The sea otter is the largest member of the Mustelidae (weasel) family, and the smallest species of marine mammal in North America. Unlike other marine mammals, sea otters have no layer of blubber and thus rely on their dense fur for insulation from cold ocean waters. Their fur ranges from dark brown to reddish brown, and they have long lighter-colored whiskers. Their forepaws have claws, are padded and are used for grooming and feeding. Their hind feet are flipper like and used for swimming. Males are generally larger than females, and reach sexual maturity around five or six years of age, while females can be sexually mature by age four. Though twins have been documented, females normally give birth to a single pup once every one or two years. Otters forage for a variety of species of invertebrates, such as crabs, sea urchins, or mussels, and some fish. Foraging dives generally last 50 to 90 seconds and can reach at least 45 meters in depth. Sea otters are considered a keystone species and thus have a significant impact on their habitat—for instance, sea otters have been shown to help maintain and even help recover kelp forests by keeping sea urchin populations in check.
Why does it need our help?
Sea otters were hunted to near extinction as a result of the international fur trade during the 18th and 19th centuries. Since the 1911 International Fur Seal Treaty banned the hunting of fur-bearing marine mammals, populations have subsequently increased and sea otters have recolonized much of the available habitat off the coast of Alaska and central California, and small, translocated colonies exist in British Columbia and Washington. However, much of their historical range remains uninhabited. The last known otter in Oregon was killed in 1907, and a reintroduction effort in the 1970s was unsuccessful. However, growing populations in Washington and recent sightings of lone sea otters off the Oregon coast, including a confirmed sighting in 2009 at Depoe Bay, indicate that Oregon could again be home to these furry creatures. However, sea otter populations still face a number of additional threats, including pollution (especially oil spills), poaching, entanglement in fishing gear, as well as parasites and infectious diseases.
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- Learn more by checking out our Lost Sea Otters of Oregon project, including a special audio program available on iTunes and other podcast platforms.
Did you know?
- The sea otter is considered to have the densest coat of any mammal, with over 100,000 hairs per square centimeter. Its soft, glossy pelt made it the most valuable fur on the world market during the height of the Northwest fur trade.
- Sea otters are the only non-primate mammals known to use tools. They often use rocks to break open prey with hard shells or exoskeletons.
- Sea otters have loose folds of skin under their armpits where they store tools and prey while diving.
- To keep from drifting away while sleeping, sea otters will sometimes wrap themselves in kelp, or hold hands with adjacent otters.