HomeMy WebLinkAboutAPA2419SPRING AND FALL MOVEMENTS
OF NELCHINA CARIBOU
IN RELATION TO
THE TRANS-ALASKA PIPELINE
Susitna J oTnt Venture
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DOCUMEN'~ CON TROL
SPRING AND FALL MOVEMENTS
OF NELCHINA CARIBOU
'
IN RELATION TO
THE TRANS-ALASKA PIPELINE
ARLIS
SPRING AND F.ALL MOVEMENTS
OF NELCHINA CARIBOU
IN RELATION TO
THE TRANS-ALASKA PIPELINE
Prepared for
Alyeska Pipeline Service Company
by
D.R. Carruthers, R.D. Jakirnchuk and c. Linkswiler
Renewable Resources Consulting Services Ltd.
March 1984
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SUMMARY
The majority ( >80%) of the Nelchina caribou herd
crossed TAPS each fall and spring 1981-1983, moving east to
traditional winter range in fall and west to traditional
calving areas and summer range in spring. Major wintering
areas included the Gulkana and Chistochina River drainages and
northern foothills of the Wrangell Mountains east of TAPS, and
the Ewan-Crosswind Lakes area west of TAPS.
The timing of migrations was similar to that recorded
prior to construction of TAPS. Spring migration across TAPS
peaked in April except in 1983 when most caribou crossed in
February because of below normal snow depths. Fall migration
across TAPS peaked in November with pre-migration movements
occurring near TAPS in September and October.
Major crossing locations were unchanged from the
period prior to pipeline construction. Lowlands of the Spring
Creek drainage and between Hogan Hill and the Gulkana River
were major spring crossing zones. Fall crossing zones were in
upland habitats from Hogan Hill to Spring Creek. Crossing
sites are traditional and appear to be related to ease of
movement. Spri'ng routes are located where snow depth is least
and large open areas (lakes and meadows) are abundant. Fall
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routes are more dispersed and follow upland areas when lakes
are not yet frozen.
Special crossing structures such as designated big
J game crossings, sag bends and special burials were used by 29
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percent of caribou crossing TAPS. Special burial sections
south of Hogan Hill were used most ( 27%) because they were
placed in a major spring crossing zone. All other structures
were used very little (<2%) since most (89%) were outside of
major caribou crossing zones. All structures were used less in
fall than in spring.
Caribou showed no preference overall for crossing at
buried or above-ground pipe. Above-ground pipe was crossed as
it was encountered, with no apparent preference for particular
BOP-TOPs. Most above-ground pipe (>90%) was over 1.8 m (6 ft)
high (median = 7.6 ft) and caribou crossed at a mean pipe
height of 2.4 m (8 ft). Pipe heights were relatively uniform
over long distances with little option for 11 choice 11 by caribou.
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• 1 Caribou crossed at heights ranging from 1 m ( 3. 5 ft) to 5. 3 m ' J
( 17.5) ft.
Crossing success was high ( 99%) and no evidence of
caribou being 11 deflected 11 by TAPS was observed. Caribou used
! _ j ·old cutlines a.s travel routes in the vicinity of TAPS and
sometimes encountered the right-of-way while travelling on
these cutlines.
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Caribou groups, upon entering the right-of-way, were
usually led by an adult female. The group characteristicalYy
stopped briefly on the right-of-way ( 7. 6 minutes) and spent
most of the time standing and feeding before crossing and
leaving the ROW. Alarm responses were infrequent with alert
behavior occurring 1.1 percent of the time. Small groups spent
less time on the right-of-way than larger groups: otherwise
there were no differences in behavior related ~o group size or
composition. Feeding activity was concentrated at the edges of
the right-of-way where forage species were more abundant than
elsewhere on the right-of-way. Small sample size precluded
tests for differences between pipe modes and group composition.
The use of TAPS by wolves corresponded to the
seasonal location of caribou migration routes. No evidence of
caribou being killed on or immediately adjacent to TAPS by
predators was observed.
The Nelchina caribou her~d continues to cross TAPS as
it did prior to construction. The herd has increased from a
low of 8,000 animals at the· time of construction to 25,000 in
1983. Movements and distribution are similar to those reported
J over the past 25 years and reflect the influence of environ-
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mental features such as snow and terrain rather than TAPS.
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ACKNOWLEDGEMENTS
Funding for this project was provided by the Alyeska
Pipeline Service Company. We wish to acknowledge the support
and assistance of Ben Hilliker and Dennis Prendeville of
Alyeska in Anchorage.
The logistic support provided by Alyeska staff in
Anchorage, Fairbanks and Pump Stations 10 and 11 was greatly
appreciated. Pump station personnel were unfailingly helpful
in providing assistance throughout the study, and a special
thanks goes to Security staff who kept a "caribou watch" for
us. Stan and Wanda Brown of Paxson Lodge and Bud and Patty
Lauesen of Sourdough Roadhouse kept us warm and well-fed during
field work.
Alaska Department of Fish and Game personnel,
particularly Ken Pitcher in Anchorage and Jim Lieb in Glenn-
allen, greatly assisted our work by sharing their data on
locations of radio-collared caribou.
Data could not have been collected without the
assistance of Peter Bente, Darleen Masiak, Don Vernam, Dave
Volsen, Jack Winters, John Rose, Nick Cassara, Mary Maurer and
Charlie Edwards.
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We acknowledge the critical review and comments on
the study design and final report provided by L. Sopuck and s.
Ferguson.
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TABLE OF CONTENTS
Page
SUMMARY. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • i
ACKNOWLEDGEMENTS. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • i v
I .. 1 LIST OF TABLES •••••••••••••••••••••••••••••••••••••••••••• viii
TABLE OF CONTENTS. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • vi
] LIST OF FIGURES •••••••••••••••••••••••••••••••••••••••••• ix
LIST OF APPENDICES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X
. J LIST OF PLATES ••••• . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
'J 1.0 INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 OBJECTIVES ••••••••••••••••••••••••••••••••••••••••
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J 2.0 HISTORICAL BACKGROUND•••••••••••••••••••••••••••••••• 4
3.0 STUDY AREA ••••••• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 11
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] 4.1 AERIAL SURVEYS ••••••••••••••••••••••••••••••••••••
4.2 CORRIDOR SURVEYS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
21
4.2.1 Initial Reconnaissance. ..•............•......• 21
4.2.2 Trail Configuration •• . . . . . . . . . . . . . . . . . . . . . . . . 24
4.2.3 Pipe Mode and Height. . . . . . . . . . . . . . . . . . . . . . . 28
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4.2.4 Vegetation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
.. ) 4.2.5 Snow Depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
l 4.3 CONTROL SURVEYS •••••••••• . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.4 BEHAVIOR ••••••••••••••••••••••• . . . . . . . . . . . . . . . . . . . 33
5.0 RESULTS • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . •· .. 35
5.1 SEASONAL MOVEMENTS TIMING ••••••••••••••••••••••• 35
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Page
: J 5.2 CROSSING SITES. .. •· ............................... . 40
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Location •• . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
J·
Topography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vegetation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
43
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Snow •••••• . . . . . . . . . . . . . . . . •· . . . . . . . . . . . . . 48
Pipe Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.2.2.5 Predators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.3 SPECIAL CROSSING STRUCTURES. . . . . . . . . . . . . . . . . . . . . . . 54
5.4 CARIBOU RESPONSE TO TAPS. . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.4.1 Crossing Success ••• e e e e e e e e • • • • • • • • e • e e e e e e e • 56
5.4.2 Approaching and Departing the ROW. . . . . . . . . . . . 57
5.4.3 Caribou Behavior on the Right-of-way. ........ 62
6.0 DISCUSSION •• . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
7.0 CONCLUSIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
8.0 RECOMMENDATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
9.0 LITERATURE CITED •• . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
PERSONAL COMMUNCATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
APPENDICES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
PLATES ••••• . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
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LIST OF TABLES
Table Page
1. Timing and sampling intensity of aerial surveys of
Nelchina caribou, 1981-1982 ••••••••••••••••••••••••• 19
2. Corridor survey dates, location and distance, 1981-
1983 •••...................••..........•............. 22
3. Vegetation classification categories used in
Nelchina study area ••••••••••••••••••••••••••••••••• 23
4. Caribou group size and habitat use, aerial surveys
April, November, December 1981 and February 1982 •••• 35
5. Numbers of caribou observed east and west of TAPS
during aerial reconnaissance surveys, 1981 and 1982. 39
6. Distribution of vegetation types along TAPS in
relation to topographic features and pipe mode •••••• 45
7. Caribou use of vegetation types within major
crossing zones along TAPS in relation to avail-
ability of types during spring and fall migration
periods. . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
8. Vegetative cover along TAPS ROW, August 1983 •••••••• 47
9. Snow depths on and off the TAPS right-of-way, 1981-
1983 ........•..............•.•.•.•••.•....•........• so
10. Percent of all caribou crossings in relation to
pipe mode during .spring and fall migration periods
{seven surveys, 1981-1983) •••••••••••••••••••••••••• 52
11. Distribution of pipe heights {BOP-TOP) at spring
and f~ll caribou crossing zones ••••••••••••••••••••• 53
12. Caribou trail configuration (change in orientation
over distance) beyond 50 m from TAPS compared to
trails crossing TAPS ••••••••••••••••••• _ ••••••••••• ·•• 58
13. Approach and departure orientations of caribou
trails within 20 m of TAPS crossing at above-ground
or bur·ied pipe ........................................ 59
14. Time spent on the ROW by Nelchina caribou in
relation to group size, fall 1981 ••••••••• ~········· 63
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LIST OF FIGURES
Figure Page
1. The range of the Nelchina caribou herd and the
location of the study area......................... 2
2. Population estimates of the Nelchina caribou herd,
1948-1982........................................... 6
3. Winter range use by the Nelchina caribou herd,
1950-1980 ••••••••••••••••••••••••••• i ••••••••••••••• 7
4. Seasonal movements of the Nelchina caribou herd ••••• 10 .
5. Aerial survey transects, 1981-1982 •••••••••••••••••• 17
6. Aerial survey transects within a 15 km corridor
centered on TAPS/Richardson Highway, 4 Dec.ember
1981 •..................••.••.••.•.•....•.•.......... 20
7. Schematic of measurements taken where caribou
trails encountered the TAPS right-of-way (ROW) •••••• 25
a. Schematic of measurements taken on fore-and back-
tracked caribou trails •••••••••••••••••••••••••••••• 27
9. Locations of control surveys •••••••••••••••••••••••• 32
10. Schematic of control surveys to sample caribou
trails adjacent to the ROW •••••••••••••••••••••••••• 33
11. Caribou distribution from aerial surveys conducted
in spring and fall 1981 and February 1982 ••••••••••• 36
12. Main caribou crossing zones, spring and fall 1981-
1983 ...•.•..........••.......••..•.•...•..•.•••••.•• 41
13. Distribution of caribou trails along TAPS during
spring and fall migration, 1981-1983 •••••••••••••••• 42
14. Distribution of snow depths along TAPS in relation
to spring and fall migration zones, l981-1983 ••••••• 49
15. Location and use (percent) of special crossing
s·tructures within 8 km ( 5 mi) sections of TAPS by
Nelchina caribou, 1981-1983 ••••••••••••••••••••••••• 55
16. Extent that TAPS is visible in relation to distance
away from TAPS •••••••••••••••••••••••••••••.••••••••. 61
17. Frequency of caribou activity on the TAPS ROW, fall
1981 ......••.•..••••....•.•.••....•.•.•.••...•...... 65
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LIST OF APPENDICES
Appendix Page
lA. Temperature and precipitation summaries, Gulkana
1981-1983 and 10-year average 1971-1980 ••••••••••• 95
lB. Frequency of occurrence of annual snowfalls
greater than 217 em (85 in) between 1916 and 1982
?nd snow-on-the-ground greater than 80 em (31 in)
between 1959 and 1982; Fairbanks •••••••••••••••••• 96
2. Widths of TAPS Right-of-way, MM 623.5-661.0 ••••• 97
3. Timing of f~eld activities in the Nelchina study
area, 1981-1983 ••••••••••••••••••••••••••••••••••• 98
4. Glossary of terms. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 99
5. Species composition and percent cover of
vegetation along ROW at selected sites, August
1983 ..•..•..•.••.••.•.•••.............•.•.......•. 101
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LIST OF PLATES
Plate 1. The TAPS right-of-way with driveable pad and above-
ground pipe on vertical support members •
Plate 2. Snow covered TAPS right-of-way at refrigerated burial
adjacent to Hogan Hill.
Plate 3. Caribou feeding craters on TAPS right-of-way.
Plate 4. Caribou trails crossing buried pipe with evidence of
feeding along ROW edge.
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1.0 INTRODUCTION
The influence of , petroleum development on wildlife
populations in Arctic and Subarctic regions has been an issue
for many years (Weeden 1971). A major concern prior to con-
struction of the Trans-Alaska Pipeline System (TAPS) was
whether it would constitute an impediment to the free movement
of wildlife (Weeden and Klein 1971, Luick et al. 1975).
