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SUSITNA HYDROELECTRIC PROJECT
1984 ANNUAL REPORT
BIG GAME STUDIES
CARIBOU
Kenneth W.Pitcher
ALASKA DEPARTMENT OF FISH AND GAME
SUbmi tted to the
Alaska Power Authori ty
April 1985
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SUMMARY
Plans to construct a large hydroelectric project on the Susitna
R1ver wi thin the western portion of the Nelchina caribou range
have raised concerns about the welfare of this important caribou
hE!rd.Impact studies,which began in April 1980,continue with
the primary objectives of delineating seasonal range use and
migratory routes of the main Nelchina herd and determining range
use,movements and herd size of the upper Susitna-Nenana subherd.
The results of these studies are being used to evaluate potential
inlpacts of project construction,to make recommendations to
minimize adverse impacts and to evaluate mi tigation measures.
The primary methodology for the study is the repeti ti ve relo-
cation of radio-collared caribou.
During the winter of 1983-84 Nelchina caribou wintered in three
general areas with interchange of animals between the groups.
The largest concentration (@15,OOO)was along the Wrangell
Mountain foothills bet\veen Copper Lake and the Dadina River.A
small group (@2,500)moved to the northeastern slopes of the
ME:ntasta Mountains while the third group (@6,500)wintered on the
Lake Louise Flat,primarily west of Lake Louise.During spring
migration to the west many animals crossed the Richardson Highway
between Gakona and Sourdough rather than the traditional route
north of Sourdough.After crossing the Lake Louise Flat,caribou
entered the Talkeetna Mountains in the lower Oshetna River area
south of the proposed Watana fmpoundment.During·the one survey
flown during the calving period,females were found primarily in
Kosina Creek and the Black River.During summer,the female-calf
sE::gment of the herd remained in the northern and·eastern
Talkeetna Mountains.Male caribou were found scattered through-
out the high country of the basin.During autumn most animals
n::mained on summer range although limi ted dispersal across the
Lake Louise Flat and north of the Watana impoundment area
occurred.During the rut most animals were found west of Lake
LClUise and in the Talkeetna Mountain foothills near the Li ttle
Nl::lchina River.Year around use of the Nelchina Range by radio-
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collared caribou during the study period encompassed an area of
about 16,000 mi 2.The northern and eastern Talkeetna Mountains
are the core of the Nelchina caribou range as they are consis-
tently used as calving and summer range and on occasion as winter
range.The northwest sector of the Nelchina range has received
minimal use during this study while historically it was important
summer and \-linter range.
HE::rd size was estimated at 24,095 caribou in October 1984 by
ADF&G management staff which was slightly lower than the 1983
e:::;timate.Sex and age composition sampling indicated 39.5 males
~1 year per 100 females ~1 year and 33.7 calves per 100 females
~1 year;both lower than average figures obtained during recent
yE::ars .Adult survival,based on radio-collared caribou,was
estimated at 0.90 for females and 0.89 for males.Calf survival
from May 1983 to April 1984 was estimated at 0.19;the lowest
e:stimate obtained during this study.The reported sport and
subsistence kill of caribou for regulatory year 1983-84 was 969
animals;827 males,137 females and 5 for which the sex was not
specified.Considering these population parameters it appears
hl:rd size wi 11 stabi lize or dec line unti 1 increases in survi vor-
ship occur.
The upper Susi tna-Nenana subherd was estimated at about 1,500
c'aribou.This group of resident animals was found in an area of
about 2,050 mi 2 in the northwestern corner of the Nelchina range.
Calving by females from this group was dispersed over three broad
regions;eastern headwaters of the Susitna River,Butte Lake-
Brushkana Creek area and the Chulitna Mountains.Summer range
w,as similar to calving range except higher elevati"ons were
glenerally used.Primary wintering areas were in the Butte Lake-
Brushkana Creek area,Monahan Flat and along and to the east of
the Susi tna River above the Denali Highway.During winters of
low to moderate snowfall the Chulitna Mountains are used as
winter range,particularly the northern area.It appears that
about half of this subherd migrates from summer range in the
Chulitna Mountains to winter range to the east.
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The proposed Devil Canyon impoundment and transportation and
powerline corridors to the west do not appear to be of serious
concern to Nelchina caribou as neither currently nor historically
have many caribou occurred in this region.The Watana impound-
me:nt area has historically been crossed by large segments of the
Nelchina herd both during spring migration to the calving ground
and during summer and fall movements to the Chulitna Mountain
foothills to the north of the impoundment.Recent crossings have
been light but it is not unreasonable to assume that large-scale
crossings will again resume at some future time.Crossings of
the Watana impoundment could be hazardous to caribou particularly
during spring.Ice covered shores,ice sheets and steep ice
ramps could present obstacles to movement.Stacked ice floes
along the southern shore of an open water reservoir could make
exiting the water difficult.Crossings during summer,autumn and
winter are not expected to present serious hazards to caribou.
Caribou could choose not to cross the impoundment which would
ei.ther increase migration routes or reduce use of portions of
their range,particularly the northwest sector.Skoog (1968)
considered this region to be the most important for year-round
use by Nelchina caribou.
The proposed Denali access road bisects summer and winter range
for about half of the upper Susitna-Nenana subherd.Considerable
disagreement exists about the effects of roads and other develop-
memt on caribou movements and behavior.Large numbers of
Ne~lchina caribou cross the Richardson Highway during many years
wi.thout apparent problems.Therefore it is unc lear how the
Denali access road and associated traffic will impact migrating
upper Susitna-Nenana caribou.Mortality from vehicle collisions
is not anticipated to be a serious problem as caribou-vehicle
collisions are infrequent at other highway crossing sites.
