A pod of orcas in the Pacific Ocean off the coast of Mexico have developed a cunning strategy to hunt and kill whale sharks — the world’s largest fish, which can grow up to 60 feet long — according to new research published Friday. (29) in Frontiers in Marine Science.
While anecdotal evidence has previously suggested that orcas can take down whale sharks, marine scientists have now documented the behavior in detail for the first time, analyzing four camera-recorded hunting events.
Orcas hunt whale sharks that congregate at feeding sites in the Gulf of California and that have not yet reached adulthood. Young sharks are typically between 3 and 7 meters long, making them more vulnerable to predators. Although a showdown between an orca and a whale shark may seem like an epic battle, the orcas make easy work of the gentle giants.
“The whale shark has the smallest brain compared to its body mass. The brain is the size of an egg,” says Francesca Pancaldi, first author of the study and researcher at the Centro Interdisciplinario de Ciencias Marinas in Mexico.
“It’s a very, very large fish that is very slow compared to other sharks. It has tiny teeth that it doesn’t use as a defense mechanism,” adds Pancaldi. “The only defense you have is to shake or dive. It can dive to 2,000 meters or more.”
The hunts described in the study took place between 2018 and 2024 and were captured in images and videos taken by scientists and members of the public.
The authors were able to identify the orcas involved by observing distinctive features such as dorsal fins or scars on the animals’ bodies. In three of the four hunting events, a male orca — nicknamed Moctezuma after the Aztec emperor — about 25 feet long was present.
A female orca, previously observed in the presence of Moctezuma, participated in an event as well, suggesting they could be related or members of the same pod, according to senior study author Erick Higuera Rivas, a marine biologist at Conexiones Terramar, a nonprofit organization. .
Orca vs. whale shark
The researchers’ analysis revealed exactly how orcas, often hunting in groups, subdue the whale shark.
First, the orcas use their bodies to hit the whale shark at high speed. They then turned the whale shark upside down, making it impossible for it to dive to escape. Orcas then bite into their prey’s abdomen, allowing its blood to flow before consuming its internal organs.
“You can clearly see how all the members of the orca pod are trying to take down the whale shark,” says Higuera Rivas. “While one orca was hitting him on the ventral (belly) side, the other was hitting him on the head. Then, eventually, the whale shark is placed in an upside-down position,” he adds.
This maneuver puts the whale shark in a state seen in other animals called “tonic immobility” — essentially a temporary paralysis resulting from extreme fear.
The study authors believe the orcas are plundering the whale shark’s large, nutrient-rich liver, which makes up a significant amount of the shark’s body weight, but the researchers did not observe the orcas consuming the organ.
“As predators at the top of the food chain, orcas are known to hunt sharks for their fatty livers,” says Sarah Teman, a doctoral candidate in the School of Aquatic and Fishery Sciences at the University of Washington.
“However, what makes this discovery exciting is that it is the first time we have seen this behavior clearly documented with whale sharks, which are the largest sharks on the planet,” adds Teman, who was not involved in the study, in an email . “It’s an incredible discovery!”
Found all over the world, orcas are the top predators of the ocean food chain. They feed on a wide variety of creatures: fish, marine mammals such as seals and dolphins, sea turtles and cephalopods such as squid.
Although there is only one species of orca, there are multiple ecotypes, or groups that share similarities in their appearance and behavior.
It is possible that orcas in the Gulf of California could form a new ecotype that specifically targets elasmobranchs — sharks and rays — according to Pancaldi and Higuera Rivas, although more research is needed to prove this hypothesis.
Moctezuma, which was first sighted in 1992, has been seen hunting other elasmobranch species, such as Munk’s pygmy devil ray, which is 1 meter wide, bull sharks and stingrays. “More research is needed to understand where this specialized group fits into our knowledge of ecotypes,” says Teman.
In South Africa, orcas have developed techniques to kill great white sharks, one of the most feared predators in the oceans. The behavior has driven sharks away from some parts of the coast near Cape Town, in what some experts consider a worrying ecological change.
However, Pancaldi explains that the orcas’ appetite for whale sharks has not resulted in significant consequences for the whale shark population that congregates in the Gulf of California or the broader ecosystem.
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This content was originally published in Images reveal how orcas hunt the biggest fish in the world; see the CNN Brasil website.
Source: CNN Brasil
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