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In the past few months, there have been several reports of orcas severely damaging sailing boats off the coast of Spain and Portugal. At least a dozen whales are taking part in the activity, sparking a flurry of speculation over whether the orcas (Orcinus orca) may be teaching each other how to bring down boats and organising into an army. But there are non-combative reasons that could be behind the rise in encounters.

Where is this happening?

In the Strait of Gibraltar, there is a pod of orcas that have been ramming boats and ripping off the rudders, sinking three sailboats and damaging dozens more over the past year. The orcas began a new wave of activity this May, and videos documenting the encounters have been sweeping the internet since.

How long has this been going on?

People have been paying more attention recently, but altercations with these orcas have been reported for years. Scientists, fishermen and locals began reporting unusual encounters in the Strait of Gibraltar in . According to the , which tracks this pod, there were 207 reported interactions in 2022, and at least 20 last month alone. While many interactions were relatively harmless, at least three ships have sunk this year, with no reported injuries to people.

Over the past few years, these orca-boat confrontations in the Mediterranean seem to have escalated during the month of May when the pod’s favourite food, bluefin tuna, is migrating through the area.

What exactly are the orcas doing to boats?

In most encounters, orcas quickly approach the stern of the boat, with an apparent interest in the boat’s rudders, which they pierce or snap with their teeth. The whales have also been seen pressing into sailboats with their head and the flank of their body, occasionally tearing holes in the hull. Sometimes, they cause no damage to the ships, instead riding in the boat’s wake. Notably, this group of whales seems less interested in large or motorised vessels. “They’re hyper-focused on sailboats,” says at the University of Washington in Seattle.

How many orcas are involved?

Each encounter usually involves only a handful of whales from a pod of around 39 total orcas. Images and video of the events are helping researchers track which individuals are most involved and which have yet to exhibit the behaviour. Currently, around 15 orcas are partaking in the boat-ramming activity. “It’s a behaviour that has probably spread from one individual,” says at the University of British Columbia in Canada.

Can orcas learn from one another? Will this behaviour spread?

Orcas are a social species capable of learning from their podmates, so it is possible the behaviour is a trend that is catching on. But that doesn’t mean that the whales are intentionally teaching their podmates to target boats, which would require communicating a motive and recruiting others to the cause. Instead, it may just look fun or interesting to the orcas.

This North Atlantic subpopulation, like many orca pods, is distinct from others in diet, culture, dialect and genetics. These orcas don’t mingle with those outside their pod, so it is unlikely this behaviour will spread to other populations of orcas, though it could spread through some of the rest of their pod.

Why are orcas doing this? Is it revenge?

Online rumours have swirled about an orca called White Gladis, who was supposedly traumatised in an encounter with a boat – this is speculation based on healed injuries on her fins, but these haven’t been confirmed to be from a boat. Orcas rake each other with their teeth, which could be the source of the scars. But most experts agree there isn’t any evidence White Gladis is training other whales to attack, and no clear motive for podmates to risk personal injury for her vengeance.

“Nobody knows why this is happening,” says Trites. “All the reports coming in have been from non-scientists, non-specialists – people that are terrified.” He says orcas are a highly intelligent species capable of self-recognition, but that doesn’t necessarily mean they are capable of planning and enacting revenge.

What else could be behind the increase in orca encounters?

Both Trites and Giles think it is more likely that the orcas are just having fun or seeking an admittedly terrifying back scratch. “These whales are very tactile,” says Giles. “They interact with things in their environment, including each other.” A pod of whales in British Columbia has been seen vigorously rubbing against rocky beaches, for example.

Wild orcas have never been documented hunting or eating humans, so it is unlikely this relates to wanting a meal.

Until researchers know what is motivating the encounters, it will be challenging to abate them. If the orcas see the activity as a game, for example, fleeing may elicit a more aggressive response. “This is something that we humans need to figure out and not place the blame on the whales,” says Giles.