Polar bears normally need sea ice to hunt seals, but an isolated group of polar bears living on the rugged, mountainous coast of southeast Greenland have found a way to make a living even as the sea ice melts at the beginning of the year.
These bears have found a way to supplement their limited supply of sea ice by hunting on freshwater ice from glaciers on land. Glacial ice is falling apart in fjords, where the chunks coalesce into a messy floating platform that polar bears use to stalk seals, according to a newspaper report Science.
Climate change is making sea ice increasingly rare. Loss of sea ice is “the biggest threat to polar bears,” says Kristin Laidre of the University of Washington, lead author of the new study. But, she says, this new work suggests that some bears might be able to cope with a reduced amount of sea ice — at least for a while — in places where they can take advantage of floating ice from glaciers, like Greenland and Svalbard, an archipelago in the Arctic Ocean.
“Glacial ice could essentially help small numbers of bears survive for longer periods under global warming,” she says.
Bears find a way
While indigenous people have long known that bears live in southeast Greenland, it is a remote and harsh environment that is not frequented by humans. “It’s a coastline with huge mountain peaks, lots of winds, extreme conditions, lots of fog,” says Laidre, who has spent years working with colleagues to study polar bears living on the east coast of the Greenland 1,800 miles long.
To see what they could find in the southeast, the team had to take helicopters from the nearest settlement and fly for two hours in a straight line to the coast. “We arrived in these fjords, very isolated fjords, and there is hardly any sea ice or very poor sea ice offshore,” says Laidre, explaining that the researchers expected to find little ‘bear.
“But there were a lot of bears in those fjords,” she says. “It was clearly just a unique habitat.”
Sea ice persists in these fjords for only about 100 days a year, she notes, which means bears don’t have much time to use it as a hunting ground. “He disappears in May, and it’s really early,” says Laidre. “That’s not enough time for a polar bear to grow big enough and survive.”
But the geography of this region means that glaciers pour freshwater ice onto mountains and into fjords, she says. The icebergs break away from the glacier and freeze into an irregular surface that polar bears can use as a platform for hunting seals. “They supplement their hunting time by using this freshwater ice,” says Laidre.
When it was safe to land their helicopter, researchers would briefly capture bears to take genetic samples or put on location trackers. “We would collect information about their movements, their physical condition, their health, their genetics,” says Laidre.
A united clan
She estimates that at least a few hundred polar bears live in southeast Greenland, and they happen to be the most genetically isolated polar bears on the planet. They are distinct from all 19 other subpopulations of polar bears that scientists currently recognize in the Arctic.
It may be because these bears are homebodies. All of the tracked bears stayed in their fjord(s) of origin. Sometimes the bears would get caught in a fast sea current that rushed down the coast towards the southern tip of Greenland, Laidre says, but the bears swam quickly to shore. “And then they would walk back over the ice cap to get back to their fjord.”
“The discovery of a potential new subpopulation in southeast Greenland is really exciting,” says Todd Atwood, a polar bear researcher at the US Geological Survey Alaska Science Center in Anchorage. He thinks the genetics, movement patterns and hunting behavior of the bears “show pretty clearly” that they are indeed a distinct subpopulation.
The way these bears hunt using freshwater ice “could buy the bears a little more time in this area as the sea ice continues to decline, because they’re not just relying on the sea ice,” Atwood says. .
But most polar bears are entirely dependent on the sea remaining frozen for a long period of time each year, Atwood says, adding that research suggests that more than 180 days of ice-free conditions lead to sharp declines in polar bear populations, as bears may not eat enough seals to survive and reproduce.
“The bears themselves have a basic job to do. They need to be on the ice long enough to be able to kill enough seals and store enough fat to live for a year,” says Ian Stirling, polar bear biologist at the ‘University of Alberta.
The few areas where polar bears have access to glacial ice, such as southeast Greenland, won’t serve as a potential refuge from climate change forever, Stirling says.
“If the climate continues to warm as predicted, these areas will also become useless or not useful enough for bears,” Stirling says, noting that the ends of the glaciers will eventually melt until they have retreated. on land rather than lying in water. By then, he says, so much of the ice will be gone that “the bears will be long gone.”