New orca population could be hunting ocean's largest predators: researchers

Scientists at the University of British Columbia say they have identified a po‐ tentially new population of killers whales that hunt the planet's largest preda‐ tors in the open ocean.

A group of 49 orcas has been seen hunting sperm whales, elephant seals, dol‐ phins and even a leatherback turtle as far as 300 kilome‐ tres off the coast of California and Oregon, according to a peer-reviewed study pub‐ lished in the journal Aquatic Mammals last week.

And it seems the killer whales haven't been studied before, according to co-au‐ thor Andrew Trites, a profes‐ sor at UBC's Institute for the Oceans and Fisheries.

"It appears that these are a unique group of killer whales," he told CBC's On The Coast on Monday. "We think they're probably related to the transient type, but for now, we're calling them oceanics and just making people aware that there's something else out there that we don't fully understand."

WATCH | New orca popu‐ lation highlights ocean's un‐ knowns:

Researchers say the orcas were observed in nine en‐ counters from 1997 to 2021, and lead author Josh

McInnes stressed the group of orcas are not a new species but likely a subpopu‐ lation.

"They're still killer whales ... that have just spent more time in the open ocean that we just haven't seen before," he said in an interview.

In a 1997 encounter around 130 kilometres from the coast of California, around 35 killer whales hunted a herd of nine sperm whales and made off with one after chasing them over three kilometres.

"Small concentrated groups of four to five killer whales randomly targeted and attacked individual sperm whales in the rosette," the study said.

A rosette is a term de‐ scribing how the sperm whales gathered in a circle with their heads together and their tails pointing out‐ ward.

"Fresh blood and an oil slick of animal fat could be seen at the surface following each attack," the study con‐ tinued.

More research needed The whales' varied diet was what stood out most to Erin Gless, executive director of the Washington-based Pa‐ cific Whale Watch Associa‐ tion, who was not involved in the study.

"I have read about killer whales attacking sea turtles in the tropics, but never in places like California and Oregon that are much colder waters," she said.

"I think that it's just indica‐ tive of the fact that they live in these really open water conditions and so they don't have the beaches full of seals, for example, like we have here in B.C., so they need to pretty much eat whatever they come across."

The killer whale popula‐ tions in B.C. include southern resident killer whales, who mostly eat salmon and other fish, and Bigg's (transient) killer whales, who hunt larger mammals like sea lions, sea otters and sometimes whales.

Researchers were able to identify the orcas as possibly a new group partially be‐ cause of cookie-cutter like shark bite scars seen on the animals, and through distinc‐ tive patches on the orcas' fins and saddles. The species of parasitic sharks involved in the bites live in the deep ocean near the tropics, ac‐ cording to researchers.

Trites says they hope to document more sightings, DNA and data from the new population in order to inves‐ tigate exactly how different these orcas are from other documented populations.

"We're up to 49, but like with all of these newly dis‐ covered populations, there's more pictures coming," he said. "And so since we put this together, we have heard and have become aware of a few more individuals.

"We don't know where it's going to top off at, but it could well be 100 or perhaps even 200."

McInnes, Trites and Gless agreed the study is an excit‐ ing step in learning more about killer whales and how much is still unknown about them in B.C. and beyond.

"With killer whales, it's a species that fascinates the entire world," said Trites. "But even as we spend time getting to better know the ones that we think we know already, we're still making new discoveries.

"And I think it just points to how much more we still have to learn about killer whales and the oceans and why it's so important that we protect them."