Disturbance from increased aircraft traffic resulting from
project construction does not seem to be of serious concern and
could be easi ly mi tigated by area and elevation restrictions.
iii
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Increased access and development in remote areas of the Nelchina
caribou range resulting from project construction must be
considered,as potentially detrimental to the herd.
The Susitna hydroelectric project should be viewed as one of a
number of probable developments which are occurring on the
Nelchina caribou range.While no one action may have catastroph-
ic:results the cumulative impact will likely be a reduced ability
for the Nelchina range to support large numbers of caribou.
PClols of radio-collared caribou should be maintained and moni-
tored in both the main Nelchina herd and the upper Susitna-Nenana
subherd to monitor range use and migratory routes and to deter-
mine relationships between the groups.
iv
TABLE OF CONTENTS
Page
SUMMARY . . . . . . . . . . .... . ... ..... . i
LIST OF TABLES
LIST OF FIGURES
INT.RODUCTION
METHODS
. . . . . . . . . . . . ..... . . .vi
.vii
1
. . . . . . . . . . 5
RESULTS AND DISCUSSION . . . . . . . . . . . . . . 7
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DISTRIBUTION AND MOVEMENTS:
MAIN NELCHINA HERD
POPULATION SIZE AND COMPOSITION:
MAIN NELCHINA HERD
MORTALITY . . . . .
UPPER SUSITNA-NENANA SUBHERD ...
POTENTIAL IMPACTS OF PROJECT CONSTRUCTION
RECOMMENDATIONS FOR CONTINUING STUDIES
. 7
21
23
26
32
.38
ACKNOWLEDGEMENTS
REFERENCES
. . . . . . . ... . . . . . . . . . .39
40
-PERSONAL COMMUNICATIONS
v
44
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Table 1.
LIST OF TABLES
Nelchina caribou herd popu-
lation estimates . . ... . ....... . .25
vi
Page
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vii
LIST OF FIGURES
(cont'd)Page
Fig.8.Distribution of Nelchina radio-
collared caribou during summer,
11 June-31 July 1980-1984 .15
,~Fig.9.Distribution of Nelchina radio-
collared caribou during autumn,
1 August-30 September 1984 . . . .17
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Fig.10.Distribution of Nelchina radio-
collared caribou during autumn,
1 August-30 September 1980-1984
Fig.11.Distribution of Nelchina radio-
collared caribou during the rut,
October 1984
Fig.12.Distribution of Nelchina radio-
collared caribou during the rut,
October 1980-1984
Fig.13.Distribution of Nelchina radio-
collared caribou during entire
study period,14 April 1980-
15 October 1984
Fig.14.Distribution of upper Susitna-
Nenana radio-collared caribou
during entire study period,
9 May 1980-15 October 1984
viii
.18
. . .19
.20
.22
..28
LIST OF FIGURES
(cont'd)Page
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Fig.15.Distribution of upper Susitna-
Nenana radio-collared caribou
during calving,15 May-l0
June 1980-1984
Fig.16.Distribution of upper Susitna-
Nenana radio-collared caribou
during summer 11 June-31 July
1980-1984
Fig.17.Distribution of upper Susitna-
Nenana radio-collared caribou
during winter 1 December-
31 March 1980-1984
ix
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.30
.31
INTRODUCTION
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The l-.Ielchina caribou herd,found primarily in the large basin
formed by the upper drainages of the Susi tna and Copper Rivers,
and surrounded by four mountain ranges,the Wrangell Mountains,
the Talkeetna Mountains,the Alaska Range and the Chugach Moun-
tains,has been an important wildlife resource because of its
size and proximity to the majority of the states human popula-
tion.During the past 30 years,in excess of 100,000 caribou
were harvested from this herd.In 1984,12,516 people applied
for 1,900 permi ts to hunt for Nelchina caribou.
Plans to construct a large hydroelectric project on the Susitna
Ri ver wi thin the western reaches of the Nelchina caribou range
have raised concerns about impacts of the development on this
1=;1,
important caribou herd.Impact studies were started in early
1980 and a comprehensive report on the results published in March
~
1982 (Pitcher 1982).Considerable background material was also
presented ip that report;primarily historical range use,move-
mE~nt patterns and population levels.In April 1983 and April
1984 progress reports were distributed updating research results
.-(Pitcher 1983,1984)0 Following is a summary of background mate-
rial,methodology,results,possible impacts and recommendations
from the 1984 report.
Plans to construct a large hydroelectric project
on the Susitna River within the western portion of
the Nelchina caribou range have raised concerns
about the welfare of this important caribou herd.
Impact studies,which began in early 1980,
continue with the basic obj ectives of moni toring
herd status,determining range use and migratory
routes and delineating subherds.The results of
these studies are being used to evaluate potential
impacts of proj ect construction,to make recom-
~
mendations to minimize adverse impacts and to
evaluate mitigation measures.Primary methodology
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for the study is the repeti ti ve relocation of
radio-collared caribou.Population estimates are
being made with a modified version of the aerial
photo-direct count-extrapolation census procedure
and by direct count.
During the winters of 1980-81 and 1981-82 the main
Nelchina herd wintered primarily on the northeast-
ern Lake Loui se Flat eastward through the middle
portions of the Gakona and Chistochina River
drainages to Slana.During the winter of 1982-83
Nelchina caribou wintered from the Lake Louise
Flat north and east from the Tok-Tetlin-Northway
area to the western slopes of Mount Sanford in the
Wrangell Mountains.Movements of Nelchina caribou
northeast of the Mentasta Mountains have only
occurred during about three of the past 30 years.
