Scientists say orcas ramming boats are playing, not attacking; pod sank yacht off Portugal

A pod of orcas that recently rammed and sank a tourist yacht off the Portuguese coast was engaging in play-like behaviour, not predatory or territorial attack, scientists and researchers said, offering an explanation for a series of similar incidents across European and North African waters.

Video released after the weekend encounters shows several orcas circling and repeatedly striking one vessel near Fonte da Telha beach; a second tourist boat reported an interaction off Cascais. All nine people aboard the two vessels were rescued by nearby craft before lifeguards arrived, officials said. The sinking adds to a pattern of boat interactions recorded in the Bay of Biscay, off the Moroccan coast, in the North Sea and elsewhere in recent years.

Renaud de Stephanis, president of the Conservation, Information and Research on Cetaceans (CIRCE) in Spain, said the behaviour represents a game-like cultural trait in a small subpopulation of Iberian orcas rather than an attack driven by food, territory or mistaken identity. De Stephanis and other marine biologists described the animals’ focus on the underside of boats—especially rudders—as an attraction to moving, vibrating objects that provide resistance when pushed.

"What we have been documenting in the Strait of Gibraltar, the Gulf of Cádiz and Portugal is a game-like behaviour developed by a small subpopulation of orcas," de Stephanis said. "They focus on the rudder of sailboats because it reacts dynamically when pushed — it moves, vibrates, and provides resistance. In other words, it is stimulating for them."

Clare Andvik, a marine mammal expert at the University of Oslo, echoed the assessment and called the recent sinking "very unfortunate," noting it is the first reported case in which an interaction led to a vessel sinking. She likened the episodes to a tug-of-war: if a person tries to steer a rudder while the animals push, the added resistance appears to increase the animals’ interest and effort.

Scientists advising mariners say the safest response differs from some local official guidance. CIRCE recommends that vessels maintain course and speed, as moving boats make the interaction less attractive; a stopped vessel leaves the rudder as an easier target and may prolong contact. Portuguese authorities in some locations have in the past advised boats to stop when orcas appear, a measure the researchers described as counterproductive.

Andvik suggested crews reduce sail, engage engines, head toward shore if safe, and avoid steering the rudder back into contact with the animals. She also advised staying in shallower water where possible, where the specific orca group has been observed less frequently.

Orcinus orca, commonly called killer whale, is actually the largest member of the dolphin family and an apex marine predator. Different orca populations specialise in different prey and hunting techniques, and the species is known to take fish, seals, other marine mammals and, in rare documented cases, large whales and sharks. Researchers have previously linked orca predation on great white sharks to shifts in local shark distributions when orcas targeted shark livers.

Scientists stressing the distinction between play and predation said the animals do not appear to mistake humans for food. "They are highly intelligent and do not mistake humans as prey," Andvik said, while noting that people in the water could be injured inadvertently if whales are attacking large prey nearby.

Researchers are continuing to monitor the Iberian orca group and compile reports from maritime authorities and eyewitnesses to map the behaviour’s spread and seasonal patterns. Maritime Rescue agencies have also investigated incidents earlier this year, including a reported interaction in August with a German-flagged sailboat north of Cíes, Spain.

The scientists warned that, despite the playful intent attributed to the animals, interactions can cause serious damage to boats, injure passengers and require coordinated rescue responses. They urged mariners operating in areas where the group has been observed to follow the precautionary guidance put forward by researchers and to report encounters to local authorities so that patterns can be tracked and public safety advice updated.