A pod of killer whales has developed “unique” skills to hunt the world’s biggest fish. A group of orcas have been spotted in the Gulf of California hunting whale sharks, which grow up to 18 metres long, in “coordinated” attacks.
Researchers believe the black and white apex predators, which normally feed on marine mammals, turtles, and smaller fish, might have gained “special” knowledge to allow them to hunt in a way never seen in their species before.
Whale sharks feed at sites in the Gulf of California, sometimes while they are still young and smaller. Scientists say that at that stage of life, they are more vulnerable to attack from predators.
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Now, researchers in Mexico have reported four separate incidents of killer whales hunting young whale sharks for the first time.
Marine biologist Erick Higuera Rivas was the senior author of the report published in the journal ‘Frontiers in Marine Science’. He said: “We show how orcas displayed a collaboratively hunting technique on whale sharks, characterised by focusing on attacking the pelvic area causing the whale shark to bleed out and allow orcas access to the lipid-rich liver.
“One individual was engaged in three of the four events, alongside with other members who might belong to a pod specialised in hunting sharks.”
The attacks have been occurring since 2018 in the southern Gulf of California and were captured in images and videos taken by members of the public and scientists.
Individual orcas were identified by analysing photographs of dorsal fins and distinctive features, like scars. A male orca named Moctezuma was present at three out of the four hunts.
A female orca previously observed in the presence of Moctezuma participated in one hunt, suggesting they could be related or members of the same pod.
Higuera Rivas said: “When hunting, all pod members work together, hitting the whale shark to turn 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.
“By keeping it under control, the orcas then have greater ease and speed in approaching the pelvic area of the shark and are able to extract organs of nutritional importance for them.”
The research team says the orcas may be targeting whale sharks’ ventral side because there their bodies are thought to be the least protected. For example, there is less muscle and cartilage in that area, allowing easier access to the aorta.
They believe that hunting in such a way could imply that some orcas in the Gulf of California have acquired “special skills” that help them prey on whale sharks. The researchers said other killer whales orcas may have learned to do the same thing in other regions, but evidence is limited.
Higuera Rivas says the fact that there is a whale shark hunting pod in the Gulf of California increases the need for managing marine adventurers and tourists.
He said: “There must be a specific regulatory norm that guarantees that any type of non-extractive use activity is carried out in a respectful and sustainable manner.”
Higuera Rivas believes that if the theory that Moctezuma and his pod have acquired ecological and behavioural information for hunting whale sharks in the Gulf of California holds, the pod could be “vulnerable” to a possible disappearance of the specific prey due to climate change.
He added: “It is very impressive how orcas work together strategically and intelligently to access only a very specific area of the prey. It highlights what great predators they are.”
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