The dinner menu for the world’s killer whales is quite varied. Some, like the cunning transient killer whales of the Pacific Northwest, use canyons to hunt other marine mammals, while others feast exclusively on salmon. One group in the Gulf of California may have learned a new skill to go after a pretty big prize: whale sharks. At almost 18 meters long, whale sharks are the largest fish in the world and can certainly feed a large and hungry orca. The findings are detailed in a study published Nov. 29 in the journal Frontiers in marine sciences.
The adult male killer whale Moctezuma and five other killer whales (two adult females, two juveniles, one calf), near the juvenile whale shark, measuring approximately 6 meters in length. The whale shark was observed swimming weakly at the surface. CREDIT: Video by Guillermo Aceves Salazar
VIDEO: The adult male killer whale Moctezuma and five other killer whales (two adult females, two juveniles, one calf), near the juvenile whale shark, measuring approximately 6 meters in length. The whale shark was observed swimming weakly at the surface. CREDIT: Video by Guillermo Aceves Salazar
Whale sharks tend to feed at staging areas in the southern Gulf of California, off the coast of Mexico. Some of the fish that gather are still quite young and small, making them a bit more vulnerable to attack by larger animals. For years, anecdotal evidence suggested that orcas might prey on whale sharks. Now a team of scientists in Mexico have reported four separate hunting events.
“We show how killer whales exhibited a concerted hunting technique on whale sharks, characterized by focusing on attacking the pelvic area, causing the whale shark to bleed out and allowing killer whales access to the lipid-rich liver,” said Erick Higuera Rivas, co-author of the study . and marine biologist at Conexiones Terramar, in a statement. “One individual was involved in three of the four events, along with other members who may have belonged to a group specializing in shark hunting.”
[Related: With new tags, researchers can track sharks into the inky depths of the ocean’s Twilight Zone.]
The predation events described in the new study occurred between 2018 and 2024 in the southern Gulf of California. The images and videos were created by citizens and scientists. The individual killer whales were identified by analyzing photos of their dorsal fins and distinguishing features such as scars and white spots.
A male orca that locals call Moctezuma was present at three of the four hunting events. A female killer whale previously observed in Moctezuma’s presence participated in one event, suggesting they may be related or members of the same group.
Orcas surface to breathe before taking down the whale shark and delivering a swift, final blow. CREDIT: Kelsey Williamson.
“During the hunt, all members of the group work together, hitting the whale shark and turning it upside down. In that position, the sharks enter a state of tonic immobility and can no longer move voluntarily or escape by going deeper,” said Higuera Rivas. “By controlling it, the orcas can access the shark’s pelvic area more easily and quickly and are able to extract organs that are of nutritional importance to them.”
The team thinks the orcas may be targeting the ventral side of whale sharks, the area near their bellies. This part of their body is the least protected and therefore particularly vulnerable. There is less muscle and cartilage on the ventral side, which makes it easier for the orcas to access important blood vessels such as the aorta. Although whale shark livers are an important part of the diet of orcas, the team did not capture images of the orcas consuming this vitamin-rich organ.
The hunting method may imply that some orcas in the Gulf of California have acquired a special set of skills – such as chasing the ventral side of young whale sharks – that help them hunt these enormous fish. Orcas may have learned to do the same in other parts of the world, but the evidence is limited, according to the team.
Collecting the data the team needed was a feat in itself. Orca attacks themselves cannot really be predicted, access to images and video can be limited, and image quality is often too low to reliably identify the animals involved.
[Related: Orca observed hunting and killing a great white shark by itself for the first time.]
Despite the challenges, the team believes these findings could have multiple implications, especially in the field of conservation. If there is a killer whale pod hunting whale sharks in the Gulf of California, the team is calling for more vessel traffic management to keep both animals safe.
“There must be a specific regulatory standard that guarantees that any form of non-extractive use activity is carried out in a respectful and sustainable manner,” said Higuera Rivas.
Furthermore, if the idea that Moctezuma and his group have acquired new ecological and behavioral information for hunting whale sharks in the Gulf of California is true, the group could be vulnerable to a future disappearance due to rising ocean temperatures in the region. Ultimately, further research on this orca pod will help scientists better understand the adaptations unique to where they live and what they eat.
“It is very impressive how orcas work together strategically and intelligently to gain access to only a very specific part of the prey,” says Higuera Rivas. “It highlights what amazing predators they are.”
