Sea Otter (Enhydra lutris)
Sea otters are members of the weasel or mustelid family. Like other members of this family, they have very thick fur. In fact, at 850,000 to one million hairs per square inch, they have the thickest fur of any mammal. Their fur actually consists of two layers, an undercoat and longer guard hairs. This system traps a layer of air next to their skin so their skin does not get wet. Sea otters are usually dark brown, often with lighter guard hairs. Alaskan sea otters tend to have lighter fur on their heads. Sea otters are the smallest marine mammal. In California 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).
Sea otters once ranged from Mexico to Alaska and even to Japan. Currently, the California population numbers around 3,300 and is found from Half Moon Bay to Point Conception. There is a much larger population in Alaska, and sea otters are still found in Russia. Sea otters inhabit shallow coastal areas and prefer places with kelp. The kelp acts as an anchor that the sea otters use to wrap themselves in when they are resting.
Females give birth to one pup and usually have their first pup at the age of four or five. Their pregnancies last four to five months. Pups can be born any time of year, but in California most are born between January and March, and in Alaska most are born in the summer. When born, the pups weigh from three to five pounds.
Sea otters are social animals, with females and pups spending time together in one group and males in another. Pups stay with their mothers for the first eight months of their life. The pups' fur traps so much air that they actually cannot dive under water. When mothers leave the pups wrapped in kelp to hunt, pups bob on the surface of the ocean like a cork. Mothers spend much time grooming pups and often carry them on their chests. Pups begin to learn to swim at around four weeks of age. Sea otters are one of the few animals to use tools. They eat animals with shells, like clams and abalone, and use a stone to break open the shells. When sea otters are under water searching for food, they store what they have found in the loose skin folds at their armpits. Adult sea otters can eat 25%-30% of their body weight in one day!
Sea otters in California are a threatened species due to past over hunting for their beautiful fur. Although sea otters are protected now, they remain vulnerable, especially to oil spills. Unlike other marine mammals, sea otters do not have a blubber layer. Therefore, they rely on their fur to keep warm. If their fur is oiled, it loses its insulating qualities and the sea otters soon chill. Otters are also affected by the oil fumes or poisoned by eating food exposed to oil. Most sea otters quickly die in an oil spill. Several thousand sea otters died in the 1989 Exxon oil spill in Valdez, Alaska. Other threats to sea otters include infectious diseases, parasites, boat strikes, entanglements, and toxins.
At The Marine Mammal Center
The Marine Mammal Center began rescuing and rehabilitating southern sea otters in 1995. Since that time, we have responded to more than 350 sea otters. In 2017, we retrofitted two pool areas to provide life-saving care to juvenile and adult sea otters, effectively increasing rehabilitation capacity for this threatened species. Not only is the Center able to provide second chances to otters in need of help, but we are also expanding our knowledge of the threats that sea otters face, such as domoic acid toxicosis and toxoplasmosis.
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Be Sea Otter Savvy
Download this helpful PDF document and learn how to look out for sea otters! Get tips on safe sea otter viewing, whether you are on land or in a boat.