North Carolina
Scientists have recorded for the first time ever an incident where a predatory shark was eaten up by another much larger shark. The shark that itself fell prey was the Porbeagle shark (Lamna nasus). It can grow to about 12 feet (3.6 metres) long and lives in the Northern Atlantic Ocean as well as parts of the oceans of the Southern Hemisphere.
They are highly vicious in appearance and have angled spear-like teeth. However, it turns out this predator shark can become prey as well.
According to a paper published Tuesday (September 3) in the journal Frontiers in Marine Science, one such porbeagle shark became one of its relative's meals.
"This is the first documented predation event of a porbeagle shark anywhere in the world," study lead author Brooke Anderson, marine fisheries biologist with the North Carolina Department of Environmental Quality said in a statement.
The pregnant female shark had a tracking device and it wasn't spared either. It was tagged in October 2020 using both a satellite transmitter and a pop-off satellite archival tag (PSAT) near Cape Cod.
Porbeagles often change their position while following their prey in the water column. The device was meant to understand its movements, tracking the depths it goes to and the geographic range. Pressure and temperature data from the tags help determine the depth, and any anomalies indicate that the animal has died or the tag fell off before time.
How did researchers know the shark was eaten up?
This shark ranged between the surface and 328 feet down until December 2020.
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It then started diving to depths of up to 2,600 feet during the day and stayed around 650 feet at night. It continued this way as it moved south from where it went to the waters off the shore of Bermuda.
The next year on March 24, the scientists noticed that the temperature patterns had changed drastically. Earlier data showed that it was moving through waters that ranged from 43.5 to 74.3 degrees Fahrenheit (6.4 to 23.52 degrees Celsius). But the tag recorded temperatures that day read between 61.5 F to 76.5 F (16.4 C to 24.72 C). The depth range hadn't changed, which led researchers to believe that the tag was inside the stomach of another shark.
The authors said that the porbeagle was either gobbled up by a white shark (Carcharodon carcharias) or a shortfin mako (Isurus oxyrhinchus).
Scientists are shocked to know that another shark ate up the pregnant porbeagle as the species is already under threat from historic overfishing. "The predation of one of our pregnant porbeagles was an unexpected discovery," Anderson said.