. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Ice as marine mammal habitat 791 pregnant sows probably also den along the rugged and complex coast of the eastern Chukotsk Peninsula. Sows with small cubs, presumed to have been born near where they were seen, have occasionally been reported near St. Lawrence, King, and Little Diomede islands; most reports come from residents of Little Diomede. Cubs may remain with their mothers for up to years (Stirling et al. 1975). Ice is important to bears as a solid sub
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Ice as marine mammal habitat 791 pregnant sows probably also den along the rugged and complex coast of the eastern Chukotsk Peninsula. Sows with small cubs, presumed to have been born near where they were seen, have occasionally been reported near St. Lawrence, King, and Little Diomede islands; most reports come from residents of Little Diomede. Cubs may remain with their mothers for up to years (Stirling et al. 1975). Ice is important to bears as a solid substrate on which they can move about and hunt (Fay 1974). Males and nonpregnant females range widely on the pack in search of prey, mainly ringed seals. Polar bears are good swimmers and do not hesitate to enter the water. All of the spotted and ribbon seals, almost aU of the walruses, and most of the bearded seals in the Bering Sea during winter are, by virtue of their distribution, essentially free from predation by bears. Ringed seals, more abundant in the Chukchi Sea, are the major prey of bears during venter and early spring. Bears have become well adapted to hunting them in leads, at breathing holes, in their snow dens, and while they are hauled out on the ice (Stirling 1974, Eley 1978). During the winter and early spring the bears hunt most successfully for these seals along narrow leads where they wait for seals to surface (Lentfer, personal communication; Burns, personal observation; Eley 1978). during spring migration (Scammon 1874, Durham 1979). The unique structure of the head and lack of a dorsal fin are thought to be adaptations to ice. Besides using natural openings in the ice, bowheads frequently break holes through thin ice—up to 25 cm or more in thickness, according to Tomilin (1957). As described by Fay (1974), the head of a bowhead is highly arched with the blowholes at the apex of a high promontory (Fig. 46-6), permitting the whales to breathe in openings
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