An influx of these powerful, intelligent predators could mean trouble for other marine mammals.
By Ian Rose, June 24, 2025
Killer whales are the ultimate marine predator. Even the great white shark is no match for the intelligence and power of an orca. They patrol every ocean on Earth, and no prey species is too large or too fierce for them. But until recently, they faced one limit: the high Arctic. Sea ice blocked narrow entries to both the east and west coasts of the North American Arctic, forming a barrier between these perfect predators and whole habitats rich in potential prey.
But as climate change warms the Arctic faster than any other region of the planet, that ice is retreating fast. Since the late 1970s, the Arctic has lost about 30,000 square miles of sea ice annually, adding up to an area the size of Alaska that is no longer covered by ice all year. All that open water means new hunting grounds for orcas.
Spring is an incredibly dynamic time for the Arctic. As the seasonal ice melts, marine mammals migrate to take advantage of rich waters teeming with plankton and fish. Historically, these waters have also offered a safe place for seals and whales to birth their pups and calves, free from most open-water predators. In Alaska, spring is calving season for the bowhead whale, the only large baleen whale that spends its entire life in Arctic waters.
“One of the species that I'm worried about is bowhead whales,” Brynn Kimber, a research scientist at the University of Washington, said. “They're such an important subsistence animal. And they also are an Arctic resident species, and so they're not as used to having their population numbers affected by killer whales as some other normal prey species like gray whales are.”
According to the Alaska Eskimo Whaling Commission, bowhead harvest yields almost a million pounds of food a year for Alaskan Indigenous communities. Beyond its cultural and nutritional value, this subsistence harvest is even more important because of high grocery prices in remote Alaskan villages.
In a recent study of acoustic signals from killer whales, Kimber and colleagues found not only a rise in the abundance of orcas in the Alaskan Arctic but also a shift in when they were arriving. As sea ice retreats, orcas are coming north up to 50 days earlier. That puts them in the bowhead calving grounds during or soon after the birthing season, when both calves and adults are at their most vulnerable.
“I think that timing is going to be a huge problem,” Kimber said.
On the other side of North America’s Arctic, off the north coast of Baffin Island in Canada, almost 100,000 narwhals arrive each spring from their offshore wintering areas. Their arrival is an important event to Inuit communities, which hunt about 600 narwhals each year. One recent analysis estimated that the new influx of killer whales may be taking more narwhals than the Inuit, up to 1,000 each year.
“The Alaskans’ bowhead is the Canadian narwhal, as far as the primary marine mammal species a lot of folks are harvesting,” Jeff Higdon, a consulting biologist who has worked extensively on orcas in the Canadian Arctic, said. “Folks are concerned about direct predation, but a lot of people also raise these sublethal impacts. Killer whales are pushing narwhals away from areas where people normally hunt them.”
The Inuit even have a word for this phenomenon: aarlirijuk, or the fear of killer whales. (Aarluk is the Inuktitut name for orca.) Western scientists use a different name. They call this fear response a nonconsumptive effect, or NCE, a behavioral shift that affects a species beyond just the direct effects of predation—an ecology of fear. Using satellite transmitters, researchers from the University of Alaska and Fisheries and Oceans Canada quantified what the Inuit already knew: Bowheads move closer to shore and into thicker ice when killer whales are present. They also found that bowheads reacted this way even when killer whales were up to 60 miles away, much farther than the range of killer whale vocalizations. This suggests that bowheads might be warning each other of the orcas’ approach—intelligent prey responding to an intelligent predator.
Higdon and his coauthors interviewed over 100 Inuit hunters in 11 different communities for a 2012 paper, which provided one of the first detailed accounts of killer whales in the Arctic. These interviews showed not only the rise in orca observations but also unique insights into hunting behavior, prey species, and more observations that only the Inuit, with their day-to-day experience in the waters of Hudson and Baffin Bays, could offer.
Though killer whales range widely throughout the world’s oceans, they are divided into several ecotypes with very different prey and behavior. These ecotypes are divided into roughly two groups: resident killer whales, which feed mostly on fish, and transients, which mostly hunt marine mammals like seals and whales. Inuit observations, genetic studies, and Kimber’s acoustic data all point to the same conclusion: Most, if not all, of the killer whales moving north and taking advantage of the less-icy Arctic springs are transients. They are the seal and whale eaters.
Killer whales have probably always been occasional visitors to the Arctic. They were noted by another whale predator, the whaling ships that decimated bowhead populations in the late 1800s. Inuit hunters certainly saw them much earlier, as evidenced by the depictions of the aarluk in their stories and artwork. But starting in the 1950s, sightings increased. Between 2000 and 2009, there were more sightings than in the three decades before combined. The reason for this sudden jump may have been a tipping point in the ice retreat that scientists call the “choke point hypothesis.”
Both sides of the North American Arctic feature narrow straits between much larger bodies of water. In the West, that bottleneck is the Bering Strait between Alaska and Russia, and on the eastern side, it’s the Hudson Strait, connecting the Atlantic Ocean to Hudson Bay. Each of these waterways represents a choke point, through which whales and other migrating sea life have to travel to make their way north. When sea ice was more plentiful, these choke points would stay essentially closed from November until June or even July. Now, the straits are opening up earlier and staying open longer, and that may be the main factor driving higher Arctic killer whale numbers.
These new hunting grounds certainly offer a bounty of prey to the orcas. But they also come with new dangers. As the killer whales venture farther north into previously ice-locked waters, they risk getting stuck when the ice returns in the fall. Strandings like this probably always happened to the few orcas that ventured farthest north, but they are on the rise.
For scientists hoping to understand the killer whales’ move north and its effects on the ecosystem, they can be a difficult study species. Even with the recent increases, they remain fairly rare.
“You're looking for a small black-and-white needle in a massive blue-and-white haystack,” Higdon said. With limited time and resources, scientists have few chances to spot killer whales, much less gather detailed data on their movements and behaviors. That makes the Inuit, Iñupiat, and Yup’ik, who spend their lives on the Arctic waters, an invaluable source of data and insight on the orca and their prey.
Inuit hunters were the first to notice the increase in killer whale numbers in the Canadian Arctic. Their observations were the basis for Higdon and others to start looking at the phenomenon, and no study of orcas in the Arctic would or could exist without Indigenous communities’ input and support. Ultimately, the people who depend most on the sea and know it best will always be the most important partners in understanding the shifting ecosystems of a changed and changing Arctic.
Author:
Ian Rose is a science and nature writer. His recent work has appeared in Scientific American, The Washington Post, Smithsonian, and elsewhere.
(Sources: Sierra Club)
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