Rapid,directed movement of caribou to the calving
grounds commenced during the last week in April
when the female segment of the herd was massed
between Lake Louise and Crosswind Lake.Most
females entered the Talkeetna Mountain foothills
in the area of the lower Oshetna River.There was
less use of the Watana impoundment area by caribou
during the 1983 spring migration than during the
previous two years.
Calving took place from Sanona Creek and the
Little Oshetna River westward to the hills east of
Stephan and Fog Lakes.Most calving activity
occurred between the Black and Little Oshetna
Rivers.
Summer range for the female-calf segment of the
herd was the northeastern Talkeetna Mountains
between Horn Mountains and the hills west of Tsisi
Creek.Males were found in the highlands through-
out the Nelchina Basin.
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Most caribou remained on summer range until late
in the autumn period (late September)when they
rapidly moved to the east.By early October most
were located between Hogan Hill and Boulder Creek
on the lower slopes of Mount Sanford.
The Nelchina herd was estimated to contain 18,713
caribou in October 1980,20,730 in 1981,21,162 in
1982 and 24,825 in 1983.Herd composi tion in
October 1983 was estimated at 53%females ~1 year,
32%males ~1 year and 14%calves.
In 1982-83 calf survival from birth to 10.5 months
of age was estimated at 0.54.Average annual
survival for radio-collared caribou throughout the
study period was estimated at 0.87 for females and
0.85 for males.Reported hunter kill of Nelchina
caribou for the 1982-83 regulatory year was 861
animals.
The population estimate for the upper Susi tna-
Nenana subherd was reduced from 2,500 to 1,500
because it was determined that animals from the
main Nelchina herd were present during the subherd
census.The subherd census should be repeated
when the two groups are well separated.Calving
by females of this subherd was not restricted to a
limited geographic area but was dispersed over a
wide region.It appears that about 50%of the
subherd crosses the proposed Denali access route
twice yearly during migration to and from summer
range in the Chuli tna Mountains.
Both the Watana impoundment and Denali access road
appear to be potential barriers to the free move-
ment of Nelchina caribou.Should the main
Nelchina herd resume use of summer and winter
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range north of the proposed impoundments the
potential for adverse impacts will greatly
increase.Increased direct mortalities may occur
during hazardous impoundment crossings and from
colli sions wi th vehicles along the access road.
Loss of habi tat does not appear to be a serious
consideration as only a small proportion of the
total range is involved and it appears to mostly
be of poor quality.Increased human access to the
calving grounds and summer range in the Talkeetna
f'lountains faci li tated by proj ect construction
could increase development and disturbance in this
now remote area.Reduced condition resulting from
extended and more difficult migratory routes could
impact herd productivity,particularly during
spring migration when pregnant females are in
relatively poor condi tion.
The Susitna hydroelectric project should be viewed
as one of a number of probable developments which
will occur on the Nelchina caribou range.While
no one action may have catastrophic results the
cumulative impact will likely be a reduced ability
for the Nelchina range to support large numbers of
caribou.
I t is recommended that
routes be moni tored by
radio-collared caribou.
be monitored with annual
composition sampling.
range use and migratory
periodic relocations of
Population status should
censuses and sex and age
The remainder of this report deals,mainly,with findings
obtaj.ned since preparation of the last progress report (November
1983 October 1984)and a discussion of the significance of
thesE~findings to proj ect construction.
4
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In 1984 the scope of thi s proj ect was substanti ally reduced per
instructions of the Alaska Power Authority.Census and composi-
"""'ti.on sampling activities were dropped leaving basically a season-
al range use and movements study of the main Nelchina herd and a
range use,movements and herd size study of the upper Susi tna-
Nenana subhe rd.
METHODS
Data on timing and routes of migration,range use and subherd
status were collected by the periodic relocations of radio-
collared animals.It was assumed that in general the behavior of
radio-collared caribou was representative of the herd.Details
~
of capture and radio-tracking techniques were previously
described (Pitcher 1982).At the end of the reporting period 50
radio-collared caribou were being monitored;42 from the main
Ne1china herd and eight from the upper Susi tna-Nenana subherd.
Methodology for data storage,retrieval and analysis was included
in the 1981 report for data management:biometrics (Miller and
Anctil 1981).
The Btudy area consisted of the entire range of the Nelchina
caribou herd (Fig.1).However,moni toring frequency of radio-
collared animals was much more frequent when they were in the
vicini ty of the proposed impoundments.
Estimates of mean annual adult survival rates were made from
radio-collared animals using a formula provided by Trent and
Rongstad (1974)which is based on the number of mortalities
detected and the period of time the radio-collared animals were
monitored.
Estimates of calf survival to 11 months of age were made by
multiplying the calf to female ~1 year ratio obtained in April by
the estimate for annual survival of females ~1 year then dividing
by the ratio of calves to females ~1 year at birth (Fuller and
Keith 1981).
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RESULTS AND DISCUSSION
DI STRIBUTION AND MOVEMENTS:MAIN NELCHINA HERD
Winter:by early October 1983 nearly the entire herd was east of
the Richardson Highway with most animals concentrated along the
lower reaches of Sinona,Indian and Boulder Creeks (Pitcher
1984).During the winter period the herd divided into three
wintering concentrations (Fig.2)with interchange between all
groups.The largest concentration (about 15,000)was along the
Wrangell Mounta'in foothills between the Dadina River and the
headwaters of the Copper River.A small group of animals
(perhaps 2,500 caribou)moved to the northeastern slopes of the
Mentasta Mountains.The third group wintered on the Lake Louise
Flat,primarily west of Lake Louise.This group probably
numbered about 6,500 animals.The three groups remained separat-
ed into mid-March.By early Apri 1 the Mentasta Mountains group
had merged with the Wrangell Mountains group.The 1982-84 winter
distribution was the most dispersed I have observed during the
four winters of thi s study (Fig.3).More use of the western
Lake Louise Flat occurred than during previous years while less
use of the eastern Lake Louise Flat and Gakona and Chistochina
River drainages took place.Wintering Nelchina caribou were
spread over an east-west range of about 150 mi les.
