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Scars offer clues into orca groups in Pacific

Study: Killer whales seen off coast are a unique population

By Irene Wright, Miami Herald
Published: March 26, 2024, 6:00am
2 Photos
Adult male oceanic killer whale OCX012 diving to feed on a successful predation event involving a pygmy sperm whale.
Adult male oceanic killer whale OCX012 diving to feed on a successful predation event involving a pygmy sperm whale. (Paula Olson/NOAA SWFSC/TNS) Photo Gallery

A group of killer whales spotted hunting off the coast of California and Oregon over two decades may actually be their own unique population of animals, a new study says.

When the notorious black fin of an orca emerges from the waves, it is almost always followed by another, and then another.

The social, family-oriented animals travel in pods, part of larger populations of animals that hunt the same species in the same waters.

But a new study published in the journal Aquatic Mammals suggests there is a group of killer whales that has gone uncategorized by researchers.

“The open ocean is the largest habitat on our planet and observations of killer whales in the high seas are rare,” study author Josh McInnes, a master’s student at the University of British Columbia’s Institute for the Oceans and Fisheries, said in a March 15 news release. “In this case, we’re beginning to get a sense of killer whale movements in the open ocean and how their ecology and behavior differs from populations inhabiting coastal areas.”

McInnis and others examined sightings and photographs of 49 different orcas from 1997 to 2021 to see if they had been cataloged in any other existing orca population.

Orcas live in three different ecotypes, or classifications. Resident orcas stay close to the shore and feed primarily on salmon along the West Coast of Canada and into the Pacific Northwest of the U.S., the researchers said. Transient orcas also visit coastlines, but they spend some of their time in deeper waters in the northern Pacific, feeding on pinnipeds and cetaceans. Offshore orcas feed on sharks and larger fish in deeper water still — rarely, if ever, coming close to the shore.

Photos didn’t match

The researchers collected examples and evidence of killer whales traveling even farther out to sea.

When they compared the photos of the animals to known populations, they didn’t match, the study said.

The orcas have been spotted only nine times, the researchers said, but it’s enough for a “solid hypothesis,” according to the release.

They also had odd scarring that doesn’t appear on other orcas, the study said.

“A key clue to the new population’s presumed habitat range lies in cookiecutter shark bite scars observed on almost all the orcas,” according to the release. “This parasitic shark lives in the open ocean, meaning the new population primarily inhabit deep waters far from land.”

Cookiecutter sharks attach to the orcas, eventually leaving behind small, circular scars that were observed in photos of the animals.