Meet the unique group of polar bears living with less sea ice

Researchers have identified a special group of polar bears described in a paper published today in the magazine Science. The bears may have found some kind of unique refuge from the effects of climate change in southeast Greenland, the authors write, where their group became genetically distinct from other polar bears. Scientists are now pushing to recognize bears as their own “subpopulation”, a move that could protect them from potential threats such as hunting and habitat loss.

Over the past decade, researchers have studied polar bears along 1,800 miles off the east coast of Greenland in an effort to better understand the animals’ health and movements. Although that’s a wide range, they thought they were only dealing with one group of polar bears living all along the coast. The bears surprised them.

After putting satellite tracking collars on some animals, researchers realized that bears living in southeast Greenland kept to themselves and didn’t venture into places where they might encounter bears from the northeast. Then, after examining genetic samples, the researchers discovered that the bears in the southeast are in fact the most genetically isolated on the planet. This means that they didn’t encounter bears much outside of their group.

“It was kind of a completely unexpected finding,” says Kristin Laidre, lead author of the new paper and associate professor at the University of Washington. “Honestly, it was a bit of a coincidence that we realized we were actually dealing with two subpopulations of bears, not just one.”

The bears had other surprises in store. The southeast group had found a way to settle in a place that should have been inhospitable. In the fjords where they roam, sea ice is only present for about 100 days of the year. Since polar bears hunt on sea ice, that would normally have given them less than a third of the year to find food.

Polar bears can fast for up to 180 days a year, but the absence of sea ice longer than in this region may have left them starving. Fortunately, the bears found another resource when the pack ice disappeared: freshwater ice floating on a glacier front. Here they could hunt seals from their breathing holes or sniff them from above, then cross the ice to reach them as they normally would on sea ice.

Although some pockets of bears are known to do so less frequently on freshwater ice, this group is considered unique in that they depend on it. Without the freshwater ice, their population couldn’t really survive here.

The disappearance of the sea ice in their home is a glimpse of what will happen in the Arctic in the future. By the end of the century, much of the frozen Arctic is expected to experience more than 100 ice-free days a year. And without ice, there’s no seal hunt and not enough bear food. It’s what made the polar bear the poster boy for stories about impending climate catastrophe.

Image: NASA

The way the newly discovered pack of polar bears have found a way to persist in this type of environment suggests that freshwater glacial ice may serve as a limited “climate refuge” for some other bears in the future, write Researchers. But Laidre cautions against overselling newly found bears as a success story or a role model for other bears facing an uncertain future. There are few areas with this kind of abundant freshwater ice, called glacial mixing, so few bears will be able to rely on it. And while this ice has so far been somewhat spared by rising temperatures in this part of Greenland, it will become increasingly vulnerable if the planet continues to warm.

All of this means that measures to slow climate change and conserve these environments will continue to be crucial to the survival of polar bears. As it stands, the global population of polar bears is expected to decline by 30% over the next three generations, according to Laidre.

She hopes that if the newly spotted group of bears are designated internationally and by the country of Greenland as a unique “subpopulation” distinct from other polar bears, they will get more attention from conservation efforts. The genetic isolation of the group makes them an important part of maintaining the genetic diversity of all polar bears – a key factor in keeping the species healthy.

Image: Kristin Laidre/University of Washington

Since this group of bears was discovered by accident, Laidre isn’t quite sure of the population size. She estimates that there may be “several hundred” and that the group has probably been here for a few hundred years. The bear band also slowly grew from migrant newcomers. His research has identified at least two “immigrants” who help keep the population healthy by adding to the gene pool. Laidre hopes to start a new research effort to focus on this special group of bears to get a better idea of ​​their numbers and their lives.