Summary of 2006 Biological Survey Activities


A. Porcupine Caribou Herd

Surveys were conducted between October 2005 and June 2006 to monitor migration, survival, choice of calving and wintering grounds, and calf production for the Porcupine Caribou Herd (PCH). The PCH used 2 major wintering areas in 2005-2006: the Ogilvie and Hart River basins in the Yukon Territory, and the East Fork Chandalar River region near Arctic Village in Alaska. The herd began it's migration to the calving grounds on May 15, 2006, which is about 2 weeks later than usual. Because of this delay in the start of migration, few caribou reached the Arctic Refuge coastal plain. Instead, the majority of calving occurred east of the Refuge on the Yukon coastal plain within Ivvavik National Park. Biologists observed 66 adult cows during the early June calving survey, of which 79% were pregnant or had already given birth. This is similar to the 20-year average of 81% calving success.

caribou aggregationRegardless 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. The results of a post-calving survey on June 25, 2006 were consistent with this. At this time, the largest concentration of Porcupine caribou was between the Kongakut and Clarence Rivers on the coastal plain of the Refuge. An aerial photo census of the Porcupine Caribou Herd was scheduled for late June to estimate total population size. The herd dispersed and moved south into the mountains in response to persistent cool, cloudy weather, however, and the photo census could not be completed. This census has been rescheduled for 2007.

The PCH declined from a high of 178,000 in 1989 to 123,000 in 2001, when the most recent photo census was completed. A study of overwinter caribou mortality was begun in October 2003 and completed in April 2006. Annual adult female survival for 2003-2006 was 82.6%, similar to observations of 83.0% survival during 1989-1991. Likewise, estimates of reproductive success for 2006 were similar to average values over the past 20 years. These data suggest that the herd may still be declining, but a herd census will be required to confirm or deny this.

caribou graph 2006

Residents of Kaktovik typically harvest caribou from the Porcupine Herd during the summer along the arctic coast. Residents of Arctic Village harvest Porcupine caribou from fall through spring in the vicinity of the village.

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. Traditionally, the majority of this herd calved west of Arctic Refuge, 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. In recent years, significant numbers of Central Arctic Herd (CAH) caribou have used the northwestern portion of the Arctic Refuge during the calving and post-calving periods. During summer, residents of Kaktovik generally harvest animals from the CAH on the coastal plain west of Kaktovik. In winter and spring, CAH animals are hunted in the Brooks Range's northern foothills and river valleys. CAH 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. In recent years, some CAH caribou have moved close enough to Arctic Village that residents have had opportunities to harvest them. The majority of the herd wintered near Arctic Village during winter 2005-2006.

The 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 western portions of the 1002 Area from early July to mid-August. This was true again in 2006, when several thousand caribou moved east of the Canning River (which in this region forms the western boundary of Arctic Refuge) to feed and seek insect relief. Increasing use of the 1002 Area has also been observed during June calving and post-calving periods. In addition, 20-30% of the herd has been wintering along the Canning River near the southern boundary of the 1002 Area.

Dall Sheep

A. Hulahula River

Biologists from the Refuge conducted a survey, on foot, for Dall sheep in the Hulahula River drainage during June 2006. 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). Adult rams were further classified according to the degree of horn curl. Similar surveys were conducted in this area in 2003-2005.

dall ewesDuring the survey biologists observed 467 sheep in 35 groups. The ratio of lambs per 100 ewes was 39.2, compared to 53.8 in 2005 and 48.6 in 2004. The ratio of yearlings per 100 ewes was 41.7, the highest ever documented in this area This indicates that overwinter survival of lambs was high this past winter, and 2006 lamb production was moderately high. These data suggest that the population of Dall sheep in the Hulahula River drainage may be increasing. Biologists plan to continue monitoring the status of this population in 2007.

B. Atigun Pass

Refuge biologists conducted a survey of Dall sheep along the Atigun River north of Atigun Pass during early June 2006, 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.

Biologists observed 290 Dall sheep in 34 groups, including 46 rams and 123 adult ewes. Average group size was 9.4 sheep, and ranged from 1 to 28. There were 44.7 lambs per 100 ewes in these counts, which is slightly higher than the 20-year average for this area (40.1 lambs per 100 ewes) but is less than observed in 2005 (53.7 lambs per 100 ewes). Biologists estimated 23.6 yearlings per 100 ewes, suggesting that approximately half the lambs seen in June 2005 survived to June 2006.

