The sea otter Enhydra lutris is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg 30 and lb , making them the heaviest members of the weasel family , but among [ 3 ] the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of fur , the densest in the animal kingdom.
Although it can walk on land, the sea otter is capable of living exclusively in the ocean. The sea otter inhabits nearshore environments, where it dives to the sea floor to forage. It preys mostly on marine invertebrates such as sea urchins , various mollusks and crustaceans , and some species of fish. Its foraging and eating habits are noteworthy in several respects.
Its use of rocks to dislodge prey and to open shells makes it one of the few mammal species to use tools. In most of its range, it is a keystone species , controlling sea urchin populations which would otherwise inflict extensive damage to kelp forest ecosystems. Sea otters, whose numbers were once estimated at ,—,, were hunted extensively for their fur between and , and the world population fell to 1,—2, individuals living in a fraction of their historic range.
The recovery of the sea otter is considered an important success in marine conservation , although populations in the Aleutian Islands and California have recently declined or have plateaued at depressed levels. For these reasons, the sea otter remains classified as an endangered species. The sea otter is the heaviest the giant otter is longer, but significantly slimmer member of the family Mustelidae , [ 6 ] a diverse group that includes the 13 otter species and terrestrial animals such as weasels , badgers , and minks.
It is unique among the mustelids in not making dens or burrows , in having no functional anal scent glands , [ 7 ] and in being able to live its entire life without leaving the water.
