Most orcas tend to stick to coastlines, from the Antarctic dwellers that make waves to knock seals off ice floes to the liver-extracting brothers around Cape Town. But now, scientists have found what could be a brand-new population of killer whales: Animals that ply the high seas, hunting large whales and other sizable prey.
These open-ocean denizens have been spotted at numerous locations far from Oregon and California, many of them well beyond the continental shelf, where waters can reach depths of 15,000 feet,according to a recent study in Aquatic Mammals.
“There haven’t been any real studies, at least in the North Pacific, looking at killer whales in the open ocean,” says study leader Josh McInnes, a master’s candidate at the University of British Columbia’s Institute for the Oceans and Fisheries.
“It was kind of a shock when … we saw animals that were out in this open ocean habitat and were completely different from the other ecotypes we know.”
Killer whales in the Pacific are grouped into three ecotypes: Residents, which live close to shore and eat salmon and other fish; offshores, which live farther out and also eat fish; and transients, also called Bigg’s, the only orcas previously known to eat mammals.(See 13 fantastic photos of orcas.)
Scientists could not match the 49 whales in the new study with any known orcas through photos and descriptions, which are based on their unique dorsal fins and saddle patches, the gray or white pattern on an orca's back.
This means the animals are either a subgroup of the transient ecotype or an entirely unique population, says McInnes, who is also a research associate with the Pacific Wildlife Foundation.
The team could also differentiate the population, dubbed the oceanics, from other known orcas due to scars or bite marks from the parasitic cookie-cutter shark, which only occur in the deep ocean.
Beyond individual variations, the oceanics don't look like other known ecotypes, for example sporting a large gray saddle patch or no saddle patch at all.
“The open ocean doesn’t support a lot of large predators; it’s often described as a giant desert, so we weren’t expecting to find so many different animals, so we’re excited to carry on more research,” McInnes says.
“We really just don't know yet what is happening with the killer whales in the open ocean. This is the mystery behind what we hope to do next.”
Following the prey
Our knowledge of orcas living in the open ocean is limited, as it’s difficult to find the widely distributed animals in a boat.
Yet the recent paper, a mixture of literature review and new observations, discovered nine instances in which marine mammal researchers, fishermen, and tourists observed whales in the northern Pacific Ocean between 1997 and 2021.
In the first documented incident, researchers watched a large pod of killer whales attack a herd of nine adult female sperm whales, managing to separate one from the pack and kill it. Other pods also hunted and ate an elephant seal, a pygmy sperm whale, a Risso’s dolphin, and a leatherback sea turtle.
With detailed records from each such encounter, the researchers plotted geo-referenced locations, determined water depth, and compared photos in databases to determine that the 49 whales sighted could potentially be a new ecotype.
It’s possible that this new population formed as prey drew them farther from shore.
“Mammal-eating killer whales are doing well, and their numbers are increasing as seal and other whale populations have rebounded since whaling and sealing became illegal,” says Robert Pitman, a marine ecologist at Oregon State University’s Marine Mammal Institute, who wasn’t involved in the study.
While prey overall is less abundant in deep-sea waters, killer whales may still find that habitat is more appealing than competing with the larger populations of resident whales closer to shore, he says.(Watch video: sperm whales vs. orcas.)
To this end, McInnes and colleagues hope this study will spark efforts to document the new whale population through genetic sampling, satellite tagging, acoustic tracking, further photo identification, and additional field observation.
Team Orca
Climate change is affecting some populations of killer whales, such as those in Antarctica, which depend on seals that live on the rapidly decreasing ice. On the U.S. West Coast, a decline in salmon has reduced a population off Puget Sound, Washington.
Worldwide, however, the species is thriving, and coming more into contact with people in coastal areas. Orcas ramming and even sinking boats off Spain made headlines in 2023, with some people rooting for the animals as fighting back against human domination.
“Killer whales are probably the most widely distributed vertebrate on the planet. They are everywhere,” Pitman says.
With many tourist cruises available worldwide, he encourages everyone to put seeing a killer whale, whose males can reach lengths of 27 feet, on their bucket list.
“This is the biggest apex predator we have on the planet today. We haven't seen anything like it since dinosaurs roamed the Earth.”