C. Arctic Village Sheep Management Area (AVSMA)

The Arctic Village Sheep Management Area (AVSMA) was established in 1991 to include that area west of the East Fork Chandalar River between Crow Nest and Cane Creeks, north and west of Arctic Village. The area was expanded in 1995 to include the entire drainages of Red Sheep and Cane Creeks. Within this area, sheep hunting by non-Federally qualified hunters was prohibited.

sheep survey aircraft 2006Studies of Dall Sheep abundance, distribution, and movements in the AVSMA and vicinity were last conducted during 1990-1995. In response to a proposal before the Federal Subsistence Board to open the Management Area to sport hunting, in June 2006 Arctic Refuge staff conducted an aerial survey of the northern portion of the AVSMA, including the Red Sheep Creek and Cane Creek drainages. They estimated that the density of Dall sheep was 1.7 per mi2 in this area, slightly less than the 1990-1991 estimates of 1.9 to 2.2 sheep per mi2.

In July 2006 the Federal subsistence board approved a temporary Special Action to open hunting for full-curl rams to non-Federally qualified hunters in the Red Sheep Creek and Cane Creek drainages only. This Special Action is effective August 10 - September 20, 2006. Refuge staff plan to continue to monitor the status of this population, including sheep density and population composition. They also plan to monitor public use of the area, including numbers of hunters and hunter success.


The number of moose in northeast Alaska declined precipitously in the early to mid 1990s and remains low on the coastal plain and North Slope of the Brooks Range within the Arctic National Wildlife Refuge. In response to the decline, subsistence and sport hunting of moose in this unit was closed in 1996.

In March-April 2005, Refuge staff conducted an aerial moose survey of the entire Refuge coastal plain and all major river drainages from the Canadian border up to, but not including, the Canning River. Observers identified 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 biologists 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, when 52 moose were observed from the Canadian border west to the Canning River. The Refuge plans 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 in the early 1970s increased rapidly from 1974 to 1986, during which time muskoxen expanded their range west beyond Prudhoe Bay and east into northern Canada. The population then remained relatively stable until 1998. In recent years, however, numbers of muskoxen in the Arctic Refuge sharply declined. Refuge biologists observed only 1 muskox in the Arctic Refuge during a population-wide pre-calving census in April 2005. About 30 muskoxen were observed in the Refuge in 2003 and 2004, and 9 were counted in 2005. During 2006, approximately 300 muskoxen were counted in the entire population area.

muskoxenThe decline in numbers of muskoxen within the Refuge was likely caused by low calf production in some years, increased adult mortality, and changes in distribution of the population. Potential factors affecting births, survival and distribution may 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. In cooperation with the Alaska Department of Fish and Game, blood samples collected from muskoxen during the past two decades are being tested for diseases that may also be affecting the muskox population.

Grizzly Bears

Density of grizzly bears in the Arctic Refuge north of the Brooks Range is estimated to be 18.3 bears per 1000 km2. This estimate was based on surveys flown by Alaska Department of Fish and Game in 2001-2003. In 2004, the Alaska Department of Fish and Game reported that hunters killed 12 grizzly bears (7 females and 5 males) from this area. By comparison, 6 and 8 were killed in 2003 and 2002.

In cooperation with Alaska Department of Fish and Game, Arctic Refuge biologists are monitoring grizzly bears that use the coastal plain and foothills of the Arctic Refuge. Four male grizzly bears are followed using satellite telemetry to determine high-use areas, important habitats, possible predation events and denning sites. Other radiocollared bears that use the Arctic Refuge are also monitored. Blood and hair samples collected from bears are being analyzed to determine diets of grizzly bears living in and near the Refuge. This will help managers understand the relationship between grizzly bears and their prey.

Polar bears

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 Fish and Wildlife Service biologists from the Marine Mammals Management office. In September 2005, the study shifted focus to examine interactions of polar bears with humans and other bears, including grizzly bears. In late September 2005, a daily peak count of 37 polar bears was recorded near Kaktovik, compared with a peak count of 65 in 2004. Fewer grizzly bears were also seen feeding on whale carcasses in 2005. A maximum of 4 different grizzly bears were seen in 2005 compared with a maximum of 12 in 2004. The highest number observed at one time was 10 polar bears and 2 grizzly bears in 2005, compared with 24 polar bears and 8 grizzly bears in 2004. The decrease in polar bears feeding at whale carcasses near Kaktovik in 2005 may be due to differences in sea ice conditions between years.

In 2005-2006, U.S. Geological Survey biologists reported no polar bear dens on the Refuge coastal plain.



The coastal plain of the Refuge is an important breeding area for several species of birds, especially shorebirds and waterfowl. In 2006, Refuge biologists conducted two studies of shorebird populations on and near the coastal plain. Additionally, they assisted in the statewide surveillance effort for highly pathogenic avian influenza (H5N1) in wild birds.

shorebird nestRefuge biologists completed a 5th year of field studies on shorebird breeding ecology at the Canning River Delta. Since 2002, researchers have conducted studies at multiple sites across the North Slope in a collaborative effort to investigate whether human developments reduce shorebird nesting success by increasing predator populations. Final results of those studies will be published in 2007. The work at the Canning Delta also provides baseline data for this important breeding site within the Refuge. Refuge biologists now have data from 5 breeding seasons on approximately 715 nests.

