In contrast with den sites in more southerly areas, bear dens in ANWR are not surrounded by shrubby vegetation with roots that stabilize the soil. Because the soils tend to be coarse textured and poorly bonded, dens cannot be dug until the ground has frozen to a depth of about four inches. Dens in ANWR usually collapse with the spring thaw and cannot be reused in subsequent years. Polar Bears Alaska polar bears spend little time on land. Throughout most of the year, most Beaufort Sea polar bears are closely associated with sea ice.
Sea ice is the habitat of ringed seals which are the predominant prey of polar bears.
Polar bears also prey on bearded seals and occasionally belugas and walrus. While some bears become stranded onshore during summer when the shore ice melts and pack ice blows far offshore, the bears generally stay with the ice when it retreats in the summer. In the fall, some bears move near shore to feed on remains of beached carcasses, especially of bowhead whales taken by whalers. In late October or November, some of the pregnant females move near shore to dig dens in deep snow drifts on the fast ice, or on barrier islands and land, while the majority den on the drifting pack ice. The pregnant females give birth to one to occasionally three cubs in December or January, and remain in the dens until April.