This story was originally posted on MyNorthwest.com
It’s long been thought that the Southern Resident orcas that live in our region have no predators, but a new article in Live Science suggests that non-resident orcas, or Bigg’s orcas, might be eating them.
Bigg’s orcas eat other mammals, while the southern resident Orcas only eat fish. Among researchers, it was generally thought that the two ecotypes of orcas avoided each other. But in 2022, a researcher at the Pacific Institute of Geography in Russia discovered a bloodied orca fin with bite marks on a beach on Bering Island in eastern Russia.
Two years later, the same researcher found a second dorsal fin from an orca with similar injuries and damage to it. Photos of the injured orca fins can be seen here.
After conducting a series of genetic tests, researchers determined that the fins came from Southern Resident orcas, which live and swim near Washington and British Columbia. The research team also believes the Southern Resident orcas were most likely attacked and eaten by Bigg’s orcas.
“At least now we know that cannibalism happens,” Olga Filatova, the researcher who discovered the fins, said, according to Live Science. “But I think it is not super common.”
Filatova additionally shared that she believes the marks on the fins aren’t related to fights with other resident orcas, because those marks tend to be on the animals’ sides.
It was previously known that the varying types of orcas can be aggressive with each other, but cannibalism had never seriously been considered before this discovery. Some researchers believe this explains why orcas swim in pods.
However, not every orca researcher is convinced.
“I think the observations of tooth marks on fish-eating whale carcasses are interesting and the idea is worthy of further investigation, but there’s not yet enough evidence to build a solid account of the social evolution of fish-eating orcas,” Luke Rendell, a biologist at the University of St. Andrews in Scotland, told Live Science.
There are fewer than 80 Southern Resident orcas left, while there are approximately 400 Bigg’s orcas circulating the oceans. Globally, there are roughly 50,000 killer whales.
Chris Sullivan is a traffic reporter for KIRO Newsradio. Read more of his stories here. Follow KIRO Newsradio traffic on X.
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