Summary of 2008 Biological Survey Activities


A. Porcupine Caribou Herd

Most of these caribou overwintered in southern portions of the Arctic Refuge, while a small group wintered in the Yukon Territory. The caribou began their spring migration in mid-April, 2008, moving east along the Brooks Range Mountains and north onto the coastal plain.

The annual calving survey was conducted in early June. Of 69 cows observed, 34 had calves, 21 were still pregnant or had given birth and lost a calf, and 14 were likely not pregnant. The majority of calving occurred around May 30. Seventy-nine percent of adult cows (4 years or older) gave birth, similar to the 22-year average of 81%.

Although snow melted early from the Refuge coastal plain, the majority (67%) of the caribou gave birth to their calves in Canada, and the rest (about 33%) gave birth on the Arctic Refuge.

By mid-June, most of the herd had moved onto the Arctic Refuge. A survey was conducted in late June to determine which calves survived and to estimate the proportion of cows accompanied by calves. Most of the herd was in the northern foothills of the Brooks Range in the Arctic Refuge at this time. Post-calving survival was estimated to be 92%, similar to the 15-year average of 88%.

Biologists planned to conduct a photocensus of the Porcupine herd if the caribou aggregated on the coastal plain. The caribou did not aggregate there, however, because the weather was generally cool and there were few insects. By late June and early July, most of the herd moved south into the Brooks Range mountains. Three attempts were made to radiotrack and monitor the herd in hopes that a photocensus could be conducted. Thunderstorms and a low cloud ceiling prevented tracking flights, however, and the photocensus had to be cancelled. Biologists now hope to complete the census in 2009.

B. Central Arctic Caribou Herd

The majority of this herd wintered along the northwestern boundary of the Refuge in the northern foothills of the Brooks Range.

The Alaska Department of Fish and Game conducted a calving survey of the herd in early June 2008. Of 46 radiocollared caribou cows, 16 were pregnant and 29 were accompanied by calves. Ninety-eight percent of adult cows (4 years or older) gave birth. By late June, 42 of 50 caribou had calves. The majority of calving occurred on June 2.

The herd has used western areas of the Arctic Refuge more frequently and in larger numbers over the past few years. The greatest increase in use of the Refuge has occurred during July, when caribou form groups near the coast where they feed in areas that provide relief from biting insects. In 2008, a large portion of the herd was found in the northwest corner of the Refuge. The Alaska Department of Fish and Game conducted a summer photocensus of the herd. Results will be available in 2009.


Moose in northeast Alaska suffered a substantial decline in the early 1990s because of a series of severe winters. The moose population is still quite low within the northern half of the Refuge. Because of the low population size, subsistence and sport hunting of these moose was stopped in 1996. A limited subsistence harvest has been allowed since the 2004-2005 season, but sport hunting remains closed.

In April 2007, Refuge biologists conducted aerial surveys of moose within northern portions of the Refuge. They saw 59 moose along river drainages. Their data suggest that the population size has not changed substantially since the last survey in 2005, during which 47 moose were observed in the same areas.

Plans are underway to conduct a similar moose survey in April, 2009. Refuge biologists also plan to conduct a study of moose movements, survival, and reproduction beginning in 2010. Up to 25 moose will be fitted with GPS (global positioning system)-satellite collars to track their movements. This study will indicate whether moose in this region migrate to other areas—for example, across the Brooks Range—and will help managers understand why the moose population in this area has not yet shown the recovery that has occurred in other areas of northern Alaska.

Dall Sheep

A. Hulahula River

Refuge biologists conducted a survey of Dall sheep in the Hulahula River area in mid-June. The researchers traveled the survey route by foot, and used a high-power telescope to observe the sheep. The animals were classified by sex and age—as lamb, yearling, 2-year old ram or ewe, and adult ram or ewe—and adult rams were classified based on the degree of their horn curl. Similar surveys have been conducted in this area for 12 of the past 16 years.

This year, 512 sheep in 46 groups were observed. The lamb to ewe ratio, an indicator of reproductive success, was 44.7 lambs per 100 ewes. This was similar to the 2003-2007 average of 41.4, and represents good lamb production. The observed ratio of 33.2 yearlings per 100 ewes in 2008 was slightly greater than the 2003-2007 average of 27.1, and suggests that overwinter survival of last year’s lambs was relatively high. New plant growth appeared to be late this year. As a result, sheep were easily observed at low elevations within the river valley during the survey.

B. Atigun Pass

Biologists conducted a Dall sheep survey along the Atigun River north of Atigun Pass in early June 2008. The objectives of the survey were to estimate the age and sex composition for this sheep population, and to document distribution of sheep within the survey area. Biologists traveled by vehicle along the Dalton Highway portion of the route, and on foot through the gorge. This survey has been conducted yearly since 1986.

Biologists observed 226 Dall sheep in 34 groups, including 40 rams and 93 adult ewes. Groups varied from 1 to 37 animals, and averaged 6.6 sheep per group. There were 49.5 lambs per 100 ewes in this count, which is greater than the 20-year average of 44.1 for this area, and also exceeded the estimated lamb production of 43.2 in 2007. Biologists estimated 17.2 yearlings per 100 ewes, suggesting that approximately 40% of the lambs seen in June 2007 survived to June 2008.

