Orca whales experienced pack hunters with ever-growing list of loot. Some killer whales eat other marine mammals, such as seals, while others primarily feed on salmon. Recently, ocean researchers discovered that apex predators are not afraid to take on equally formidable opponents –great white sharks. Now the study, published Nov. 3 in the journal Frontiers of Marine Science recorded even more remarkable hunting behavior. In the Gulf of California, members of a well-studied Moctezuma capsule young white sharks have been observed killing young white sharks by turning them upside down to feast on their energy-packed livers.
Recent observations show that killer whales may be including great white sharks in their diet more often than marine biologists thought, but researchers have not drawn any definitive conclusions. However, study co-author Eric Higuera Rivas believes it is possible.
“I believe that killer whales that feed on elasmobranchs—sharks and rays—could eat a great white shark if they wanted to, wherever they went in search of it,” Project Director of Conexiones Terramar and Pelagic Life. says the statement. “This behavior is evidence of the advanced intelligence, strategic thinking and complex social learning of killer whales as hunting techniques are passed down from generation to generation within their pods.”
However, Rivas and his colleagues do know that at least some members of Moctezuma's pack in the Gulf of California regularly harass great whites. In 2020, the team documented two separate hunts that collectively resulted in the deaths of three white sharks during a routine orca sighting. In the first case, five killer whales ambushed a juvenile great white shark, then pushed it to the surface and then worked together to flip it onto its back. The whales and their prey soon disappeared underwater, and later only the attackers appeared – with pieces of shark liver in their mouths. Soon after, they repeated this strategy with another young great white. Another documented great white shark celebration took place two years later and followed similar steps.
Turning sharks upside down isn't just about disorienting them. This encourages tonic immobilitywhich actually paralyzes them and changes their ecological awareness.
“This temporary condition leaves the shark defenseless, allowing the killer whales to remove its nutrient-rich liver and likely eat other organs before abandoning the rest of the carcass,” Rivas said.
The sharks' injuries imply that the pod's orcas have developed this signature technique to reduce the likelihood of being bitten. The researchers believe that focusing on juvenile targets may be easier than focusing on a life-size adult shark.
“Adult white sharks respond quickly to killer whale predation by leaving their seasonal gathering grounds entirely and not returning for months. But these juvenile white sharks may be naive to killer whales,” said study co-author Salvador Jorgensen. “We just don't know yet whether white sharks' anti-predator responses are instinctive or whether they need to be learned.”
Great white sharks may not be killer whales' first prey. Instead, they can become food of opportunity for this capsule. Climate change, coupled with events such as El Niño, has likely altered white sharks' feeding areas, thereby increasing their presence in the Gulf of California. Perhaps this is what ultimately led to the first skirmishes with Moctezuma's capsule. Young sharks could now become a seasonal addition to the orcas' diet.
All this remains speculation for now. The authors say more detailed research is needed before offering specific answers. However, by now it is at least abundantly clear that when push comes to shove, killer whales will willingly take on some of the ocean's most feared predators.
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