Sharks Are Mysteriously Killing Sea Otters in the Pacific, But Not Eating Them

June 28, 2016 | Erica Tennenhouse

A great white shark
Photo credit: Elias Levy/flickr (CC BY 2.0)

"The truth is, we're deep in I-just-don't-know land."

Sea otters in California are falling victim to great white sharks at an unprecedented rate. Over the past three decades, scientists have collected nearly 2,000 sea otter carcasses bearing the telltale tooth marks of great whites.

"Throughout the otter's range, shark-bitten animals now account for more than half of the carcasses we find," Tim Tinker, a wildlife ecologist at the U.S. Geological Survey's Western Ecological Research Center, tells National Geographic. "It exceeds all other sources of death combined.

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Though the recent increase in these incidents is of great concern due to the endangered status of sea otters, whose California population is just over 3,000, what really mystifies the scientists is that great white sharks are not known to consume sea otters.

"As far as we can tell, a white shark has never eaten a sea otter," says Tinker. "We always get the whole animal back."

Some have suggested that sharks are mistaking otters for their normal blubber-rich seal or sea lion prey. Only after biting them do the sharks realize their error and release the sea otter carcasses.

As for the recent explosion of shark attacks on otters — more than 750 carcasses were found between 2000 and 2013, and another 270 over the following two years — it might simply be the result of shark population growth due to conservation efforts in recent years. Alternatively, rising water temperatures that are pushing sharks further north may bring more great whites into contact with otters.

For now, though, the situation continues to perplex scientists. "The truth is, we're deep in I-just-don't-know land," Tinker says.

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