A pod of orcas repeatedly rammed a yacht in the Strait of Gibraltar this week, damaging it enough to require Spanish rescuers to come to the aid of its four crew members.

It was the latest episode in a perplexing trend in the behaviour of orcas populating the Atlantic coast of the Iberian Peninsula that has left researchers searching for a cause.

Spain’s Maritime Rescue service said that orcas repeatedly ran into the Mustique, a 20-metre vessel sailing under a U.K. flag, late on Wednesday, rendering its rudder inoperative and cracking its hull. Rescuers needed to pump out seawater before towing her to safety.

The alert reached the Spanish service via their British counterparts, who relayed the distress call, the Spanish service said. A helicopter and a rescue boat were deployed to help the damaged boat to dock in Barbate.

This was the 24th such incident registered by the service this year. The service didn’t provide data from last year.

A whale's dorsal fin appears in the water, seen from the deck of a nearby boat.
A whale swims next to a boat in the Strait of Gibraltar, Spain, on Wednesday. Orcas in the area have recently been ramming watercraft. (April Boyes/Instagram/Reuters)

But the Atlantic Orca Working Group, a team of Spanish and Portuguese marine life researchers who study orcas near the Iberian Peninsula, says such incidents were first reported three years ago. In 2020, the group registered 52 such events, some of which resulted in damaged rudders. That increased to 197 in 2021 and to 207 in 2022.

The orcas seem to be targeting boats in a wide arc covering the western coast of the peninsula, from the waters near the Strait of Gibraltar to Spain’s northwestern Galicia.

According to the group, these orcas are a small group of about 35 that spend most of the year near the Iberian coast in pursuit of red tuna. The so-called Iberian orcas average from five to 6.5 metres in length, compared to the orcas of Antarctica which can reach nine metres.

There have been no reports of attacks against swimmers. The interactions on boats seem to stop once the vessel becomes immobilized.

The bottom of a boat is seem damaged.
A view shows a sailing boat damaged by orcas off the coast of southern Spain, at a port in Barbate, on Wednesday. (April Boyes/Instagram/Reuters)

Biologist Alfredo Lopez, of the University of Aveiro and member of the research group, said that the incidents are rare — and enticingly odd.

“In none of the cases that we have been able to see on video have we witnessed any behaviour that could be considered aggressive,” Lopez told The Associated Press by phone on Friday. “They appear calm, nothing at all like when they are on the hunt.”

Lopez said that while the cause of the behaviour is unknown, his group has identified 15 individual whales that have been involved. He said that 13 are young whales, which could support the hypothesis that they are playing, while two are adults, which could support a competing theory that the behaviour is the result of some traumatic event with a boat.

In either case, he said the whales are showing once again that they are social animals.

“Orcas are animals with their own culture,” he said. “They transmit information to one another.”

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