Killer whales near the Atlantic coast of Spain and Portugal have been living up to their name. From May 2020 through the end of 2023, they “killed” four boats and attacked hundreds of others. Marine biologists are still trying to explain why.

They’re not the first reported whale attacks in that part of the world. In fact, the earliest known attacks anywhere took place in the northeastern Mediterranean, near Constantinople. Those attacks were blamed on a single whale: Porphyrios.

The attacks took place about 1500 years ago. They lasted for 50 years. The attacker might have been a sperm whale, although orcas—killer whales—are more common in that region. Porphyrios attacked all types of boats. Sailors traveled around its home waters to avoid the danger.

Most of the recent attacks have involved sailing vessels. Orcas approach from behind a boat and ram into the rudder, disabling the craft. They sometimes hit the hull as well, poking holes that sink the boats.

All of the attacks have been near the coast or in the Strait of Gibraltar. They may have been started by a single female, named White Gladis. The groups often are led by a larger orca, with smaller, younger ones learning from their elder.

Scientists have speculated that White Gladis was injured in a collision with a boat, or entangled with a fishing net, and was after revenge. Others say it’s just a fad—a type of play that’s passed from whale to whale—a scary fad for sailors.