Gibraltar- Groups of orcas have been sinking ships by ramming into them in the Gibraltar straight. Researchers aren't sure what's causing the animals' unusual behavior.

On May 4, three orcas rammed into a yacht, bashing their bodies into the boat until it capsized.

The yacht's skipper Werner Schaufelberger told Germany’s Yacht magazine, "The two little orcas observed the bigger one’s technique and, with a slight run-up, they too slammed into the boat."

The killer whales sank the ship. Luckily, no one was hurt and the crew and passengers were rescued.

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This incident is just the latest in a series of similar attacks by killer whales, as per The New York Times.

The research group Orca Ibérica GTOA has been monitoring the behavior of killer whales in the region since 2020. They have recorded three similar capsizing incidents since last summer.

But there have been more than 500 instances in which killer whales have approached or reacted to boats in the waters around Morocco, Portugal, and Spain, since 2020. In about 20% of these, the animals have also caused damage to boats and vessels.

This behavior is unusual, and researchers don't know why the animals are doing it or how to stop them.

Researchers don't know why these incidents are becoming more frequent, but they have several theories.

Some think the behavior is learned, and that the animals of this area shared the knowledge they gained after having an adverse experience with a boat.

Others are skeptical and think the behavior stems from the whale's natural hunting instinct. Orcas are the largest animal in the dolphin family and apex predators. "They’re getting some sort of reward or thrill from it," said Erich Hoyt, an orca expert and research fellow with Whale and Dolphin Conservation. He added, "Play is part of being a predator."

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Alfredo López Fernandez, a biologist at the University of Aveiro in Portugal and co-author of a study on orca behavior, said one thing is certain: "We know that it is a complex behavior that has nothing to do with aggression."

The orcas are an endangered species and unfortunately, scientists don't know what to tell mariners to do. They've said avoidance is the best solution, but that doesn't always work when sometimes, the orcas go after the boats.