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Sea Otter Facts

Sea otters are amazing marine creatures. Although they are an endangered species, they have captivated us for years as these sea otter facts reveal.

Sea Otter Facts

Sea otters are members of the weasel family (Mustelidae) and are related to mink and river otters. Adult males weight 70 to 90 pounds with some individuals weighing 100 pounds. Females average 40 to 60 pounds. Adults reach a length of 4.5 feet. The hind feet are webbed and are adapted for swimming. The toes on the forefeet are short and stiff, enabling the animal to deftly handle food. On land their gait is clumsy. Probably because of this vulnerability, they are seldom found more than a few yards from water.

The fur, which is possibly the finest in the world, consists of a very dense underfur of inch-long fibers and sparse guard hairs. The underfur ranges from brown to almost black. Guard hairs may be black, pale brown, or silver, often giving a veiled effect of silvery hairs on a dark background. Older animals often develop a silvery head. This, combined with the prominent whiskers, leads to the nickname of "Old Man of the Sea."

Unlike seals, which rely on a heavy layer of blubber for protection against the cold North Pacific waters, sea otters depend on air trapped in their fur for maintaining body temperature. If the fur becomes soiled or matted by material such as oil, the insulation qualities are lost. This results in loss of body heat and eventual death. For this reason, otters spend much time grooming their fur to keep it clean.

Sea otters mate at all times of the year, and young may be born in any season. However, in Alaska most pups are born in late spring. Like other marine mammals, they have only one pup during each breeding cycle. A pup weighs 3 to 5 pounds at birth and is light brown in color. The female's maternal instinct is very strong and she seldom leaves her pup except when diving for food. When traveling, sleeping, or preening, the pup usually rides its mother's chest as she floats on her back. The pup may weigh 30 pounds (14 kg) when weaned and looks almost as big as its mother. Females can produce one pup a year, but in areas where food is limited, they may produce pups every other year.

Sea otters usually do not migrate. They seldom travel far unless an area has become overpopulated and food is scarce. They are gregarious and may become concentrated in an area, sometimes resting in pods of fewer than 10 to more than 1,000 animals. Breeding males will drive nonbreeding males out of areas where females are concentrated. In some areas, the nonbreeding males will concentrate in "male areas" which are usually off exposed points of land where shallow water extends offshore. Bald eagles prey on newborn pups and killer whales may take a few adults, but predation is probably insignificant. Many sea otters live for 15 to 20 years.

Sea otters eat sea urchins, crabs, clams, mussels, octopus, other marine invertebrates, and fish. They usually dive to the bottom in 5 to 250 feet of water and return with several pieces of food, roll on their backs, place the food on their chests and eat it piece by piece using their forepaws and sometimes a rock to crack shells. In the wild, sea otters never eat on land.

The southern sea otter (Enhydra lutris nereis), the smallest of marine mammals, usually lives for 15 years and feeds primarily on a variety of  large invertebrates, including sea urchins, abalone, rock crabs, kelp crabs, and clams. Their ability to use tools to break open their food makes them unique among marine mammals. Most adult female sea otters give birth to one pup each year. It was listed as threatened in 1977 under the Endangered Species Act, and as a depleted species under the Marine Mammal Protection Act.

Southern sea otters depend on clean, water-resistant fur (about one million hairs per square inch) for insulation against cold ocean water. Due to their small body size and lack of blubber, sea otters also stay warm by producing a high level of internal heat. To satisfy their high energy requirements, sea otters spend the majority of their time foraging for food and eat an average of 25% of their body weight each day.

Historically, the southern sea otter ranged from Oregon south to Baja California, Mexico. During the 18th and 19th centuries, otters were hunted for their luxurious pelts; by the early 1900s the species was believed to be extinct. Southern sea otters are descended from a small colony discovered off the Big Sur coast in 1938. The otter population declined about 5 percent per year between 1995 and 1999 and now totals about 2,200 animals. Today the species ranges from Half Moon Bay to Point Conception off the coast of central and southern California.

The sea otter (Enhydra lutris) lives in shallow water areas along the shores of the North Pacific. Its range once extended from southern California north then west through the Aleutian Islands, to the Kamchatka Peninsula, and south to the northern islands of Japan. In 1742, Vitus Bering's men returned with sea otter pelts from the historic voyage of discovery of Alaska. Interest in these rich furs initiated an era of exploitation, which almost wiped out the sea otter.

The early Russian settling of Alaska was largely a result of the sea otter industry. In 1867, when Russian exploitation had greatly reduced the numbers of sea otters, Alaska was sold to the United States. The few conservation measures that had been instituted by the Russians in their final years of occupation were dropped by the Americans, and hunting intensified. Sea otters became alarmingly scarce.

Finally in 1911, when so few animals were left that it was no longer profitable to hunt them (in many areas they were completely exterminated), sea otters were given full protection under the Fur Seal Treaty. The treaty was signed by the United States, Great Britain, Russia, and Japan.

In 1960, the state of Alaska assumed management authority for sea otters. The management program conducted by the state included the successful reintroduction of sea otters to unoccupied habitat in Southeast Alaska, British Columbia, and Washington. The Marine Mammal Protection Act transferred management authority to the U.S. Fish and Wildlife Service in 1972. Recovery of the Alaska sea otter population has been dramatic. Perhaps as few as 2,000 total animals existed in 1911, but by the mid-1970s the Alaska population numbered between 110,000 and 160,000. Most of the sea otter habitat in Alaska has now been repopulated. The principal exception is Southeast Alaska where numbers are increasing rapidly and otters are moving into new areas. Smaller populations exist in the Commander and Kurile islands, British Columbia, Washington, and California.

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