During the winters of 1980-81 and 1981-82 the primary wintering
areas were the eastern Lake Loui se Flat and Chi stochina and
Gakona River drainages.In 1982-83 wintering caribou ranged from
northeast of the Mentasta Mountains to the Wrangell Mountains
foothi lIs throughout the Gakona and Chi stochina River drainages
and onto the eastern Lake Louise Flat.
Spring.migration:by early April most females were grouped in
two atreaSi the Wrangell Mountains foothills and the western Lake
Louise Flat.By 23 April many of the females had moved out of
Wrangell Mountains foothills and were crossing the lower Gakona
drainage.This movement occurred south of Sourdough (Fig.4)
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rather than the traditional route in the Sourdough to Hogan Hill
area.By 8 May females were scattered across the Lake Louise
Flat from the Ewan-Fish Lakes area to the lower Oshetna River
where they entered the Talkeetna Mountains calving area.The
migratory route appeared to run south of the Watana impoundment
area similar to 1983 (Pitcher 1984).This was in contrast to
1981 and 1982 (Fig.5)when numerous animals either crossed the
proposed impoundment or used the frozen Susitna River as a travel
route (Pi tcher 1982,1983).
CalVing Period:only one survey was flown during the calving
season (4 June)so the full geographical extent of the area used
for calving is unknown.During the survey (Fig.6)females were
found from the Oshetna River west into th~hills west of Tsisi
Creek.Primary concentrations were found in Kosina Creek and the
Black River.Locations of radio-collared females during the
calving period throughout the study (1980-84)are di splayed in
Figure 7.The core calving area included the Oshetna and Black
Ri vers and Kosina Creek.
These observations are consistent wi th those made of calving
locations since 1949,the first year for which records are avail-
able.While the local areas utilized have varied,calving has
taken place between Fog Lakes and the Little Nelchina River.The
only deviations have been during years with extremely heavy snow
accumulations when some calving took place during migration to
the ca.lving grounds (Lentfer 1965,Skoog 1968,Bos 1973).
Summer:summer distribution of Nelchina caribou has been similar
throughout the five years of study (Fig.8).The female-calf
segment has utilized the northern and eastern Talkeetna Moun-
tains.Particularly heavy use has occurred between the Little
Nelchina and Black Rivers.Radio-collared male caribou were
found scattered throughout the high country of the Nelchina
Basin.It appeared that the largest concentration of summering
bulls was located in the southeastern Talkeetna Mountains in the
vicini ty of Caribou Creek.
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Historically,the female-calf segment has summered nearly
exclusively in two areas;the eastern Talkeetna Mountains (the
area utilized during this study)and north of the Susitna River
in the eastern benchlands of the Chulitna Mountains (Skoog 1968,
Hemming 1971).To my knowledge main herd Nelchina caribou have
not utilized the latter area as summer range to any significant
degree since about 1976 although between about 1950 and 1973 it
was utilized during most years (Pitcher 1982).Movements from
the Talkeetna Mountains across the Susi tna River ranged from
mid-June through July.Crossings apparently occurred between
Deadm.an Creek and V Canyon (Skoog 1968).
Autumn:most radio-collared caribou remained on summer range
during the autumn period in 1984 (Fig.9).Four radio-collared
animals crossed the Lake Louise Flat to the Alphabet Hills but
then three returned to the Talkeetna Mountains.Three other
radio-collared caribou crossed the Susitna in the Watana Impound-
ment area and dispersed to the north.This was generally the
same pattern as seen during previous years (Fig.10 )although
most caribou remained in the Talkeetna Mountains longer and there
was l,ess dispersal to the Lake Louise Flat.
Rut:during a 8 October 1984 radio-tracking survey nearly all
radio-collared caribou were found on the Flat west of Lake Louise
or in the Talkeetna Mountain foothills near the Li ttle Nelchina
River (Fig.11).Several radio-collared animals which had moved
north of the impoundment area and one in the Alphabet Hills were
still in those locations.This was the farthest west the herd
has been during the rut period since the study began'in 1980.
During the entire study period rutting caribou have been found
from the Talkeetna Mountains east to the Wrangell Mo~ntains (Fig.
12).Historically Nelchina caribou have rutted in a wide variety
of locations with the eastern Talkeetna Mountains and Lake Louise
Flat being most extensively used.The Deadman-Butte Lakes area
16
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20
was also heavi ly used during years vlhen maj or segments of the
herd summered or wintered in the area.During the fall period
Nelchina caribou are moving extensively and the rut may take
place in a number of locations (Skoog 1968).It appears that
habitat type is not a critical determinant of rutting locations
but rather rutting occurs in virtually any area that caribou
might be moving through during that period.
Current Distribution:year around use of the Nelchina Range by
radio-collared caribou from the main herd during the entire study
period is shown in Figure 13 and encompassed an area of about
16,100 mi 2.The northern and eastern Talkeetna Mountains can be
considered the core of the Nelchina caribou range.The herd has
shown near perfect fidelity to the calving grounds located in the
Talkeetna Mountains.The Talkeetna Mountains are also the prima-
ry summer range and have been used on occasion as winter range
(Skoog 1968).Winter ranges are the most variable (Skoog 1968)
and during the four winters of this study have included the Lake
Louise Flat,Chistochina and Gakona River drainages,Wrangell
Mountains foothills and to a lesser extent the area to the north-
east of the Mentasta Mountains.The northwestern portion of the
Nelchina Range including drainages of the upper Chulitna,Nenana
and Susi tna Rivers received minimal use by main Nelchina herd
animals during the study period while historically it was impor-
tant summer and winter range.