The coastal plain of Alaska's North Slope also provides important habitat for shorebirds after breeding as they prepare for long-distance southward migrations to wintering grounds. From July to September, shorebirds aggregate in large groups near the coast to feed, thereby acquiring energy reserves necessary for successful migration. In 2005 and 2006 Refuge staff joined other researchers to study the abundance, distribution, movement patterns, feeding habits, and physiology of shorebirds during the critical post-breeding period. Study sites were chosen between northwestern Alaska and the Canadian border. Refuge biologists established study sites at the Canning, Hulahula and Okpilak River Deltas. They also surveyed staging birds at all other deltas within the Refuge during visits by boat. Results will show how post-breeding shorebirds are distributed across Alaska's North Slope and will suggest which sites are particularly important.

juvenile long-billed dowitchersIn conjunction with other shorebird projects conducted on the Refuge coastal plain, biologists collected samples to test for evidence of highly pathogenic avian influenza (H5N1) in selected bird species. At the Canning River Delta a total of 93 samples were collected from 28 Dunlins, 7 Ruddy Turnstones, 39 Pectoral Sandpipers, 5 Long-billed Dowitchers, and 14 Buff-breasted Sandpipers. During the post-breeding project at the Okpilak River Delta, Refuge biologists expected to collect another 60 samples from these species. To date, no samples collected on the Refuge have tested positive for this virus.

Smith's Longspurs

Refuge biologists began a multi-year study of known and potential nesting habitats for Smiths's Longspurs on Arctic Refuge in summer 2006. The birds are recognized as a species of concern by the Fish and Wildlife Service and others because of their small population and limited distribution. As the only Refuge in the United States with breeding populations of Smith's Longspurs, the Arctic Refuge plays an important role in the birds' existence. Research within the Refuge is being conducted in partnership with sister agencies U.S. Geological Survey, National Park Service, and the Bureau of Land Management, and with the University of Alaska Fairbanks. Biologists found sufficient numbers of birds in 2006 to warrant additional studies in 2007, which will investigate breeding ecology, abundance, distribution and habitat associations of Smith's Longspurs on the Refuge.


peregrine chicksPeregrine falcons that nest on cliffs along the Porcupine River have been studied since the late 1970s. Peregrine populations became dangerously low early in the 1970s throughout their range because of the toxic effects of the pesticide DDT. At that time it was feared that the species would become extinct. Fortunately, after the use of DDT was banned in the United States, populations began to recover. These trends are evident in the data from the Porcupine River: from a low of 9 pairs between the U.S. Canada border and the Yukon Flats in 1979, the population increased to a high of 34 pairs in 2001 (see figure below). Although the number of pairs varies annually because of weather conditions and prey availability, the population of peregrines along the Porcupine River appears to be thriving. During 2006, Refuge staff observed 28 pairs and a total of 44 chicks in the study area.

peregrine graph 2006

Fisheries Work

A. Dolly Varden on the Hulahula River

A study using a fixed-location, Dual Frequency Identification Sonar (DIDSON) was initiated in the summer of 2004 to assess the population status of Dolly Varden in the Hulahula River. During 2005, operational methods and procedures for generating an abundance estimate from the DIDSON data were developed and finalized.

DIDSON is a high frequency, multi-beam sonar with a unique acoustic lens system designed to focus the beam to create high-resolution images. The high-resolution image provides a clear and distinct fish image and a wide viewing angle in the horizontal and vertical plane.

Full 24 hour data collection started August 1 and continued through September 15, 2005. A total of 996.5 hours of data were collected. An estimated 13,045 Dolly Varden migrated upriver past the sonar during this time period. To ensure proper identification, a total of 18 fish were caught by hook and line, 10 of which were caught from within the sonar zone while viewed on the DIDSON. All fish were measured, sexed, and identified as Dolly Varden moving upriver. The remaining fish counted with the DIDSON were assumed to be Dolly Varden.

dolly varden smallFull 24-hour data collection in 2006 again ran from August 1 through September 15. Operational methods and procedures for generating an abundance estimate and describing the variability in run size and timing will continue through the 2007 season. During winter 2006, the Fairbanks Fish and Wildlife Field Office staff will travel to Kaktovik to discuss the nature and status of this project with local residents. Funding has been requested to hire a Kaktovik local to utilize his/her knowledge of Dolly Varden and the area. Also, the possibility of placing a Kaktovik sonar intern on the project will be researched for the 2007 field season.