Efforts were'made to address this concern during-planning and
construction (Child 1973, Van Ballenberghe 1978) but few
studies have been conducted since completion of the project
(Cameron and Whitten 1980). Consequently, Alyeska Pipeline
Service Company in 1981 contracted Renewable Resources
Consulting Services Ltd. for a three-year study to determine
the status of four mammal populations and their interactions
with TAPS. These populations include the Central Arctic and
Nelchina caribou herds (Rangifer tarandus granti), Dall's sheep
(Ovis dalli dalli) in the Central Brooks Range and moose (Alces
alces gigas) in the Interior.
This report presents results of a study of the
Nelchina caribou herd conducted along the TAPS corridor between
Paxson and Glennallen, Alaska (Figure 1) from April 1981 to
November 1983.
The Nelchina caribou herd is well sui ted for study
because the herd has moved through and wintered in the area now
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Figure 1. The range of the Nelchina caribou herd and the
1 location of the study area.
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crossed by TAPS during much of its documented history (see
Section 2.0 Historical Background). Movements during fall and
spring provide an excellent opportunity to examine caribou
interactions with the pipeline. In addition, the Nelchina herd
has been intensively studied for longer than any other caribou
herd in Alaska (Doerr 1980) and, hence, more information is
available for comparison of pre-and post-pipeline
construction on movements and distribution.
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Since the turn of the century a highway has bisected
the range of the Nelchina herd and in 1973 the Trans-Alaska
Pipeline was constructed next to this highway. The herd was
large during the 1960s but declined to less than 10,000 animals
in the early 1970s through a combination of overhunting and
predation (Bos 1975, Bergerud 1980, Doerr 1980). Since then
the herd has increased to about 25,000 caribou (Pitcher, pers.
cornrn. ) •
Skoog (1968) and Hemming (1971) have documented the
distribution and movements of the Nelchina herd over a 15 year
period. Pitcher ( 1982, 1983), using radio telemetry, has
provided more detailed documentation of distribution and
movements in recent years which is similar to those reported by
Skoog and Hemming. Emphasis in this study was on the spring
and fall periods when caribou have maximum interaction with
TAPS.
1.1 OBJECTIVES
· The overall objectives of the study were to document
crossing of TAPS by Nelchina caribou, determine characteristics
of crossing areas, and describe behavior of caribou when they
encounter the pipeline.
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Specific objectives were:
1} To document crossing of the TAPS corridor by the Nelchina
caribou herd during spring and fall migration,
2} To determine and describe the phys.ical characteristics of
TAPS crossing sites used by caribou,
3} To assess the use of special crossing structures by
caribou,
4} To quantify the crossing success and behavior of caribou
encountering TAPS,
5} To document caribou group characteristics (e.g., size,
composition} which may influence crossing success,
6} To document habitat use by caribou adjacent to the TAPS
corridor.
2.0 HISTORICAL BACKGROUND
The Nelchina caribou herd has traditionally occupied
an area of 82,000 km2 ( 20,000 mi2 }. in southcentral Alaska
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Alaska Oil Pipeline (Figure 1).
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Population levels and distribution of the Nelchina
caribou herd have fluctuated widely in the previous 100 years.
l _j Although documentation is lacking prior to the late 1940s, the
herd seems to have reached a peak population level of
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approximately 70,000 animals in the mid-1800s (Skoog 1968).
The number of caribou in the herd declined to a low of possibly
10,000 animals in the late 1930s-early 1940s (Watson and Scott
1956). As the number of caribou declined, so did the
proportion of range they used. In the mid-1800s the entire
range was used, but only the southwestern third was used in the
early 1800s when the herd was much smaller. This southwestern
portion of the range has been defined as the .. center of
habitation.. by Skoog (1968) because it has been used
perennially, regardless of fluctuations in herd size.
Since 1948, population fluctuations and changes in
-~ distribution of the Nelchina caribou herd have been more
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closely monitored. The herd rapidly expanded in size to its
l ~J former level of approximately 70,000 animals in the early 1960s
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(Skoog 1968) and then, in the following decade, declined
sharply to fewer than 10,000 animals in the early 1970s
(Hemming 1975, Bos 1975, Doerr 1980). Since then, population
numbers have slowly increased to the current estimate of almost
25,000 animals (Figure 2) (Pitcher, pers. comm.).
Population fluctuations in the past 35 years have
been accompanied by changes in the distribution of the herd.
The calving area and summer range (Figure 1) have remained ~t
the center of habitation described by Skoog (1968), but winter
ranges have varied greatly. As the herd grew in the early.
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1948 50
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60
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Figure 2. Population estimates of the Nelchina caribou herd,
1948-1983 (Watson and Scott 1956, Skoog 1968, Siniff
and Skoog 1964, Hemming and Glenn 1969, Eide 1980,
Pitcher 1982, 1983, pers. comm.).
1950s, it used winter range west of the Richardson Highway
Figure 3a). In the late 1950s, winter ranges were used, also
generally west of· the Richardson Highway but overlapping the
Highway near Sourdough (Figure 3b). Several thousand caribou
commonly wintered between Paxson and Isabel Pass. Erratic long
distance movements also began during this period, a phenomenon
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1950 -1955
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1960 -1965
7
1 64 km.1
40 mi.
1955-1960
1965-1970
1975-1982
Figure 3. Winter range use by the Ne1china caribou herd, 1950~
1982. (a-d· Hemming 1971: e-f Pitcher 1982, 1983).
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that has been associated with increasing herd size (Skoog
1968). Similar erratic movements have been observed in recent
years (Pitcher 1983).
Between 1960 and 1965, as population levels reached a
maximum, caribou began using winter ranges to the east of the
Richardson Highway (Figure 3c). Specifically, the Chistochina
River drainage, dra~nages of the Mentasta Mountains, and the
low north slopes of the Wrangell Mountains became important
wintering areas (Hemming 1971). For the rest of the 1960s,
these were primary winter ranges of Nelchina caribou (Figure
3c) (Skoog 1960, 1961, 1962, 1963, Lentfer 1965, McGowan 1966,
Glenn 1967, Hemming and Glenn 1969, Johnson 1971).
During the decade of very low population levels in
the 1970s, caribou use of winter range was continuous east and
west of the Richardson Highway (Figure 3e), although use of the
Mentasta Mountains declined in the early 1970s. In the late
1970s, the north slopes of the Wrangells were a major wintering
area (Figure 3f) (Mcilroy 1972, 1975, 1976, Bos 1973, 1974).
In the past three years, winter range use has been continuous
east and west across the Richardson Highway.
Routes followed by Nelchina caribou to and from
winter ran·ges and timin'g of movements are consistent over the
years, despite variability in relation to population size.
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Caribou encounter TAPS in the spring and from the fall to early
winter (Skoog 1968). The total length of the annual migration
increased from 600 km (370 mi) in 1955 to 1,580 km (980 mi) in
1964, as herd size increased (Skoog 1968).
In spring, movement from winter range east of TAPS
towards the calving area to the west typically begins in April.
Caribou in the Mentasta Mountains move south and those in the
Wrangells move north to the Copper River (Figure 4). They
travel west down the Copper River valley and most cross the
river near Chistochina. From there, they generally move
directly west towards Fish Lake. The major zone where most
animals cross the Richardson Highway/TAPS is within a few
kilometers on either side of Sourdough (Figure 4) (Skoog 1968).
In the fall, Nelchina caribou commonly move east
along the Alphabet Hills from summer ranges with some crossing
the Richardson Highway/TAPS in early October (Skoog 1968,
Pitcher 1983). From there, they make a clockwise swing south
and west to the flats around Lake Louise (Figure 4). Dispersal
from the flats to winter range occurs after the rut and con-
tinues through November and December. Caribou that winter east
of the Richardson Highway typically cross the Highway and TAPS
in early November.
Lake to Sourdough;
The major crossing area extends from Paxson
the Spring Creek drainage south of Meiers
Lake has traditionally been a location of intensive use by fall
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Figure 4.
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Above ground pipe
Buried pipe
... Fall,
Spring
Seasonal movements of the Nelchina caribou herd
(Skoog 1968, Hemming· 1971).
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migrating caribou (Skoog 1968, Hemming, pers. comm.). In
recent years the Nelchina caribou herd has generally continued
this pattern of movement (Pitcher 1982, 1983).
3.0 STUDY AREA
The study area lies in southcentcal Alaska (63000'N,
145000'W) within a region referred to as the Nelchina Basin
(Figure 1). The Trans-Alaska Oil Pipeline was constructed in
1974-76 in the eastern: portion of the area from TAPS Mile
Marker (MM) 618 at Paxson to MM 683 at Glennallen (105 km, 65
mi). This study is based on the section of TAPS between MM 620
to MM 660 (64 km, 40 mi).
The Richardson Highway which generally parallels TAPS
was first a wagon road constructed at the turn of this century.
It was upgraded to automobile standards in the 1920s and paved
in 1957. Unt~l 1971, the Richardson Highway was the only road
between Fairbanks and Anchorage. In 1972 average traffic
volume was 500 vehicles per day.
Elevations average 550 m (1,800 ft) in the south and
gradually increase to 1,600 m (5,450 ft) in the north. Lakes
and ponds are numerous, particularly in the southern half of
the area. Major rivers are oriented generally north-south.
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Skoog (1968) provides a detailed description of the topography
of the area.
The climate is classified as continental with a
maritime influence (Selkregg 1974). Temperatures range from
-sloe (-6QOF) to near 32oc (9QOF)~ mean monthly temperatures
in the last decade have ranged from a minimum of -26.70c)
-16.10F) in January to 20.1oc (68.20F) in July (Apppendix 1).
Precipitation averages 28 em (11 in) annually, including 118 em
(47 in) of snow at Gulkana. Ten-year averages of precipi-
tation, temperature and maximum snow depth at Gulkana are
presented in Appendix 1. To the north, montane influence is
strong, and precipitation is over 43 em
including 277 em (109 in) of snow at Paxson.
(17 in} annually,
The frequency of
years when total snowfall is likely to exceed a 68 year mean
maximum (156 em, 61 in, Fairbanks) is presented in Appendix 1.
Data for local stations were insufficient, so Fairbanks was
used as an index.
A variety of vegetation types are present, ranging
from lowland coniferous forest to alpine tundra. The dominant
tree species are black spruce (Picea mariana) and white spruce
(P. glauca). Birch (Betula papyrifera), aspen (Populus tremu-
loides) and cottonwood (P. balsamifera) are present on warmer,
_j drier sites •
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Common shrubs are willow (Salix spp.), alder (Alnus
crispa) and dwarf birch (B. glandulosa and B. nana); the
latter occur over large areas at elevations of 915-1,220 m
(3,000-4,000 ft). Mat and cushion tundra is present above
1,200 m (4,000 ft). Extensive areas of herbaceous cover,
largely sedges (Carex spp.), are associated with the many lakes
and ponds. Pegau and Hemming (1972) provide a detailed
description of vegetation in the study area.
Intensive studies were conducted between TAPS MMs 620
and 660 (Figure 4). In the north TAPS crosses gently-rolling
hills with the exception of the rather steep drainages of
Haggard Creek (TAPS MM 642.7) and an unnamed creek on the north
side of Hogan Hill (TAPS MM 644.8). All of this area is above
700 m in elevation. South of Hogan Hill (TAPS MM 64 7-660)
terrain is generally flat, and elevation decreases gradually
from 700 m to 550 m. Most of the area is overlain by glacial
or alluvial deposits with extensive permafrost, especially
south of Hogan Hill (USDI 1972). Vegetation along TAPS is
typical of the study area, consisting mostly of spruce forest
frequently mixed with shrubs. Spruce forest is more common at
lower elevations in the southern part of the area whereas shrub
communities are more common to the north. Because TAPS was
constructed across uplands as much as possible, fewer wetlands
I occur along TAPS than in the study area overall. Wetlands are
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most common south of Hogan Hill. Aspen and birch are found
most frequently on well-d~ained south-facing uplands.
The TAPS right-of-way (ROW) within the study area
includes the pipeline, a driveable workpad and adjacent cleared
area. The ROW averages 30 m (100 ft) in width and includes a
gravelled pad elevated a meter or less above the surrounding
terrain. The pad ·averages seven meters ( 28 ft) wide .. ROW
width at above-ground pipe ( 27 m, 90 ft) was less than at
buried pipe (37.5 m, 124 ft) (Appendix 2). Vegetation is
generally sparse on the ROW and consists mostly of introduced
grasses: at the lower edges of the ROW, however, grasses and
sedges are often abundant.
The 122 em (48 in) diameter pipeline was constructed
above ground over 61 percent of the study area (38.9 km, 24.2
mi) and is supported by vertical support members (VSM) at 18 m
(60 ft) intervals. The average height of the pipe (BOP-TOP) is
2.4 m (7.9 ft) above ground with 92.6 percent of its length
greater than 1. 8 m ( 6. 0 ft) in height. Above ground pipe
occurs most frequently (80.3%) from immediately north of
Haggard Creek (MMs 640-620) to Paxson Lake and south of Sour-
dough (MMs 655-660) (Figure 4).
Buried pipe occurs between MM 638 and MM 654 near
Sourdough and comprises 39 percent of TAPS in the· study area
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(Figure 4). Two buried sections (each 2.9 km, 1.8 mi)
separated by 6.4 km (4 mi) of above ground pipe and located
between Hogan Hill and Sourdough are specially refrigerated
burials installed as special crossing sites for caribou (Figure
4). The remaining four sections of buried pipe (18.6 km, 11.6
mi) were installed for geotechnical reasons and coincide with
well-drained uplands including Hogan Hill and the high ground
south of Spring Creek. These sections range in length from
2.4-3.2 km (1.5-2.0 mi).
