Polar Bear Feeding Ecology
Polar bears are an integral component of the marine environment and
serve as an indicator of contamination, climate change, and other potential
changes to the Arctic ecosystem. Polar bears spend most of their time
on drifting pack
ice and feed primarily on ringed seals (Phoca hispida) and
bearded seals (Erignathus barbatus). In Alaska, polar bears
have also been observed feeding on stranded marine mammal carcasses
during fall months while traveling along the coast and barrier islands
of the Beaufort, Chukchi, and Bering seas. The near shore environment
is an area that is subject to oil and gas development and other human
activities that have the potential to impact polar bears and their foraging
Native residents of the North Slope of Alaska consistently harvest
bowhead whales (Balaena mysticetus) for subsistence purposes
in the fall. Large numbers of polar bears congregate at whale harvest
sites near the villages of Kaktovik, as well as near Barrow, and at
Cross Island (the village of Nuiqsut’s bowhead whale hunting camp)
and other barrier islands along the Beaufort Sea. Marine mammal carcasses
provide tons of potential food for polar bears and may be an important
food source before the onset of winter. Supplemental food sources such
as stranded marine mammal carcasses may enhance the survival of nutritionally
stressed bears. In turn, use of carcasses may be linked to reproductive
success of female polar bears, which is critical to the continued health
and stability of the population.
The FWS, with Minerals Management Service funding, is conducting a
three-year study on polar bears using Barter and Cross Islands during
fall months (late open water season) using coastal areas of the Beaufort
Sea. The objectives of the study are to:
- determine the number, age and sex composition of polar bears;
- record habitat use and behavior of polar bears; and
- determine the magnitude of interchange of polar bears between Barter
Island and Cross Island.
The Alaska Nanuuq Commission, North Slope Borough, and Native villages
of Kaktovik and Nuiqsut are cooperators on the study. Field crews conducted
observations of polar bears during 2002 and 2003. Observations were
made by a combination of scan, continuous, and focal sampling, as well
as direct observations, and video and still photography.
A preliminary report is available by contacting Susanne Miller at 1-800-362-5148.
A final report will be ready in 2005 pursuant to additional field work
currently scheduled for September 2004.
Last updated: September 10, 2008