As the Arctic warms, some polar bears are injured by painful ice build-ups on their paws: study

Some polar bears living in the far north are showing up with ice-related injuries that in some cases seriously affect their mobility and may be linked to the warming Arctic.

Researchers observing polar bears in two different populations in Northern Canada and Greenland found that some suffered from hair loss, cuts and sometimes severe icing on their paws.

Two bears had developed ice blocks up to 30 centimeters in diameter around their paws, causing deep cuts.

“It was obviously very painful for the bears,” Kristin Laidre, a professor at the University of Washington and lead author of the paper, told CBC News.

The observations were made by researchers between 2012 and 2022 while studying a population of bears in the Kane Basin, which lies between Nunavut and Greenland, and another population in eastern Greenland. Their findings were published last week in the scientific journal Ecology.

Ice buildup causes some bears to hobble

Among the Kane Basin bears, 31 of the 61 bears they observed had icing-related injuries, including cuts, scars and hairless patches that formed when the hair got wet, re-froze and was torn off.

In the East Greenland population, the prevalence of injuries was lower, with 15 of 124 bears observed showing similar injuries. But the two worst cases of icing occurred in bears in Greenland; it took researchers more than 30 minutes to chisel the ice buildup off the hind legs of two anesthetized bears.

“The bears with the ice buildup had difficulty walking and running,” Laidre said.

Injuries were most common in adult males, who are heavier than females or cubs and tend to travel longer distances.

Laidre cautioned that they don’t have enough data to point to a trend for these populations, or to suggest this is happening on a broader scale.

However, she said it is the first time these types of injuries have been reported among these two polar bear populations.

When researchers consulted with Inuit hunters in nearby communities in Nunavut and Greenland, most said they had never seen such extreme ice buildup on polar bears.

Andrew Derocher, a professor at the University of Alberta who has studied polar bears for more than 40 years, said iceball injuries also occur in other animals in the Arctic. But it is an “unusual event,” he said.

“Typically, the damage that occurs is not nearly as severe as what was observed in these situations,” he told CBC News.

If a polar bear sustains these types of injuries in the spring, it could be “really quite catastrophic” for their chances of survival, he said. “In the spring you have to fatten up. And if you can’t move and hunt effectively, it will have negative consequences.”

Discover the factors that may be behind the injuries

Changing temperatures in the Arctic are one of the big factors potentially contributing to these injuries, researchers said.

“The Arctic can get so warm that instead of snow on the sea ice, you get rain. And that can create wet conditions that, when it freezes again, can cause injuries,” Laidre said.

In addition to more rain-on-snow events, increasing temperature fluctuations can also cause the surface of the snow to melt just enough to become muddy and refreeze shortly afterwards.

“These bears, because of their evolutionary history, have lived in extremely stable, extremely cold environments,” Laidre said. “Polar bears in these high Arctic populations are not used to that (freeze-thaw cycles), and that’s what we think we see here on these paws.”

A third scenario is that these two bear populations are particularly sensitive to icing because of where they live.

Polar bears in other regions could swim longer stretches in the ocean, which could help melt away the ice that has built up. The bears in these two regions live close to glaciers and thick ice, so they don’t have to navigate open water often or for long periods of time, researchers point out.

This is the most likely cause for these specific injuries, Derocher said.

“Personally, I think these are just some unlucky bears in an unusual place,” he said.

But Laidre says the cause of the temperature fluctuations in the Arctic that allow ice to form is clear to her.

“What’s causing these injuries is these warmer conditions,” she said. “Given that (these injuries) have never been seen before, they are new and we have all these changes, you can say this is very likely climate change.”

The fieldwork, which was supported by the Canadian and Nunavut governments as well as Greenland, demonstrates the value of continued monitoring of polar bear populations, Laidre said. That’s the only way researchers can tell if there’s a trend in these injuries that could affect the bears at a population level, she said.

As a species, polar bears cover a vast area, with some populations traveling to the North Pole and others hanging out around Churchill, Man. But there is one problem — changes in sea ice — that affects all populations, regardless of location, Derocher said.

And that issue has a clear connection to climate change, he said.

“There is a very strong correlation between global greenhouse gas emissions and sea ice loss,” he said.

People concerned about polar bear health should push for climate action, not just climate awareness, Laidre said.

“The way to help polar bears is to reduce greenhouse gases and slow or stop the warming of the Arctic and the rest of the world.”