From the Strait of Gibraltar to Galicia, orcas have been harassing yachts, damaging vessels and injuring crew.

Reports of orcas striking sailing boats in the Straits of Gibraltar have left sailors and scientists confused. Just what is causing such unusually aggressive behaviour?

hen nine killer whales surrounded the 46ft boat that Victoria Morris was crewing in Spain on the afternoon of 29 July, she was elated. The biology graduate taught sailing in New Zealand and is used to friendly orca encounters. But the atmosphere quickly changed when they started ramming the hull, spinning the boat 180 degrees, disabling the autohelm and engine. The 23-year-old watched broken bits of the rudder float off, leaving the four-person crew without steering, drifting into the Gibraltar Straits shipping lane between Cape Trafalgar and the small town of Barbate.

The pod rammed the boat for more than an hour, during which time the crew were too busy getting the sails in, readying the life raft and radioing a mayday – “Orca attack!” – to feel fear. The moment fear kicked in, Morris says, was when she went below deck to prepare a grab bag – the stuff you take when abandoning ship. “The noise was really scary. They were ramming the keel, there was this horrible echo, I thought they could capsize the boat. And this deafening noise as they communicated, whistling to each other. It was so loud that we had to shout.” It felt, she says, “totally orchestrated”.

The crew waited a tense hour and a half for rescue – perhaps understandably, the coastguard took time to comprehend (“You are saying you are under attack from orca?”). To say this is unusual is to massively understate it. By the time help arrived, the orcas were gone. The boat was towed to Barbate, where it was lifted to reveal the rudder missing its bottom third and outer layer, and teeth marks along the underside.

Rocío Espada works with the marine biology laboratory at the University of Seville and has observed this migratory population of orca in the Gibraltar Straits for years. She was astonished. “For killer whales to take out a piece of a fibreglass rudder is crazy,” she says. “I’ve seen these orcas grow from babies, I know their life stories, I’ve never seen or heard of attacks.”

Highly intelligent, social mammals, orcas are the largest of the dolphin family, and behave in a similar way. It is normal, she says, that orcas will follow close to the propeller. Even holding the rudder is not unheard of: “Sometimes they will bite the rudder, get dragged behind as a game.” But never with enough force to break it. This ramming, Espada says, indicates stress.