One orca held a sunfish by the tail. Another smashed it to smithereens.

Gripping the underwater camera, marine biologist Katy Ayres couldn't help but scream at what had just unfolded in front of her: “Oh my god, oh my god, oh my god!”

She watched as an orca held a sunfish by the tail while another orca swam toward the enormous fish and pummeled into it so fast that it smashed into smithereens. The impact was so violent that a sickening crunch echoed through the water. 

“It was chaotic,” says Erick Higuera, a marine biologist at Conexiones Terramar, who also witnessed the event in the Gulf of California in Mexico. At first, he didn’t know why the orca was holding onto the sunfish, but watching the footage back he realized something: “It was definitely a direct target,” he says. “It was intentional.”

Researchers have theories about what the killer whales are doing, including that this might be a game. This behavior is now scientifically described in the journal Frontiers in Ethology. 

Orcas’ complex hunting tactics 

Orcas are known for their intelligence and ingenious hunting strategies. “Complex behaviors of orcas have been observed and described in many studies before, ranging from feeding on white sharks to strategic joint hunts of seals,” says Olaf Meynecke, a marine ecologist at Griffith University who was not involved in the study. 

Among their varied prey, killer whale pods have been seen targeting sunfish. 

The heaviest bony fish on the planet, these large, flattened animals look like 1,000-pound dinner plates with faces. “Sunfish are among the strangest-looking fish in the ocean,” says Ayres, a National Geographic Explorer and research scientist at Beneath the Waves. “They can grow to several meters in length and weigh over a tonne.” 

There are five known species of ocean sunfish but experts have documented killer whales ramming only one: the sharptail sunfish (Masturus lanceolatus). Its tail-like rudder—known as a clavus—sticks out further than that of other species, which could give the killer whales something to grip onto, like a handle. 

But why are the orcas doing it? After the sunfish was smashed to bits, “a young orca instantly started eating the smaller pieces,” says Ayres, who is also a tourism guide at Latitude Encounters and is studying the diets of different orca pods in Baja California. This made her wonder whether “the adults were breaking up the sunfish [into] more manageable pieces” for the juveniles. 

However, Meynecke doesn’t think the killer whales need to torpedo the sunfish to be able to consume its flesh. “They can be killed easily by one orca and then shared amongst the family members without destroying it like shown in the video,” he says. 

Killer whales can hunt sharks or marine mammals with very tough skin and devour large chunks of flesh, adds co-author Higuera. Breaking up the sunfish carcass is not because they can’t digest larger pieces, he says. 

But researchers do have another theory for why the orcas might be ramming into sunfish until they shatter into tiny fragments: The orcas might be playing. “Orcas are highly intelligent and are known to play with prey,” says Ayres. These games are “thought to strengthen social bonds and help younger individuals develop hunting skills.”

By watching the adults, juveniles could be learning the skills they need to hunt. “The behavior requires detailed coordination including communication, orientation, and timing,” says Meynecke. This is one way that pods pass survival tactics down through the generations. 

Slow-moving sunfish make good target practice because they won’t fight back. “It's basically a defenseless fish,” says Higuera. “They present a low-risk opportunity for these sub-adults, so they can practice strike precision and reinforce social bonds.” 

The nutritional benefits of sunfish smoothies 

Killer whales hunt large marine mammals whose blubber is much denser and energy-rich than sunfish tissue. But Higuera thinks eating sunfish could have other benefits, such as hydration, since their tissues contain a lot of water. “It has to have other properties because they keep constantly doing it,” he says. 

The study suggests breaking up the fish’s thick, jelly-like outer layer may release microbes and change the nutrient makeup of the water. Higuera believes young orcas may benefit from these bits, like a human drinking a protein shake. “We go and get supplements to pump up our bodies for better strength,” he says. 

Meynecke thinks proving this theory needs more data, saying the idea is “difficult to demonstrate unless there is a clear link established of nutritional benefits to break up a sunfish like this.” 

Regardless of the reason, there’s a benefit to knowing where this behavior takes place. In fact, understanding where orcas teach their calves critical survival behaviors—like ramming sunfish—can help experts identify important places, like the Gulf of California, that should be protected. 

“The reality is that seeing orcas here is not guaranteed at all, and I think that’s part of what makes when we do see them so special,” Ayres says.