Hey there, time traveller!
This article was published 28/5/2020 (329 days ago), so information in it may no longer be current.
Slipping through the frigid water, the sleek black dorsal fin of a killer whale is iconic; but they’re being seen in new parts of the world more frequently, thanks to climate change breaking up sea ice.
Researchers at the University of Manitoba have been working to identify and quantify the expansion of the apex predator’s range into the eastern Arctic off the northern coast of Baffin Island for the past few years. They use unique markings on whales to understand their movements and estimate the number that have taken up residence farther into the Arctic archipelago in the summer.
As early as the mid-1800s, orcas were spotted in the area during the open-ice season, but as that season lengthens, their presence is becoming more prominent, the research found.
"I am interested in how climate change influences animal populations. A climate change-related predator range expansion and influence on endemic prey was right up my alley," said Kyle Lefort, lead researcher on the paper being published by peer-reviewed science journal Global Change Biology.
Lefort, as a part of his master’s research at the U of M, attempted to quantify what the change in orca habitat will mean for other species that typically live in that water, which will have to adapt to the increased threat of predation. Specifically, Lefort considered the effect on narwhals.
Narwhals are summer residents in the water off the northern coast of Baffin Island, with an estimated 95,000 whales migrating there in the late spring. Until recently, the area was a refuge because it remained at least partially ice-covered until the late summer, protecting the narwhal from predators such as the killer whale. That protection has now vanished.
Narwhals are a primary source of food for orcas. Lefort’s research estimates that in a single summer, orcas could be responsible for killing more than 1,200 narwhals. This would likely change the balance in the ecosystem and would have a significant effect on Indigenous communities that hunt narwhal.
Lefort explains his estimates are based on significant unknowns with regards to orca habits in the Arctic, but he plans to continue research as he enters PhD studies.
"You may have heard of the expression, ‘You are what you eat.’ Well, the same is true for killer whales. Our team has collected skin samples from free-ranging Canadian Arctic killer whales to clarify what they’re eating," Lefort said. "Our team has also attached tracking devices to killer whales to record their movements.
"Collectively, these studies will contribute to an improved understanding of killer whales’ influence on the Canadian Arctic marine ecosystem."
The range expansion of certain animals, especially predators near the top of the food chain, can destabilize an ecosystem. Killer whales expanding where they live is a great example of the effects of climate change that are poorly understood.
Colin Garroway, an assistant professor of biology at the U of M and one of Lefort’s thesis advisers, explains this is called a trophic cascade, where the effect from one change at a top trophic level is felt throughout the food chain.
"We know for certain that human-caused climate change is happening, but the consequences of (that) are endlessly surprising," Garroway told the Free Press. "(Climate change) is pretty clearly going to have bad effects on all sorts of things, but really working out the details of what those possible negative effects are is really hard work."
Garroway supervises a number of researchers that look at how human impact is changing animal life — from urbanization to climate change. He said as recently as when he was in school, it was taught that evolution and adaptation couldn’t happen over one or two generations, but now human activity is forcing that kind of change for a variety of species if they hope to survive.
Those changes are much more likely to be accommodated by species that have more offspring, Garroway said. In the case of long-lived whales, rapid adaptation could be much more difficult.
"(Killer whales) are moving into the Arctic, and all of the Arctic-adapted whales — like narwhal… beluga, bowhead — they’ve all adapted to live underneath the ice, we think, in large part to avoid killer whales eating them. So, the increasing ice-free season is opening up a whole buffet of slow, chubby Arctic whales that rather than having evolved to outrun the killer whales, they just evolved to hide from them," Garroway said.
"So we’re just trying to figure out what happens when we change things quickly."
Sarah Lawrynuik reports on climate change for the Winnipeg Free Press. Funding for the Free Press climate change reporter comes from the Government of Canada through the Local Journalism Initiative.