In the North Pacific, orca fins with signs of cannibalism are washing up on a Russian beach. The findings suggest that killer whales occasionally participate in cannibalism, which might explain why some orca pods are so tight-knit.
Two types of orcas inhabit the North Pacific: resident orcas and Bigg’s orcas. Resident orcas live in large family groups and consume fish, while Bigg’s orcas live in smaller groups and hunt other mammals, such as seals, whales and dolphins.
It was previously believed that the two types of orca avoided each other, but they actually experience some run-ins from time to time.
In August 2022, an orca fin was found on a beach in Bering Island, located in eastern Russia. The fin was bloody and covered in killer whale tooth marks.
A second orca fin was found in July 2024. The second fin was slightly bigger and belonged to a young male, but there were still killer whale tooth marks on it. At that point, it appeared to be a pattern.
According to genetic tests, the fins came from southern resident orcas. They live in the waters near Washington and British Columbia. Researchers think that the southern resident orcas were killed and eaten by Bigg’s orcas.
In general, orcas don’t have any natural predators, but they are known to be aggressive toward each other. The researchers suggest that occasional cannibalism among orcas is the reason why resident orcas form large, close-knit groups.
It is how they protect themselves from predators and boost their chances of survival. Large groups of resident killer whales are able to chase away smaller groups of Bigg’s orcas.
Resident orcas may have formed tight-knit social groups around 100,000 years ago when they started running into killer whales that had been evolving separately in the Pacific and the Atlantic.
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The marks on the washed-up resident orca fins are likely unrelated to fights with other residents. Those marks tend to be on the animals’ sides.
After feasting on a resident killer whale, Bigg’s orcas will discard the fins. The fins are tough, so killer whales don’t typically eat those.
Although events like this do happen, they are uncommon. They may not be definitively cannibalism, either. It’s possible that the marks on the fins were from scavenging by Bigg’s killer whales or aggression from other resident orcas while they were still alive.
Orcas eating another orca may not seem like cannibalism to them because they don’t consider each other as members of their own species. Some experts are even calling for them to be named as separate species.
“They never socialize; they never spend time together,” pointed out Olga Filatova, a whale researcher at the University of Southern Denmark. “For them, it’s just another whale. So why not eat it?”
The findings of the study were published in the journal Marine Mammal Science.
By Emily Chan
Emily Chan is a writer who covers lifestyle and news content. She graduated from Michigan State University with a degree in... More about Emily Chan
