Summary of 2005 Biological Survey Activities


A. Porcupine Caribou Herd

Several surveys were conducted this year to monitor migration, survival, choice of calving and wintering grounds, and calf production for the Porcupine Herd. Calving typically occurs in early June on the North Slope of the Arctic National Wildlife Refuge and/or within Ivvavik National Park in the northern Yukon Territory, Canada. In early June 2005, a survey of the calving grounds was conducted by the Alaska Department of Fish and Game, assisted by the Arctic Refuge. There was still extensive snow cover on the Refuge coastal plain, which delayed migration of the herd from its wintering grounds. As a result, radiocollared caribou cows were approximately evenly split between the Arctic Refuge and Canadian calving grounds. Twelve percent were within the 1002 Area, and 100% of these had calves or were pregnant. Among the cows located on the Refuge outside the 1002 Area, 76% had calves or were pregnant. Only 50% of the adult cows in Canada had calves or were pregnant.

Regardless of where Porcupine caribou calve, most of the herd is typically found on the Arctic Refuge in late June because of the high-quality forage and insect-free habitats available here. An aerial photocensus of the Porcupine Caribou Herd was scheduled for late June, a time when the herd typically gathers in large groups near the coast. The objective of the photocensus is to estimate the total population size of the herd. However in 2005, the animals aggregated only briefly along the foothills near the Hulahula River and the east end of the Sadlerochit Mountains before beginning their southward migration back to their wintering grounds. The photocensus was therefore cancelled and rescheduled for 2006. The last photocensus was conducted in 2001, and resulted in an estimated population size of 123,000.

During the fall and winter of 2005-2006 we will continue to closely monitor the Porcupine Caribou Herd to estimate over-winter survival. This work will be conducted in cooperation with the US Geological Survey, the Alaska Department of Fish and Game, the Canadian Wildlife Service, and Environment Yukon.

B. Central Arctic Caribou Herd

Research and monitoring of the Central Arctic Caribou Herd is being conducted primarily by biologists from the Alaska Department of Fish and Game. This herd uses calving grounds east and west of the Sagavanirktok River, between the coast and the northern foothills of the Brooks Range. The most recent census of the herd in 2002 yielded a population estimate of 32,000. Significant numbers of Central Arctic Herd caribou use the northwestern portion of the Arctic National Wildlife Refuge during the calving and post-calving periods. Central Arctic Herd caribou typically migrate south beginning in October to winter ranges on both the north and south sides of the Brooks Range, including areas north and west of Arctic Village within the Arctic Refuge.

The Central Arctic Caribou Herd (CAH) has been using western sections of the Arctic Refuge, including the 1002 Area, more frequently and in larger numbers over the past few years. The greatest increase in use of the 1002 Area has occurred during July, when caribou aggregate near the coast to forage in habitats that provide relief from biting insects. Studies of radio collared caribou have demonstrated use of the area between the Canning and Sadlerochit Rivers within the 1002 Area from early July to mid-August. This was particularly true in 2004, when the majority of the CAH moved east of the Canning River to feed and seek insect relief during this period. Increasing use of the 1002 Area has also been observed during June calving and post-calving periods. In 2005, CAH caribou moved east of the Canning River earlier than usual, starting in early June, and at least one radiocollared female apparently calved within the 1002 Area. In addition, 20-30% of the herd has been wintering along the Canning River near the southern boundary of the 1002 Area. In 2004-2005, the remainder of the herd wintered along the East Fork of the Chandalar River in the vicinity of Arctic Village.

Dall Sheep

A. Hulahula River

Biologists from the Arctic Refuge conducted a sex and age composition survey for Dall sheep in the Hulahula River drainage during June 2005. Biologists traveled the route by foot. Sheep were observed with a high-power telescope and classified by sex and age, i.e., lamb, yearling, 2-year old ram or ewe, adult ewe, and adult ram. The latter were further classified according to the degree of horn curl. Similar surveys were conducted in this area in 2003 and 2004.

dall sheep ewesDuring the 2005 composition survey we observed 513 sheep in 34 groups. The number of lambs per 100 ewes was 53.8, compared to 39.1 in 2003 and 48.6 in 2004. The number of yearlings per 100 ewes was 29.9, which was also relatively high (the estimates for 2003 and 2004 were 12.5 and 17.1, respectively). This indicates that overwinter survival of lambs was high this past winter, and 2005 lamb production was also high. We plan to continue monitoring the status of this population in 2006.

