From playful antics such as the trend-setting emergence of wearing salmon for hats to astonishing new evidence of whale shark predation, the pendulum has certainly swung through the extremities of killer whale behaviour this week – one that could be chalked up as a win for observational research among the whale-watching community.

The latest occurrence takes us to the Gulf of California, where a pod of killer whales appears to have developed a unique set of hunting techniques to target the largest fish in the known world.

A worthy adversary, whale sharks can grow up to 18 metres long and often gather in specific locations in the Gulf. It’s here that juveniles and smaller individuals become more vulnerable to predators and a delicacy of choice for orca. But until very recently, the only evidence in existence to suggest that orcas were exploiting the opportunity to dine on whale sharks has been purely anecdotal. 

A study published in Frontiers in Marine Science this week, however, has made public a series of photographic evidence documenting a succession of whale-shark predation events while evidencing a sequence of hunting techniques adopted by the orcas, enabling them to successfully take down these gentle giants.

The details – revealed in the new study titled Killer whales (Orcinus orca) hunt, kill, and consume the largest fish on Earth, the whale shark (Rhinocodon typus) – have left scientists astonished, as the study’s team of marine biologists recount as many as four separate events in which orcas were observed hunting these giants of the ocean.

And it is the specific technique they appear to have adopted that have left many open-mouthed.

“We show how orcas displayed a collaborative 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,” writes Erick Higeura Rivas, a marine biologist at Conexiones Terramar, and senior author of the study.

All taking place in the southern Gulf of California, these documented predation events span the six years between 2018 and 2024. Across all four events, both photographic and video evidence reveal the orcas to have displayed the same approach to collaboratively hunting and killing whale sharks. 

In fact, upon deeper analysis of the photographic evidence, the team drew the conclusion that one specific individual adult male – nicknamed Moctezuma (recognised by his distinct markings) – was engaged in three out of the four events.

It was the further recognition that the female orcas involved in the fourth event had previously been sighted with Moctezuma, that led the researchers to the conclusion that this was a pod of killer whales specialised in hunting and killing whale sharks in the Gulf of California.

“Across all four events, several behavioural consistencies were observed that provided insights into apparent killer whale strategy for hunting and killing gigantic prey such as whale sharks,” said Higuera Rivas.

“In all events, the whale sharks were observed profusely bleeding from the ventral side of the body. [These] killer whales displayed cooperative and coordinated hunting behaviour which included repeatedly hitting the whale shark at high speed to stun and immobilise it, manipulating and positioning the shark ventral side up, and biting the shark in the exposed ventral region to allow access to the organs for consumption.”

Higuera Rivas notes in the paper that while the whale sharks were indeed positioned by the orcas “for access to organs” such as the nutrient-dense liver, no observations were made of the whales consuming this specific organ. 

But that’s not to say it didn’t occur. Higuera Rivas notes that at this point in the predation event, the whale shark had sunk to depths unobservable by both scientists and citizen scientists playing equal parts on the documentation of events. 

However, it speaks volumes for the assumed calculations of the whale shark-hunting orca.

“The ventral portion of the shale shark is likely the least-protected area of the body, as the dorsal side of the whale shark’s body consists of a thin and dense external layer of denticles that overlie a layer of connective tissue,” writes Higuera Rivas. “In adult whale sharks, the connective tissue can be more than 20cm thick, making juvenile individuals the easiest prey to target (where the connective tissue is around 5cm thick).

“In addition, in the circulatory system of sharks, the aorta in the dorsal area is protected by a dense thickness of muscles. On the contrary, the same artery in the ventral area is not protected by muscle; it enters the liver and passes under the intestines.

“This type of anatomy turns the ventral part of a shark into an extremely vulnerable area where deep bleeding can be caused by bites from large predators.”

Killer whales have the highest brain to body mass ratio of any studied apex predator, suggestive of enhanced cognitive abilities. It’s this, suggests Higuera Rivas, that allows them to overcome the challenges associated with hunting the largest fish in the world.

It’s an astonishing and eye-opening find. ‘Sigh’ – remember when we were all talking about them wearing cute little salmon hats?

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