Orcas keep sinking boats off Europe, and scientists cannot explain why

Since 2020, sailors crossing the waters off the Iberian Peninsula have reported a strange and unnerving pattern: pods of orcas approaching their boats, focusing on the rudder, and pushing, biting or ramming until the steering gear breaks. In most cases the crews are shaken but unhurt and the vessel limps back to port. In a handful of cases the boat has taken on water and gone to the bottom. The behavior has spread among the local killer whales, and years into the phenomenon, marine biologists still cannot say with confidence what is driving it.

The encounters cluster along the Atlantic coasts of Spain and Portugal and through the Strait of Gibraltar, a narrow, heavily trafficked channel where sailing routes overlap with the whales’ feeding grounds. Reports have accumulated into the hundreds, enough that researchers now treat the behavior as an established feature of this particular population rather than a string of freak events. What they lack is a settled explanation.

Hundreds of encounters since 2020

The scale of the phenomenon is documented rather than anecdotal. Researchers have logged roughly 665 interactions between orcas and vessels around the Iberian Peninsula between January 2020 and May 2025, with several boats sunk over that span, and coverage of the animal behavior has tracked each new incident as it surfaced. The interactions are not evenly distributed through the year; they peak in the warmer months, when both bluefin tuna — the whales’ preferred prey — and recreational sailors converge on the same stretches of water. Most encounters end without a sinking, but the pattern has been consistent enough, and destructive enough, that maritime authorities have issued guidance to sailors on how to respond, generally advising them to slow or stop the boat and avoid drawing the animals’ attention rather than trying to outrun a pod that can easily overtake a yacht.

The rudder is almost always the target

One detail stands out across the reports: the orcas concentrate on the rudder. They approach from behind, push against the blade, and in many cases bite or snap it off, disabling the boat’s ability to steer. That specificity is part of what fascinates researchers, because it suggests the behavior is deliberate and repeated rather than random collision. Eyewitnesses and researchers have described what looks like transmission of the behavior through the group, with individuals appearing to learn the technique from others in the pod. The Atlantic Orca Working Group, a body of Spanish and Portuguese scientists that coordinates the response and maintains the incident records, has cataloged these events since the interactions began and shares its findings through its public reporting platform. The consistency of the rudder focus is one of the few things about the phenomenon that is not in dispute.

A small, endangered population off Iberia

The whales responsible are not a large, thriving group but a small and vulnerable one. The Iberian orca subpopulation numbers only a few dozen animals and is considered critically endangered, which raises the stakes for how authorities respond to the encounters. Only a subset of the population appears to engage in the rudder behavior, and researchers have identified specific individuals — many of them juveniles — that turn up repeatedly in the reports. Because the group is so small, the actions of a handful of animals can define the reputation of the entire population, and any intervention aimed at protecting boats has to be weighed against the risk to an endangered species. Spanish authorities have convened experts to assess the situation, and the government’s environment ministry published a workshop report reviewing what is known about the interactions and how to manage them.

Competing theories, no consensus

The central mystery is motive, and here the experts diverge. One leading idea is that the behavior is a form of play or a passing social fad, with young orcas treating boat rudders as toys and imitating one another, much as other animal populations have adopted and dropped novel behaviors over time. A second is straightforward curiosity — the whales investigating an unfamiliar object in their environment. A third and more dramatic hypothesis, examined by Scientific American, holds that a single traumatized female may have started the behavior after a distressing encounter with a vessel, with others copying her. There is also the possibility that the whales perceive boats as competitors for tuna. None of these explanations has been confirmed, and they are not mutually exclusive; the true driver may be some combination, or something not yet identified.

Why researchers avoid the word “attack”

Despite the popular framing, many of the scientists studying the whales are careful not to call the encounters attacks. The orcas do not target the people aboard, no human has been killed in the incidents, and describing the behavior as aggression toward humans imposes a motive the evidence does not support. The researchers prefer the more neutral term “interactions,” precisely because the animals’ intent is unknown and because loaded language can fuel calls for harmful retaliation against an endangered population. That caution captures the honest state of the science: the whales are unmistakably damaging boats, the behavior is spreading through a small and closely watched group, and the reason remains, for now, an open question that years of observation have narrowed but not resolved.

This article was researched and drafted with the assistance of AI and reviewed before publication.

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