Special wildlife crossing sites include 30 elevated
designated big game crossings (DBGC) characterized by BOP-TOPs
>3.3 m (10 ft) over at least 18 m {60 ft), and six short (<18
m, 60 ft) sections of buried pipe called sag bends. All DBGCs
occur north of MM 635, as do all but one sag bend.
TAPS lies approximately parallel to the Richardson
Highway through the study area, crossing to the west at the
base of Hogan Hill. The pipeline is less than 2 km {1 mi) from
the Highway over 88 percent of its length in the study area
and, in the vicinity of Hogan Hill and north of Haggard and
Spring Creeks, it is less than 400 rn {0.25 mi) from the highway
over 25 percent of its length in the area. Fourteen gated
access roads at irregular intervals connect the highway to
TAPS. Access to the TAPS ROW is restricted to authorized
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personnel and helicopter surveillance flights (<50 m above
ground} occur about twice a day.
4.0 METHODS
The interaction of the Nelchina caribou herd with the
pipelin~ was measured using five techniques: aerial surveys,
corridor surveys, forward-and back-tracking of caribou trails,
control trail surveys, and behavioral observations. Field work
coincided with usual periods of migration of the Nelchina
caribou herd to and from winter range adjacent to and east of
TAPS (Appendix 3).
4.1 AERIAL SURVEYS
Aerial surveys were conducted to assess caribou
distribution and monitor movement of caribou in relation to
TAPS. Surveys were conducted only in the first year of the
study to verify distribution and movement patterns reported in
the past. Data on distribution in subsequent years were
obtained from reports by K. Pitcher (1982, 1983}.
Aerial survey sampling consisted of parallel strip ·
transects perpendicular to caribou movements (Figure 5}
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NOV.-DEC. 1981
_ ... TAPS
--SurwyT,_
0 s 10 15 21Dkm.
SCALE P"""SiJ"'""Si .,..
J..i..§UR
18-19 FEB. 1982
_; •• TAPS
0 s 10 15 2011rn.
SCALE~
Figure 5. Aerial survey transects, 1981-1982.
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(Eberhardt 1981)). The area was sampled systematically
(without replacement). This method is 11 ••• .:by far the.:: most
efficient means of mapping the distributioJJ of anima-:Us ••• "
(Caughley 1977:611). The precision of tnis sampling tecWhique
is as good or better than random sampling (Cochrane 196~) and
precision was most important for this portioc :of the stud:¥'•
Helie Courier and Cessna 185 fixe~ing aircraff:were
flown at 120 m (400 ft) above ground at an ~ir~peed of 160~kmph
( 100 mph). The survey team included two observers in th~ rear
seats and a navigator and pilot in the front, Transeot: width
was controlled through markings on the air~t wing st~u~s and
windows or a wire strung from eye bolts und.€-rc-the wing-~f the
Helie Courier (Miller et al. 1977). Tnese markings were
checked against a known distance on the groan~. while f1~ng at
120 m (400 ft) above ground.
Five aerial surveys were flown .trt-=~1981-1982l~able
1) • Transects flown during 1981 were 1. 0 krtr._: ( 0. 6 mi) wi~ and
spaced 10 km ( 6 mi) apart. Transect spacing in Februa~· 1982
was 12.5 km ( 7. 25 mi), which reduced the sample from l~i to 8
percent of the study area. The location of each caribo~rgroup
observed was plotted on 1:250,000 scale topographic:;cmaps.
Observers recorded the number and compositii.Grrt'Of caribou·tn the
group, the vegetation in which they were located, andWtt.heir
direction of travel. Also noted were orientatibn and in~~nsity
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Table 1. Timing and sampling intensity of aerial surveys of
Nelchina caribou, 1981-1982.
TRANSECT
AREA PERCENT TOTAL AREA
CARIBOU LIFE SAMPLED SURVEY SAMPLED
DATE CYCLE PHASE km2 (mi2) COVERAGE km2 (mi2)
1981
22 Apr. Spring mi9ration 380 (148) 10 3800 (1485)
30 Apr. Spring migration 238 ( 93) 10 2380 ( 930)
11 Nov. Fall migration 446 (173) 10 4460 (1734)
2 Dec. Fall migration 442 (173) 10 4420 (1734)
4 Dec. Fall migration 452 (177) 60 753 ( 294)
1982
18-19
Feb. Mid-winter 793 (306) 8 9916 (3062)
of use of caribou trails, the presence of feeding craters and
observations of other wildlife species.
One intensive aerial survey was conducted in December
1981 to determine caribou distribution in an approximately 15
km ( 9. 3-mi) wide area centered on TAPS/Richardson Highway
between TAPS MMs 627.6 and 653.4 (Figure 6). Those transects
were oriented approximately east-west, perpendicular to the
pipeline and extended 5 km (3 mi) east or west of either the
pipeline or the highway. Transects were 600 m (0.5 mi) wide
and 1 km apart, providing a 60 percent sample of this ·area
(Table 1, Figure 4c) • Observations were recorded as on the
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aerial reconnaissance
surveys, except that
locations of caribou were
plotted on 1:63,000
topographic maps.
For the
analysis of spring and
fall aerial surveys a
line estimating the
orientation of caribou
movements was calculated.
An east/west ( x axis)
south/north (y axis) grid
overlain on distribution
maps of caribou group
locations was used to
regress a line. The
slope and inteFcept of
this line described
objectively the alignment
of caribou groups with
respect to the TAPS
corridor during migration.
20
LEGEND
-·TAPS
Paxson
Lake
_ Survey Transect
SCALE: 1cm-6km
Figure 6. Aerial survey tran-
sects within a 15 km
corridor centered on
TAPS/Richardson
.Highway, 4 December
1981.
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4.2 CORRIDOR SURVEYS
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Corridor surveys were conducted to locate and
describe caribou crossings of TAPS. Surveys by snow machine or
truck were conducted several times during 1981-1983 to document
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crossing of the pipeline by caribou (Appendix 3). Sections of
the TAPS ROW were driven daily (Table 2) and trails that could
be followed across the ROW were measured.
4.2.1 Initial Reconnaissance
I .J During initial ground reconnaissance in each survey
period, emphasis was on determining where caribou were crossing
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1) Location in relation to a vertical support member
(VSM) or mile marker (MM),
2) Pipe mode (above-ground, buried, special crossing) at
the point of encountering the ROW,
3) Estimated number of caribou,
4) Direction of travel,
5) Crossing success (successful or unsuccessful, and
distance of any lateral movements along ROW, see
Glossary, Appendix 4),
6) Vegetation type (one of 15 categories, Table 3),
7) Topography, slope and aspect.
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Table 2. Corridor survey dates, location and distance, 1981-
1983.
SURVEY DATE
1981
24 April - 2 May
22 October
5-6 November
5-6 November
28 November
1982
6-9 April
17-19 November
1983
30 March
3 October
22 October
7 November
SAMPLE AREA
TAPS Mileage Marker
639.2 -653.0
627.6 -653.4
633.0 -642.0
644.8 -653.4
636.6 -653.4
623.5 -661.0
623.5 -660.0
623.5 -660.0
623.5 -660.0
632.5 -660.0
623.5 -660.0
SAMPLE DISTANCE
km (mi)
22.1
41.3
14.4
13.8
26.9
60.0
58.4
58.4
58.4
44.0
58.4
(13.8)
(25.8)
( 9.0)
( 8.6)
(16.8)
(37.5)
(36.5)
(36~5)
(36.5)
(27.5)
(36.5)
During several surveys, large numbers of trails in
some areas made counts difficult because individual trails were
obscured. In these instances, one count was made on each side
of the ROW where individual trails were more easily discerned
J and the mean of these values was used in analyses. Where this
was impossible, an estimate was made of· the number of caribou
-_l crossing the pipe between VSMs.
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Table 3. Vegetation classifiqation categories used in Nelchina
study area.
DETAILED CATEGORIES* COMBINED CATEGORIES
) Open conifer
Closed conifer
Conifer woodland
) Conifer
)
Open deciduous )
Closed deciduous )
Deciduous woodland ) Deciduous/mixed
Open mixed conifer/deciduous )
Closed mixed conifer/deciduous )
Open tall shrub )
Closed tall shrub )
Open low shrub ) Shrub
Closed low shrub )
Lake )
Wet meadow ) Wet meadow/lake
Disturbed ) Disturbed
*Viereck and Dyrness 1980.
The number of caribou using a trail was visually
estimated from the various trail characteristics. Sometimes a
trail branched on the ROW and we could then count how many
animals had used it. More often our estimate was based on the
width of the trail and the extent to which separate hoofprints
remained with snow ridges in between. In our opinion these
estimates represent a minimum number of caribou that· used a
trail.
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4.2.2 Trail Configurations
Subsequent to the reconnaissance survey, a subsample
of trails was measured to describe their configuration within
c} 20 m of the TAPS ROW. We made these measurements to quantify
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the degree to which caribou were or were not "deflected" by
TAPS upon approach. This has been a concern expressed for over
a decade (Klein 1971, 1980, Geist 1975, Berger 1977), yet
quantitative measurements have not been made.
In fall 1981, a systematic subsample of every third
trail was used. In fall 1982 and spring 1983, most individual
I trails were obscured: our subsample then consisted of all J
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trails whose configuration we could determine!. The following
following information was recorded for these trails:
1
2
1)
2)
Pipeline bearing (degrees true),
Trail bearings (degrees true) for approach and
departure (Figure 7), from pipeline centerline to a
point on the trail 20 m (66 ft) distant from the ROW
edge (20 m to center, #1 and #2)2,
We do not believe the trail sampling scheme in 1982 and
1983 biased the data as trail orientations did not differ:
Mean 1981 = 65.00, S.E. = 1.9, n = 115: 1982 = 68.6°,
s.E. = 4.0, n =22: 1983 = 64.7o, s.E. = 2.9, n = 67.
In order to ensure against potential bias related to
caribou encountering the open ROW, we analyzed changes in
orientation of caribou trails upon encountering the ROW
edge (X= 24.lo, s.E.·= 2.1, n = 111) and concluded that
this change did not differ from changes elsewhere on the
trail on or off the ROW (t = 1_.72, df = 252, p>0.05).
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@ @ @ w ~/~ a.
w a. w
0 0
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w w
31: 31:
0 0 ~· /
a: a: ~ /
VSM //:~
/.. .........:
vs .• .,..-+-+--e
Figure 7. Schematic of measurements taken where caribou trails
encountered the TAPS right-of-way (ROW).
3) Distance of the trail at the point of crossing the
pipe from the nearest VSM if above-ground pipe ( #3,
Figure 7),
4) Bottom of pipe to top of pad (BOP-TOP) height at the
trail crossing (above-ground pipe),
5) Snow depth at the ROW center line, the ROW edge and at
a point on the trail 10 m (33 ft) distant from the ROW
edge (#4, Figure 7).
26
Mean bearings (degrees true) for approach and
departure segments of caribou trails were calculated (Zar
1974). To determine the mean overall ·change in direction of
trails, we calculated the difference between departure and
approach bearings. Values fall between oo -180o. If an animal
completely reversed direction the change would be 180o. These
differences were then compared between pipe modes, and to other
difference values measured on caribou trails that were
back-tracked from the ROW (see below).
The configuration of trails up to 200m (660 ft) from·
TAPS was measured in 1981. A systematic subsample of every
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compare angular changes within 20 m (66 ft) of TAPS to changes
measured beyond SO m from TAPS. Beyond SO m the pipeline and
ROW are partially obscured from view due to vegetation and
topography which may provide a different stimulus to an
approaching caribou. These trails were followed forward and
backward to a point 200 m along the trail from the ROW edge
(Figure 8). Each trail was divided into SO m segments; at
each SO m station the bearing to the previous station and
vegetation type over a SO x SO m area were recorded. The mean
~J change in bearing between SO m stations was compared to the
mean differences of trails measured within 20 m and crossing
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"" a.
a.
VSM ~-+--e
VSM ~-t-e
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Figure 8. Schematic of measurements taken on fore-and back-
tracked caribou trails.
E ..
Since we could not determine group size from trail
records in most instances, we examined. potential bias related
to group size based on observations of 124 caribou groups.
crossing TAPS. None of these crossings suggested that
differences in trail configuration relative to group size would
be significant as most animals crossed directly. In addition,
group size remained relatively constant during the study
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(aerial survey and observations on the ROW) with means never
exceeding 9 animals (n = 493).
Bias in determining crossing success was possible in
1982 and 1983 because of trail mixing. When a trail entered
and followed the ROW it commonly intersected other trails and
its destination could not always be determined. These trails .
were not measured: only trails that could be followed onto and
off the ROW (whether it crossed or not) were selected. There-
fore, our sampling may have been biased to direct crossings
(successful) of the ROW. We do not believe this bias was
significant since differences in crossing success between
I unbiased trail measurements in 1981 and measurements in 1982
J and 1983 combined were not evident (Success: 1981 = 100%, n =
j 134: 1982 = 96.4%, n = 28: 1983 = 100%, n = 68).
