Three recent incidents of orcas apparently attacking and sinking ships off the southwestern tip of Europe are drawing intense scrutiny over whether the animals deliberately invaded ships and are learning aggressive behavior from one another.
Encounters between killer whales or killer whales and boats have been on the rise since 2020, though no human injuries or fatalities have been reported. In most cases, the whales have not sunk the ships.
The series of incidents since 2020 led a scientist in Portugal to say that the attacks may indicate that the whales intend to cause damage to sailing ships. Others, however, are more skeptical, saying that while the behavior may be coordinated, it is not necessarily coordinated aggression.
«I think it’s counted as aggression because it’s causing harm, but I don’t think we can say the motivation is necessarily aggressive,» said Monika Wieland Shields, director of the Orca Behavior Institute, a state-based nonprofit research organization. of washington. .
In 2020, at least 15 interactions between killer whales and boats were recorded off the Iberian coast, according to a study published last June in the Marine Mammal Science Journal.
In November 2020, the National Maritime Authority of Portugal issued a statement alerting sailors to «curious behavior» among juvenile killer whales. The statement said that whales may be attracted to rudders and propellers and may try to get close to ships.
Subsequent sinkings have caused further alarm.
The most recent encounter occurred on May 4 off the coast of Spain. Three orcas struck the rudder and side of a sailing yacht, causing her to eventually sink, as reported earlier this month in a German publication called Yacht.
A theory put forward by Alfredo López Fernández, a biologist at the University of Aveiro in Portugal, suggested that the aggression began with a female orca perhaps being struck by a boat, a traumatic experience that caused her to start ramming sailing ships. López Fernández, co-author of the June 2022 study published in Marine Mammal Science, told Live Science that other orcas may have acquired such behavior through social learning, which whales are known to exhibit.
But Shields said killer whales have not historically been known to be aggressive toward humans, even when they were being hunted and held in captivity.
“They certainly have had reason to engage in that type of behavior,” he said. “There are places where fishermen shoot them, they have seen family members taken from their groups into captivity in the 1960s and 1970s. And if something was going to motivate direct aggression, you would think something like that would have done it.”
Shields added that there are no clear cases of orcas exhibiting what could be considered revenge behavior against humans.
She said the recent attacks on ships are likely more consistent with what’s known as «fashionable» behavior, which describes novel but temporary behavior by one whale that can be imitated by others.
«It’s sort of a new behavior or game that a whale seems to make up for itself, and it seems to spread through the population, sometimes for weeks or months, or in some cases years, but then, in many cases, it’s just gone,» he said.
In the Pacific Northwest, for example, Shields and his colleagues observed fashionable behavior among southern resident orcas who began carrying dead salmon on their heads for a while before the behavior suddenly stopped.
Shields said the orcas’ behavior off the Iberian coast may also be temporary.
“This feels like the same kind of thing, where a whale would play with a rudder and go, ‘Hey, this is a fun game. You want to try?’ And it is the current fashion for that orca population,” she said.
While Shields didn’t rule out the trauma response theory, he said it would be difficult to confirm without more direct evidence.
«We know that their brains are wired to have really complex emotions, so I think they might be capable of something like anger or revenge,» he said. “But again, it’s not something we’ve seen examples of, and we’ve given them plenty of opportunities around the world to want to get back at us for various things. And they just choose not to.»