About the project

Of the 20 population units in the world, the southern Beaufort Sea unit (Figure 1) contains about 1500 polar bears (Regehr et al. 2006) and includes northern Alaska and northwestern Canada.

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Figure 1. Map showing the world’s polar bear population divided into 20 units.

The red arrow indicates the southern Beaufort Sea unit. Map reproduced from:

Distribution of polar bear populations in the Arctic. 1998.

UNEP/GRID-Arendal Maps and Graphics Library. Retrieved December 16, 2008 at

http://maps.grida.no/go/graphic/distribution_of_polar_bear_

populations_in_the_arctic

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Every summer, sea ice in the southern Beaufort Sea retreats northward (Figure 2) and most bears follow the ice. However, a proportion of the bears remain on shore for the ice-retreat period (Schliebe et al. 2008). These bears face warm temperatures and probably a lack of prey, because seals generally are not found on shore. The polar bears of western Hudson Bay, Canada, encounter a similar situation during the period of ice-retreat and respond by going into “walking hibernation” (Nelson et al. 1980). This is a state in which the bears remain active but their physiological processes appear to slow down, much like brown bears or black bears hibernating in winter dens.

However, the polar bear population of western Hudson Bay is declining, likely due to warmer temperatures creating a longer ice-free season (Stirling et al. 1999; Regehr et al. 2007). The longer ice-free season can reduce the amount of time the bears have on the ice to hunt, and increase the amount of time the bears must rely on fat stores while living on land. Many places in the Arctic are experiencing a sea ice decline (Meier et al. 2007), creating a need to understand the mechanisms of walking hibernation and how bears may be affected by changes in sea ice.

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Figure 2. Satellite image showing snow and ice cover in the Arctic on January 1^st 2008 (left panel)

and August 1^st 2008 (right panel). White areas indicate snow-covered land, and pink and purple areas

indicate ice-covered water. The southern Beaufort Sea is indicated by a bright green circle; on

January 1^st it is covered with sea ice, but by August 1^st most of the sea ice has melted. Satellite images

reproduced from: "Compare Daily Ice" function on “The Cryosphere Today” website. Accessed 16 December

2008. Polar Research Group, Department of Atmospheric Sciences, University of Illinois at Urbana-

Champaign. Web address is http://arctic.atmos.uiuc.edu/cryosphere/.

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In this project, we propose that polar bears in the southern Beaufort Sea, like bears in western Hudson Bay, enter walking hibernation during the summer on shore. To test this idea, we are gathering data from bears that spend the ice-retreat period on shore and bears that spend the ice-retreat period on sea ice.

Research methods and goals

We locate bears from the air with a helicopter, dart the bear with an anesthetic and immobilization drug, then we land and take measurements and samples from the bear. All of our capture operations are permitted and coordinated with USGS (US Geological Survey) and USFWS (US Fish and Wildlife Service), and our main focus is bear and personnel safety.

The data from this project will be used to understand polar bear movements, behavior, and physiology in the summer. Other bear species have remarkable abilities to stay healthy despite practically not eating or moving for limited amounts of time (for example, hibernating black bears). However, these abilities have not been investigated in polar bears that face warm temperatures and little food during the summer. With the data gathered in this project, we will create models of what may happen to polar bear populations as sea ice changes. This will enable better management and conservation strategies. Towards that goal, data gathered in this project will be analyzed and published in publicly-accessible journals, and the data will be shared with USGS, USFWS, and other agencies involved with polar bear management and conservation.

References

Meier WN, Stoeve J, Fetterer F. 2007. Whither Arctic sea ice? A clear signal of decline regionally, seasonally and extending beyond the satellite record. Annals of Glaciology. Volume 46. Pages 428-434.

Nelson RA, Folk GE, Pfeiffer EW, Craighead JJ, Jonkel CJ, Steiger DL. 1980. Behavior, biochemistry, and hibernation in black, grizzly, and polar bears. International Conference on Bear Research and Management. Volume 5. Pages 284-290. 

Regehr EV, Amstrup SC, Stirling I. 2006. Polar bear population status in the southern Beaufort Sea. Open-file report 2006-1337. US Geological Survey. US Department of the Interior.

Regehr EV, Lunn NJ, Amstrup SC, Stirling I. 2007. Effects of earlier sea ice breakup on survival and population size of polar bears in Western Hudson Bay. Journal of Wildlife Management. Volume 71. Number 8. Pages 2673-2683.

Schliebe S, Rode KD, Gleason JS, Wilder J, Proffitt K, Evans TJ, Miller S. 2008. Effects of sea ice extent and food availability on spatial and temporal distribution of polar bears during the fall open-water period in the southern Beaufort Sea. Polar Biology. Volume 31. Number 8. Pages 999-1010.

Stirling I, Lunn NJ, Iacozza J. 1999. Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climatic change. Arctic. Volume 52. Number 3. Pages 294-306.