Orcas that hunt sperm whales may be new population, study suggests

Researchers from the University of British Columbia said they've identified a potentially new population of open-ocean orcas, which hunt the biggest predators on the planet.

Researchers from the University of British Columbia said they’ve identified a potentially new population of open-ocean orcas, which hunt the biggest predators on the planet.

In a study published Friday, researchers said a group of 49 orcas has been observed hunting sperm whales off the coast of California and Oregon.

Lead author Josh McInnes said the orcas were seen hunting a herd of nine adult sperm whales, “eventually making off with one.”

It’s the first time killer whales have been reported attacking sperm whales on the West Coast, he said.

“Other encounters include an attack on a Pygmy sperm whale, predation on a northern elephant seal and Risso’s dolphin, and what appeared to be a post-meal lull after scavenging a leatherback turtle,” said McInnes, who is a masters student in the UBC Institute for the Oceans and Fisheries.

Researchers said the orcas that were observed in nine encounters from 1997 to 2021 could either belong to a subpopulation of transient killer whales or a unique oceanic population.

The study said the encounter that was witnessed with the sperm whales occurred in 1997 about 130 kilometres off the California coast. Many of the sperm whales in the pod were left with “extensive injuries,” while one was killed, the study said.

“Approximately 12 killer whales were initially involved in the hunt, but this number increased to an estimated 35 killer whales spread out over 3 km. Small concentrated groups of four to five killer whales randomly targeted and attacked individual sperm whales in the rosette,” the study said, describing how the whales gathered in a circle with their heads together and their tails pointing outward.