Creature Feature – Sea Otter


Happy Sea Otter Awareness Week!

Enhydra lutris
Range: North America & Asia
Length: 3-5 feet
Weight: 40-90 pounds
Lifespan: 10-20 years in the wild

The Sea Otter is a marine mammal that has 3 subspecies: Southern Sea Otter, Northern Sea Otter, and Russian Sea Otter. The Southern Sea Otter is found in California. The Northern Sea Otter is found in Washington, Canada, and Alaska. The Russian Sea Otter is found off the eastern coast of Russia and several have been reported in Japan.

Currently there are less than 3,000 Sea Otters in California, between 65,000 and 78,000 in Washington, Canada, and Alaska combined. And, the Russian population consists of approximately 15,000 with about a dozen in Japan.

Sea otters are members of the weasel family and are related to the mink, fisher and river otters. Males weigh 70-90 pounds, and females are much smaller weighing only 40-60 pounds. Adult otters grow to be about 4 1/2 feet in length, although some males can grow to 6 feet and weigh up to 100 pounds.

The sea otter’s fur is the thickest fur of any mammal, having 850,000 to 1,000,000 hairs per square inch. They have 10 times as many hairs in one square inch as you have on your entire head! The fur has two layers, an undercoat and longer guard hairs. The otter’s undercoat can be brown to black in color, and the guard hair may be silver, dark brown or black.

Otters are the only marine mammal that don’t have blubber. They carefully groom their fur to trap insulating air bubbles to keep warm. A sea otter’s skeleton is loosely jointed. They can reach the middle of their back when grooming. An adult sea otter spends about 15% of the day grooming. A baby sea otter’s fur traps so much air they cannot dive under the water.


Sea otters eat 25 to 30 percent of their body weight each day in seafood, including sea urchins, fish, clams, snails, worms, sea stars, crabs, squid, octopus, and abalone. They need to eat that much to stay warm. Otters can dive 100 feet or more and stay underwater for up to 5 minutes when searching for food. They use a flap of skin located under their forearm to store food until they can reach the surface. They set rocks on their chests and smash shellfish against them so they can get at the meal inside.

Sea otters are threatened by oil spills, habitat loss, food limitations, and fishing gear entrapment. In 1989 the Exxon Valdez oil spill in Prince William Sound, Alaska killed thousands of sea otters. The oil damages the otter 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.

Sea otters are a keystone species for kelp forests, meaning they have a disproportionate effect on this habitat. When sea otters are present, they keep the invertebrate grazers of kelp in check and balanced and the result is a healthy kelp forest ecosystem.

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