Why did a group of killer whales suddenly start attacking ships?

A trio of killer whales attacked a ship in the Strait of Gibraltar earlier this month, damaging it so badly that it sank shortly after.

The May 4 incident was the third time that orcas (orcinus orca) have sunk a ship off the coast of Portugal and Spain in the last three years. The orca subpopulation in this region began harassing ships, most often by biting into their rudders, in 2020. Nearly 20 percent of these attacks caused enough damage to render the ships unusable, says Alfredo López, orca researcher at the Atlantic Orca Working Group. GTOA), which monitors the population of Iberian killer whales. “It’s a rare behavior that has only been detected in this part of the world,” he says.

The researchers aren’t sure why the orcas are chasing the boat. There are two hypotheses, according to López. One is that killer whales have invented a new fad, something subpopulations of these members of the dolphin family have been known to do. Just like in humans, orca fads are often led by juveniles, Lopez says. Alternatively, the attacks may be a response to a past bad experience involving a ship.

The first known incident occurred in May 2020 in the Strait of Gibraltar, an area with heavy boat traffic. Since then, GTOA has recorded 505 cases of orcas reacting to boats. Sometimes they just walked up to the boats, and only a fraction of the cases involved physical contact, says López. In a study published in June 2022 in marine mammal science, he and his colleagues cataloged 49 cases of orca-boat contact in 2020 alone. The vast majority of attacks were on sailboats or catamarans, with a handful of fishing boats and motorboats. The average length of the vessels was 12 meters (39 ft). For comparison, an adult orca can be 9.2 meters (30 feet) long.

The researchers found that killer whales preferentially attack the rudder of ships, sometimes scraping the hull with their teeth. Such attacks often break the rudder, leaving the ship unable to sail. In three cases, the animals damaged a ship so much that it sank: in July 2022, they sank a sailboat with five people on board. In November 2022 they caused the sinking of a sailboat with four people. And finally, in this month’s attack, the Swiss sailing ship champagne it had to be abandoned and the ship sank while being towed to shore. In all cases, the people on board were safely rescued.

In 2020, researchers observed nine different individual killer whales attacking ships; it’s unclear if others have joined since. Attacks tended to come from two separate groups: a trio of juveniles occasionally joined by a fourth, and a mixed-age group consisting of an adult female named White Gladis, two of her young calves, and two of her sisters. Because White Gladis was the only adult involved in the initial incidents, investigators speculate that she may have become entangled in fishing line at some point, giving her a bad association with the boats. Other adult orcas in the region have injuries consistent with boat collisions or entanglements, Lopez says. “All this has to make us reflect on the fact that human activities, even indirectly, are at the origin of this behavior,” she says.

However, the safe rescue of all involved suggests to Deborah Giles that these killer whales have no malevolent motivations against humans. Giles, director of science and research for the Washington state-based nonprofit conservation organization Wild Orca, points out that humans relentlessly harassed orcas off the coast of Washington and Oregon in the 1960s. and 1970, capturing young orcas and taking them to display in marine places. parks “These are animals that, each and every one of them, have been taken at one time or another, most whales multiple times. And these are whales who watched as their babies were taken from them and put on trucks and taken away, never to be seen again,” says Giles. “And yet these whales never attacked ships, they never attacked humans.”

While it’s possible that killer whales on the Iberian Peninsula react to a bad experience with a boat, Giles says, it’s pure speculation to attribute that motivation to the animals. The behavior seems to be learned, he says, but it could just be a fad with no rhyme or reason, to the human mind, anyway. It is well known that some members of the southern resident killer whales who cruise Washington’s Puget Sound each summer and fall spent the summer of 1987 with dead salmon on their heads. There was no apparent reason for salmon-colored hats to become fashionable in orca circles, but the behavior spread and persisted for a few months before disappearing again. “We are not going to know what is happening with this population,” says Giles, referring to the Iberian killer whales.

Iberian killer whale attacks typically last less than 30 minutes, but can sometimes last up to two hours, according to the 2022 study. Champagne, Two juvenile killer whales chased the rudder while an adult repeatedly rammed the boat, crew members told the German magazine. Yacht. The attack lasted 90 minutes.

The Iberian killer whale subpopulation is considered critically endangered, numbering just 39 animals when a full census was last conducted in 2011. A 2014 study found that this subpopulation follows the migration of its key prey, the Atlantic bluefin tuna, a route that puts them in close contact with human fishing, military activities and recreational navigation. Maritime authorities recommend that boaters in the area slow down and try to stay away from orcas, Lopez says, but there’s no guaranteed way to avoid the animals. He and his colleagues fear that the boat attacks will return and bite the orcas, either because boaters will attack or because the attacks are dangerous to the animals themselves. “They are at great risk of getting hurt,” Lopez says.