Sea Otters and Polar Bears: Marine Fissipeds
Two Alaska marine mammals are neither pinniped nor cetacean: the polar bear and sea otter. They are both fissipeds, "split-footed" members of the order Carnivora, and are more closely related to terrestrial carnivores, like weasels, than seals or whales. Evolutionary newcomers to the marine environment, these species lack many of the physiologic adaptations to marine life seen in pinnipeds and cetaceans. Both species are considered marine mammals under U.S. laws because of the roles they play in the marine environment.
Polar bears, in the bear family (Ursidae), spend most of their lives associated with marine ice and waters. Although competent swimmers, they are the marine mammal least adapted to aquatic existence. They rest, mate, give birth, and suckle their young on the ice.
Sea otters, in the weasel family (Mustelidae), live a primarily marine life: they rest, mate, give birth, and suckle their young in the water. Their hind limbs are webbed for swimming, but their front paws are padded with separate, clawed digits. They lack blubber, but are insulated by air trapped in their thick fur, which is densest among all mammals.