B. Atigun Pass

Arctic Refuge biologists conducted a survey of Dall sheep along the Atigun River north of Atigun Pass during early June 2005. The objective of the survey was to estimate age and sex composition for this sheep population. The survey route followed the Dalton Highway from Atigun Pass to Galbraith Lake, then continued along the Atigun River through Atigun Gorge. Biologists traveled by vehicle along the road portion of the route, then on foot through the gorge. This survey has been conducted annually since 1986.

In 2005 we observed 355 sheep in 22 groups, including 3 groups of rams and 18 groups of ewes accompanied by varying numbers of lambs, sub-adult sheep, and rams. Group size ranged from 1 to 118 sheep, averaging 4 for rams and 18 for other groups. The number of sheep seen was higher than average for this survey, but this is not a reliable indicator of the total population size, because additional sheep occurred out of sight of the survey route. This survey is not a population census. This year's lamb per 100 ewes ratio was 53.7, which was substantially higher than both the estimate for 2004 (24.6) and the long-term (1986-2004) average (43.5). The yearling per 100 ewe ratio was low, however (12.8 in 2005, compared to 21.0 in 2004 and a long-term average of 32.7), consistent with low lamb production in 2004. We plan to repeat this survey in June 2006.


The number of moose in northeastern Alaska declined precipitously in the early to mid 1990s, and remains low within Game Management Unit (GMU) 26(C) - the coastal plain and North Slope of the Arctic National Wildlife Refuge east of the Canning River.

In March-April 2005, Arctic Refuge staff conducted an aerial moose survey within GMU 26C. We observed 47 moose along river drainages, but none on the coastal plain away from rivers. The majority of moose occurred in the Kongakut and Aichilik drainages. Alaska Department of Fish and Game surveyed the Canning River in late April and observed 46 moose. These data suggest that the population has remained stable since the last survey in 2003, in which we observed 52 moose from the Canadian border up to the Canning River. We plan to repeat this survey in 2007 and periodically thereafter to evaluate the status of this North Slope moose population.


A population of muskoxen restored to the Arctic National Wildlife Refuge (GMU 26C) grew rapidly from 1974 to 1986 and was relatively stable until 1998. In recent years, however, numbers of muskoxen in the Arctic Refuge have sharply declined. We observed only 9 muskoxen in the Refuge (GMU 26C) during a pre-calving census in April 2005 compared with about 30 seen during censuses in 2003 and 2004.

The muskoxen in the Arctic Refuge are part of a larger population extending from the Colville River in Alaska to the Babbage River in the Yukon Territory. A declining trend in this entire muskox population has been observed since 2000. Numbers in north-central Alaska and northwestern Canada were relatively stable until 2004, when fewer muskoxen were counted in GMU 26B in north-central Alaska. The decline observed in recent years in the Arctic Refuge may now be occurring across the entire North Slope population. Factors responsible for the muskox decline may include low calf recruitment, increased adult mortality, and changes in distribution of the population. Potential causes of these factors include predation by grizzly bears and adverse weather conditions such as icing events, deep snow, and long snow seasons that reduce access to winter forage and increase energetic costs.

Grizzly Bears

Density of grizzly bears in GMU 26B and the Canning River drainage of GMU 26C is estimated to be 18.3 bears per 1000 square kilometers. This estimate was based on surveys flown by the Alaska Department of Fish and Game in 2001-2003.

blond grizzlyIn cooperation with Alaska Department of Fish and Game, Arctic Refuge biologists are monitoring grizzly bears near areas occupied by muskoxen. Two radiocollared grizzly bears are being followed to determine where they live and where they den. Blood and hair samples collected from bears are being analyzed to determine diets of grizzly bears living in and near the Arctic Refuge. This will help managers understand the relationship between grizzly bears and their prey.

Polar bears

A number of pregnant polar bears den within the Arctic Refuge each winter. Of these, biologists only locate those few that are wearing radio collars. In 2004-2005, USGS biologists located one radio-collared polar bear den on the Arctic Refuge coastal plain along the Sadlerochit River. Another den was found adjacent to the Refuge on Flaxman Island. At least two other female polar bears were known to have denned inland near the arctic coast in 2004-2005. Additional dens were located near Dease Inlet, east of Barrow, and on Herschel Island, Canada, east of the Arctic Refuge.

