Anatomy: Sea otters are up to about 4 feet (1.3 meters) long and weigh from 45 to 82 pounds (20-37 kilograms). They have webbed hind feet which they use to swim; the forefeet are smaller. The claws are semi-retractible. The ears and nostrils close when the otter is underwater. Sea otters sleep and rest on their backs, usually anchored in a kelp (seaweed) bed.

Fur: Sea otters are kept warm in the cold Pacific Ocean by their dense fur and high metabolism; they are the only marine mammal that has no layer of insulating fat. Sea otters have the densest fur of any mammal; the coat has over half a million hairs per square inch. Careful grooming with the forepaws keeps the fur waterproof. Oil spills cause the fur to lose its waterproof quality, causing the sea otter to get hypothermia, usually killing it.

Diet: Sea otters are carnivores (meat-eaters). They eat crustaceans (like crabs), bivalves (like clams, mussels, and abalone), octopuses, squid, sea urchins, and fish. They hunt for their prey in the ocean and on the sea floor. These intelligent mammals use rocks to help crack open clams and abalone.

Predators: Some sharks and birds (including the Great White Shark and the Bald eagle) prey upon sea otters. On the land, some bears and coyotes eat sea otters.

Classification: Kingdom Animalia, Phylum Chordata, Class Mammalia (mammals), Order Carnivora, Family Mustelidae (weasels, ferrets, minks, skunks, otters, badgers), Genus Enhydra, Species E. lutris.