Researchers found the first evidence of a large shark killing a porbeagle shark, which can grow up to 12 feet long and weigh 500 pounds. Their study was published in the journal Frontiers in Marine Science.

The porbeagle shark

While juvenile porbeagle sharks prey on squid mainly, they shift to a primarily fish-based diet of mackerel, herring, hake, cod and dogfish as they mature. Unlike their larger relatives in the white shark family, porbeagle sharks do not prey on marine mammals. Their numbers have been drastically reduced by industrial overfishing.

It is well known that the biggest sharks prey on smaller sharks, however this is the first evidence that a shark as large as a porbeagle shark could be taken. The study, led by Dr. Brooke Anderson from the North Carolina Department of Environmental Quality, suggests that predation among the great sharks might be more common than previously thought. With new technology, researchers might discover more about these incidents.

Tracking Penelope

The researchers were tracking porbeagle sharks in the Northwestern Atlantic to learn about their habits and habitats. They were particularly interested in pregnant females, who travel long distances to give birth. 

One of the tagged sharks, named Penelope, was tracked off Cape Cod in 2020 and 2022. The tags, which were attached to her dorsal fin to record data on water depth and temperature, were intended to remain affixed to the shark for a year, but after only five months, Penelope's tag sent data revealing unusually high water temperatures, suggesting something strange had happened.

The data led researchers to believe that Penelope had been eaten by another shark. Although they cannot be certain, the diving patterns from the tag were similar to those of great white sharks, so they suspect  that a mature female white shark could have been the predator.

Danger of losing more pregnant females

Porbeagle sharks are endangered, especially in the North Atlantic, due to seven decades of industrial overfishing, so losing pregnant females like Penelope could significantly impact the population of those that remain. As apex predators, sharks are crucial to maintaining the balance of marine ecosystems, and their extreme depletion is having unknown effects on the ocean's ecological make-up. 

So unfortunately, the study has identified yet another cause of death for the beleaguered porbeagle shark.