For several years, polar bears have congregated at whale carcasses near the community of Kaktovik. The feeding ecology of these bears was studied during September 2001-2004 under the direction of US Fish and Wildlife Service Marine Mammals Management biologists. In late September 2004, a peak single-day count of about 65 different polar bears were recorded near Kaktovik. Grizzly bears also frequent the area to feed on whale remains. The highest number of bears observed during a single 3-hour observation period was 24 polar bears and 8 grizzly bears. In September 2005, the study shifted focus to examine interactions of polar bears with humans and other bears, including grizzly bears.


The coastal plain of the Arctic Refuge is an important breeding area for several species of birds, especially shorebirds and waterfowl. In 2005, Refuge biologists conducted two studies of shorebird populations on and near the Arctic Refuge.

red-necked phalarope chicksAt the Canning River Delta, Refuge biologists completed field studies for a 4th year on a cooperative project with nongovernmental conservation organizations and oil companies looking at how nesting success of birds may be affected by human development on the North Slope. There has been a concern that populations of predatory species such as ravens, gulls, and foxes may be benefiting from development in this region. In developed areas there is increased availability of human foods and man-made structures which may be used as predator nest or den sites. These situations could lead to an increased predator population which might, in turn, have a negative impact on birds nesting in the vicinity of developments because of increased predation on their eggs and young. The details of these predator-prey interactions are poorly understood, however. Since 2002, researchers have been conducting studies at a number of developed and undeveloped sites across the North Slope. The study site on the Arctic Refuge is one of the undeveloped "control" sites. Biologists now have data from approximately 2,000 nests (all sites and years combined). The data are being analyzed by an independent statistician, and results will be presented when they are available.

postbreeding shorebird watersThe Arctic Coastal Plain also provides important habitat for shorebirds after breeding, as they prepare for long-distance southward migrations to their wintering grounds. This survey investigates how post-breeding shorebirds are distributed across the Arctic Coastal Plain and will help managers determine which sites are particularly important. During August, shorebirds aggregate in large groups near the coast to feed, thereby acquiring the fat reserves they need for successful migration. In 2005 Arctic Refuge biologists joined with other researchers to study the abundance, distribution, movement patterns, feeding habits, and physiology of these birds during the critical post-breeding period. Study sites were chosen across the North Slope. Sites within the Arctic Refuge included the deltas of the Canning, Okpilak, Hulahula, and Jago Rivers as well as Kaktovik Lagoon. This work is scheduled to continue in 2006.

Fisheries Work

A. Kaktovik Lagoon Study

Information to evaluate the stock status and trends of Arctic cisco and Dolly Varden in lagoons adjacent to the village of Kaktovik was collected for a third year. Objectives were to measure relative abundance, determine length and weight characteristics, and compare data from 2003-2005 with baseline data from 1988-1991. Fyke nets (non-lethal fish traps) were set and checked daily at four stations in Kaktovik and Jago lagoons (two in each lagoon) from July 7 to September 7, 2005. Approximately 1,500 Arctic cisco and 1,000 Dolly Varden were captured and released. Numbers of incidental species ranged from 600 Arctic cod, 200 saffron cod, and 200 fourhorn sculpin, to smaller numbers of Arctic sculpin, threespine stickleback, and least cisco. Lengths and weights were measured for Arctic cisco and Dolly Varden to compare with historic values. A final report is expected in 2006.

B. Dolly Varden on the Hulahula River

dolly varden smallDIDSON sonar is an advanced instrument with many sonar beams which may, for the first time, allow accurate abundance estimation of Dolly Varden in North Slope Rivers. Sonar uses a sound wave that is reflected off of fish, then the returning echoes are counted. This technique has been tested on Chinook and sockeye salmon throughout Alaska, as well as with chum salmon on the Chandalar River in the Arctic Refuge. An appropriate site to use DIDSON on the Hulahula River was identified in 2004. Operations in 2005 began on July 7 and continued until September 19. During the 2005 season the crew counted more than 9,000 fish moving upstream. Several fish that were in the DIDSON beam close to shore were captured by hook and line and identified as Dolly Varden. The sonar count will be repeated in 2006 and a final report will be completed in 2007.

didson animation  didson hulahula