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Diseases Attack Calif. Sea Otters
By Larry O'Hanlon, Animal Planet News
A Healthy California Sea Otter
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May 8, 2003 — California's beloved southern sea otters are being ravaged by diseases and no one is sure why.
After making an almost miraculous comeback from what was thought to be extinction by hunting in the late 19th century, the southern sea otter populations were growing at a rate of five to seven percent each year, said Greg Sanders, southern sea otter coordinator for the US Fish and Wildlife Service.
"The highest count that we had was in 1995 at 2,377 animals," said Sanders.
Then in 1998, adult sea otters in the prime of their lives started washing up dead on the beaches of California's Central Coast.
A study of the causes of deaths of 105 otter carcasses by the University of California at Davis and the California Department of Fish and Game has identified not one, but several different killers, making scientists wonder what has changed in the marine environment to suddenly make it so unhealthy for sea otters.
"There are four causes (of death) that are kind of competing," said veterinarian Chris Kreuder of the U.C. Davis Wildlife Health Center.
Two of the killers are protozoan parasites called Toxoplasma and Sarcocystis, which infects otters' brains. The otters either die from brain infections or from shark attacks, since the brain infection can cause seizures and other movements and behaviors that attract sharks, Kreuder explained.
Toxoplasma is normally associated with domestic cats, and Sarcocystis with opossums, said Kreuder. Just how the parasites found their way from land mammals to sea otters is still under investigation.
Another cluster of otter deaths along a 1.25-mile section of beach in Monterey Bay was traced to acanthocephalen worms, which cause fatal abdominal infections. Usually otters get this parasite when they eat too many sand crabs, which carry the worms.
The fourth and most surprising cause of otter deaths is heart disease, said Kreuder. Apparently some disease is infecting the heart tissues of otters and causing inflammation, scarring and eventually congestive heart failure, she said.
The fact that there are so many diseases at work tells researchers that something has changed to make the sea otter's near-shore ecosystem very unhealthy. "The underlying processes need to be investigated," Kreuder said.
Kreuder and her colleagues will present their discoveries next week at the meeting of the International Association of Aquatic Animal Medicine in Waikaloa, Hawaii. Their results are also expected to be published later this year in the Journal of Wildlife Disease.
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Name: Sea Otter ( Enhydra lutris)
Primary Classification: Mustelidae (Skunks, Martens, Badgers, Minks, Otters and Relatives)
Location: Coasts of Russia, Alaska and California.
Habitat: Temperate coastal waters with rocky shores or sandy bottoms. Often found in kelp forests.
Diet: Mainly mussels, sea urchins, abalone and snails. Also crabs, octopus, squid, sea stars and fish.
Size: Up to 5 ft in length and 100 lbs in weight.
Description: Dense brown fur. Straw-colored fur on head. Long heavy body. Short forelimbs with retractable claws. Long hind legs with broad, flat, webbed paws. Strong flattened tail.
Cool Facts: Their fur is the densest of all mammals with up to 1 million hairs per square inch; their skin never gets wet. They can drink saltwater, thanks to a pair of large complex kidneys. They are one of the only mammals that use tools; they use rocks to break open shellfish.
Conservation Status: Endangered
Major Threat: Pollution.
What Can I Do?: Visit Monterey Bay Aquarium's Sea Otter Research & Conservation Program and Friends of the Sea Otter for information on how you can help.
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