Sea otter - Enhydra lutris

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Sea otters are part of the weasel family. They are the smallest marine mammal. Adult females weigh 35-60 pounds (16-27 kg); males reach up to 90 pounds (40 kg). Alaskan sea otters are bigger with males weighing up to 100 pounds (45 kg). Otters are dark brown in color and the Alaskan sea otters have lighter colored heads. Their brown fur is very thick (more then 850,000 per sq. inch!) and actually traps air against the skin to help them keep warm.  Otter dentition is specially adapted to help feed on hard-shelled prey such as urchins, clams, and crabs. Underneath each front flipper is a pouch of skin that they use to store food collected during extended dives to the bottom. The front flippers also have retractile claws, while the hind flippers are longer, broadly flattened and webbed. They have a fairly short, thick, muscular tail.

Sea otters are found in near-shore waters of Russia, Alaska, and California. This is drastically reduced from when they used to be found along the entire Pacific Rim.

Sea otters are found in shallow water habitats of less then 50 meters. They are usually found in areas with rocky bottom and kelp forests. They use the kelp to hang onto while resting.

Males and females are separate except for when it’s time to mate. Gestation is 4-6 months and the pups only weigh 4-5 pounds when born. The pups are able to feed relatively early, but cannot dive until they are about four weeks old. Sexual maturity is reached around the age of 4-6 years and otters can live up to 23 years in the wild.

Sea otters use tools to help them eat. They will often use a rock to help break open the shells of the clams, crabs, urchins, and abalone that make up their diet. They often float on their backs and use their body as a table to work on while they eat. Otters are active during the day, and forage in a series of relatively short dives. Otters eat up to 20-25% of their body weight each day!

Otters were extensively hunted by the Russians in the 1600s and 1700s, and the Americans and Japanese as well until the early 1900s. When hunting was finally banned in 1911, less then 2000 otters existed and many thought the otter would go extinct. A remnant population was found along California and today the total population is estimated to be 108,000 animals. Threats today include loss of habitat, disease, vessel strikes, entanglement in fishing gear, and predation by killer whales.

• iOBIS
• World Register of Marine Species (WoRMS)
• Encyclopedia of Life
• Catalog of Life
• Integrated Taxonomic Information System (ITIS)
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The Marine Mammal Center. 2011. Sea otter. Available online. Accessed 2011.

IUCN Otter Specialist Group. 2006. Enhydra lutris (Linnaeus, 1758), the sea otter. Available online. Accessed 2011.