Changes in killer whale hunting patterns raise important questions about winners and losers in our planet’s future.
When it comes to climate change, scientists are finding that killer whales may be nature’s equivalent of rich Westerners: able to move, adjust, and perhaps even profit from it, when others less fortunate are unable to do so.
It’s not a perfect analogy, but the animals do have something in common with rich countries, some of whom are already scrambling to exploit new resources, long locked beneath snow and ice. Killer whales, also known as orcas, are highly mobile, free to adjust to change, and quick to take advantage of new opportunities – something they are already doing in the Arctic Ocean offshore of Russia and Alaska.
In research presented last week at the 181st meeting of the Acoustical Society of America, in Seattle, US, Brynn Kimber, a researcher with the US National Oceanic and Atmospheric Administration and the University of Washington, examined eight years of sound recordings from monitoring buoys at four locations between Alaska and Siberia, looking for the telltale calls of killer whales.
She found that the whales moved northward earlier each year as the ice melted – not surprising, because killer whales hunt prey at the edge of the ice, but need open water in which to surface and breathe. If they venture too far from open water, they risk becoming trapped beneath the ice and suffocating, especially because their dorsal fins can make it hard for them to punch through even thin ice to create emergency breathing holes.
Kimber found that whales are appearing earlier and earlier each year at any given location, as climate change thins the ice and causes it to melt off earlier. In places where as recently as 2012 killer whales didn’t appear until June, she says, they are now arriving about a month earlier.
But they are also showing up in places where they’d never been known to go before, including a monitoring station in the Chukchi Sea, well north of eastern Siberia. “We absolutely did not expect them this far north,” she says. “But with less ice, there is less risk, so they are able to venture farther north.”
Killer whales, as their name implies, are hunters, often working in packs to isolate large prey, much as early humans once chased down mastodons and other animals much larger than themselves.
Among other things, they hunt other whales, including bowhead whales, and the change in this predator-prey relationship, Kimber says, may become increasingly important as the ice retreats.
To begin with, a limited number of bowhead whales are allowed to be taken each year by peoples of the far north, who retain the legally protected subsistence hunting practices of their ancestors. An influx of killer whales is not only an unexpected source of competition, but a threat that might drive away the bowhead whales they and their ancestors have long relied on.
But it’s not that simple.
Bowhead whales are known to flee from killer whales by swimming away beneath the ice.
Being larger, and with no dorsal fin to get in the way, they are much more able to break through the ice when they need to breathe. But to escape, they need ice thick enough to deter killer whales.
If the ice continues to thin, as it most probably will, it’s important to figure out how this prey-predator balance shifts. “Killer whales are very efficient predators,” Kimber says, “so it’s important to see if they would have an impact on bowhead. They’re good at their jobs. They get their name for a reason.”
But that’s not the only concern about an influx of killer whales into the high Arctic. Killer whales also eat seals and other marine mammals more normally the prey of polar bears. “There could be some overlap between these two predators vying for prey,” Kimber says.
The bottom line is that with animals, just as with nations, climate change really is going to produce winners and losers.
“It’s definitely something to think about,” Kimber says. “As the ice is going away, that’s really bad news for ice-dependent species like bowhead whales or polar bears.” For others, it opens the way to new prospects. “The Arctic is so rich in nutrients,” she says. “There is opportunity for migratory species that might have new unexploited niches to go into.”
“It’s a cascading effect,” adds Larry Frum, press officer for the Acoustical Society. “We lose sea ice and it affects so many things we didn’t think about.”
Kelly Benoit-Bird, a marine scientist at the Monterey Bay Aquarium Research Institute, California, who was not part of Kimber’s study team, carries it a step further. When it comes to thinking about climate-change winners and losers, she says, the focus is too often on single species, such as killer whales. “But we know that animals are part of complex, interconnected webs,” she says, “so they experience both benefits and costs that aren’t always obvious at first look.”
In other words, what might be good in the short term might also be bad in the long term. “For example,” she says, “it’s plausible that killer whales might win for a bit, but if their preferred prey, bowhead whales, lose, then the killer whales will eventually lose as well.”
Which takes us back from ecology to social science.
If the Arctic opens up to mining, but tiny, low-lying nations like Vanuatu drown in rising sea levels, how do we decide who are truly the winners and who are the losers? If Australian forests burn in ever hotter, drier summers, while other areas discover riches long-buried beneath ice and snow, who are the winners then?
Geopolitically, that’s a tough question. To ecologists, it’s not so difficult.
“This,” says Benoit-Bird, speaking not about politics but the interplay between killer whales and bowhead whales, “is why I believe it’s important to continue moving from single-species management to ecosystem management.”
Richard A Lovett
Richard A Lovett is a Portland, Oregon-based science writer and science fiction author. He is a frequent contributor to Cosmos.