<Tr> <Td_colspan="2"> Enhydra lutris (Linnaeus, 1758) </Td> </Tr> <Tr> <Td_colspan="2"> Sea otter range . </Td> </Tr> <P> 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 (31 and 99 lb), making them the heaviest members of the weasel family, but among 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 . </P> <P> 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 molluscs and crustaceans, and some species of fish . Its foraging and eating habits are noteworthy in several respects . First, 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 . Its diet includes prey species that are also valued by humans as food, leading to conflicts between sea otters and fisheries . </P>

What is the average size of a sea otter