Scientists finally know the clever tricks orca use to hunt whale sharks

For the first time, scientists have captured video evidence of orcas cooperatively hunting whale sharks, the largest species of fish on Earth. This graphic footage proves that whale sharks are a regular part of some orcas’ diets, and solves the mystery of how they are able to kill the massive fish.    

On May 26, shark ecologist Kathryn Ayres was guiding tourists on an ocean safari near La Paz, Mexico when she saw a pod of orcas circling. “I knew some poor animal was being tormented,” Ayres said. “They like to play with their food.”

Along with photographer Kelsey Williamson, Ayres jumped in the water with her camera just in time to document five orcas taking down a juvenile 16-foot-long whale shark. Their video, published today in Frontiers in Marine Science shows the behavior in unprecedented detail. 

Before now, only one other scientific report documented orcas eating a whale shark, videoed by sport fisherman further south in Mexico, but it didn’t detail the full predation sequence. Along with Ayres’s footage from this spring, the new research includes photos and videos of three other instances of orcas preying on these massive fish in Mexico’s Gulf of California. The first event in 2018 was caught on camera by a group of tourists planning to snorkel with sea lions on a rocky island north of La Paz. (They stayed in their boat once the attack began.) The second and third events were also captured by tourists in 2021 and 2023.

Now, with all these conclusive photos and videos, scientists can fully describe how the orcas take down the huge prey.

How orcas team up to hunt a whale shark

First, the orcas repeatedly ram a slow-swimming whale shark to stun it. When the fish loses its equilibrium, the orcas work together to flip it upside down to expose its unprotected belly. “You could hear the crunch of the final blow,” Ayres recalls, which incapacitated the shark. Next, the orcas bite off the whale shark’s pelvic fins, causing it to bleed to death. Then, they eat the fish’s organs, including its enormous fatty liver. It’s gruesome, and effective. Even birds capitalized on the feast, diving down for chunks of meat. “It was raining whale shark,” Ayres says.

A male orca named Moctezuma, first sighted in 1992, participated in three of the four recorded predation events. This male orca may be the son of one of the matriarchs of the pod, and perhaps learned his shark-eating techniques from her. He’s often joined by four or five female or juvenile whales who, in one recorded instance, initiated an attack without him.

This pod of orcas—dubbed the Moctezuma pod—seems to specialize in hunting cartilaginous fish.  They also go after stingrays, pygmy devil rays, and bull sharks off the coast of southern Baja. (Moctezuma is named after the famous Aztec emperor. Females in the pod have also been given Aztec names like Quetzali, Niich or Waay, which means ‘witch’ in Majan since her dorsal fin is shaped like a witch’s hat). 

This pod’s taste for whale shark might be unique. “I’ve never heard of whale sharks being targeted by orcas anywhere else in the world,” says Simon Pierce, a whale shark conservation specialist not involved in the study and the executive director of the Marine Megafauna Foundation. “But I can’t imagine a whale shark has much of a chance if a pod of killer whales zeros in on one.”

Whale sharks put up a fight

The Gulf of California is known as a hotspot for whale sharks, and, in particular, for juveniles that congregate to feed in La Paz Bay each fall through spring. These younger sharks “may be naïve to this kind of predator,” Pierce says, which could be why orcas are targeting them. All four of the documented attacks happened in April or May when whale sharks leave the protection of the bay to migrate south.

Whale sharks are gentle giants, eating only tiny plankton with their three-foot-wide mouths. But that doesn’t mean they are easy to kill. Adults can grow up to 60 feet, as long as a bowling lane. Even juveniles are already larger than predators like great white or tiger sharks. When whale sharks grow past 15 feet, “I think only orcas can prey on them,” says Francesca Pancaldi, a marine biologist who co-authored the new research.

They have some of the thickest skin of any animal, especially on their backs, which is too tough for predators’ teeth to punch through. When threatened, a whale shark will roll its back toward the predator. But that defense only works if there’s one predator, not a whole pod.

A whale shark can also “crash dive” to avoid threats, Pierce says, sinking quickly to depths greater than 6,000 feet. To counteract that defense, orcas in the Moctezuma pod repeatedly bump and hit a whale shark to bring it back to the surface during their attack. This allows the orcas to breathe during the attack and prevents the whale shark from escaping to the depths.

A whale-shark hunting hotspot

 One reason the Moctezuma pod’s remarkable underwater hunts have been documented is because of the many tourists who flock to Baja to swim with sharks, whales, and other charismatic marine animals. Over the years, local fisherman and tour operators sent videos and photos to Erick Higuera, a marine biologist and underwater photographer who co-authored the study. He has been studying orcas feeding on sharks and rays in Baja since 2008.

After Higuera saw images from the first attacks, he and Pancaldi assumed the orcas were targeting the shark’s vulnerable pelvic area. But since the first few recorded events didn’t show the full sequence of the hunt, they couldn’t confirm that orcas were targeting this weak spot until Ayers and Williamson were lucky enough to film an attack and “finally complete the puzzle,” Higuera says.

Now that people know where to look, they are starting to see more orcas versus whale shark events. Just a few weeks ago, tourists and guides saw the Moctezuma pod take down a juvenile whale shark on two consecutive days.

While nearly all of the whale sharks near La Paz are juveniles, Pancaldi believes that “orcas are smart enough to put down a big whale shark, as well,” such as the 30-foot-long adults she has seen further north in the Gulf of California. 

No one has yet seen an orca take down an adult whale shark. To kill a full-grown adult would be “an epic battle”, Higuera says, requiring several orcas to work together. But since orcas can take down a big blue whale, it stands to reason that the ocean’s top predator can prey on the largest fish in the world, too.

“We will have to prove it,” Higuera says, by waiting for more videos from people in the right place at the right time.