroelectric development along the Susitna River would impact both
resident and transient moose populations. Analysis of the telemetry
Table 2. Habitat utilization by radio~collared moose along the Susitna River in the Devils'
study area. · ·
Canyon
Total
Moose Habitat Open Medium Dense Spruce{. Alpine Upland Riparian
Number Observations Sj!ruce Sj!ruce Sj!ruce Hardwood Tundra Alder Willow Willow Marsh
1 22 3 9 6 2
2 23 7 10 2 2
3 19 6 10 1
4 2 1
5 1
6 7 3 2
7 7 4 1 2
8 21 3 2 6 6 2
9 11 1 1 5 2 2
10 14 6 2 2 2 2
11 17 8 7 1
12 23 6 7 4 5
13 25 6 12 1 2 2
14 4 3 1 ~ 15 5 1 1 1
16 27 7 5 9 5
17 21 12 2 2 2 2
18 22 5 5 3 2 6
19 28 6 11 9 1
20 30 6 8 7 2 2 4
21 23 6 9 6 1 1
22 24 5 6 4 4 4
376 TOf Ti4 51 TI 7 22 % 'i9 3
Percent of Total 27 30 14 3 2 6 12 5
* Spruce categories include both white spruce and black spruce.
** Hardwood category includes birch, aspen and cottonwood.
182
data revealed that moose from several surrounding areas of the Susitna
River basin migrate across or utilize this portion of th~ river· duringe
some period of the year. Estimates of the total upper Susitna River
basin population, based on a total .of 2,037 moose counted during fall
1977 sex and age composition surveys in a portion of the'basin, range
between 4,000 and 5,000 moose (ADF&G, unpublished data).
Although water levels in the Devil's Canyon reservoir are expected
to remain relatively constant, the Watana reservoir may fluctuate as
much as 78 m. The resulting ice shelving may provide an effective
barrier 87 km long to those moose that migrate across this portion of
the river to their seasonal ranges. This disruption of movements to
traditional breeding and ~alving grounds may adversely affect productivity.
Increased mortality of neonates during post calving movements may also
occur.
Data available indicate moose depend heavily upon the river banks
and adjacent areas for winter habitat both above and below the Watana
and Devil's Canyon dam·sites. The lower spruce covered reaches of
Watana Creek are probably critical for moose in this area during severe
winters. The reservoir created by construction of the Watana dam would
inundate a major portion of this winter habitat which in turn would
substantially reduce the carrying capacity of those drainages lying
~etween Jay Creek and Devil Creek.
183
.A reduction in moose carrying capacity would impact recreational
sport hunting in this portion of the Susitna.River drainage. Harvests
have averaged 146 moose taken annually since 1974 within the immediate
drainages a 1 ong the upstream portion of the Sus.i tna R.iver (ADF&G,
unpublished data). Approximately 475 to 500 sportsmen participate in
moose hunts in this area each fall (op. cit.). It.is premature at this
time to attempt to quantify the possible impact of the hydroproject on
moose but if project impacts reduced local moose populations by 50
percent, the corresponding loss of harvest would be 7,500 moose during
the life of the dam, presently estimated at 100 years by the Corps of
Engineers. We would expect ungulate· populations to be more severely
impacted than the endemic predator species by dam construction as
predators are less directly dependent on their habitat for sustenance.
The resulting imbalance in predator-prey densities may further depress
moose population and keep them at· low densities for several years. How
significantly dam construction.might reduce or increase the level of
hunter activity for both predators an.d ungulates is difficult to say at
this time. Certainly, the construction of an access road ·to the Watana
site through a presently roadless area would, if it remained open to the
public, stimulate an increase in hunting pressure as would the creation
of the proposed airstrip at the Watana site.
