‘Killer Seals’ Could Attack UK Swimmers After Mutilated Porpoises Found, Experts Warn

November 28, 2014 Updated: July 18, 2015

Experts have warned that grey seals could attack swimmers in British waters after they discovered the animals were mutilating and killing harbor porpoises.

The mutilated porpoises, which are related to dolphins and whales, were found around the North Sea. Many of the animal carcasses were found on Dutch shores.

Grey seals mostly eat fish and it is unclear why they’re attacking porpoises. They apparently use their claws and jaws to rip their prey apart.

According to a study published in the Proceedings of the Royal Society B, grey seals attack larger animals and could go after people, reported Discovery.

“People go on excursions to swim or dive with grey seals, unaware that these animals can be quite dangerous for human-sized animals. Most people consider them quite cute,” said study co-author Lineke Begeman, who works with Utrecht University’s Faculty of Veterinary Medicine.

The study’s lead author, Mardik Leopold with the Wageningen University and Research Center, told the site: “Grey seals use their ‘hands’ to hold large prey and their teeth to tear off bits and pieces, so they do not have to swallow large prey whole. This is why they can also take on large prey.”

There’s about 200,000 grey seals off the coast of the UK.

The study authors evaluated more than 1,000 mutilated harbor porpoises on the Dutch coastline. Some of the animals had seal DNA.

“This is a new behaviour. They’re normally fish eaters, they can eat a large fish, around half a metre. It’s a switch from fish-eating to mammal-eating. I don’t think it’s indicative of lower fish stocks, they just learned a new trick,” Leopold told The Guardian.

He noted there have been seal-related incidents involving humans in northern Europe but no deaths. He said that “people have been bitten while swimming.”