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Range and Habitat: Sea otters were once found from Mexico to Alaska on the western side of the Pacific Ocean and to the coast of Japan in the Eastern Pacific. Sea otters live in shallow coastal areas and in and around the kelp forests of the ocean. Today sea otters can be found off the coast of California, Alaska and Russia. A small translocated population of Alaskan otters is found off the coast of Washington State, and British Columbia. They were reintroduced into the area in the 1960’s. The largest population of sea otters is in Alaska.
Habits and Adaptations: The sea otter’s fur is the best in the world and is the thickest fur of any other mammal. They have 850,000 to 1,000,000 hairs per square inch. The fur has two layers, an undercoat and longer guard hairs. The sea otters carefully groom their fur to trap a layer of insulating air bubbles between their warm skin and the cold, cold ocean water. Sea otters are often seen rolling in the water and rubbing themselves, which insulates air into the hair. Their skeleton is very loosely jointed which allows the otter to groom every inch of its body. They can even reach the middle of their back.
Sea otters are the only marine mammal that does not have blubber to keep it warm. The otter’s hind feet and tail are not as well insulted as the rest of its body so it will keep them out of the water if possible to conserve heat.
The sea otter can dive to 100 feet or more when searching for food. Sea otters usually dive for 1 to 2 minutes but can stay under water for up to 5 minutes when looking for food. It uses its nose and whiskers to help find food and detect vibrations in the water. The sea otter uses a flap of skin located under its forearm to store food until it can reach the surface. The otter uses its sense of hearing, smell, touch and sight to hunt for food and avoid danger.
Sea otters mate, sleep, groom, hunt, rest, play and give birth in the ocean. They spend most of their life floating on their backs at the surface of the ocean. Sea otters are able to drink salt water because of their large complex kidneys.
Diet: Sea otters eat a wide variety of invertebrates. They will eat clams, snails, worms, sea stars, sea urchins, crabs, squid, octopuses and abalone. The sea otters in Alaska will also eat fish. Sea otters eat about a quarter of their body weight each day.
At the zoo the otters are fed prepared shrimp, squid, clam meat (out of the shells), whole clams, crabs, mussels, krill, pollock and capelin.
Breeding and Maturation: Sea otters can mate any time during the year. They do not mate for life. Males become sexually mature around 4-5 years of age and females mature around 2-5years of age. During mating time, the male remains with the female for 3 to 5 days. Sometimes females will mate with the same male again. A male sea otter will bite the nose of the female during mating season. A sexually mature female can sometimes be spotted by a bloody nose or a scared nose. The gestation is about 6 months for sea otters. Like other mustlids, the female is able to delay implantation for several weeks or months. Delayed implantation may allow the pup to be born when food is more abundant.
Baby sea otters pups weigh 3 to 5 pounds at birth. They are born with light fur and guard hairs that keep them afloat. The pups are born with a full set of milk teeth and their eyes open. A sea otter mother carries her pup on her stomach and spends much of her day caring for her baby. Young sea otter pups are dependent on their mother for around a year. A baby otter emits a high pitch sound when in distressed or can’t find its mother!
Sea otters segregate by sex. Groups of female and their pups stay in the center of the range and the breeding males stay close to the females groups and the sub adults males are found on the outskirts of the range. The sub adult males are the first to move into to a new area.
The male sea otter lives to be about 10-15 years of age and the female’s life span is 15-20 years. Sea otters living in zoo and aquariums have been found to live longer than sea otters in the wild.
Conservation: Sea otters are threatened by oil spills, habitat loss, food limitations, fishing gear entrapment and conflicts with the shell fisheries.
In 1989 the Exxon Valdez oil spill in Prince William Sound, Alaska killed thousands of sea otters. The Oil damages the sea otters fur and causes the otter to get cold and wet. When an otter attempts to groom its fur it ingests the oil, which can cause liver, kidney and lung damage.
Russians came to Alaska because of the sea otters. By 1867, the otter population was greatly reduced. Some believe this is why the Russian government sold it to the United States. The Americans quickly dropped some conservation measures the Russian instituted to protect the otters. By 1911, the sea otter was extremely hard to find. The sea otters were given full protection under the Fur Seal Treaty.
The pre fur trade population of sea otter was thought to be between 150,000 to 300,000 worldwide. By the early 1900’s, the population worldwide was thought to be 1000 to 2000 due to fur trade. In the early 1900’s, the southern sea otter was thought to be extinct, but in 1915, scientists discovered a group of 50 or so otters still living in a remote cove in Big Sur California. To save the southern sea otters, the scientists kept it a secret until 1938. The building of Highway 1 along the California coast made it impossible to keep the secret anymore. All of the California sea otters swimming in the ocean today are descended from the Big Sur group.
Sea otters have been protected by law since 1911 and are listed as “threatened” under the Endangered Species Act of 1972.
In 2006, the population of sea otters was thought to be between 64,000 to 77,300 in Alaska, Canada and the Washington state coast, about 15, 000 in Russia (Kamchatka peninsula and Kuril Islands) and about 2,750 off the coast of California. There are thought to be less than 12 Russian sea otters off the coast of Japan
Miscellaneous: Sea otters have blunt rounded teeth for crushing invertebrate shells and are the only carnivore with 4 incisor teeth in the lower jaw.
Sea otters live in loose knit groups called “rafts”. A raft can consist of two or more resting otter although rafts of several hundred otters have been spotted.
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