Scientists believe a traumatized killer whale launched an attack on a boat after a "painful critical moment" and that the behavior is spreading among people through social learning.
Orcas are mainly aimed at sailing ships and go straight to the rudder. (Image: Shutterstock)
Orcas attacked and sank a third ship off Europe's Iberian coast, and experts now believe other killer whales are following suit.
On the night of May 4, three orcas (Orcinus orca), also known as killer whales, attacked the yacht in the Strait of Gibraltar off the coast of Spain and pierced the rudder. "There are two smaller and one larger orca," captain Werner Schaufelberger told German publication Yacht. "The small one rocks the rudder in the back, the big one repeatedly retreats, and hits the boat hard from the side."
Schaufelberger said he saw smaller orcas mimicking larger orcas. "Two baby killer whales observed the technique of the big killer whale, jumped lightly, and also crashed into the boat." The Spanish Coast Guard rescued the crew and towed the boat to Barbat, but sank at the port entrance.
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Two days ago, a group of six orcas attacked another sailing ship sailing through the strait. Greg Blackburn on board watched as the female orca seemed to be teaching her calf how to rush to the rudder. "It's definitely some form of education, teaching that is going on," Blackburn told 9news.
According to a study published in June 2022 in the journal Marine Mammal Science, aggressive encounters with orcas off the Iberian coast have been reported since May 2020 and are becoming more frequent. The attacks appear to have been aimed primarily at sailboats and followed a clear pattern: orcas approached from the stern and tapped the rudder, losing interest once they managed to stop the ship.
"Reports of interactions have been ongoing since 2020 in places where orcas were found, both in Galicia and in the strait," said co-author Alfredo López Fernandez, a biologist at the University of Aveiro in Portugal and representative of Grupo de Trabajo. Orca Atlántica, or Atlantic Orca Working Group.
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Most encounters were harmless, López Fernandez told Live Science in an email. "Of the more than 500 interactive incidents recorded since 2020, 3 ships sank. We estimate that for every hundred boats passing through a location, killer whales will only touch one. ”
López Fernandez says the surge in attacks on ships is a recent phenomenon. Researchers believe that a traumatic event may have triggered a change in the behavior of one killer whale, while others learned to imitate.
"Killer whales do this on purpose, of course, we don't know the origin or motive, but trauma-based defensive behaviors as the origin of it all, are adding strength to us every day," López Fernández said.
Experts suspect that a female killer whale they call White Gladis experienced a "painful critical moment" — colliding with a vessel or being trapped during illegal fishing — triggering a behavior switch. "That traumatized orca was the act of starting physical contact with the boat," López Fernandez said.
According to a 2022 study, orcas are social animals that can easily learn and replicate the actions of others. In most reported cases, orcas go straight to the rudder and bite, bend or break the rudder.
"We don't think orcas are teaching young people, although this behavior has spread vertically to young people, simply by imitating, and then laterally among them, because they think it's important in their lives," López Fernandez said.
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López Fernandez added that killer whales seem to see this behavior as favorable, even though they may crash into moving vessel structures. Since the beginning of the anomalous interaction in 2020, four killer whales living in a subpopulation in Iberian waters have died, although their deaths are not directly linked to the encountering vessel.
This unusual behavior could also be fun, or what the researchers call "fad" — an act initiated by one or two people and temporarily accepted by others before being abandoned. "They're very curious and playful animals, so this might be more of a playful thing than an aggressive thing," Deborah Giles, a orca researcher at the University of Washington and a nonprofit wild orca group, told Live Science.
As the number of incidents has increased, so have concerns about sailors and an Iberian killer whale subpopulation listed as critically endangered on the IUCN Red List. According to a 2022 study, the last census in 2011 recorded only 39 Iberian orcas. "If this continues or intensifies, it could become a real concern for sailors' safety, as well as a conservation concern for this endangered subpopulation of killer whales," the researchers wrote. ”