Sea otters inhabit kelp forests in the shallow, coastal waters of the North Pacific Ocean, seldom ranging more than one to two kilometers from shore. They forage on the sea floor, within kelp forests, and in the intertidal zone. Otter diets are extensive and adaptable, but typically include shellfish, sea urchins, sea stars, squid, and snails. They spend their time floating on their backs, eating and sleeping in this position. As a keystone species, the sea otter prevents sea urchins from overgrazing on the kelp and thus maintains the healthy and diverse kelp forest ecosystem that benefits numerous other marine species. Males mate with multiple females, and the female usually gives birth to one pup, or occasionally to twins. Sea otters breed and give birth year-round, and the mother cares devotedly for the pup for approximately one year, often wrapping the pup in kelp to prevent it from floating away while she forages.
There are three subspecies of sea otter in North America, with the Southern sea otter (E. l. nereis) ranging from Baja California to northern Calfornia, and two subspecies called “Alaskan” (E. l. kenyoni and E. l. lutris) found from Oregon to the Aleutian Islands and from the Commander Islands to Kamchatka, respectively. Sea otters once occupied a range across the Pacific Rim, from Baja California, Mexico to northern Japan, once numbering up to 300,000. By the early 20th century, commercial fur hunters extirpated the sea otter from much of its historic range and fewer than 2,000 animals remained. Presently, the species occupies about half of its historic range and the population trend is generally stable or increasing. However, the otters in the Gulf of Alaska have undergone dramatic population decline.
The hunting of sea otters is still reported in Russia, but is much less of a threat to the species than in the past. Today, the major threats to sea otters include oil pollution, which coats their fur and allows them to die from hypothermia in the cold water; predation by killer whales, which target otters more frequently now that seals and sea lions are less abundant; entanglement in fishing gear and crab traps, and lack of prey, such as the over-fished abalone.