POPULATION SIZE AND COMPOSITION:MAIN NELCHINA HERD
A herd census was conducted by the area management staff of ADF&G
in late June 1984.The extrapolated October population.estimate
of 24,095 (ADF&G unpublished data)was slightly lower than the
1983 estimate (Table 1).the lower estimate resulted primarily
from a low bull ratio (39.5 males ~1 year per 100 females ~1
year)obtained during the fall sex and age composition sampling.
This ratio was considerably lower than those obtained during the
previous four years (x =59.7i range =55.4 -61.9)and resulted
21
-
0
0 a 0
000 0 00
0 0 0~
~0 0
0
"
"0
-
(
0
~(0
t\1'-0
\~o 0
,-
Figure 14.Dlstrll;)utlon.of upper Susltna-Nenana radio-collared caribou during entire study
period.9 May 1980-15 October 1984.(!)..females.'IE =males.
22
in an estimate about 3,000 animals lower than would have resulted
from a ratio similar to those obtained during the previous four
years.The ratio of calves per 100 females ~1 year (33.7)was
,_also lower than the average for the past 4 years (41.6)although
slightly higher than the 1983 ratio of 27.1.This also con-
tributed to the lower herd estimate.
It seems unlikely than the actual bull ratio declined from 61 to--40 in one year.Misclassification of sexes could be responsible
for the di f f erenc e s . I conducted the s a.mp 1 ing between 1980 and
1983 while the management staff conducted the 1984 effort.Over-
estimation of the bull ratio by me would have inflated earlier
-population estimates T,yhile underestimation of the bull ratio in
1984 would have resulted in an underestimate of herd size.It is
also possible that the bull segment of the herd was not full
represented in the area where composition sampling took place in
1984 which would account for the seemingly low bull ratio.
The ratio of calves per 100 females ~1 year at 33.7 was al so
..-
lower than the average for the past four years (x =41.6,range =
27.1 -54.0).Low values were obtained for both 1983 and 1984
probably indicating reduced or even negative herd growth.
MORTALITY
Natural mortality:only one radio-collared caribou,a female
from the upper Susitna-Nenana subherd,died during the past year
(1 October 1983-30 September 1984).Cause of death was not
determined but it was assumed to have been from natural causes
because of the remote location.The death occurred during the
calving season.Skoog (1968)reported that complications of the
birth process occasionally caused deaths of parturient females.
-
23
Estimates of x annual survival rates oj:radio-collared animals
for the entire study period (1 July 1980-30 September 1984)
0.90 (0.94-0.86,80%confidence interval)for females,
(0.96-0.76,80%confidence interval)for males and
(0.93-0.86,80%confidence interval)for sexes combined.
were
0.89
0.90
-
Calf survival from birth to about 11 months of age (20 May 1983
to 24 April 1984)was estimated from a t:heoretical birth rate of
0.66 calves per 100 cows ~1 year,an observed ratio of 14 calves
per 100 cows ~1 year in April and estimated survival of females
of 0.90 between 20 May and 24 Apri 1.Estimated calf survival was
(0.14 x 0.90)=0.19.
0.66 This was the lowest esti-
mate of calf survival obtained during this studYi 1981=0.43,
1982=0.58,1983=0.54.
Hunting mortality:the reported sport and subsistence hunter
kill of caribou from the Nelchina herd in regulatory year 1983-84
was 969 animalsi 827 males,137 females and 5 for which the sex
was not specified.These figures do not include illegal or non-
reported kills nor are they adjusted for crippling loss.Prelim-
inary returns for the 1984-85 season indicate a slightly higher
harvest.
Considering the population parameters of calf survival,adult
survival and hunting mortality just described it seems unlikely
that the herd could sustain the"growth observed over the past few
years.Indeed an actual decline in numbers will probably occur
unless changes in survivorship take place.
24
-Table 1.Nelchina caribou herd population estimates,in fall
unless otherwise noted.
-
Year
1955
1962
1967
1972
1973
1976
1977
1978
1980
1981
1982
1983
1984
Total
Estimate
40,000 1:/
71,000 ~/
61,000
7,842
7,693
8,081
13,936
18,981
18,713
20,694
21,356
24,838
24,095
Female
Estimate
4,800
4,646
4,979
7,509
9,866
9,164
10,154
10,199
13,212
13,912
I'liale
Es"timate
1,622
1,268
1,663
2,868
4,429
5,673
6,184
5,650
8,046
5,495
Calf
Estimate
1,420
1,779
1,439
3,559
4,686
3,876
4,356
5,507
3,580
4,688
..-
,-
1:/\"1atson and Scott (1956),February census.
2/Siniff and Skoog (1964),February cen:;iUS,perhaps should be
adjusted downward by as many as 2,000 caribou due to
presence of Mentasta herd .
25
-
.-.
UPPER SUSITNA-NENANA SUBHERD
Herd size:an attempt at a total count of this resident group of
caribou which occupy the northwestern portion of the Nelchina
Range was made on 4 and 5 April 1984.Snowfall in the area was
above normal during the 1983-84 winter and caribou were concen-
trated in several locations.We counted a total of 913 caribou
in the area 'vIi th major concentrations found in the following
areas:hillside to the east of the middle portion of Brushkana
Creek (352);foothi lls to the east of Butte Lake (198);Rusty
Hill Ridge between Valdez Creek and the Susitna River (199);and
Reindeer Hills (57).
