Researchers captured and tagged a pregnant porbeagle shark near Cape Cod in October 2020. The 7-foot shark had two trackers attached: one was a geolocator; the other was a pop-off satellite archival tag (PSAT) that relayed info about water temperature and depth. As the scientists write in a paper published Monday in Frontiers in Marine Science, the PSAT should have stayed on the shark for roughly a year, but it detached near Bermuda after just five months, and the data it relayed before it came off was weird.
"All of a sudden, the temperature spiked, even at 600 meters depth, and stayed elevated," study co-author Brooke Anderson tells NBC News. The geolocator, which should have transmitted a signal when the shark's fin came above the surface, went silent. Their conclusion? The tracker was in the stomach of a much larger shark, which they believe ate the porbeagle in what they say is the first evidence of a porbeagle being eaten by a larger predator. The scientists note that their find "provides novel insight into inter-specific interactions for this large, threatened shark species."
Fox News reports the temperature readings narrowed the list of possible predators to endothermic sharks. Per the study, two types are "large enough to predate upon mature porbeagles and located within the vicinity and at the time of year": the white shark Carcharodon carcharias or the shortfin mako Isurus oxyrhinchus. Anderson's best guess? That it was "a mature female white shark, probably 15-plus feet," she tells NBC. Prior to the study, it was assumed porbeagle sharks were at the top of their food chain. (More discoveries stories.)
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