Some killer whales like liver, specifically the liver of great white sharks.
Videos taken by scientists in Mexico reveal how cunning whales manage to bite the fatty organs of super predators.
Researchers filmed two killer whale hunts in the Gulf of California, one in 2020 and another in 2022. They show the pods attacking young great white sharks, flipping them onto their backs to stun them and then slicing into their sides to remove their livers. The team published the results of their video studies on Monday in the journal Frontiers in Marine Science.
In one of the videos, all members of the group share the pink liver fat while the rest of the shark’s body sinks to the depths of the ocean. During the hunt, a sea lion lurks, apparently trying to get away with a free meal. But orcas blow bubbles, apparently to deter the pest.
Erick Higuera-Rivas, a marine biologist and documentary filmmaker who filmed the hunts from a nearby boat, said he didn’t immediately recognize the significance of the footage until he went to edit it.
“I saw on the monitor that the shark had its liver hanging to one side, already detached. And a few minutes later, they appeared with the liver in their mouth,” said Higuera Rivas, co-author of the study. “I was surprised that it could be a white shark. I didn’t believe it.”
Heather Bowlby, a research scientist at Fisheries and Oceans Canada who was not involved in the research, said the images offered a compelling reminder that even top predators need to watch their backs.
“We’re so conditioned to think that white sharks are the top of the food chain,” he said. “It’s always surprising to remember that they are prey.”
Higuera-Rivas and his fellow researchers said the hunts appear to be the work of the same group of orcas, which they called “Moctezuma’s pod.” The pod frequents the waters of Baja California and only hunts elasmobranchs: sharks and whales. Higuera-Rivas has been following the pack for more than a decade and filming their behavior, and has observed how the whiles adapt their behavior to whatever species the group targets.
The only previous evidence that orcas hunt great white sharks comes from South Africa, where they have been hunting sharks for years and harvesting their livers, leaving shark carcasses washing up on the beach.
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 have been feeding on young sharks, while those in South Africa have focused primarily on adults.
The groups of orcas probably learned the behavior independently, Towner said.
“Seeing this behavior in Mexico suggests that specific groups of orcas have developed their own strategies for hunting sharks,” he said by email. “The target is the same organ, but the manipulation technique differs slightly from what we have documented in South Africa, which points to group-specific learning.”
The new study shows that orcas in Mexico have identified a weakness that makes great white sharks vulnerable.
“When you turn the shark over, you force it to enter the state called tonic immobility,” said Francesca Pancaldi, a co-author of the study and a shark researcher at the National Polytechnic Institute Interdisciplinary Center for Marine Sciences. “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 a shark’s body, he added, providing “a lot of energy.”
Researchers from both South Africa and Mexico agreed that this behavior is probably not new for orcas. Rather, it’s new to scientists, who can now witness and document these hunts more easily thanks to improvements in drone technology.
“I think this has been going on for centuries. The thing is, it’s not easy to observe something like this,” Pancaldi said.
However, changes in climate may have increased interaction between great white sharks and Montezuma’s pod, he added.
“In fact, we are seeing an increased 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 weather patterns like El Niño.
In South Africa, scientists became aware of killer whale attacks on great white sharks about a decade ago, Towner said. The attacks caused the sharks to flee their usual places where they feed, rest and reproduce, called aggregation zones.
“Repeated predation has caused white sharks to completely abandon former central aggregation sites,” Towner said. “Many sharks have likely moved offshore or to less monitored regions, reshaping the coastal ecosystem.”
After the sharks left their haunts, populations of Cape fur seals and sevengill sharks increased. That subsequently caused a drop in those species’ primary prey, such as small fish and small sharks, according to research published in Frontiers in Marine Science earlier this year.
Towner said only two adult male killer whales, named Port and Starboard, have been behind repeated attacks on white sharks in South Africa. The attacks have put pressure on great white sharks, which grow and reproduce slowly, and it’s possible that could happen in Mexico, too, if the behavior becomes more frequent, he said.