C. Arctic Village Sheep Management Area

The Arctic Village Sheep Management Area was established in 1991 in an area north and west of Arctic Village, in the southern portion of the Refuge. The area was expanded in 1995 to include the entire drainages of Cane and Red Sheep Creeks.

Refuge biologists conducted a ground-based survey during mid-June 2008 in the headwaters of Cane and Red Sheep Creeks to assess lamb production and age structure of the sheep population in this northern portion of the Sheep Management Area. The sheep were concentrated at 2 mineral licks. Researchers observed 130 sheep, primarily ewes, lambs, yearlings, and 2-year olds. Based on the stage of vegetation green-up and snowmelt, biologists believe that ram groups had dispersed from the river corridors and mineral licks into higher elevation areas that were not surveyed. Survey results indicate that there were 58.7 lambs per 100 adult ewes, which represents excellent productivity. There were also 19.6 yearlings per 100 ewes in this survey. The Refuge plans to repeat this survey in 2009 to evaluate overwinter survival of lambs in this area.


The population of muskoxen in northeastern Alaska and northwestern Canada declined between 1999 and 2006, and muskoxen almost disappeared from the Arctic Refuge. In April 2008, biologists conducted a pre-calving muskox census across the coastal plain tundra within the northern portion of the Refuge. They counted 44 muskoxen in 3 groups during the census. Based on these observations, and other counts east and west of the Refuge, biologists estimate that there are about 250 muskoxen in northeastern Alaska, and that the total population is about 350 animals, including 100 muskoxen in northwestern Canada.

The decline in muskoxen was likely caused by low calf recruitment in some years, increased adult mortality, and changes in distribution of the animals. Factors likely having a negative effect on the number of muskoxen in northeastern Alaska include: (1) severe weather conditions such as icing events and deep snow that reduce access to winter forage and increase energetic costs; (2) diseases and parasites that affect body condition; and (3) predation, primarily by grizzly bears.

Grizzly Bears

The estimated density of grizzly bears in the northern half of the Refuge is 18.3 bears per 1000 square kilometers. Arctic Refuge, the Alaska Department of Fish and Game, and others have monitored grizzly bears on the coastal plain and in the northern foothills of the Refuge since 2006. They use GPS (Global Positioning System) satellite telemetry to determine high-use areas, important habitats, possible predation events, and den sites.

Preliminary results suggest that grizzly bears feed on carcasses (mostly caribou) and plant roots from April until early June before new vegetation emerges. During summer, bears feed mostly on horsetails, sedges, grasses and leaves, plus ground squirrels, lemmings and voles in areas where small mammals are abundant.

Biologists are analyzing blood and hair samples that have been collected from bears over the last 33 years to evaluate long-term trends in diet. These studies will help managers understand the relationship between grizzly bears and their prey over time. Results from these studies suggest that the relative amount of vegetation versus meat in grizzly bear diets has remained fairly constant during this 33-year period.


A. Avian Influenza Surveillance

Researchers collected samples from several shorebird species to test for exposure to highly pathogenic avian influenza (H5N1), a viral disease of birds that has been known to cause human illness and death in other areas of the world. The virus has not been documented in birds from Alaska. Certain species were targeted for sampling because they migrate through areas of the world known to have had outbreaks of H5N1 avian influenza, raising the possibility that these birds could have been exposed to the virus and might bring it into the United States. Similar sampling efforts in 2006 and 2007 did not detect the presence of this virus in any of the samples collected on the Refuge. In 2008, 133 birds were sampled at three sites on the coast of the Arctic Refuge, including 115 Dunlin, 17 Pectoral Sandpipers, 1 Buff-breasted Sandpiper, and 1 Long-billed Dowitcher. As was the case in past years, all this year’s samples were negative for H5N1 avian influenza.

B. Shorebirds on the Beaufort Sea coast

Several species of shorebirds use coastal areas of the Arctic Refuge after their breeding season. Feeding in these areas is critical for fattening prior to migration. However, reduced sea ice cover and changing ocean conditions in the Beaufort Sea are causing flooding and increased coastal erosion, which threatens coastal mudflats used by shorebirds. In addition, offshore areas north of the Refuge have recently been leased for oil exploration. This raises the potential that oil spills and increased on-shore and offshore industrial activities may negatively affect shorebirds in the region. Studies of how and why post-breeding shorebirds use coastal habitats will help Refuge Managers protect the birds in the face of future changes. Researchers have studied shorebird use of Refuge coastal areas since 2005. They identified several high-use sites, but also found considerable variability in habitat use between years and even between days within the same year. Their observations suggest that habitat use is influenced by weather and water conditions, which likely determine food availability for birds. In 2009, continued studies will investigate shorebird diets, and the factors affecting the abundance and distribution of the small invertebrates that are known to be the birds’ primary food source. This research is part of a 5-year study of how and why post-breeding shorebirds use the mudflats along the Beaufort Sea coast of the Arctic Refuge.