Some killer whales like liver, especially the liver of great white sharks.
Videos taken by scientists in Mexico show how cunning whales manages to catch the bites of the fatty organs of top predators.
Researchers filmed two orca hunts in the Gulf of California—one in 2020 and another in 2022. They show the pods attacking young great white sharks, turning them on their backs to stun them, then cutting into their sides to remove their livers. The team published their video findings Monday in the journal Frontiers in Marine Science.
In one video, all members of the school share pink liver fat while the rest of the shark's body sinks into the depths of the ocean. During the hunt, a sea lion lies in wait, apparently trying to make off with a free meal. But killer whales blow bubbles, apparently to scare away the pest.
Eric Higuera-Rivas, a marine biologist and documentarian who filmed the hunt from a nearby boat, said he didn't immediately realize the significance of the footage until he started editing it.
“I saw on the monitor that the shark’s liver was hanging on the side and had already come off. And a few minutes later they found the liver in the mouth,” said Higuera Rivas, co-author of the study. “I was surprised that it could be a great white bird. I didn't believe it.”
Heather Bowlby, a scientist with Fisheries and Oceans Canada who was not involved in the study, said the footage is a powerful reminder that even top predators must be careful.
“We tend to think of white sharks as being at the top of the food chain,” she said. “It’s always amazing to remember that they are prey.”
Higuera-Rivas and his fellow researchers said the hunt appears to be the work of the same group of killer whales, which they called the “Moctezuma pod.” This capsule frequents the waters off the coast of Baja California and hunts only elasmobranchs – sharks and whales. Higuera-Rivas followed the herd for more than a decade, filming their behavior and observing how they adapted their behavior to whatever species the group targeted.
The only preliminary evidence that killer whales prey on great white sharks comes from South Africa, where they spent years hunting sharks and removing their livers, leaving the sharks' carcasses to wash ashore.
Alison Towner, a marine biologist at Rhodes University who has studied the phenomenon in South Africa, said the behavior in Mexico is similar but not identical. Killer whales in Mexico hunt young sharks, while killer whales in South Africa primarily hunt adult sharks.
Groups of killer whales likely learned the behavior on their own, Towner said.
“This behavior in Mexico suggests that certain groups of killer whales have developed their own strategies for hunting sharks,” she said by email. “The target is the same organ, but the handling technique is slightly different from what we documented in South Africa, indicating group training.”
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“When he turns the shark upside down, he forces the shark to go into a state called tonic immobility,” said Francesca Pancaldi, co-author of the study and a shark researcher at the National Polytechnic Center for Interdisciplinary Sciences Marinas. “They freeze. It's like a catatonic state. They just don't do anything.”
The liver is a fatty, nutritious organ that takes up about a quarter of the shark's body and provides “a lot of energy,” she said.
Researchers from South Africa and Mexico agreed that this behavior is likely nothing new for killer whales. Rather, it's something new for scientists, who are now finding it easier to observe and document these hunts thanks to improvements in drone technology.
“I think this has been going on for centuries. It's just not easy to watch,” Pancaldi said.
However, it is possible that climate change has increased interactions between great white sharks and Moctezuma's stock, she added.
“We've actually seen an increase in the presence of great white sharks in the Gulf of California over the last 10 years,” Pancaldi said, adding that the species responds to changes in ocean temperatures during climate events such as El Niño.
In South Africa, scientists noticed killer whales attacking great white sharks about a decade ago, Towner said. Attacks sent the sharks fleeing from the usual places where they feed, rest and reproduce, called aggregation sites.
“Repeated predation has caused white sharks to completely abandon former primary aggregation sites,” Towner said. “Many sharks have likely moved out to sea or to less controlled regions, changing the coastal ecosystem.”
After the sharks left their habitats, the populations of Cape fur seal and sevengill sharks began to rise. This subsequently led to the extinction of the species' main prey, such as small fish and small sharks, scientists say. The study was published in the journal Frontiers in Marine Science earlier this year.
Towner said only two adult male killer whales, named Port and Starboard, were behind repeated attacks on white sharks in South Africa. The attacks have put pressure on great white sharks, which are slow to grow and reproduce, and it's possible the same could happen in Mexico if the behavior becomes more common, she said.
