Many decades ago, someone first noticed the grisly remains of a gray seal pup along the sands of Sable Island, a thin sliver of land along Canada’s East Coast, just over 100 miles southeast of Nova Scotia. It was initially written off as the aftermath of a shark attack or maybe some kind of boating accident.

Every breeding season, hundreds of gray seal pups would turn up dead, with the same grotesque spiral wounds that would “corkscrew” from their mouths to their chests. It wasn’t too long before people realized this was no accident. This seemed premeditated, like someone had been butchering these baby seal pups with power tools.

What was actually going on had remained a mystery for decades, until now. According to a study published in Marine Mammal Science and first highlighted by Science Magazine, researchers say they finally know who did it, and it wasn’t a person as they initially thought. It was an adult male gray seal. Probably several of them.

This ended up being a much more troubling answer than if a human had done the horrifying killings.

Marine ecologist Izzy Langley from the University of St. Andrews witnessed firsthand an adult bull gray seal attacking a pup on Sable Island, which is home to the world’s largest gray seal breeding colony. Scientists followed up with a series of surveys across the beaches, cataloging hundreds of carcasses with the same spiral gashes, which, upon closer inspection, were much deeper than previously thought, as they found bite marks from a large seal’s canines and claw marks left by flippers.

In 2024 alone, researchers counted 765 dead pups with the same corkscrew-style cuts along their bodies. On a single day in 2025, they documented 359 carcasses. The gruesome violence was happening much more frequently, and they were no closer to figuring out why.

After tons of observation, the attacks appear to be carried out almost exclusively by adult males during breeding season, when the males fast for long stretches while competing for mates, “to boost their mating value during the breeding season,” Langley told Science Magazine.

While the researchers may not have any definitive answers just yet, they think the males may have learned to use seal pups as a high-calorie food source.

To put it another way, horny male seals were so ravaged by hunger in their desperate quest for sex that they turned to literally cannibalizing the babies of their own species, likely because they were readily available, so they could have a quick meal before getting back to mating.

There was no deranged human carrying out grisly seal pup murders for decades. There were no boating accidents. Nature can sometimes be horrifying all on its own.