>>3008659Most bears have few natural enemies except for humans and the human impact on bear habitat. An exception to this is threat walruses pose to polar bears. Polar bears and adult walruses are rivals, occasionally coming into contact while feeding on whale carcasses or in the process of killing seals. On land, a polar bear has the edge over a walrus, but once in the water, the walrus has the edge. It can grab the polar bear from below, stab the bear with its tusks, and repeat this resulting in serious if not fatal injury to the bear