Although this moose population study focused on habitat upstream of
the proposed hydropower development, the downstream effects of dam
construction should be considered; The lack of adequate wintering areas
is a major limiting factor to moose populations inhabiting the lower
Susitna River valley (Chatelain 1951). · Periodic flooding of major river
184
systems causing rechannelization and subsequent colonization of the dry
stream beds by riparian willows and cottonwoods provides a major portion
of the presently available winter range in the valley. 1000 moose were
observed in the western Talkeetna mountains between the Talkeetna River
and ~/ill ow. Creek during fall composition counts in November 1978 (ADF&G,
unpublished data). Most of these moose winter along the lower Susitna
River as do many from the Matanuska Valley and the Mt. Susitna area
(Didrickson pers. comm.). Much of the flooding action of the Susitna
River occurs during the spring when the volume of water flow may be as
high as 2,550 cubic meters per second. Maintaining a steady flow year
round of 230 to 280 cubic meters per second as proposed by the Corps of
Engineers would effectively prevent this flooding activity. Without
these periodic reversions to successional growth stages, it is likely
these riparian areas would become mature stands of hardwoods in 25 to 30
years and would provide little forage to overwintering moose. Hence,
these dams will not only adversely impact moose populations upstream,
but will have far reaching effects on moose throughout the entire Susitna
drainage.
ACKNOWLEDGEMENTS
Several biologists with the Alaska Department of Fish and Game
assisted us during the initial phase of this study. Drs. A. Franzmann
and T. Bailey from the moose research center participated in the collaring
operation. S. Eide, T. Spraker and T. Balland helped during all phases
of field work. We wish to thank Drs. W. Gasaway and V. Ballenberghe for
their helpful comments during the preparation of this manuscript.
185
LITERATURE CITED
Alaska District, Army Corps of Engineers. 1975. Hydroelectric power
and related purposes for the upper Susitna River Basin. Interim
Feasibility Rept., 125 p.
Alaska District, Army Corps of Engineers. 1977. Plan of study for
Susitna hydropower, feasibility analysis. Prepared for the State
of Alaska. 297 p.
Ballard, W.B. and K.P. Taylor. 1978. Upper Susitna River moose population
study. Alaska Dept. of Fish and Game P-R Proj. Rept. W-17-10, Job
IB-1.20, 62 p. (multilith).
Chatelain, E.F. 1951. Winter range problems of moose .in the Susitna
Valley. Proc. Alaskan Sci. Conf., 2;343-347.
Franzmann, A.W., A. Flynn and P.D. Arneson. 1975. Levels of some
mineral elements in Alaskan moose hair. J. Wildl. Mgmt. 39(2):374-
378.
Franzmann, A.W., P.D. Arneson, R.E. LeResche and J.L. Davis. 1974.
Developing and testing new techniques for moose management. Alaska
Dept. Fish and Game P-R Proj. Rept., W-17-2, W-17-3, W-17-4, W-17-5
and W-17-6. 54 p. (multilith).
186
Franzmann, A.W. and P.D. Arneson. 1973. Moose Research Center studies.
Alaska Dept. Fish and Game P-R Proj. Rept., W-17-5.:1 OQ.ip\ (mult.ilfth,)
Gravel, M. 1977. Tapping Susitna's power. Sen. Mike Gravel Reports to
Alaskans. July Newsletter. 4 p.
Greer, K.R. and W.W. Hawkins. 1967. Determining pregnancy in elk by
rectal palpation. J. Wildl. Mgmt., 31:145-149.
LeResche, R.E. 1974. Moose migrations in North America with emphasis
on Alaska. Naturaliste Can. 101:393-415.
Mech, L.D. 1974. Current techniques in the study of elusive wilderness
carnivores. Proc. XI Internat. Congress of Game Bio., 315-322 p.
Sergean~ D.E. and D.H. Pimlott. 1959. Age determination in moose from
sectioned incisor teeth. J. Wildl. Mgmt. 23(3) :315-321.
U.S. Fish and Wildlife Service. 1975. Southcentral railbelt area upper
Susitna River Basin hydroelectric project two dam plan. U.S. Dept.
Interior, Anchorage, AK. 25 p.
U.S. Soil Conservation Service. 1976-1978. Snow depths and water
outlook for Southcentral Alaska. Monthly bulletin publiShed
February through June.
NUMBER 15
SOLDOTNA -KENAI , ALASKA MARCH, 1979