Just weeks before a pregnant porbeagle shark was expected to give birth, one of the two tracker tags marine scientists had placed on the animal floated to the surface near Bermuda.<\/p>\n\n\n\n
The team hadn\u2019t expected the tag to surface for months. They had attached it to the 7-foot creature just 158 days earlier, after hoisting the shark onto a boat off the coast of Cape Cod, Massachusetts, in October 2020 and giving it an ultrasound. The pop-off tag was designed to stay on for about a year. <\/p>\n\n\n\n
\u201cSomething had gone very wrong,\u201d said Brooke Anderson, who worked as a shark researcher at Arizona State University at the time.<\/p>\n\n\n\n
A second tag, which was designed to transmit a signal when the shark\u2019s fin broke the sea surface, would never do so again. <\/p>\n\n\n\n
The data from the recovered \u201cpop-off\u201d tag showed a curious pattern. For about five months, the depth and temperature information seemed normal for the species. Then it went haywire. <\/p>\n\n\n\n
\u201cAll of a sudden, the temperature spiked, even at 600 meters depth, and stayed elevated,\u201d Anderson said. <\/p>\n\n\n\n
The creature\u2019s diving pattern also became strange.<\/p>\n\n\n\n
\u201cAll of the data pointed to the same conclusion: She had been eaten,\u201d Anderson said.<\/p>\n\n\n\n
The researchers determined that the explanation for the tag\u2019s anomalous readings was that the device had spent several days inside the stomach of a different animal. <\/p>\n\n\n\n
Anderson and her fellow researchers laid out their findings in a study published Tuesday morning in the journal Frontiers in Marine Science. It represents the first evidence of a porbeagle being eaten by something even bigger. <\/p>\n\n\n\n
The study authors named a few possible killers. They narrowed down the suspects based on their biology. The tag\u2019s temperature readings didn\u2019t fit the profile of a mammal like an orca, for example. So the scientists centered on endothermic sharks, which have some warm-blooded capabilities. <\/p>\n\n\n\n
\u201cIt had to be a shark that can elevate its body temperature above the surrounding water. It had to be large enough to do enough damage to the porbeagle, and it had to inhabit the area where the predation occurred,\u201d Anderson said. <\/p>\n\n\n\n
The researchers concluded that a white shark or shortfin mako shark must have munched on their pregnant porbeagle and ingested the tag temporarily. <\/p>\n\n\n\n
\u201cI would guess this would have been a mature female white shark, probably 15-plus feet,\u201d Anderson said.<\/p>\n\n\n\n
Before this, researchers didn\u2019t think it was even possible that porbeagle sharks could be preyed upon, she added. <\/p>\n\n\n\n
The team\u2019s original goal was to trace pregnant porbeagle sharks throughout their pregnancy and figure out where the creatures typically go to give birth.<\/p>\n\n\n\n
In total, they found and tagged 11 porbeagle sharks during two seasons in the Atlantic, hoisting each one into their boat, laying the creature out on deck, giving the shark a hose of aerated saltwater and covering its eyes with a wet towel. <\/p>\n\n\n\n
\u201cWe work like a NASCAR pit crew,\u201d Anderson said. Eight of the sharks were pregnant. <\/p>\n\n\n\n
Her team never imagined they\u2019d uncover a deep-water murder mystery. <\/p>\n\n\n\n
Matt Davis, a marine resource scientist for the Maine Department of Marine Resources who was not involved in the research, said the new study\u2019s conclusion \u201ccertainly falls within believability.\u201d <\/p>\n\n\n\n
The incident shows that scientists still have much to learn about life and predator-prey relationships in the intermediate depths of the ocean, Davis added.<\/p>\n\n\n\n