An isolated group of polar bears lives in southeastern Greenland that differs genetically and in terms of lifestyle from their congeners. These polar bears hunt seals in Greenland’s fjords all year round. They do this from ice that has broken off from glaciers that reach into the sea. So they don’t hunt, like polar bears elsewhere in the Arctic, from the edge of the sea ice (frozen seawater). That means that the melting of the Arctic sea ice due to climate change does not necessarily have to be the death blow for polar bears, write American, Norwegian, Danish and Canadian researchers this week in science†
The Arctic is warming about two to four times faster than the rest of the Earth. As a result, the ice covering the Arctic Ocean is rapidly melting. The European Space Agency ESA figured that the Arctic Ocean will be virtually ice-free in summer by the year 2050. That’s a problem for polar bears. They mainly hunt seals. They catch them from the edge of the sea ice, in places where seals rest or feed their newborn young. No polar bears without sea ice, was the thought until now.
But now it turns out that there are polar bears that do not need sea ice. This concerns a group of at least a few hundred animals, according to a genetic analysis. The researchers brought together data collected over the course of 36 years: genetic data from blood samples, as well as knowledge from native hunters and data from polar bears with a radio transmitter.
This showed that the Southeastern Greenland polar bears are exceptionally homeless. Some individual bears stay in the same fjord for years. Their congeners further north in Greenland migrate annually for distances of more than 1,500 kilometers, hunting along the edge of the sea ice, which moves north in summer and south in winter.
Southeastern Greenland’s polar bears are contained, researchers say† Surrounding this fjord area are mountains that rise about two thousand meters steeply from the sea. On the west side is the Greenland ice sheet, on the east side the open sea, with a strong southward current. And just outside this rugged area are villages, with people who hunt polar bears.
This study takes a new look at polar bears’ resilience, the authors said. The distinct hunting behavior can be learned, they saw: polar bears from elsewhere that occasionally joined this population quickly learned to hunt from glacial ice. Polar bears elsewhere can therefore also learn that when there is no more sea ice, they write. But they do add a caveat: glaciers that open into the sea are only found in Greenland and Spitsbergen. So that strategy wouldn’t help the polar bears of Siberia, Canada and Alaska.
“It is very clear that this population of polar bears is genetically different from the rest, and the authors also give a nice explanation for this,” says ecologist Maarten Loonen of the Arctic Center of the University of Groningen. He wasn’t there himself science-research involved, and responds from Spitsbergen. “I do feel that they are talking too quickly about a special subpopulation that has adapted to climate change.”
Conclusion too easy
Loonen suspects that people too easily conclude that polar bears need sea ice and only eat seals. “The hunt has forced the polar bear onto the ice,” he says. “We see that now on Spitsbergen: now that polar bears are no longer hunted here, they are returning to the west coast and other food sources appear to be available to them, such as eggs.” It has also been seen elsewhere that polar bears switch to other food when there is no sea ice: in Canada, for example, they eat a lot of plant roots and berries, but also reindeer and geese.
Loonen does not think that these genetic differences ensure that the Southeastern Greenland polar bears are different or behave differently from their congeners elsewhere. “I believe the polar bear has quite a variety of food options and can survive without sea ice in the future,” he says. “Probably in lower numbers than now, because a large surface of possible food-hunting area, namely sea ice, no longer exists.”
Disappearing sea ice poses a serious threat to polar bears, Loonen emphasizes, but concludes that the hunt will be decisive. “People think the polar bear has no alternative because it was kept away from those alternatives. The biggest question for the polar bear will be whether it will be tolerated if it comes ashore more.”
Also read this article: You can recognize polar bears by their scars