The count was probably considerably 10111 as counting conditions
were poor in places and not all animals were wi thin the area
counted.Some knolls and ridges werE~windblown and caribou
appeared to select these areas probably because vegetation was
readily accessible.Animals in these windblown,bare areas were
difficult to see and count.At the time of the census I had nine
radio-collared caribou in this subherd.However,only seven were
wi thin the count area at the time of the census.None of 34
radio-collared animals from the main Nelchina herd were found
within 50 miles of the count area and most were over 100 miles to
the east;therefore it was unlikely that main herd animals were
included in the count.
Because of the factors affecting the count;poor counting con-
di tions (bare patches),subherd animals outside of count area
(demonstrated by radio-collars)and low probability of main herd
animals being included in the count -it is likely that "the count
was a substantial underestimate of subherd size.Previously I
had estimated subherd size at about 2,500 animals based on a
count of 2,077 caribou (Pitcher 1983).Subsequently,movements
of caribou which were radio-collared at the time of the count
revealed that significant numbers of main Nelchina herd animals
were probably included in the count resulting in a substantial
overestimate.
26
....
-
-
It seems reasonable that the two counts,one of which was an
overestimate and the other which was an underestimate,are likely
outer bounds of true population size.The upper Susitna-Nenana
subherd likely ranges between 1,000 and 2,000·caribou with the
mid-point 1,500 being a reasonable estimate.
Distribution:year around observations of radio-collared caribou
from the upper Susi tna-Nenana subherd during the enti re study
period are shown in Figure 14 and encompass an area of about
2,050 mi 2 (excluding relocations of female 152.410 who spent the
winter and calved with the main Nelchina herd during one year).
Distribution of the herd extended west from the Clearwater Moun-
tains and headwaters of the Susi tna River,across Monahan Flat
and the Butte Lake-Brushkana Creek country into the Chuli tna
Mountains.Observations of females during the calving period
(Fig.15)have been dispersed over a wide area,primarily in
three general regions;eastern headwaters of the Susitna River,
the Butte Lake-Brushkana Creek-Deadman Creek area and the
Chuli tna Mountains.In 1984,one upper Susi tna-Nenana radio-
collared female (152.410)calved in the Talkeetna Mountains with
the main Nelchina herd.By mid-August she had returned to summer
range north of the Susi tna River.ThE~previous year she had
calved in the upper Brushkana-Deadman Creeks region.This was
the first instance in this study in which a radio-collared female
has not shown complete fidelity to one calving area.The dis-
persed calving demonstration by this group is in contrast to the
main Nelchina herd where females formed a relatively cohesive
group and gave birth to their calves in a restricted geographic
area.Summer range was similar to calving distribution (Fig.16)
al though animals were often found at higher elevations.The
primary wintering areas were in the But:te Lake-Brushkana Creek
area,Monahan Flat and along and to the east of the Susitna River
above the Denali Highway (Fig.17).Some use of the Chulitna
Mountains occurred,particularly the northern slopes,although
during deep snow winters such as 1983-84 nearly all animals moved
to the east.During deep snow conditions caribou concentrated in
27
G "II
.....II 0I:.....
cD •
:I
III --~~..
~0•II ~
:I ~
III er
-I:·..III 0-·;:,'
o...
('-o
,J
13
o
..
III
Q,
o
Ino
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cD
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o
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-<Dc»...·
-Dc»o
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on-o
17
cD..
-...
:-
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17o
I:
C&,
I:..
;'
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:;'•
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C
Q,
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0-
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--
28
-
-
,.,.
-.
-0
.o~
D 0 D~0
0
0 0
\
(
-Figure 15.Distribution of upper SusUna-Nenana radio-collared caribou during calving.
15 May -10 June 1980-1984.e=female ••It=male.~
29
-
-
.....
I
~
(
\
Flgur.18.Distribution of upper Susltna -Nenana radlio-collared caribou during summer.
11 Jun.-31 July 1980 -1984.e-females.
30
i~
....
.-
~.,\
Figure 17.Distribution of upper Susltna-Nenana radio--collared caribou during winter.
1 December-31 March 1980-1984.e =females,.=mahts.
31
the hills surrounding Butte Lake and on Rusty Hill Ridge between
the Susitna River and Valdez Creek.It appeared that wind blown
areas in this higher terrain were being used by caribou.About
half of the radio-collared caribou from the upper Susitna-Nenana
subherd migrated from summer range in th.e Chulitna Mountains and
winter range to the east (thereby crossing the proposed Denali
access route).Therefore probably about 750 upper Susi tna-Nenana
caribou spend the summer in the Chulitna Mountains plus an....
r
unknown number of bulls from the main Nelchina herd.
POTENTIAL IMPACTS OF PROJECT CONSTRUCTION
~,
-
The proposed Susi tna Hydroelectric proj ect is located in the
western portion of the Nelchina caribou range.The Devil Canyon
impoundment and transportation routes and powerlines to the west
do not appear to be of serious concern as neither currently nor
historically have many caribou occurred in this region.Recent
use (1980-1984)of the Watana impoundment area by Nelchina
caribou has been moderate.During spring migration from winter
range to the east some use of the Watana impoundment area often
occurs,particularly the upper end.Duri.ng the spring of 1981 it
appeared that many caribou used the frozen SusitnA river between
the confluences of the Oshetna River and Kosina Creek (within the
proposed Watana impoundment)as a travel route (Pitcher 1982).
In 1982 I estimated that perhaps in excess of 50%of the female
segment was in the upper reaches of the lNatana impoundment during
spring migration to the Talkeetna Mountains calving grounds
(Pitcher 1983).The following spring,1983,less use of the
impoundment area appeared to occur as most females entered the
Talkeetna Mountains in the vicinity of the Oshetna River and
Goose Creek (Pitcher 1984).In the spring of 1984 little use of
the Watana impoundment area occurred,similar to 1983.It is
apparent that considerable variation occurs in use of the
impoundment area during spring migration from eastern winter
32
....
