Comments: Polar bears are closely tied to arctic pack ice. They prefer areas with ice that is periodically active, such as at the interface of landfast ice and drifting pack ice along the arctic coasts or near polynyas. Polar bears show a preference for sea ice located over and near the continental shelf, likely due to higher biological productivity in these areas and greater accessibility to prey in near-shore shear zones and polynyas (areas of open sea surrounded by ice) compared to deep-water regions in the central polar basin; they are most abundant near the shore in shallow-water areas, and also in other areas where currents and ocean upwelling increase marine productivity and serve to keep the ice cover from becoming too consolidated in winter (see USFWS 2008 for specific sources of this information).
Sometimes polar bears wander inland as much as 150 km from the coast. In the Bering and Chukchi Seas, Alaska, where sea ice melts in summer, bears migrate up to 1,000 km to remain with the southern ice boundary (Garner et al. 1990, 1994 in Amstrup 2003); in Hudson Bay, James Bay and parts of the Canadian Arctic, bears may be forced onto land for up to several months when sea ice melts in summer (Jonkel et al. 1976, Lunn et al. 1997 in Amstrup 2003). During ice-free period along western Hudson Bay, adult males occupy the coast while family groups and pregnant females occur farther inland. Pregnant females remain on or near land in dens through winter while males and non-breeders winter on sea ice. On land, range of subadults overlaps that of adult males (Derocher and Stirling 1990).
Female denning habitat may be found in mountain, fjord, or even relatively flat tundra areas, but generally it is near the coast and contains microhabitats which catch and collect snow in fall and early winter (Amstrup 2003). While most denning occurs on coastlines, bears may also den on drifting pack ice and on land-fast ice adjacent to shore (Amstrup and Gardner 1994). Females typically dig maternity dens in a hillside snowbank (in southwestern Hudson Bay, however, pregnant females commonly overwinter in earth dens 20-100 km from the coast). Dens often are built within 8 km of coast and rarely more than 48 km offshore (though sometimes in active offshore pack ice as much as 550 km north of Alaskan coast). Polar bears exhibit a general fidelity to denning areas and even after months of long-distance passive transportation on sea ice females often return to specific den habitats (Amstrup 2003).
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