Groups of orcas have been staging intentional attacks on sailing boats in Europe since 2020 Credit: Spanish Ministry of Transport, Mobility, and Urban Agenda)

Killer whales, or orcas, are the largest members of the oceanic dolphin family. The intelligent mammals, which hunt in large pods, are known for their coordinated attacks on unsuspecting marine animals. But they rarely pose a threat to humans. However, since July 2020, groups of orcas have been deliberately attacking sailboats off the coasts of Spain and Portugal.

The latest incident occurred in the Strait of Gibraltar on the night of May 4, 2023. Three orcas repeatedly rammed into a Swiss yacht called Champagne. The situation got so dire that the ship's crew had to call the coast guard to tow the boat to shore. Everyone made it safely to the nearest port. But the damaged boat sank soon after.

"There were two smaller and one larger orca," skipper Werner Schaufelberger told the German publication Yacht. "The little ones shook the rudder at the back while the big one repeatedly backed up and rammed the ship with full force from the side."

Schaufelberger thinks the younger whales were copying the larger one. He says, "The two little orcas observed the bigger one's technique and, with a slight run-up, they, too, slammed into the boat.

Greg Blackburn had a similar encounter with a pod of six orcas on May 2, 2023. The British sailor also noticed that the two older orcas were teaching the younger ones how to strike the boat. "It was definitely some form of education, teaching going on," Blackburn told 9news.

Researchers are not sure of the reason for the animals' unusual behavior. But Alfredo López Fernandez, a biologist at the University of Aveiro in Portugal, has some theories. He thinks the attacks can be traced back to a female orca nicknamed White Gladis. The researcher suspects that a traumatic encounter with a boat has caused the marine mammal to become aggressive. Fernandez speculates that other orcas may have learned to attack ships by observing White Gladis.

Researchers have few theories about the orcas' unusual behavior (Credit: Spanish Ministry of Transport, Mobility, and Urban Agenda)

Alternatively, the killer whales could just be displaying playful behavior or what researchers call a fad. Juvenile orcas are well known for spearheading strange conduct that gets copied by others. In the 1990s, some orcas in the Pacific began to kill fish and swim around with them on their heads. That custom has since been abandoned.

Deborah Giles, an orca researcher at the University of Washington, thinks this could be plausible. She told Live Science, "They [orcas] are incredibly curious and playful animals, and so this might be more of a play thing as opposed to an aggressive thing."