-
'"""
range.No apparent correlations were noted between migratory
routes and snow conditions during different years.However,it
may well be advantageous for caribou to migrate through the
impoundment area under certain conditions,an option that would
be lost or at least altered after proj ect construction.
Historically Nelchina caribou wintered north of the impoundment
area particularly between 1955 and 1964 (Skoog 1968,Hemming
1971).Spring migration for these caribou entailed a crossing of
the Susitna River in the Watana impoundment area enroute to the
Talkeetna Mountains calving area.Animals usually crossed the
Susitna between the mouths of Deadman Creek and Jay creek.It is
unclear how caribou would react to the sudden presence of a large
reservoir.Refusal to cross would extend the distance traveled
to the calving grounds by perhaps 60 miles and might result in
isolation and reduced use of the nor"thwestern corner of the
Nelchina range.Crossing conditions during spring might be
hazardous as ice covered shores,ice sheets,ice shelves and
steep ice ramps formed by winter drawdown of the reservoir could
present hazardous obstacles to movemen-t (Hanscom and Osterkamp
1980).Skoog (1968)mentioned several instances of injuries and
death resulting from falls on or through ice.Both Klein (1971)
and Vilmo (1975)mention ice shelving as a mortality factor of
reindeer on reservoirs in Scandinavia.If crossings were
attempted during the period of reservoir breakup and ice floes
were stacked along the southern shore by a northerly wind,
mortali ties might result from animals being unable to exit the
water.
There are indications that migratory mammals will on occasion
attempt to follow traditional routes even after changes have
occurred which make them hazardous.Hule deer (Odocoileus
hemionus)fell from a precipice created by highway construction
across migratory trails (Reed et al.1979).Possibly more than
10,000 caribou from the George River herd were killed while
attempting to cross a river at flood stage during fall migration
(Sullivan 1984,Goddard 1985).
33
During the course of this study the female-calf.segment of the
main Nelchina herd utilized summer range in the Talkeetna
Mountains.However I during most years between 1951 and 1976
(Pitcher 1982)segments of the female-calf component of the herd
crossed the Susitna in the Watana impoundment area to use summer
range in the greater Deadman Lake area.This crossing occurred
between mid-June and late July.It seems reasonable to assume
that resumption of use of this summer range will take place at
some time.If the Susitna project is constructed the caribou
will be faced with crossing an open water reservoir vd th minimum
widths in the traditional crossing areas of about 1.25 mi.
Caribou are known to be strong sw~mmers.Skoog (1968)saw a band
cross Lake Louise a distance of 5 mi.He also stated that
caribou commonly crossed much larger bodies of water in Canada.
__Calves would'be quite small during early summer crossings.
However,Skoog (1968)observed that caribou take readily to the
water at an early age.Crossings during this period would not
appear to pose a great hazard except perhaps to young calves .
.....
During autumn dispersal low to moderate rates of crossing in the
Watana impoundment area have taken place during the past 5 years.
Rather than large scale migrations,movements during this period
appear to be of a wandering nature.Impoundment crossing during
this period would probably be relati vE:ly nonhazardous.Light
rates of crossing were noted during the rut and winter periods I
nei ther of which appear to pose seri.ous threats because of
reservoir conditions and numbers of animals involved.The
transi tory phase of freeze-up might pr1esent increased hazards,
but would probably be similar to conditions already occurring on
large lakes.
The proposed Denali access road from the Denali Highvlay to the
Watana dam site runs between summer and winter range for about
half of the upper Susitna-Nenana subherd.Relocations of
radio-collared carlbou indicate that the Chulitna Mountains are
important calving and summer range with most animals moving to
34
....
'"""
"""
the east for the winter,particularly during deep snow years.
Thus about half of this subherd would be crossing the road twice
annually.Some calving occurs in the vicinity of the proposed
access road.However,because females from this subherd do not
congregate on a discrete calving ground.but rather calve while
dispersed over a large area it is probably impossible to route
the Denali access road to completely avoid calving females.Con-
versely only a small amount of calving would occur wherever the
road is constructed.
Based on the c'omposi tion of caribou sampled along the Trans-
Ala"skapipeline haul road and compared to region wide surveys
(Cameron et al.1979)and based on the relocation of collared
caribou (Whitten and Cameron 1983)it was concluded that the
cow-calf segment of the Central Arctic herd tended to avoid the
pipeline corridor and associated acti vi ty.Carruthers et al.
(1984)maintained that these conclusions were erroneous because
the differences in composition were the result of differential
habitat selectivity rather than avoidance of the corridor.
Horejsi (1981)reported that caribou showed signs of anxiety and
fear in the presence of a fast-moving vehicle and react strenu-
ously to escape.Johnson and Todd (1977)concluded that a group
of mountain caribou became habituated to a highway and traffic
and continued to use a traditional movement route despite harass-
ment and mortality.Klein (1971)reported that well traveled
highways and rai lroads have obstructed the movements of wi Id
reindeer in Norway.Bergerud et al.(1984)failed to find strong
correlations with construction of road::;through caribou ranges
and population declines except when the roads were uses as access
routes for hunters resulting in overharvests.Despite these con-
tradictory findings on the impacts of highways on the free
movement and behavior of caribou it does appear that high levels
of activity along highways may influence behavior in certain
situations (Klein 1971,Horejsi 1981,Smith and Cameron 1983).
