Some polar bears living in the Far North are presenting with ice-related injuries that in some cases seriously affect their mobility and could be linked to Arctic warming.

Researchers observing polar bears in two different populations in northern Canada and Greenland found that some suffered hair loss, gashes and sometimes significant ice buildup on their paws.

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

“It was clearly 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, located between Nunavut and Greenland, and another population in eastern Greenland. Their findings were published last week in the scientific journal Ecology.

Ice accumulation bothers some bears

Among the Kane Basin bears, 31 of the 61 bears observed had injuries related to ice accumulation, including cuts, scars, and hairless patches created when hairs got wet, refrozen, and were pulled out.

In the East Greenland population, injury prevalence was lower, with 15 of 124 bears observed having similar injuries. But the two worst cases of ice accumulation involved bears in Greenland; It took researchers more than 30 minutes to remove ice buildup from the hind legs of two sedated bears.

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

Injuries were more common among 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 indicate a trend for these populations or to suggest this is happening more generally.

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

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

Andrew Derocher, a professor at the University of Alberta who has studied polar bears for more than 40 years, said other Arctic animals are sometimes injured by ice balls. But it was an “unusual event,” he said.

“Typically, the damage that occurs is nowhere near as severe as what we see in these situations,” he told CBC News.

If a polar bear suffers this kind of injury in the spring, it can be “really catastrophic” for its chances of survival, he said. “In the spring, that’s when we have to bulk up. And if we can’t move and hunt effectively, it’s going to have negative impacts.”

Inside the factors that can cause injuries

Temperature changes in the Arctic are one of the main factors that may contribute to these injuries, researchers say.

“The Arctic can get so warm that instead of snow on the sea ice, there’s rain. And that can create wet conditions that, when they refreeze, can cause injuries,” Laidre said.

In addition to more frequent rain-on-snow events, increased cycles of temperature fluctuation can also cause the snow surface to melt just enough to become muddy, then refreeze shortly afterward.

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

A third scenario is that these two bear populations are particularly susceptible to ice accumulation because of where they live.

Polar bears in other regions may engage in longer periods of ocean swimming, which could help melt accumulated ice. Bears in these two regions live near glaciers and thick ice and therefore do not need to navigate open water often or for long periods of time, the researchers pointed out.

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

“Personally, I think they’re just unlucky bears in an unusual place,” he said.

But Laidre says the source of temperature fluctuations in the Arctic that allow ice buildup to form is clear to him.

“What’s creating these injuries are these warmer conditions,” she said. “Given that (these injuries have) never been observed before, that they are new, and that we are facing all these changes, we can say that it is most likely climate change.”

The field work, which has been supported by the governments of Canada and Nunavut as well as that of Greenland, shows the importance of continued monitoring of polar bear populations, Laidre said. That’s the only way researchers can see if there’s a pattern in these injuries that could affect bears at a population level, she said.

As a species, polar bears range over a wide area, with some populations traveling near the North Pole and others hanging around Churchill, Manitoba. But there is one problem – changes in sea ice – that affects all populations, regardless of their location, Derocher said.

And this issue is clearly linked 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 the health of polar bears 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 warming in the Arctic and around the world.”