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Do large sharks eat each other? Scientists say it’s likely.

Shikarov
Do large sharks eat each other? Scientists say it’s likely.

A team of scientists from Arizona, Oregon and Rhode Island tracked a pregnant female porbeagle hundreds of miles from New England to Bermuda until she was killed.

For the first time ever, scientists have found evidence that a predator killed a shark at the top of the food chain, according to a study published Tuesday in the peer-reviewed journal Frontiers in Marine Science.

The team of scientists who wrote the study decided to study pregnant porbeagle sharks and track their movements, because they are endangered in many parts of the world. The scientists are from Oregon State University, Arizona State University and the Rhode Island-based Atlantic Shark Institute.

One shark studied measured 8 feet and was tracked for five months, said James Sulikowski, director of the Coastal Oregon Marine Experiment Station at Oregon State University.

Scientists discovered that the large, warm-blooded shark fell victim to another warm-blooded predator, probably another shark.

The team says the porbeagle was eaten by a warm-blooded predator

Sulikowski said the team tagged the sharks with two different tags.

The first tag, the finmount tag, is placed on the shark’s fin and provides scientists with “a very precise geolocation when the fin is out of the water,” he told USA TODAY on Tuesday.

The second tag, called an archival satellite tag, provides the temperature and depth at which the shark is in the ocean.

“That’s how we knew the shark had actually been eaten or attacked,” Sulikowski said, referring to the archival label.

The second shark, also a porbeagle, died nearby a year after the first shark was killed and sank to the ocean floor before its transmitter surfaced, scientists said.

The shark was tracked for hundreds of miles

Scientists say the dead shark was tracked for hundreds of miles from New England to Bermuda.

The shark spent time at depths ranging from 1,640 feet to 3,280 feet. Because the shark swam so far from the sun, its temperature readings were much lower. Suddenly, while the shark was still deep in the ocean, one of the shark’s tag readings went from 15 degrees Celsius to 25 degrees Celsius.

“We knew something had happened,” Sulikowski said. “We knew the marker was inside a warm-blooded creature… And we knew it wasn’t a whale or a mammal, because mammals are much warmer.”

The predator that ate the porbeagle was most likely another lamnid shark, Sulikowski said, adding that the “iconic trio” of lamnid sharks are porbeagle sharks themselves, great white sharks and mako sharks.

Their body temperature is usually between 25 and 27 degrees, he added.

“In my opinion, it’s probably a mako or a great white shark because they’re bigger than a porbeagle,” he said.

The second shark sank to the bottom of the ocean

There was another shark that researchers collected data on that they found interesting. The porbeagle was swimming at a depth of about 1,968 feet when it suddenly sank closer to the ocean floor, Sulikowski said.

The team believes something killed the shark without eating it or its tags. After the shark sank, the tag — set to break off when sharks remain motionless for long periods — resurfaced after about three days.

“Both sharks were attacked at the same depth, in the same location, a year apart,” Sulikowski told USA TODAY.

What does this mean for porbeagle sharks and science?

Sulikowski said that because sharks are as big and fast as porbeagle sharks, the only animals that hunt them are other sharks that are bigger than them.

Scientists expect a smaller shark to fall victim to a larger shark, but the case of the 8-foot shark was quite unexpected, he said.

The fact that this happened shows how little we know about the ocean, he added.

“It makes us want to study more and learn more about how susceptible other large sharks are to being eaten and who is most likely to be eaten there.”

Saleen Martin is a reporter on the NOW team at USA TODAY. She is from Norfolk, Virginia. – 757. Follow her on Twitter: @SaleenMartin or write to her e-mail address [email protected].

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