The heaviest members of the weasel family, sea otters are also the second smallest marine mammals. Unlike other marine mammals, they do not have a layer of blubber to help them keep warm. Instead, sea otters have the densest fur in the animal kingdom, ranging from 250,000 to a million hairs per square inch, which insulates them.
© Marc Mantione
Sea otters are a keystone species, meaning their role in their environment has a greater effect than other species. As predators, sea otters are critical to maintaining the balance of the near-shore kelp ecosystems. Without sea otters, the undersea animals they prey on would devour the kelp forests off the coast that provide cover and food for many other marine animals. Additionally, sea otters indirectly help to reduce levels of atmospheric carbon dioxide, a prevalent greenhouse gas, as kelp forests play an important role in capturing carbon in coastal ecosystems
Sea otters eat urchins, abalone, mussels, clams, crabs, snails and about 40 other marine species. Sea otters eat approximately 25% of their weight in food each day to support their high metabolism.
Historically, sea otters numbered between several hundred thousand to more than a million. But due to the fur trade, worldwide numbers plummeted down to a total of 1,000-2,000 in the early 1900s. Today, there are estimated to be just over 106,000 worldwide, with just under 3,000 in California.
Habitat & Range
Sea otters live in shallow coastal waters off the northern Pacific. Their historic range stretched from Japan, along the coast of Siberia and the Aleutian Chain and down the Alaska, British Columbia, Washington, Oregon and California coast to Baja California. Currently sea otters can be found in Canada, Russia, Japan, California and Washington, but the majority of all wild sea otters are found in Alaskan waters. Recent reports of sea otter sightings have also occurred in Mexico.
In the U.S., there are two distinct sea otter subspecies, the Northern sea otter (Enhydra lutris kenyoni) and the Southern sea otter (Enhydra lutris nereis). Northern sea otters are found in the Aleutian Islands, Southern Alaska, British Columbia, and Washington. Southern sea otters, also known as California sea otters, live in the waters along the California coastline and range from San Mateo County in the north to Santa Barbara County in the south.
Sea otters spend much of their lives in the water and can dive up to 330 feet when foraging for food. They sometimes rest in coastal kelp forests, often draping the kelp over their bodies to keep from drifting away.
Sea otters are also one of the few mammals other than primates known to use tools. They use small rocks or other objects to pry shellfish from rocks and to hammer them open.
Mating Season: Throughout the year
Gestation: 6-8 months
Litter Size: Generally one pup, but sea otters can give birth to twins