Scientific Name: Enhydra lutris kenyoni
Family: The sea otter is the largest member of the Mustelidae, or weasel family, and the only one which lives almost entirely in the water.
Lifespan: Sea otters can live up to 25 years of age, although the average lifespan is 10 to 12 years.
Length and weight: Although the sea otter is the smallest marine mammal, the average adult can be as large as 5 feet in length and weigh up to 70 lbs. The average length of an adult female is 4 feet and average weight is 60 lbs. At birth, sea otters weigh approximately 5 lbs and are 10 inches in length.
Color: Sea otter fur ranges from brown to almost black with guard hairs that may be silver, light brown, or black. As a sea otter ages, their hands and necks will lighten until almost white.
Fur: Sea otter fur is the finest of any mammal, consisting of 850,000 to 1 million hairs per square inch. Sea otters depend on these hairs to keep them warm while in the water. If a sea otter’s fur becomes soiled with foreign substances such as oil, the sea otter will not be able to keep itself insulated. Consequently, sea otters spend much of their time cleaning and grooming their fur.
Behavior: Sea otters are social animals who may float together in groups of less than 10 to more than 100, called rafts. Usually these groups are separated by sex, females and pups spend time in one group and males in another. Otters usually swim on their backs but have been known to swim on their stomachs while traveling. Sea otters will only eat while they are floating, but may also groom, rest, and nurse their young. It is also common for sea otters to wrap themselves in kelp beds when resting or sleeping.
Body: Sea otters have long flat tails and since the majority of their time is spent in the water, webbed hind feet which are perfect for swimming. Retractable claws on a sea otter’s front paws allow the sea otter to grab food. Sea otters have round heads, small eyes, and visible ears.
Habitat: Sea otters are coastal, shallow water dwellers. Their habitat consists of two areas in these waters- the ocean floor where they find their food, and the ocean surface where they eat, groom, rest and social interactions occur.
Food Habits: Sea otters mainly eat benthic invertebrates such as clams, mussels, urchins, crabs, and fish. They must dive to capture their food, sometimes up to 250 feet. Sea otters also use “tools” such as a rock to open their hard-shelled prey. Adult sea otters can eat 25 to 30 percent of their body weight per day in order to stay warm. Feeding is a very important activity for sea otters, and occurs mainly in the morning and afternoon.
Life History: A sea otter becomes sexually mature at 3 to 6 years. A female’s pregnancy usually lasts 5 to 8 months and can have one pup per year. In Alaska, most pups are born during May and remain dependent on their mothers for 5 to 12 months.
Predators: Include humans, sharks, bears, eagles (on pups), and killer whales
Distribution in Alaska:
Map used courtesy of the Alaska Region of the U.S. Fish and Wildlife Service
Related Sea Otter Links and Downloads:
US Fish and Wildlife Service, Alaska: Marine Mammals Management
Sea Otters and the ESA (pdf)