Pregnant Shark Eaten by Even Bigger Shark

BERMUDA - A pregnant porbeagle shark tracked off Bermuda has provided unexpected data for researchers after its tracking tag ended up inside a larger predator.

The porbeagle, a species known to grow up to 12 feet and live as long as 65 years, was part of a research study aimed at understanding their migration patterns and reproductive behaviors. Porbeagles are slow to reproduce, with females not giving birth until age 13, typically having only four pups every one to two years, making them particularly vulnerable.

For five months, the 7-foot-long shark, fitted with a pop-off satellite archival tag (PSAT), swam at depths of 500 to 2,000 feet. The data revealed she mostly stayed at those depths, only surfacing once during that time. However, on March 24, 2021, something unusual occurred. The shark’s PSAT began transmitting a constant temperature of 71.6°F for four days, a sign the shark had been eaten by a larger predator, researchers said. The tag was eventually excreted and began floating at the surface, continuing to transmit.

According to the study, two possible culprits are the great white shark and the shortfin mako, both of which are large endothermic predators known to hunt in the region. Mako sharks, though capable, typically feed on smaller prey, while great white sharks have been known to eat whales, dolphins, and seals, making them the more likely attacker.

This study was published in the Frontiers in Marine Science on September 3.