The sea otter (Enhydra lutris) is a marine mammal that lives along the North Pacific coast, preferring convoluted shallow seas and bays near shore. It has little subcutaneous fat and instead relies on exceptionally dense fur for insulation, spending about 30% of its active time grooming its coat. It forages in shallow waters mainly on sea urchins, shellfish, and crustaceans, and has the habit of using tools to break open prey. There is no strict breeding season; the gestation period is 6–7 months, and delayed implantation can occur. Populations were once threatened by overhunting, oil pollution, and changes in predation pressure, and the species is listed as Endangered IUCN Category IB.