In the marine food chain, large sharks generally Killer whale But new research suggests that apex predators may also have to keep their peers safe.
Researchers have found evidence that this marks the first time a porbeagle shark, which can grow to 12 feet long and weigh 500 pounds, has been killed by a larger shark predator. The findings were published Tuesday in the journal Frontiers in Marine Science.
John Dodd, executive director of the Atlantic Shark Institute, which led the study, said this isn’t the first case of “shark cannibalism.” It’s common for larger sharks to eat smaller ones. “Size matters in the open ocean, but there’s always something bigger,” he said.
In some cases, bull sharks, mako sharks, Baby Grey SharkFor example, sharks may eat other creatures of their own species.
But instances of large sharks like the ones in this study eating other large sharks are extremely rare, said Dr. Brooke Anderson, a marine biologist with the North Carolina Department of Environmental Quality and lead author of the paper.
The death of the female porbeagle shark raises the question of whether the incident reflects a broader trend among large predators, Anderson said. “With advances in technology, it’s possible that this is happening more often than we’ve actually been able to detect,” he said.
Dodd said it’s impossible to know how many sharks are being eaten by other sharks, “but if the experience at the Atlantic Shark Institute is any indication, it may be more than we think.”
A group of scientific researchers from across the United States discovered the porbeagle’s body while conducting a satellite tracking project in the Northwest Atlantic to better understand the location, behavior, and environmental preferences of porbeagle sharks. They were particularly interested in female porbeagle sharks, which are known to travel long distances to give birth.
“We’ve been really focused on understanding the habitat that pregnant females use and figuring out where they give birth,” Anderson said.
The victim of the attack, nicknamed Penelope by researchers, was one of 11 sharks that scientists tagged off the coast of Cape Cod in 2020 and 2022. The tracking tag was attached to the shark’s dorsal fin and was used to collect information about water depth and temperature. The tag stored the data until it was eventually released from the shark, at which point it was transmitted via satellite to researchers.
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The tracking device was designed to remain on for a year, but five months into the experiment, Penelope’s data was already coming in. “When we received the data from the tag, we knew right away that something strange had happened,” Anderson said.
A few days before Penelope’s tag came off the Bermuda coast, water temperatures suddenly rose – and remained relatively warm even 600 metres below the surface – which Anderson explained was “highly unusual”.
Anderson and his colleagues came to the bleak conclusion that the porbeagle shark was caught and eaten by another ocean giant. “The only explanation for this data is that this tab is currently in the stomach of a predator,” Anderson told CBS News.
While the researchers aren’t 100% sure what the culprit was, the diving patterns of the predator they tracked by looking at depth data collected by the tag were similar to those of great whites the researchers had monitored in the past. “Based on that, our guess is that it was likely a mature female great white,” Anderson said.
Porbeagle sharks have been historically overfished and are considered endangered in some parts of the world. They are already critically endangered, but the loss of pregnant females and their calves could have a devastating effect on the population, Anderson said.
And sharks aren’t the only ones feeling the ripple effects of this change: These masters of the deep keep underwater ecosystems in balance by keeping populations of smaller predators in check and adding vital nutrients to shallow waters.
“Humans depend heavily on the ocean for food and many other things, and the ocean needs healthy shark populations,” Anderson said.
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