It is not clear how the Denali access road and associated traffic
will impact caribou migrating from the Chulitna Mountains to and
35
from winter range to the east.Nelch,ina caribou continue to
cross the Richardson Highway often in large numbers,and have
done so during many years since about 1960 (Hemming 1971).The
area where the Richardson crossings take place is timbered in
contrast to the open tundra and shrublands of the proposed Denali
access route.Nelchina caribou also cross the Glenn Highway
(primarily the Tok-Cutoff),Denali Highway,Lake Louise Road and
Nebesna Road on occasion.The Glenn Highway and Nebesna Road are
crossed twice yearly during those years (perhaps half of recent
years)when the Nelchina herd winters in the vlrangell
Mountains-Mentasta Mountains area.Small numbers of caribou,
primarily bulls,cross the Glenn Highway west of Glennallen
during winter and spring each year.Most years small numbers of
caribou cross the Lake Louise Road during the autumn dispersal
period.
Some mortality of caribou from collisions with vehicles along the
Denali access road may occur although it is not expected to be a
serious problem.Caribou-vehicle collisi.ons along the Richardson
Highway where maj or crossings occur probably do not result in
over about 50 deaths per year (Tobey,pers.commun.).Vehicle-
caribou accidents are reportedly uncommon along the Dalton
Highway (Cameron,pers.commun.).
Increased aircraft traffic in the western Nelchina range would be
expected in conjunction with project construction.Several
~
studies (Miller and Gunn 1979,Calef et al.1976)have recorded
responses of caribou to aircraft disturbance and made recommenda-
tions to mitigate possible adverse impacts.Davis and Valkenburg
(1984)reported that the Delta caribou herd has been exposed to
more disturbance than any other Alaskan caribou herd including
considerable civilian and military aircraft traffic and yet has
grown at a rapid rate and is now larger than ever recorded.
Bergerud et al (1984)concluded that caribou can tolerate
periodic severe disturbance without adverse effects on
productively and survival.Based on these reports I would not
36
expect aircraft disturbance to be a serious problem impacting
caribou if the Susitna project is constructed.Restricting
aircraft access in the Talkeetna Mountains calving grounds and
summer range and the area north of the Watana impoundment
combined with minimum elevation requi.rements should provide
adequate safeguards.
increase human access
range for the Nelchina herd.
Project construction would likely
northeastern Talkeetna Mountains
and summer
which
to the
include calving grounds
The Denali access road
~would also increase access to important caribou habitat which is
currently used primarily l:>Y the ,upper Susitna-Nenana subherd.
The area has in the past and probably will again be important
summer and winter range for the Nelchina herd.The calving
grounds are currently in one of the most remote and inaccessible
regions wi thin the Nelchina range.Smi th and Cameron (1983 )
reported decreased use of the Prudhoe Bay oilfield complex by
calving caribou during recent years.While it seems unlikely to
me that development in the northern Talkeetna Mountains could
reach thi s level in the near future,·the possibi Ii ty must be
considered.
l"'-
I
.....
I
Perhaps the major impact of the Susitna hydroelectric development
on the Nelchina caribou herd will be a contribution towards
gradual,long term cumulative habi tat degradation rather than
immediate,severe impacts.The proposed hydroelectric project is
only one (although the maj or one)of a number of developments
which may occur on the Nelchina rangre.Considerable mining
acti vi ty already is taking place in the~southeastern Talkeetna
Mountains,traditional summer range.A state oil and gas lease
sale is planned for the Lake Louise Flat,a major wintering area.
The Bureau of Land Management is planning to open much of the
Nelchina Basin to oil exploration.Considerable land is passing
from public to private ownership through the Alaska Native Claims
Settlement Act and through state land disposal programs.While
no single action may have a catastrophic impact it seems likely
that long-term cumulative impacts will result in a lessened
37
I""'",
I
-
ability for the Nelchina range to support large numbers of
caribou.Habitat destruction,increased access and human activi-
ty,disturbance,and barriers to free movement will all probably
contribute to this.
Some biologists (Bergerud et al.1984)feel that caribou are
adaptable and can tolerate considerable human activity and devel-
opment if protected from overharvest.They maintain however,
that caribou require space to successfully deal wi th a changing
environment and that some Concern must be directed towards
ensuring their.mobili ty.They state Ii we must not permi t the
dis'section of caribou populations into small di screte units ..." .
RECOI-.TI1ENDATIONS FOR CONTUlUING STUDY
Range use and migration routes of the main Nelchina herd should
be documented by maintaining and monitoring a pool (25+)of
radio-collared caribou.Particular emphasis should be given to
determining herd use of range to the nort:h of the proposed Watana
impoundment.Up to 10 radio-collared caribou from the upper
Susitna-Nenana subherd should also be monitored to document range
use and seasonal movements and to determine relationships with
the main Nelchina herd.This would be particularly relevant if
large numbers of main herd animals began sharing summer or winter-range wi th thi s subherd.
38
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ACKNOWLEDGEMENTS
Polly Hessing,Jim Lieb and Bob Tobey all made important contri-
butions in field acti vi ties.Ken Bunch,Don Deering,·Craig
Lofstedt,Chuck McMahon and Harley McMahon all piloted aircraft
for the project.Danny Anctil,Larry Aumiller and SuzAnne Miller
provided support in data management and analysis.Larry Aumiller
prepared figures for thi s report.Penny Mi les and Susan Lawler
provided typing support.Karl Schneider supervised the study.I
appreciate the contributions made by each of these individuals.
39
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Iflatson,G.W.,and R.F.Scott.1956.
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Whitten,K.R.,and R.C.Cameron.1983.Movements of collared
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43
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PERSONAL COMMUNICATIONS
Raymond Cameron,Alaska Department of E'i sh and Game,Research
Biologi st,26 November 1984.
Robert Tobey,Alaska Department of Fish and Game,Area Management
Biologist,21 November 1984.
44