In July 2024 marine biologist Kathryn Ayres was shark diving in the Gulf of California when she and her crew spotted a pod of orcas. Sensing a rare viewing opportunity, the team followed the pod by boat. Eventually and from a respectful distance, Ayres hopped in the water to get a better look at the whales.
Everything that happened next was captured on camera—and to Ayres, it was shocking. Not far below the surface, she saw an adult female orca holding a dead sharptail sunfish—one of the ocean’s largest bony fish—in her mouth. The fish’s internal organs had already been hollowed out. And then, suddenly, a male orca soared into view, belly up, and smashed his head into the dead fish. The carcass was obliterated, exploding in a plume.
“Oh, my god, oh, my god, oh, my god. Holy shit. What the heck?” Ayres can be heard to say in the recording.
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“In that particular moment, I couldn’t help my reaction,” Ayres now recalls. “I’d seen [orcas] hunt sunfish before, but I had never, ever seen a sunfish explode.”
This kind of behavior, which Ayres and her colleagues refer to as “high-impact ramming,” wasn’t entirely unknown to marine biologists, but it had never been documented in detail, says Erick Higuera, a cinematographer and marine biologist at the nonprofit Orcas México. Higuera, Ayres and their colleagues’ account of the explosion, as well as a similar event involving three female orcas and a calf that also occurred in the Gulf of California a little more than a year after the first one, were published in the journal Frontiers in Ethology on Thursday.
It’s unclear why orcas seem to ram sunfish. It might make the big prey fish easier to eat, the researchers speculate—in the video Ayres took, a juvenile gobbles up some of the exploded bits as they float in the water. Sunfish have a gelatinous layer under their skin that could be a source of water and nutrients for the orcas, Higuera says. Or the whales might do this for fun.
Orcas are known to play with their food—passing dying prey around to one another, for example, like a macabre game of hot potato. This might help teach younger generations how to hunt, Higuera says. And in the sunfish case, it may provide a unique learning opportunity.
“It proves that their hunting strategies are not rigid,” Higuera says. Orcas may “actively modify” their predatory or feeding techniques depending on the prey, he adds. They’ve been seen, for example, corralling schools of rays, creating waves to push penguins from ice blocks and extracting the livers of white sharks.
That’s bad news for sunfish. But for biologists, it’s a boon.
“Understanding these behaviors is vital for defining distinct orca cultures [and] ecotypes and managing local conservation,” Higuera says.