The sea otter is an almost exclusively marine animal, spending little time ashore. Its fur is thick and glossy and ranges in colour from black to dark brown, with some white tipped hairs. The large, blunt head, throat and chest are all creamy white. Its ears are almost hidden in its fur and its eyes are small. Sea otters are propelled through the water using their long, well-defined flipper-like hind feet. The forelegs are comparatively small, with five-fingered forepaws, which are used to grasp shell fish and other prey.
The sea otter is the only carnivore to have four incisor teeth in its lower jaw. These are used to break open the shells of crabs, sea urchins and other shellfish.
It is also unusual in that it has no layer of fat or blubber under the skin. Instead, air trapped inside the thick fur provides insulation and prevents excessive heat loss. Up to 10% of a sea otter's life is occupied with the cleaning and grooming of its fur. If the fur is damaged or polluted with oil, it loses its effectiveness, so the sea otter may die from cold and exposure.
Their luxurious coats brought sea otters to the brink of extinction. Killer whales and sharks are their natural predators, but humans have proved to be by far their biggest enemies. In the 18th century they were mercilessly exploited by European fur hunters until only a few were left.