(Monterey Herald) California's sea otters have struggled for years with diseases, parasites and even the occasional collision with boats. But now the fuzzy coastal mascots are increasingly facing another threat: shark attacks.
For reasons still a mystery to scientists, the number of sea otters killed by sharks, with great whites as the leading suspects, has soared in recent years.
"It's been very dramatic," said Tim Tinker, a Santa Cruz-based wildlife biologist with the U.S. Geological Survey. "It's having the biggest impact on population growth of any factor."
In the mid-1990s, about 10 percent of the dead sea otters found along the California coast had shark bites. Today, it's about 30 percent — and growing. The shark attacks now represent the largest hurdle to the otters' recovery from the endangered species list.
Last year, 70 sea otters bearing the telltale signs of shark attacks washed ashore between San Mateo County and Santa Barbara.
Among the carcasses with clear shark bite wounds, some have teeth from white sharks embedded in their bodies. Others have scratch patterns on bones that match the serrated edges of white shark teeth. Still others have bite marks in the half-moon pattern of shark jaws.
"We have found some that have survived," Tinker said. "But I don't think it's a very large percentage. I would guess 80 to 90 percent of the time it's lethal."
Nobody knows why sharks seem to be killing otters at rates greater than ever recorded off California's central coast. Great whites have never been filmed or even confirmed to have eaten an entire otter for food.
One leading theory, Tinker said, is that the populations of sea lions and elephant seals — the marine mammals that white sharks regularly eat — has grown in recent decades, expanding to new places.
Sharks might be changing their hunting patterns and accidentally be biting sea otters, mistaking them for seals and sea lions, and then leaving them to die.
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