The smallest marine mammals in North America, sea otters occupy chilly coastal waters in the central and north Pacific Ocean. Averaging 1.2 metres in length, male sea otters typically weigh about 45 kilograms. Females are slightly smaller. Otters have large, flat heads, large teeth to crush shells, and blunt noses with long, stiff whiskers. The animals have black eyes, very small ears, and a short, stout tail. Their front legs are small and fairly weak; their rear legs are also small, but much stronger as they're used for paddling. The otters' thick fur varies in colour from rust to dark brown to black, and is lighter on the head, throat and chest. Female sea otters mature at five to six years of age, and bear a single pup—very occasionally two—at one or two year intervals. Pups are usually born in the water. Sea otters favour shallow, coastal waters, seldom ranging more than one or two kilometres from shore. All otters, particularly mothers with pups, seem to prefer areas with kelp canopies, but seaweed is not an essential habitat requirement. Habitat use varies with weather and marine conditions. Otters have been known to move offshore during extended periods of calm, and congregate in sheltered, inshore areas during storms. Once extinct from Canada, the sea otter has successfully been reintroduced to British Columbia. The otters mainly live off Vancouver Island, but can also be seen near Goose Island.