Some polar bears living in the far north are developing ice-related injuries that, in some cases, severely affect their mobility and may be related to the warming of the Arctic.

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

Two bears had blocks of ice up to 30 centimeters in diameter develop 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, which is located between Nunavut and Greenland, and another population in eastern Greenland. Their findings were published last week in the scientific journal Ecology.

Ice accumulation harms some bears

Among the Kane Basin bears, 31 of the 61 bears they observed had injuries related to ice dams, including cuts, scars and hairless patches created when hair became wet, refrozen and pulled out.

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

“Bears with ice dams had trouble walking and running,” Laidre said.

Injuries were more common among adult males, which weigh more 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 more broadly.

However, he said, it is the first time that these types of injuries have been reported between these two populations of polar bears.

When researchers consulted with Inuit subsistence hunters in nearby 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 also suffer injuries from ice balls. But it is an “unusual event,” he said.

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

If a polar bear suffers this type of injury in the spring, it can be “really quite catastrophic” for its chances of survival, he said. “In the spring, that’s when you have to put on weight. And if you can’t move around and hunt effectively, that’s going to have negative impacts.”

Among the factors that may be behind injuries

Researchers said temperature changes in the Arctic are one of the big factors that may be contributing to these injuries.

“The Arctic can get so warm that instead of snowing on sea ice, it rains. And that can create wet conditions that, when it freezes again, can lead to injuries,” Laidre said.

In addition to more rain-on-snow events, increasing cycles of temperature fluctuation can also cause the surface of the snow to melt enough to become slushy and then refreeze shortly thereafter.

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

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

Polar bears in other regions could swim longer stretches in the ocean, which could help melt accumulated ice. Bears in these two regions live near glaciers and thick ice and therefore do not have to navigate open water frequently or for long periods of time, the researchers noted.

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

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

But Laidre says the source behind the temperature fluctuations in the Arctic that allows the ice dam to form in the first place is clear to her.

“What creates these injuries are these warmer conditions,” he said. “Since (these lesions) have never been observed before, they are new and we have all these changes, you can say that it is very likely that this is climate change.”

The field work, which was supported by the governments of Canada and Nunavut as well as Greenland, shows the value of continued monitoring of polar bear populations, Laidre said. That’s the only way researchers will be able to see if there are any trends in these injuries that might affect bears at a population level, he said.

As a species, polar bears span a huge area, with some populations traveling near the North Pole and others hanging around Churchill, Man. But there’s one problem — changes in sea ice — that affects all populations, regardless of their location. Derocher said.

And that issue has a clear connection with 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 the world.”