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, and as such, are vulnerable to reductions in the
extent and duration of sea ice. Sea otters, in the weasel family
(Mustelidae), live a primarily marine life: they rest, mate,
give birth, and