4.2.3 Pipe Mode and Height
1 Heights of above-ground pipe (BOP-TOP) beneath which
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caribou crossed (based on trail measurements) were compared
with the BOP-TOP heights available between TAPS MMs 623 and
660. Availability of BOP-TOPs was determined by consulting
Alyeska Pipeline "As-Built" design sheets. These values did
not include the 0. 25 ft of insulation surrounding .the pipe:
this value was subtracted from the "AS-Built" data. Based on a
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sample of BOP-TOPs measured in the study area (n = 536), 13 em
( 5 in) was then added to the 11 As-Bui 1 t 11 data as a correction
factor: this difference was probably a consequence of settling
and erosion of the pad.
4.2.4 Vegetation
Vegetation in the study area was classified according
to Level III categories of Viereck and Dyrness (1980). Several
categories were combined to facilitate analysis.
The proportion of each vegetation type in the study
area was determined from aerial surveys. Points were randomly
selected (n = 209) along survey transects (December 4, 1981)
within 7. 5 km of TAPS, after Skoog ( 1968) and Marcum and
Loftsgaarden (1980).
The proportion of each vegetation type along the ROW
was determined from a ground survey conducted 26-27 August
1983. The percent cover of vegetation types present within 50
m of the ROW was estimated continuously between TAPS MMs 623
and 660.
In major crossing areas used by caribou, . feeding had
commonly occurred on and at the edge of the ROW. We therefore
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sampled vegetation in these areas to determine percent cover of
plants (usually revegetation grasses) and species present.
Three 60 m line transects were established in each area: over/
under the pipe, between the pipe and the ROW edge, and at the
edge of the ROW. The transect at the ROW edge was divided into
two 30 m segments, one on either edge of the ROW. Twenty 0.5 m2
plots at 3 m intervals were sampled along each 60 m transect.
Percent cover of each species present was estimated in each,
and could range from 0 to > IOO percent in plots with dense
cover by several species (Daubenmire 1959). Species with
flowering parts present were collected and later identified
using a botanical key (Hulten 1968) •
4.2.5 Snow Depth
Snow depths were measured every 0. 8 km ( 0. 5 mi)
during corridor surveys. Three measurements were taken at the
ROW center and 10 m off the ROW. The average of each group of
three measures was used to describe snow depth.
4.3 CONTROL SURVEYS
Six control trail surveys were conducted at both
above-ground and buried pipeline to determine caribou trail
.. 1
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31
orientation at various distances from the TAPS corridor (Figure
9). These surveys were made in areas of high caribou use, as
determined from a ground reconnaissance survey along the ROW.
Each survey consisted of walking:
1) a transect parallel to the ROW and 500 m distant
from it on the approach side of TAPS (east side in
spring, west side in fall: c, cl, Figure 10),
2) a series of 250 m transects perpendicular to the
pipe on both approach and departure sides (E-H,
Figure 10).
All transects were established with a compass, measured with
.J hip chain or paced, and travelled on foot.
---.
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--;
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J
At each trail encountered, trail bearings over 10 m
were measured with a compass, and the extent to which the pipe-
line (ROW) was visible (percent) was estimated within the field
of view of the observer. When trails were encountered on
transects perpendicular to TAPS, distance from the ROW edge was
also recorded.
A mean of trail bearings relative to the pipeline
(angle) was calculated. If a caribou walked parallel to the
ROW, the angle would be oo: if a caribou walked perpendicular
to the ROW (the most direct route), the angle would be goo
Individual angles were then regressed on distance to dete~mine
any relationship.
1 J
32
1
~ l
]
~ ..
]
J
J
cl
.J
l ,.,_ ....
: l
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J
Above ground pipe.
Buried pipe
Control survey
_]
Figure 9. Locations of control surveys.
. i
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. )
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A
250m
e
A1
e
0
"' N
33
Figure 10. Schematic of control
surveys to sample
caribou trails
adjacent to the ROW.
4.4 BEHAVIOR
Direct obser-
vations of caribou
behavior within the ROW
were made in fall 1981
( 213 hours). Observation
sites were selected on the
basis of previously
observed frequency of use
by caribou and were
located between TAPS MM
638.7, north of Haggard
Creek, and TAPS MM 648.9,
south of Hogan Hill.
Sixty percent (128 hr) of
the observation effort was
at buried pipe and 40
percent at .above-ground
pipe. One hundred twenty-two caribou groups were observed
crossing the ROW, 105 (86%)' at buried pipeline and 17 (14%) at
above-ground pipeline.
B'ehavior was measured during daylight hours using the
instantaneous scan method (Altmann 1974). Observers were
positioned at the edge of the ROW, generally on a hill-top
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34
affording the greatest possible view of the ROW. Observation
began for· each caribou group when the first member of the group
entered the ROW and was terminated when the last animal in the
group departed the ROW. Information recorded on each group
included sex-age composition, group leadership (sex-age of the
first animal in the group to enter the ROW) and the length of
time spent within the ROW. Activity scans were made at one-
minute intervals and the number of animals feeding, standing,
walking, lying, running, alert or exhibiting alarm behavior,
within each group, was recorded. The distance of each group
from the observer, direction of travel, pipe mode, location and
weather conditions were also recorded. All observations where
caribou were visibly disturbed by the observer were discarded.
Mean time on the ROW and mean group size were
calculated and compared in relation to pipe mode and sex-age
classification. Activity budgets (frequency of activity) were
calculated for different group sex structures and comparisons
were made between pipe modes • These data were . statistically
analyzed with non-parametric tests (median test -Zar, 1974)
due to serial correlation between activity scans and small
sample size.
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35
5.0 RESULTS
5.1 SEASONAL MOVEMENTS -TIMING
During spring and fall 1981 and mid-winter 1982,
caribou were consistently located east and west of TAPS with
the distribution oriented along a northeast-southwest axis
(Figure 11). They were in small groups (x = 5.6, s.E. = 1.2,
n = 121, range = 1-15) with 44 percent (n = 48) of groups
observed on lakes, 22 percent in meadow (n = 24) and 34 percerit
(n = 37) in spruce forest (Table 4). use of lakes was higher
Table 4. Caribou group size and habitat use, aerial surveys
April, November, December 1981 and February 1982
(numbers in parentheses= percent).
SURVEY DATE
1981
22 April
30 April
11 Nov.
2 Dec.
4 Dec.
Meadow
5 (71)
6 (46)
4 (16)
5 ( 15)
1 ( 9)
HABITAT
Lake
2 (29)
3 ( 23)
16 ( 64)
18 (54)
3 (27).
Spruce
0 ( 0)
4 (31)
5 (20)
10 ( 30)
7 ( 64)
GROUP SIZE
Mean ~ S.E. (n)
7.0
4.2
5.9
6.4
7.7
2.1
0.7
1.1
1.2
2.1
7
17
26
34
12
1 1982
• J
. I
18-19 Feb. 3 ( 15) 6 ( 30) 11 (55) 4.6 0.5 37
TOTAL 24 (22) 48 (44) 37 (34) 5.6 2.3 121
Comparison of use of lakes during fall and spring migration
. Chi-squared test: x2 = 6.31, df = 1, p = 0.025, n = 89.
Comparison of use of meadow during fall and spring migration
Chi-squared test: x2 = 11.96, df = 1, p = 0 .• 001, n = 89.
}
I : 1
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36
...
LEGEND
• ... OICA-
_ a.....,.....,..z.z _.a
.......... • 1 • • ••• • ··10·· • e >ao • ---
SCALE
__ .,... ... -----
11 •••
----.n .....
e I 8 ·• •·• I . .... . . ,. ..
Figure 11.· Caribou distribution from aerial surveys conducted
in spring and fall 1981. and February 1982.
-J
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1
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37
...
....
•
•
Figure .11. (Continued)
LIGIND
4 oec:/81 _ .................... ..... ..... ........ : ; .. . ... ---... . .. ,...
e I • ,. • ••
SCALf ...
•
LEGEND
NQ.OIJCAIIIIMU -................. ,.. ...
••••• ........... • 1
... ........ • 2 .. . . ... .. . ,.. .
...
l
(
• j
. j
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38
during fall migration (54%, n = 69) than during spring
migration (25%, n = 20; p<0.025) when meadows were used most
(55%, n = 20; p<O.OOl). Caribou were observed in spruce
forest more (55%, n = 20) in mid-winter than during migratory
periods (29%, n = 89).
Caribou distribution and the location of major trail
systems were dependent on season. In spring 1981, migration
from the Gakona and Chistochina Rivers drainages westward
across TAPS peaked in mid-April. A major shift in caribou.
distribution was observed between the 22 April and 30 April
aerial surveys (Table 5, Figure 11). Heavy east-west trails
indicated migration within the survey area was under way by 22
April, mostly south of Hogan Hill.
Spring migration occurred at a similar time in 1981
and 1982, but in 1983 migration occurred considerably earlier.
In February 1983, caribou were observed moving across TAPS to
the west (Pitcher, pers. comm.) • Approximately half of the
herd ·crossed at this time with the remainder crossing in
April._
During fall, caribou move east across TAPS in early-
to mid-October, although most of the herd swings southwest back
across TAPS in late October before moving east across TAPS
again in November and December. In fall 1981, 7, 000-10,000
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39
Table 5. Numbers of caribou observed east and west of TAPS
during aerial reconnaissance surveys, 1981 and 1982.
NUMBER OF
TRANSECT AREA CARIBOU CARIBOU
km2 {mi2) OBSERVED /100 km2
SURVEY DATE EAST WEST EAST WEST TOTAL EAST WEST
1981
22 April 185 ( 72} 195 ( 76) 41 20 61 22 10
30 April 106 { 42) 132 ( 52) 34 41 • 75 32 31
11 Nov. 185 ( 72) 259 (101) 65 121 186 35 47
2 Dec. 185 ( 72) 259 (101) 159 75 234 86 29
1982
18-19 Feb. 430 (168) 290 (113) 57 99 156 13 34
caribou (35-55% of total population) moved east across TAPS in
mid-October from northern Lake Louise Flat and then returned
across TAPS moving west (Alyeska Security, pers. comm. ) • Of
124 groups observed crossing TAPS between 24 October and 8
l ) November 1981, 91 (74%) were moving west. Although these move-
l
J
ments were not as sudden in 1982 and 1983, the same pattern was
evident since more caribou (68%) crossed west in October than
in November (24%) during the study period. The 11 November
1981 survey showed a higher density of caribou west of TAPS on
the Flat (Table 5, Figure 11). By December, densities were
higher to the north and east in the Gakona and Chistochina
Rivers drainages, indicating a major eastward movement (Table
l 5, Figure 11). Trail systems across TAPS were mostly north of
J
-~ 40
--!
I
Hogan Hill. By February, caribou were dispersed, mostly at low
_l densities and located on winter range (Figure 11, Table 5).
l
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Five groups were observed near TAPS moving both east and west
across TAPS.
5.2 CROSSING SITES
5.2~1 Location
Specific sections of TAPS were consistently crossed
by caribou during migration although the locations of high use
zones changed between spring and fall {Figures 12 and 13).
In spring, most caribou (66%) crossed over a 20 km
(12 mi) section (34% of ROW length) of TAPS south of Hogan
Hill. The Spring Creek drainage (4 km, 2.5 mi wide) north of
Hogan Hill was of secondary (29%) importance and Haggard Creek
(1 km, 0.6 mi wide) was used least (5%) (Figure 13). This
pattern was consistent in 1982 and 1983. In 1981 snow
conditions precluded trail counts but aerial survey data
suggest that the same sites were used in 1981.
In fall, most caribou (80%) crossed TAPS over a 20 km
(12 mi) section (34% of ROW length) north of and including
Hogan Hill (Figures 12 and 13). A few ( 13%) crossed in the
l . J
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Above ground pipe
Buried pipe
., Fall
·~ Spring .... ~----
Figure 12. Main caribou crossing zones, spring and fall 1981-
. J 1983. J
J
J
]
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.... z w
(.)
a: w a.
30
20
10
D SPRING
(n=4200)
mJ FALL
1!111 (n=3705)
623-630 630-635
42
~
~
3:
z.
4(
0
0· :
635-640 640-645 645-650
TAPS MILE MARKER
650-655 655-660
Figure 13. Distribution of caribou trails along TAPS during
spring and fall migration, 1981-1983 {n = number of
caribou trails).
Spring Creek drainage late in the fall after freeze-up, while
1 only seven percent crossed south of Hogan Hill.
l
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43
5.2.2 Characteristics
5.2.2.1 Topography
Topographic features associated with crossing sites
were similar between years and within either the spring or fall
period. However, differences in the location of spring versus
fall crossing sites were principally related to topography.
Topographic features associated with spring crossing
sites were usually depressed, flat terrain adjacent to uplands
(Figure 13). These lowlands are contiguous on either side of
TAPS and characterized by high densities of small lakes
(wetlands) and meadows (Figure 12).
In the fall, crossing sites were strongly associated
l with upland and sloped topography between the major lowlands of
Spring Creek and the area south of Hogan Hill. These uplands
are contiguous with uplands to the west of TAPS and with slopes
east of TAPS.
