As the Arctic warms, some polar bears are being injured by painful ice buildup on their paws: study

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

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

Two bears had developed ice blocks up to 30 centimetres 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, which lies between Nunavut and Greenland, and another population in East Greenland. Their findings were published last week in the scientific journal Ecology. 

Ice buildup hobbling some bears

Among the Kane Basin bears, 31 of the 61 bears they observed had injuries related to ice buildup, including cuts, scars and hairless patches created when hair would get wet, refreeze and be torn off.

In the East Greenland population, the prevalence of injuries was lower, with 15 of the 124 observed bears showing similar injuries. But the two worst cases of ice buildup were on bears in Greenland; it took researchers more than 30 minutes to chisel the ice buildup off of the rear paws of two sedated bears.

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

Injuries were most common among adult males, which 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 that this is happening more broadly.

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 subsistence hunters in nearby communities in Nunavut and Greenland, most said they had never seen such extreme ice buildup on polar bears before. 

Andrew Derocher, a professor at the University of Alberta who has studied polar bears for more than 40 years, said injuries from ice balls do occur to other animals in the Arctic. But it’s an “unusual event,” he said.

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

If a polar bear has this kind of injury in springtime, it can be “really quite catastrophic” to their chances of survival, he said. “In the springtime, that’s when you’ve got to be fattening up. And if you can’t move and hunt effectively, that’s going to have negative impacts.”

Inside the factors that may be behind the injuries

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

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

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

“These bears have, for their evolutionary history, lived in extremely stable, extremely cold environments,” Laidre said. “Polar bears in these high Arctic populations aren’t 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 uniquely susceptible to ice buildup because of where they live. 

Polar bears in other regions might engage in longer stretches of ocean swimming that could help melt away built-up ice. The bears in these two regions live close to glaciers and thick ice and so don’t have to navigate open water often or for long stretches of time, researchers pointed out. 

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

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

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

“What creates these injuries are these warmer conditions,” she said. “Given that [these injuries have] never been observed before, they’re new and we have all of this change, you can say this is very likely climate change.”

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

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

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

“There’s a very strong correlation between global emissions of greenhouse gases and sea ice loss,” he said. 

People who are 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 warming in the Arctic and the globe.”