Believe it or not, Jaws has something to fear



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Jaws are afraid of Free Willy.

A new study published in Nature This week showed that when pods of killer whales entered an area around the island of South Farallon, off the coast of San Francisco, the area's large white sharks emptied – and did not return for months.

No ocean predator is more fearsome in the public imagination than the great white shark, but even they seem to move away from the orcas, highly intelligent hunters who have been observed on rare occasions to attack large whites – and to eat their livers.

"On one occasion, we had 17 sharks that were tracking simultaneously on the island when a group of orcas appeared," said Salvador Jorgensen of the Monterey Bay Aquarium, who led the study involving Stanford University and Point Blue Conservation Science.

"We could see from the data that all the sharks left the side of the island where the orcas had come," he said, "and in a few hours the island has completely disappeared."

The findings are the result of 27 years of research, but Jorgensen suspected the two predators were doing this dance for a while.

Scientists have labeled 165 large white sharks between 2006 and 2013, luring them to boats with carpet-sealed baits every day before posting them with beacons that shipped sensor codes across the territory. In this way, scientists could track their movements. Point Blue Conservation Science researched orcas activity around southeast Farallon Island, helping the team understand how orcas and sharks interacted.

"There is an irony in the fact that one of the main cards that this predator has is his ability to know when to give up and run," Jorgensen said of the sharks. "We do not always think of a white shark as having decided to flee, but that may be a fundamental aspect of their behavior that may have led to the success of the last few million years."

The true winner of this ecological dance of predators, however, may be prey. Large white sharks gather around Farallon Island in the southeast when the population of juvenile marine elephants is abundant and are more likely to overlap killer whales in late fall or early winter. Although killer whales pass only briefly, large white sharks leave for a long time, leaving the seal population alone.

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