Although these relationships were consistent overall,
increased use of the Spring Creek drainage was recorded in late
November 1982 (Figure 13). That survey was 2-3 weeks later
)
l than all other surveys and took place well after lakes had.
frozen. Average temperatures were lower in fall 1982 than 1981
1
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44
and 1983 and snow on the ground was low (Appendix 1). At this
time, 56 percent of caribou trails along TAPS were located
within the lowlands of Spring Creek and 39 percent on the
upland slopes immediately to the south.
5.2.2.2 Vegetation
•
Caribou trails were not associated with any.
particular vegetation type. Vegetation types associated with
crossing sites reflected topographic differences observed
between spring and fall. Spring crossing sites had a prepon-
derance of wetland meadow, most of which is interspersed with
coniferous forest {Table 6). Although spring crossing sites
represented less than 42 percent of ROW length, 95 percent of
wetland meadow along TAPS occurred at these sites.
Fall crossing sites were characterized by upland
vegetation types. Deciduous/mixed-wood occurred frequently
(83%) within these sites which represented 31 percent of the
length of the ROW (Table 6). Wetland meadow was notably scarce
at these sites (Table 6).
Differences in vegetation along the ROW and elsewhere
in the study area were minimal except for shrubs and wetland
meadow. The ROW had more shrub {p<O.lO) and less wetland
--""!
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45
Table 6. Distribution of vegetation types along TAPS in relation to topographic features
and pipe mode.
TAPS LOCATION ~MM)
623.5-633.5-636-642-645.6-647.3-649.1-652-653.8-
633.5 636 642 645.6 647.3 649.1 652 653.8 660
AREA Paxson Spring Haggard Ck-Hogan Special Abov-Special South TOTAL
FEATURE Area Creek Hogan Hill Hill Buried S!round Buried SourdouS!h (AveraS!el
VEGETATION TYPE
Conifer 54 69 88 43 60 66 73 59 80 (66)
Deciduous/
mixed wood 3 0 1 32 5 0 0 4 <1 (6)
Shrub 42 29 9 22 27 8 16 25 12 (23)
Wet meadow/
lake <1 .l. <1 <1 0 22 10 5 6 ( 3)
Disturbed 1 0 1 2 9 3 1 8 2 (2)
PIPE MODE
Above
ground (mil 8.5 2 .• 5 3.0 1.0 o.o o.o 2.8 o.o 6.2 24
Percent 85 100 so 28 0 0 100 0 100 66
Buried (mil 1.5 o.o 3.0 2.6 1.7 1.8 0 1.8 o.o 12.4
Percent 15 0 50 72 100 100 0 100 0 34
DISTANCE
Kilometers 16 4 9.6 5.8 2.7 2.9 4.5 2.9 9.9 58.3
(Miles) (10) (2.5) (6) (3.6) (1. 7) ( 1.8) (2.8) (1.8) (6.2) 36.5
Percent 27 7 16 10 5 5 8 5 17 100
meadow (p<O.lO) than did the entire study area (Table 7).
These difference~ relate principally to geotechnical consider-
ations for pipeli~e location since uplands were preferred over
lowlands ~hich decreases the occurrence of wet meadows and
increases the occurrence of shrubs (see Table 6). Consequently
along the ROW c<;~.ribou trails were located more in shrubs and
less in meadows than the occurrence of these types in areas
away from TAPS (Table 7) •
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Table 7. Caribou use of vegetation types within major crossing
zones along TAPS in relation to availability of types
during spring and fall migration periods (values in
parentheses= availability).
VEGETATION
TYPE
Conifer
Deciduous-
mixed wood
Shrub
Wet meadow-
lake
Disturbed
No. of trails
PERCENT CARIBOU USE
SPRING
1982-1983
Mean Range
69 66-80
(73)
1 0-4
(<1)
18 8-29
( 17)
9 2-22
( 8.)
3 0-8
(2)
3,990
FALL
1981-1983
Mean Range
64 43-88
(69)
13 1-32
(12)
19 9-27
(16)
<1 0-<1
(<1)
4 1-9
( 3)
2,964
AWAY
FROM
TAPS
(62)
( 5)
( 1)
ALONG
TAPS
(66)
(6)
(23)
( 2)
Comparison of habitat proportions available and used by caribou
crossing the TAPS for (a) shrubs, and (b) wetland meadow •
a) Chi-squared test: ;x2 = 2.7668, df = 1, p = 0.100
b) Chi-squared test: x2 = 3.0927, df = 1, p = 0.081
Comparison of habitat proportions available and used by caribou
crossing the TAPS over (a) spring, and (b) fall, and (c) both
migration seasons.
a) Chi-squared test:
b) Chi-squared test:
c) Chi-squared test:
x2 =
x2 =
x2 =
1 .. 4030, df =
1.-2663, df =
1.1561, df =
4, p
4, p
4, p
= 0.816
= 0.874 = 0.886
Caribou use of vegetation within major crossing zones
did not differ significantly (p>O.OS) from the availability of
47
l
J
vegetation in the same area (Table 7). This observation
app'lied both to spring (p>0.05) and fall (p>0.05) crossing
l zones.
C,J
No relationship could be found between forage
= I quantity or quality and the frequency of caribou crossings.
Caribou frequently foraged on the TAPS ROW especially at the
] edges where cratering was most evident. Most of the ROW has
been seeded with a revegetation seed mix (Appendix 5) but plant
J cover is highly variable except at the ROW edge (Table 8) •
' l
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'")
_j
Table 8. Vegetative cover
PIPE TAPS
LOCATION MODE MM
Spring Creek A/G 635.2
Hogan Hill A/G 646.5
Hogan Hill B 646.5
Special Burial B 648.8
Between
Special
Burials A/G 651.8
Special Burial B 652.6
* n -15.
along TAPS ROW, August 1983.
PERCENT COVER (MEAN ::!: SE, n = 20)
PIPE ROW CENTER ROW EDGE
3.7 0.6 9.1 1.4 90.9 9.6
13.7 2.2* 24.9 3.2* 88.3 4.3
110.6 8.2 60.2 5.6 92.5 11.0
26.4 2.4 12.0 1.4 64.6 9.1
10.6 3.6 18.4 2.4 " 22.8 3.0
61.6 4.4 55.0 8.8 79.2 8.0
48
Sedges (Carex spp.), Equiseturn spp. and grasses were abundant
at the ROW edges at both pipe modes while virtually absent
elsewhere on the ROW. Within the central part of the ROW,
buried pipe sections supported four times more plant cover than
at above-ground pipe (Table 8).
5.2.2.3 Snow
Snow depth and hardness can influence caribou distri-
bution by affecting their rate of travel and ability to obtain
forage. Maximum snow depths during this study were normal or
i below normal with the exception of November 1981 to January
c J
1982 when snow depth exceeded the normal by 10-20 ern (Appendix
'-1
~1 lA). The greatest accumulation of snow occurs by March (50 ern,
. )
j
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20 in) and diminishes rapidly thereafter. Spring snow depths
(33 ern, 13 in) are generally two to three times greater than in
the fall period (Appendix lA). Snow depths exceeding 80 ern (32
in) occur infrequently in the Fairbanks area (Appendix lB) and
even less frequently in the study area (Appendix lA) and it is
doubtful that snow accumulation in either spring or fall would
restrict caribou passage across the TAPS ROW.
Along TAPS snow depth increased from south to north
(Figure'l4). Snow was twice as deep in the north compared to
the south· end of the study area. Greatest snow depths occurred
1
\
~1
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: l
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J
~J
I
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l .
' 'J
80
70
60
50
e u 40
: ... a. w
Q 30
~ z rn
20
10
Figure 14.
49
SPRING
m FALL
624 628 632 636 640 644 648 652 656 660
TAPS MILE MARKER
Distribution of snow depths along TAPS in relation
to spring and fall migration zones, 1981-1983.
north of Spring Creek ( MM 636) and the least snow occurred
south of Hogan Hill (MM 646). Snow depths were 32 percent less
on the TAPS ROW than in adjacent areas (Table 9).
snow depth during the spring migration period was low
( <44 em, 17 in) at the major crossing sites . south of Hogan
Hill. North of this area, snow depths increased to 52 em (20
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Table 9. Snow depths on and off the TAPS right-of-way, 1981-
1983.
Mean
SPRING
31 March 1983 36.9
FALL
19 November 1982 28.8
*21 October 1983 9.4
7 November 1983 20.6
*MM 632.5 -660.0
SNOW DEPTH { em)
ON ROW 10 m OFF ROW
± s.E.
+ 1.4 -
+ 1.3
+ 1.1
+ 1.0 -
{ n)
(62)
(53)
(56)
(72)
Mean ± S • E • ( n)
53.2 + 2.3 (62)
39.0 + 2.0 (53)
15.8 + 1.8 (56)
32.3 + 2.0 (72)
in) in the Spring Creek area and over 70 em (28 in) near Paxson
Lake.
In the fall the same pattern prevailed but the major
crossing sites had intermediate snow depths ranging between 25
_ j and 38 em (10 and 15 in). However, in late October 1983, rain
!
. 1
had created a crust on the snow and caribou crossed farther
south than in previous years. By November, caribou were again
using the upland areas north of Hogan Hill crossing sites.
Between Paxson Lake and Haggard Creek (MMs 625-642), the crust
would support a man weighing 75 kg (170 lbs) which equates to a
hardness of· >1.8 kg/cm2 (Miller 1976), but its hardness
·diminished south of Haggard Creek. Adult caribou are supported
j by a crust of.>2.1 kg/cm2 (Miller 1976) •
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51
5.2.2.4 Pipe Mode
The distribution of above-ground and buried pipeline
is mostly a reflection· of geotechnical considerations. Above-
ground pipe is most common where frozen soils are present, and
buried pipe in well-drained, frost-free soils. However, in two
instances the pipeline was refrigerated and buried to
accommodate caribou movements south of Hogan Hill (MMs 647.3 -
649.2 and 652.0-653.8) (Figure 12, Table 6).
There were differences between seasonal crossing
sites and the available pipe mode (above-ground or buried).
Spring crossing sites were located in sections of TAPS with a
high proportion (76%) of above-ground pipe in contrast to fall
crossing sites where most (65%) of the pipe was buried (Table
6). However, it was only between MMs 635 and 655 that caribou
had a "choice" of pipe mode. Crossings in this section were
made in proportion to occurrence of pipe mode; no selection
for either above-ground or buried pipe was evident (p>O.OS,
Table 10) •
The distribution of pipe heights between spring and
fall crossing zones did not differ (Table 11). Most pipe (91
and 92% respectively) was greater than 1.8 m (6 ft) in height
yet caribou crossed pipe at BOP-TOPs ranging from 1.0 m (3.3
ft) to 5.1 m (16.7 ft) .• The median BOP-TOP at both spring and
--1
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Table 10. Percent of all caribou crossings in relation to pipe
mode during spring and fall migration periods (seven
surveys, 1981-1983).
TAPS
SECTION
(Mile)
(Marker)
PIPE MODE
AVAILABILTIY
(Percent)
A/G B
625-630 100
630-635 100
635-640 64
640-645 24
645-650 16
650-655 62
655-660 100
Average 67
No. of trails
Average for
sections where
selection l.S
possible 41
0
0
36
76
84
38
0
33
59
PERCENT OF CARIBOU CROSSING
SPRING
A/G B
0 0
100 0
91 9
34 66
1 99
39 61
100 0
57 43
2400 1800
48 52
x2=2.02
p=O.l79
FALL
A/G B
0 0
100 0
66 34
6 94
6 94
67 33
100 0
39 61
1452 2253
38 62
x2=o.37
p=0.585
BOTH
A/G
100
100
77
11
3
42
100
49
B
0
0
23
89
97
58
0
51
3852 4053
43 57
x2=o.l6
p=0.692
fall crossing sites was 2.3 m and the mean BOP-TOP at which 253
caribou trails crossed the pipe was 2.5 m (S.E. = 0.03).
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53
"
Table 11. Distribution of pipe heights (BOP-TOP) at spring
and fall caribou crossing zones (percent in paren-
theses).
MIGRATION <1.8 m 1.8-3.0 m >3.0 m . TOTAL 18 m
PERIOD (6 ft) (6-10 ft) (10 ft) PIPE SECTIONS
Spring 107 1,024 82 1,213
( 9) (84) ( 7) (100)
Fall 33 332 42 407
(8) (82) (10) (100)
5.2.2.5 Predators
Monitoring of predators is important because of
~1 concern that they may disrupt movements of caribou as they
approach TAPS and kill more caribou along the ROW than in
adjacent areas (Miller 1984, Roby 1978). Wolves and their sign
l were observed along or adjacent to· the ROW throughout · the
study. In spring, wolf sign (n = 5) was observed in the
I southern half of the area (MMs 642-659) whereas, in fall, wolf
sign (n = 11) occurred throughout the area (MMs 628-660). Most
( 82%) sign in fall was located north of MM 644 whereas, in
.J' spring, most (60%) was located between MMs 651 and 658. Three
moose carcasses were located, one at MM 633 in fall and two at
MMs 651 and 658 in spring.
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Wolf tracks, except in two instances, did not follow
the ROW. In fall, wolf tracks were consistently observed over
a 1.6 km section of TAPS at MMs 633 and 643 and some of these
tracks followed the ROW less than 1.6 km.
5.3 SPECIAL CROSSING STRUCTURES
Special wildlife crossing structures included 30
designated· big game crossings, six sag bends and two
refrigerated (special) buried sections each 2.9 km (1.8 mi) in
length (Figure 15). The two · special buried sections were
! designed especially to facilitate caribou movements •
. .J
Designated big game crossings and sag bends were
-"i
located in the northern third of the study area (Figure 15).
I
•.) Both types of structure are in an area with high snow depth
(>60 ern, April 1982) and are associated with conifer (51%) and
shrub (49%) vegetation types. Most (74%) are located on ridges
with the remainder in valleys. Special buried sections are
located in the southern third of the study area which has low
snow depth (<40 em, April 1982), a relatively high (14%)
J proportion of the wet meadow-lake vegetation type, and flat
• J
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topography.
SEASON PERCENT OF
Spring 0 0 7
n = 21· (0) N/A 0-322
(0) (640)
Fall 0 0 2
n = 5 (0) N/A N/A
(0) (500)
Total 0 0 5
n = 7 (0) (0) ( 1140)
1 Number of surveys
2 Range (percent)
,_....~., __ --... ol ' i ·~
SPRING
CREEK
TAPS MILE
TRAILS CROSSING
N/A
N/A
(620)
N/A
N/A
(988)
N/A
(1608)
HAGGARD HOGAN
CREEK HILL
MAfiiKER
SPECIAL CROSSING
N/A 96
N/A 14-100
(210) (1050)
N/A 54
N/A 0-89
(1093) (896)
N/A 76
(1303) (1946)
; ' ~ L...-..,._1
Spring
Fall
Designated big game crossing
Sag bend
-Special burial
• Buried pipe
Above ground pipe
STRUCTURES
GULKANA
RIVER
65
13-88
(900)
33
0-100
(133)
61
(1033)
1 4
0-33
(730)
0
N/A
(95)
2
(1825)
Figure 15. Location and use (percent) of special crossing structures within 8 km (5 mi) sections of
TAPS by Nelchina caribou 1981-1983 (number of trails in parentheses).
U1
U1
TOTAL
41
(4200)
13
(3705)
29
(7905)
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Within 8 km ( 5 mi) sections of TAPS where caribou
could encounter a special crossing structure, special burials
were used most. Of those animals crossing between MMs 645 and
650, 75 percent crossed at the special burial (Figure 15) which
accounted for only 35 percent of the section. At the other
section between MMs 650 and 655, 61 percent of caribou crossing
did so at the special burial ( 35% of . section). In both
instances, the proportion of caribou using these structures was
greater in spring (82%) than in fall (51%).
Designated big game crossings and sag bends were used
very little (<8%) by caribou since most (89%) were outside of
major caribou crossing zones.
About 29 percent of the estimated number of caribou
crossing TAPS did so at a special crossing structure and most
( 27%) used special burials (Figure 15). All structures were
used less in fall (13%) than in spring (41%).
5.4 CARIBOU RESPONSE TO TAPS
5.4.1 Crossing Success
Based on trail surveys,
were known to approach the ROW.
an estimated 7, 905 caribou
All trails but one ( 3-4
--1 57
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animals) crossed (99.95%). This group of caribou entered the
ROW from the west (fall 1982) at a buried pipe section where
they foraged and bedded along 40 m of the ROW prior to exiting
to the west. Of all trails, 49 percent crossed at above-ground
pipe (Table 10)
Direct observations of 149 caribou groups entering
the ROW were made in the spring and fall of 1981. All of these
groups crossed TAPS.
5.4.2 Approaching and Departing the ROW
Measurements of· trails approaching and crossing TAPS
indicated that the configuration of caribou trails (changes in
orientation over distance) was similar in areas away from TAPS
as it was where caribou crossed TAPS (Table 12). A slightly
larger average change in orientation occurred where caribou
crossed TAPS but the difference was not significant (t = 1.71,
df = 270, p>0.05) except at above-ground pipe (t = 2.54, df =
170, p<0.05) where the difference was 7.2 degrees.
Caribou, upon entering the ROW, crossed directly (<25
m lateral movement) in most (92%) instances.· However, certain
trails (n = 32) that successfully crossed TAPS either ('1)
approached or departed the pipe on old cutlines ( n = 4), ( 2)
1 -·
58
Table 12. Caribou trail configuration (change in orientation
over distance) beyond 50 m from TAPS compared to
trails crossing TAPS.
CHANGE IN BEARING (DEGREES)
50 m Trail Sections
Approach and Departure Approaching Beyond
PIPE MODE 20 m to Pipe 50 m from TAPS
Mean + s.E. n Mean + s.E. n --
Above-ground 24.8 2.1 99 17.6 1.6 73
Buried 24.1 2.9 94 20.9 2.1 70
Both 23.8 1.9 193 19.2 1.9 143
noticeably paralleled the pipe (>25 m) either on (n = 2) or off
.· -1 ( n = 5) the ROW, or ( 3) encountered a transition between , __ l
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above-ground and buried pipe sites ( n = 6) • The approach and
departure sections of these trails at above-ground and buried
pipe sites were classified as direct (perpendicular to pipe) or
paralleling the pipe for >25m (Table 13). Caribou approached
the pipe directly at a slightly higher frequency (57%) than did
caribou approaching parallel to the pipe (43%), but this
difference was not significant (g = -0.55, p>O.OS). The same
pattern was evident for trails departing the ROW (Table 13).
Thus, no differences were observed for appr~ach-departure
orientations between pipe modes.
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Table 13. Approach and departure orientations of caribou
trails within 20 m of TAPS crossing at above-ground
or buried pipe.
DEPARTURE PIPE MODE
Above-ground
Direct
Buried
Above-ground
Parallel
Buried
TOTAL
APPROACH
DIRECT PARALLEL
3 5
3 5
7 2
4 1
17 13
Paralleling above-ground pipe
TOTAL
8
8
9
5
30
during approach
occurred off the ROW at 5 trails (17%) for an average of 88 m
1
. J (S.E. = 5, range= 330-160 m). Two trails (7%) paralleled off
the ROW approaching buried pipe, but distances were not l
. J measured. No paralleling during departure occurred off the ROW
· 1 for either above-ground or buried pipe.
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Paralleling above-ground pipe during approach
occurred on the ROW at two trails (7%) for an average of 55 m
(S.E. = 25, range = 30-80 m) compared to two trails (7%)
paralleling buried pipe for an average of 51 m (S.E. = 1.2,
1
1
I . I Go
range = 50-52 m). Paralleling on the ROW during departure at
above-ground pipe occurred in nine instances (30%) for an
J average of 111 m (s.E. = 4, range = 30-314 m) compared to five
instances (17%) over an average of 52 m (S.E. 14.1, range =
: -]
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30-100 m) at buried pipe (Table 13).
Caribou followed cutlines that were parallel to or
that intersected the ROW. Four trails were noted funnelling
through a sag bend after paralleling the pipe along a cutline
30 m off the ROW. At a point perpendicular to the sag bend,
they left the cutline and crossed the sag bend, departing
directly.
At 35 percent of the above-ground pipe sites (n = 17)
a cutline intersected and crossed the ROW at 90 degrees. At
these sites, caribou encountering the cutline off the ROW
fol.lowed it directly across the ROW.
At transition sites, where above-ground pipe turns
qnderground (n = 8), six caribou trails approached directly to
the point of transition and crossed the buried pipe directly.or
paralleled either the above..-ground or huried sections on the
l ·-· J departure side. The other two trails approached the point of
1 transition after paralleling above-ground pipe and crossed the
.J buried section directly •
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c 1
61
n•8
100
-w
CJ z c 80 n=32 a:
Q z c
z c
Q w 60 2 -w ....
Ill u;
>
(I) 40 a. c ...
II.
0 ... z w 20 (J a: w a.
1-25 26-50 51•75 76-100 101-125 126-150 :::0150
DISTANCE FROM TAPS (m)
Figure 16. Extent that TAPS is visible in relation to distance
away from TAPS.
As caribou approached TAPS, their perception of the
open ROW may alter the angle at which they were travelling
relative to TAPS. ROW vi.sibili ty .was assessed over distance
from TAPS and it was found that visibility declined rapidly
over 50 m from the ROW but variability was high depending on
forest density (Figure 16). B~yond 125m (400 ft), the ROW was
seldom visible.to field workers.
~1
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. ·-&:2· . ··-·---.
Upon analyzing the angle of caribou trails relative
to TAPS (X bearing = 4.6oT, S.E. = 3.80) over distance, no re-
lationship was found either for above-ground ( r = -0.29, t =
-0.299, n = 283, p>0.05) or buried pipe (r = -0.35, t = -0.372,
n = 214, p>0.05). This observation was consistent between 1
and 500 m away from TAPS. Caribou approached TAPS at an
average angle of 50.4 degrees (S.E. = 1.7, n = 497) up to 500 m
from the ROW, but variability was high (CV = 53.6%). At 500 m
from TAPS, caribou approached at a mean angle of 56.6 degrees
(S.E. = 6.2, n = 202) compared to 63.8 degrees (S.E. = 3.8, n
= 158) within 20 m of the ROW. This difference is not signifi-
cant (t = 0.93, df = 358, p>0.05).
During fall caribou approached TAPS at an average
bearing (True North) of 92 degrees ( S .E. -1. 9, n = 550)
whereas, in spring, they approached at an average bearing of
259 degrees (S.E. = 3.6, n = 190).
5.4.3 Caribou Behavior on the Right-of-Way
Direct observations of 145 groups ( 1, 140 caribou)
between MMs 637 and 649 on the TAPS ROW were made from 24
October to 8 November 1981. Data for groups ( 2 3 ) that were
disturbed by the observer • s presence were not used in the
analyses. Of the 122 groups (880 caribou) that were not
1
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63
disturbed, 14 percent were at above-ground pipe and 86 percent
at buried pipe. All groups crossed TAPS.
Mean size of groups observed was eight (S.E. = 1.2,
n = 122) while most groups ( 77%) ·were less than 11 caribou
(Table 14). The largest group observed was 27 individuals.
Caribou spent an average of 7. 6 minutes on the ROW before
departing regardless of pipe mode (Table 14). Small groups
Table 14. Time spent on the ROW by Nelchina caribou in
relation to group size, fall 1981 (n = number of
groups).
INDEPENDENT
VARIABLE n
Above-ground 17
vs.
Buried pipe 105
Bull 7
vs.
Cow 41
vs.
Mixed so
TIME ON ROW
(Minutes)
MEAN ± S.E.
8.4 2.2
6.7 0.8
1.7 0.3
5.9 0.8
8.4 1.3
SIG.l
nsd
n/a
nsd
GROUP SIZE
MEAN ± S.E.
8.4 1.4
6.9 0.5
3.1 1.2
s.o 0.6
9.0 0.7
1 nsd
n/a
=
=
no significant difference, p>O.OS,
sa~ple size prohibits comparison.
SIG.l
nsd
n/a
t=4.50,p<0.05
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64
generally spent less time on the ROW than did large groups •
' Group leadership was assessed in 59 groups and was predom-
inantly adult females (92%). Adult bulls were leaders in five
percent and calves in three percent of groups.
While on the ROW, caribou were most often standing
(37%) or walking (32%). Feeding activity occurred 23 percent
of the time adjacent to, over and under the pipe, and lying.
only 7 percent (Figure 17).
Differences in frequency of activity were apparent
between above-ground and buried pipe modes but none of the
differences were significant (p>0.05) (Figure 17). Caribou
spent more time feeding (44%) and less time standing (28%) at
J above-ground pipe than at buried pipe ( 20% and 38% respec-
. j
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tively). Caribou were rarely observed lying at above-ground
pipe. However, these observations are based on few (17) groups
at above-ground pipe compared to buried pipe (105) which limits
comparability. Proportions of different caribou groups (male,
female and mixed) observed at above-ground and buried pipe were
not significantly different (x2 4.259, df = 2, p = 0.087).
Alarm behavior (run, alert, excitation leap) was
observed in 15 groups (12%) consisting of a total of 91 caribou
(mean group size =·6.1, S.E. = 1.4, range= 1-17). Four groups
were observed at above-ground pipe and 11 at buried pipe. A
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Figure 17.
FEEDING
FEEDING
WALKING
65
e ~ Above ground pipe ~ n • 17groups • 0 Buried pipe n •105 groups
438• no. of sc-
551
278
LYING
ACTIVITY
STANDING
.._mm Mate
IUll1l n • 7 groups
• ~Female t:;;;;;l n =41 groups
•D Mixed n•50groups
240•no. of sc-
WALKING LYING
ACTIVITY
STANDING
RUNNING
RUNNING
Frequency of caribou activity on the TAPS ROW,. fall
1981 (median and range included).
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66
·maximum of 41 caribou were observed in some form of alarm
behavior, the most common (8 of 15 groups) of which was alert
posture (head up, ears erect). Running was observed in six
groups and excitation leaps in two groups of which one was
elicited by the presence of a wolf. In another instance where
caribou ran, they did so in apparent response to other caribou
moving onto the ROW. All other (13 of 15 groups) alarm
behaviors could not be linked to a specific stimulus.
Of the alarm behaviors observed, alert behavior was
the most common (1.1%) and the excitation leap the least common
(0.1%), with the total occurrence accounting for 1.4 percent of
the time.
6.0 DISCUSSION
Klein (1980) discussed potential consequences of
interaction between caribou and pipelines which included
increased predation (mortality), loss of range (fewer caribou),
reduced dispersal (establishment of other herds) and energetic
stress due to deflections and inhibited movements (mortality).
All of the caribou and reindeer herds discussed by Klein (19SO)
have since · increased in numbers and their movement patterns ..
have not been disrupted (except in one .instance in the Soviet
Union when an absolute barrier was ·created)· since the
67
introduction of roads, railways, pipelines and electric
transmission lines (Jakimchuk 1980, Klein and Kuzyakin 1982,
Bergerud et al. 1984).
Klein (1980:526) believed that disruption of caribou
movements by development activity is more likely when popu-
lations are at low levels. Although TAPS was built when the
Nelchina herd was at a population low ( <10, 000 caribou), the
herd's movements have not been significantly affected. We
found no evidence that TAPS impeded caribou movements or
altered movement patterns that have been described in the past.
Skoog (1968) described Nelchina caribou movements in the early
fall as a clockwise swing from the Alphabet Hills to Lake
Louise Flat. After the rut (late October, November), caribou
undertook an eastward migration across the Richardson
Highway/TAPS. Since TAPS bisects the winter range of the herd,
caribou commonly used habitats adjacent to TAPS throughout the
winter.
We observed caribou in the vicinity of TAPS as early
as late September and throughout October. During this period,
caribou were observed adjacent to TAPS but they did not show
any consistent directional movement until November when
eastward movement began. Pitcher (1983) confirmed these
observations and estimated that 80 percent of the herd crossed
TAPS (Pitcher, pers. cornrn.).
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68
During the winter of 1982-1983, the Nelchina herd
exhibited a movement that has occurred only three times in the
past 30 years. Up to 40 percent of the herd moved northeast of
the Mentasta Mountains to the vicinity of Tok and Northway on
the Alaska-Yukon border (Pitcher 1983). Klein (1980) expressed
concern that such movements, which can involve exchange of
individuals with other herds, would be adversely affected by
the presence of structures such as the Trans-Alaska Pipeline.
He stated (Klein 1980:525), "The opportunity for this
occurrence, which may be essential to reverse the decline of
large herds, will clearly be reduced through the construction
of major transportation corridors s~ch as the Trans-Alaska Oil
l Pipeline and associated haul road." TAPS has been in existence .J
for 10 years and one such movement has occurred. This rate of
'-l occurrence does not differ from the historical record.
l
.... j Klein ( 1971, 1980), Miller et al. ( 1972), Banfield
l (1973), Jakimchuk (1975) and others have expressed concern that l
.,
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structures such as TAPS could alter· traditional movements of
caribou and affect survival. Klein
disruptions would be more likely to
encounter obstructions seasonally such
(1980) suggested that
occur if caribou only
as in the case of the
j Nelchina herd. This concern relates primarily to disruption of
__ j
pre-calving movements. If caribou are preven~ed from reaching
J
_j the traditional calving ground, new calving grounds will be
j
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69
established, but subsequent survival would be lower since
optimal habitat is no longer available (Klein 1980).
The traditional calving ground for the Nelchina herd
remains intact as does the pattern of spring migration (Pitcher
1982, 1983). Spring migration usually occurred in April with
caribou moving from the southeast part of the study area to the
west (Skoog 1968, Hemming 1971). The same pattern was observed
in 1981 and 1982 but in 1983 most caribou moved west in
February. This variability is characteristic of winter and
spring movements and may be related to snow conditions (Skoog
1968, Kelsall 1968, Gauthier et al. 1984). Snow depth during
the winter of 1982-1983 was more than 30 percent below normal
(Appendix 1) and probably accounted for the different timing in
1983.
The locations where caribou crossed the Richardson
Highway were not accurately defined prior to the construction
of TAPS. Skoog (1968:447) depicted major fall migratory zones
in the northern portion of our study area south· of Paxson Lake,
and spring crossing zones in the vicinity -of Sourdough.
However, both the Spring ·creek drainage and the flat between
Hogan Hill and the Gulkana River were recognized as traditional
crossing zones prior to TAPS construction (Hemming, pers.
comm.) • Local residents de·scribed major fall crossing zones at
Hogan Hill,.Haggard Creek and Spring Creek and'it was in these
l
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areas that hunters in the 1960s concentrated ( Chimielowski,
pers. comm.).
The same seasonal crossing zones as described above
were identified in this study and Pitcher (1983) confirmed our
observations through relocations of radio collared caribou from
1981-1983. These zones were characterized by different
physical conditions that reflected caribou responses to snow
cover and terrain as described in other studies (Kelsall 1960,
1968, Skoog 1968, Miller 1984). Fall crossing zones were
characterized by upland topography and vegetation types,
whereas spring zones were in lowlands.
In fall prior to freeze-up, caribou are usually found
-J dispersed over uplands and well drained slopes where travelling
J
I J
is easiest; after freeze-up lakes are used as travel routes
(Skoog 1968, Kelsall 1968). In spring travel is more
j restricted to frozen lakes and rivers and in snow-free terrain
(Bergerud 1974, Kelsall 1968, Skoog 1968, Miller 1976,
Carruthers and Jakimchuk 1981, Pitcher 1983). Fall crossing
zones were located on uplands between Spring Creek and Hogan
Hill. Caribou crossed TAPS in this zone and showed no
J preference for vegetation type, pipe mode or pipe height. Up-
land topography was the only consistent feature associated with
fall crossing locations. However, adverse snow conditions may
71
have caused a shift to a more southerly crossing zone in one
instance.
During spring migration, caribou travelled in low-
lands. Frozen lakes and ponds serve as direct and rapid travel
~1
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routes as well as escape terrain, unlike in the fall when
caribou are forced to swim or move around lakes (Kelsall 1968,
Miller 1974, 1975, Bergerud 1978). Deep snow would inhibit or
prevent movement to the calving ground and escape from
predators so caribou often travel where snow cover is least
(Miller 1975, 1976, Kelsall 1968, Skoog 1968, Carruthers et al.
1983). During years of above average snowfall, a later spring
1 migration is expected whereas low snow depths may prompt
J earlier migration as occurred in 1983.
)
"1 ---'
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Special crossing st-ructures were seldom used by
migratory caribou since most structures were outside the
crossing zones. The apparent differential use of refrigerated
burials in spring versus fall reflects different movement
characteristics at these seasons. ·The more diffuse fall
l migration (Jakimchuk 1980, Carruthers and Jakimchuk 1981) would
entail less contact with special burial sections, which are the
' ] most heavily used special crossing structures. In spring, snow
._)
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depths and the impetus of migration to calving grounds result
in more directed and channeled movements along traditional
routes (Jakimchuk 1980). Special burials were placed at such
•
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locations and, as a consequence, are heavily used during
spring. In fall, caribou also follow traditional routes o.f
movement but in a more diffuse pattern and in different
terrain. They do not seek out special burial but use it only
as they encounter those sections. This accounts for the 30
percent difference in seasonal use of these particular
structures between spring and fall.
Caribou crossings of TAPS in relation to pipe mode
were highly variable. Where options were available, there was
no significant (p>O.OS) preference for buried or above-ground
pipe. However, in spring most caribou crossed south of Hogan
Hill where use of special buried sections was higher than
elevated sections. However, in the Spring Creek drainage,
another major spring crossing site, elevated pipe predominated.
In fall, caribou selected buried pipe in one instahce within
the main crossing zone but otherwise they crossed according to
availability of pipe mode. In a few instances (8 pipe
transitions) where caribou had a choice of crossing at
above-ground or buried pipe, they chose buried pipe most of the
time.
Most (>90%) above-ground pipe was higher than 1.8 m
(6 ft) and caribou on average crossed at BOP-TOP heights of 2.5
l J m ( 8. 2 ft) • An average prime adult bull caribou measures 1.1 m
(43 in) at the shoulder and with antlers would stand
l
1 73
approximately 1. B m ( 6 ft) to the top of its antlers. Less
than 10 percent of above-ground pipe is lower than 1.8 m. The
distribution of BOP-TOP height was so uniform that selection
for a particular BOP-TOP could not be determined. Since
J caribou crossed at a wide range of BOP-TOP height and, on
average, crossed at the median pipe height, we do not feel that
caribou selected for a specific range of BOP-TOP heights. The
'] general absence of paralleling behavior on the ROW and the
range of BOP-TOP height that were crossed also suggest that
caribou crossed above-ground pipe as they encountered it.
J Comparable data from other studies are non-existent
. l
J but examples of caribou and moose crossing above-ground pipe
support the hypothesis that factors other than pipe height are
I
' _j
more important in determining the location of crossing sites
,] ( Eide and Miller 1979, Curatolo et al. 1982). Roby (1978)
reported a range of BOP-TOP height from 1.1 to 5.1 m (n = 41)
· 1 where caribou crossed TAPS, but the availability of pipe
' l
heights is not presented. Curatolo et al. ( 1982) reported
l equivocal data on caribou selection of pipe heights and . J
J
concluded that topography may have affected choice of crossing
sites. Eide and Miller ( 1979) studied moose crossings in
j relation to pipe heights and noted inconsistencies between
_j
areas and between their study and that of van Ballenberghe
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overall, Eide and Miller's (1979) data show that 83
percent of the pipe is above 1. 8 m ( 6 ft) in height and 84
percent of moose crossed at these heights, but their use of an
analysis technique described by Neu et al. (1974) has
limitations which create inconsistencies in their results.
Johnson (1980:65) discussed a serious shortcoming of this kind
of technique by pointing out how conclusions are "critically
dependent upon the array of components the investigator deems
available to the animals." Eide and Miller (1979) and Van
Ballenberghe ( 1978), by using the technique of Neu et al.
( 1974), assume that all pipe heights are available to moose,
but as Johnson (1980) points out, this is seldom the case.
Other features of the animal's environment are also important
and the operation of a hierarchical selection process would
invalidate this assumption. The inconclusive nature of studies
on choice of BOP-TOP heights by caribou and moose reinforces
the hypothesis that other factors are more important (Eide and
Miller 1979, Curatolo et al. 1982). As we have pointed out,
snow depth, topography and seasonal migratory orientation are
important in the case of the Nelchina herd.
Both Klein (1980) and Geist (1975) have emphasized
energetic costs to caribou of "deflected" movements resulting
from encounters with man-made obstacles. Jakimchuk (1980)
1 _j · reviewed the supposition that caribou "deflected" by man-made
structures are incurring an energy debt and concluded that
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caribou have a wide tolerance to allow for environmental
.1 contingincies. He hypothesized that "deflection" along linear
features (natural or otherwise) is part of an energy
conservation adaptation consistent with the hypothesis that
caribou follow (on average) the path of least energetic
resistance.
We found no evidence of caribou being deflected by ]
TAPS. Caribou approached and crossed TAPS on approximately the
J same bearing as the direction of spring and fall movements 1
with no change in orientation as they approached TAPS. Upon
J encountering the right-of-way 1 most caribou crossed directly 1
spending less than eight minutes on the ROW. Similar
observations have been made for highways and rights-of-way
.. 1 , .. l (Carruthers and Sopuck 19821 Gauthier et al. 19841 Miller
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1984). McCourt et al. (1974) and Decker (1976) found that
caribou followed cutlines such as the TAPS ROW only if the line
was approximately (± 150) oriented in the direction caribou
were moving. Fall movements of caribou in this study were
generally oriented in an east-northeast direction (0600 to 0920)
whereas TAPS was oriented generally north (0050) or a minimum
J of 55 degrees off the course of migratory caribou. This would
I ~J
account for the minimal paralleling behavior observed.
similar relatioqship prevailed in spring.
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Klein (1980) and Geist (1975) both refer to increased
physiological costs to an animal that is disturbed by
threatening stimuli such as pipelines and roads. Klein
(1980:523) suggested that sharp breaks in habitats, such as the
J TAPS ROW, ..... may be reacted to with a high level of alarm, ..
and that the .. avoidance response.. to man-made features is
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partially associated with predator avoidance behavior.
Caribou and other ungulates encountering different
terrain or vegetation features exhibit different behavior than
while moving through uniform habitats (Walther 1969, Henshaw
1970, Urquhart 1971, 1972, Miller et al. 1972, Baskin 1974,
Curatolo 1975, Surrendi and De Bock 1976, Klein 1980, Jakimchuk
and Carruthers 1983). Such behavior is not necessarily
.. disturbance.. related • Jakimchuk and Carruthers (1983)
reported higher frequencies of alert (head up) and alarm
(running and excitation leaps) behavior when caribou
encountered a lake shoreline after travelling over the frozen
lake surface. Henshaw ( 1970), Miller et al. ( 1972), Curatolo
_ j (1975), and Surrendi and DeBock (1976) observed increased
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frequencies of alert or investigative behavior in caribou as
did Walther (1969) in gazelles encountering changes in habitat
features, especially in relation to predator threats • Baskin
(1974) described how sheep would not leave a corral if snowfall
changed the features of the landscape. In each situation the
animal is confronted with a new set of stimuli and the
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subsequent behavior is composed of elements that have
significance to the animal's surroundings (Baskin 1974).
Upon entering the ROW caribou foraged along the edges
where sedges and horsetails, a preferred forage especially in
the fall, were abundant (Miller 1974, 1976, Bergerud 1978, Roby
1978). Snow depth on the ROW was less than in adjacent areas
and, as Miller (1974, 1976) and Jakimchuk and Carruthers (1983)
have noted, caribou often feed in areas with less snow cover -
during migration. This behavior is also a function of caribou
encountering a different terrain or vegetation feature which
permits foraging (Pruitt 1959, Miller 1974, 1984, Jakimchuk and
Carruthers 1983).
Although caribou, upon entering the TAPS ROW, spent
some time feeding, the most frequent activities were standing
and walking. Animals entering the ROW usually stopped and
looked up and down the ROW prior to feeding or walking further.
Alarm responses were infrequent, with the alert posture
occurring most frequently and within the first couple of
minutes after entering the ROW.
Alert and alarm behaviors on the ROW are probably
related to predator detection and avoidance. Roby (1978) has
·suggested that wolves learned to use the Dalton Highway on the
North Slope of Alaska to ambush caribou, and Miller (1984) has
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suggested a similar possibility on the Dempster Highway. We
observed wolf sign in the study area that generally corres-
ponded to caribou crossing zones, as did Miller ( 1984), but
only carcasses of moose were found on the ROW. Forested areas
adjacent to TAPS were not actively searched to locate wolf sign
or carcasses. The only opportunity to find evidence of
predator activity was during control trail surveys up to 500 m
off the ROW, but no carcasses or sign were observed.
Roby (1978) found seven of 12 caribou carcasses
within 200 m of the Dalton Highway, three of which were killed
on the road. He assumed all were killed by wolves. Miller
(1984) found two caribou carcasses within 20 m of the Dempster
Highway, both killed by wolves, one after having been hit by a
vehicle. These observations suggest that even though wolves
may use a highway or ROW to ambush caribou, kills probably
occur in adjacent areas. A wolf-caribou encounter was observed
which further supports this suggestion. A cow and calf caribou
entered the ROW and were alarmed by a wolf ( 2 excitation
leaps). The caribou ran approximately 200 m north on the ROW
before exiting to the east. The wolf continued to walk for a
. J short distance along the ROW then moved off to the east.
· ] Apparently the TAPS ROW could be used by wolves to locate prey
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but its use by caribou as escape terrain in the same sense as
natural open areas may be limited by its width. In this
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situation, caribou have greater security in deep snow which
limits the mobility of wolves.
The "spatial confinement" of caribou within a narrow
zone of open habitat could encourage animals to cross quickly
or not to cross if previous experiences with predators were
common (see Miller 1984). Neither behavior was observed in
this study~ instead, we observed alertness in conjunction with
a high frequency of standing. Although caribou are known to
travel long distances on narrow (<15 m) cutlines through
forested areas (Banfield 1974, McCourt et al. 1974, Decker
1976, Riewe 1979, Carruthers and Sopuck 1982), wolves, on the
1 other hand, infrequently travel on unplowed seismic lines in
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winter, usually crossing directly when encountering the line
(Riewe 1979, 1980). Wolves usually create their own travel
runs which are often traditional (Mech 1970) but the extent to
which they incorporate man-made features is unknown. Both Roby
(1978) and Miller (1984) refer to wolves using highways (hard
surface) as travel corridors but the distance travelled is not
specified and Bibikov (1980) described the use of logging roads
by wolves. Although most wolf tracks on TAPS crossed direct!~,
two areas had numerous wolf tracks. We found no evidence that
l TAPS contributed to increased mortality of caribou through
J
predation.
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The present status of the Nelchina herd is largely a
function of management efforts. Prior to and during
construction of TAPS, the herd was hunted excessively which,
along with natural sources of mortality, caused the herd to
decline (Doerr 1980). Upon restricting human harvest of the
herd and controlling wolves, the herd began to increase
(Bergerud et al. 1984). Since 1973 the herd has increasd at
an average annual rate of 13 percent, similar to other Alaska
caribou herds such as the Western Arctic herd (Davis et al.
1980, r = 0.14,) and the Central Arctic herd (Whitten and
Cameron 1983, r = 0.13). The arrested decline of the herd
occurred during the construction and operation of TAPS which
bisects the migration routes of the herd.
The herd continues to migrate as it is has done in
the past and crosses the TAPS corridor at least twice annually.
The evidence from this study shows that environmental
influences such as snow and terrain are more important than the
Trans-Alaska Pipeline in determining the migration patterns and
crossing locations of the Nelchina caribou herd.
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7.0 CONCLUSIONS
1. The Nelchina herd exhibits similar patterns of spring and
fall migration to that described prior to the construe-
tion of TAPS.
2. Spring migration occurs in mid-April from east to west
with most crossing~ of TAPS occurring between Hogan Hill
and the Gulkana River.
3) Fall migration occurs in November and December from west
to east with most crossings of TAPS occurring between
Hogan Hill and Spring Creek.
4) Fall movements are associated with upland topography and
vegetation whereas spring movements are associated with
lowlands •
5) Special crossing structures are generally located outside
of major caribou crossing zones except for two refriger-
ated burials which were used by 27 percent of caribou
mostly during spring migration.
6) Virtually all caribou that encountered TAPS crossed
successfully (99.95%).
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7} Pipe mode and height did not influence where caribou
crossed TAPS (p>O.OS}.
8} Caribou approached and crossed TAPS without significantly
changing their direction of travel.
9) Caribou spent most of their time in the fall (an average
of 7.6 minutes} walking and standing while on the right-
of-way.
10} There was no evidence that wolves were successfully
ambushing caribou along TAPS.
12} Factors governing the population size and seasonal
distribution of the Nelchina caribou herd are independent
of TAPS and have not been affected by the presence of
TAPS within the range of the herd.
8.o RECOMMENDATIONS
This report reflects a post-construction monitoring
,. '
1 study and cannot address questions pertaining to the actual
<cj
construction period.
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Future projects must, of course, be specifically
evaluated according to their proposed design and the nature of
expected interactions with large mammals. Based on the
findings of this study we recommend the following for similar
future projects:
1) Determine where major (seasonal) caribou movements will
intersect proposed pipeline routes. Ths determination
should include data over long periods of time (>30 years)
and take into account changes in population size.
2) Where major movement corridors are identified, route
selection should be aimed at allowing pipe burial with-
out special facilities or construction of elevated pipe-
line within the BOP-TOP height ranges successfully
crossed by caribou in this studys
3) Local snow conditions should be analyzed with respect to
deposition, microclimatic modification and frequency of
occurrence of above-normal snow accumulation to ensure
adequate crossing window~.
4) Human hunting activity in close proximity to pipelines
should not be ·permitted.
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5) Elevated big game crossings and sag bends are not
necessary as design features to enable successful caribou
crossings of elevated pipelines.
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Selkregg, L. 1974.
central Alaska.
Alaska Regional Profiles. Vol. 1, South-
Univ. Alaska, AEIDC, Anchorage, AK.
Siniff, D.B. and R.O. Skoog.
caribou using stratified
Manage. 28(2):391-401 •
1964.
random
Aerial
sampling.
censusing of
J. Wildl.
I Skoog, R.O. 1960. Annual Report of Progress Investigations
J
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Project. Proj. W-6-R-1. Report c-2a. Alaska Dept. of
Fish and Game. p.l76-181.
1961. Annual Report of Progress Investigations
ProJect. Proj. W-6-R-2. Report C-2a. Alaska Dept. of
Fish and Game. p.l3-31.
1962. ·Annual Project Segment Report. Prog. W
Report C-2a. Alaska Dept. of Fish and Game. p.l5-33.
1963. Annual Project Segment Report, Proj.
W-6-R-4·. Alaska Dept. of Fish and Game. p.lB-19.
1968. Ecology of the caribou (Rangifer tarandus
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Berkeley. 698 P•
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Surrendi, D.C. and E.A. DeBock. 1976. Seasonal distribution,
population status and behaviour of the Porcupine caribou
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Investigations. 145 p.
Urquhart, D.R. 1971. Caribou distribution and behaviour in
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Fish and Wildlife Service, Yellowknife, N.W.T. 40 p.
Urquhart, D.R.
wildlife.
105 p.
1972. Oil exploration and Banks Island
Game Manage. Div., Northwest Territories Govt.
U.s. Dept. of Interior. 1972. The environmental setting of
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Interagency Task Force for the Task Force on Alaskan oil
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40 P•
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' l I -J
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PERSONAL COMMUNICATIONS
J.E. Hemming
K.W. Pitcher
B. Chimielowski
Alyeska Security
93
u.s. Bureau of Land Management
Alaska Department of Fish and Game
Resident, Sourdough area.
•
Glennallen, Alaska.
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APPENDICES
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JFMAMJJA
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SONDJFMAMJJASOND
1982 1983
1982 1983
1982
·Appendix 1A. Temperature and precipitation summaries, Gulkana
·1981-1983 and 10-year average 1971-1980.
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97
Appendix 2. Widths of TAPS Right-of-way, MM 623.5 -661.0.
J
WIDTH (meters)
.J AREA Mean + s.E. n ---
:~I Buried
623.5 -624.1 45.2 7.7 2
] 636.7 -637.0 35.0 1
637.7 -639.2 35.8 1.4 4
640.3 -642.1 48.8 9.0 5
642.5 -644.3 34.3 2.0 6
J 644.8 ·-649.2 34.7 o.8 13
652.0 -653.5 35.6 1.2 4
r' l, Sum of Buried 37.5 1.6 35 j
i Above-ground J
' ) 624.1 -632.0 27.9 0.9 23
I 632.0 -636.6 27.6 1.2 14 ~--1 637.0 -637.7 25.6 0.7 3
639.2 -640.3 34.5 4.3 3
"l 642.1 -642.5 31.8 6.4 2 J 644.3 -644.8 22.0 1
649.2 -652.0 25.0 0.6 10
654.7 -661.0 26.3 0.5 19
Sum of A/G 27.2 0.5 75
l
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. l Above-ground
' and Buried 30.5 1.2 110
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99
Appendix 4. Glossary of terms.
DISTURBED:
Referring to land that has been
man's activity where vegetation
(excludes burned areas).
CROSSING SUCCESS:
physically
cover has
altered through
not stabilized
A successful crossing of TAPS by caribou was defined as any
caribou that approached the pipe on one side (either buried or
above ground) and moved across to the other side.
A crossing was unsuccessful when a caribou approached the pipe
on one side and failed to cross the pipe to the other side.
TRADITION:
A continuity of social interactions over long periods of time
(generations) reflecting favorable interaction between caribou
and their environment.
ALARM BEHAVIOR:
Alert -standing with head high and ears oriented
forward.
j Excitation Leap -When a caribou suddenly raised both forelegs
_ J off the ground.
I
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Run - A gait causing a moderate to fast rate of
movement.
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100
Appendix 4. (Continued)
GROUP:
An aggregation of animals where behavior and distance
relationships imply a functional unit.
Male -adult male animals only.
Female -adult female and sub-adult animals present.
Mixed -at least one adult male and one female one sub-adult
present.
LATERAL MOVEMENT:
When a caribou trail moved laterally from a point where it
contacted the TAPS right-of-way or pipe for a distance of more
than 25 m.
I
._~... .. ___;
Appendix 5. Species composition and percent cover of vegetation along TAPS ROW at selected sites, August 1983.
P E R C E N T C 0 V E R
TAPS MM 635.2 646.5 646.5
BETWEEN SPECIAL
SPRING CREEK A£G HOGAN HILL A£G HOGAN HILL B AMR-1 SPECIAL B B's A/G
UNDER ROW ROW UNDER ROW ROW UNDER RO\'ll ROW UNDER ROW ROW UNDER ROW ROW
SPECIES PIPE CENTRE EDGE PIPE CENTRE EDGE PIPE CENTRE EDGE PIPE CENTRE EDGE PIPE CENTRE EDGE
*Areta red fescue
Festuca rubra 5.6 10.1 8.3 1.8 8.8 0.8
*Boreal red fescue
Festuca rubra 36.5 9.5 10.8 9.6 55.5 28.2 23.0
*Nugget bluegrass)
~ eratensis )
·) 0.4 0.4 0.9 1.9 0.2 4.8 2.0 0.1 5.2 2.0 1.3 0.4
*Sydsport blue )
Po a )
*Manchar brome
Bramus isermis 3.7 12.0 4.9 0.2 1.1
• *Meadow foxtail
Aloeecuris eratensis 5.3 0.2 6.4 5.1 38.2 15.3 8.6 11.1 1.6 3.5 1.0 3.8 0.2
*Annual rye
*Climax timothy
Phleum 0.2
Arcta2rostis latifolia 1.0 0.5 4.6 4.7
Willow
SaliX .!J2E.. 14.8 6.4 0.3 0.3 24.8 3.4
Sedge
~.!E.E.· 1.5 14.2
Horsetail
E9uisetum .!E.E.· 62.3 9.5 19.6 35.2
*Alyeska revegetation mix.
---...!
AMR-2 SPECIAL B
UNDER ROW now
PIPE CENTRE J~DGE
30.2 19.5 7.0
......
0 5.3 0.2 ......
8.8 9.8
21.7 19.6 5.2
21.5
12 .. 8
H .. o
13.3
------ - -- -- - - -- -- --
3.