In the southeast corner of Greenland, scientists have discovered an unexpected population of polar bears. This population has evolved distinct habits for surviving in its strange habitat, as far as polar bears go, and the bears’ genomes are quite different from those of many of their fellows. Beyond the novelty these animals represent, they could also help inform scientists about how more traditional bears will behave in a warming Arctic, new research suggests.
Several things set this group of bears apart. For much of the year, they survive by chasing ice that falls into the ocean after breaking off a glacier in Greenland; ice floats in the fjords these bears inhabit. This is unlike most other polar bear populations, which require sea ice to hunt. According to the World Wildlife Fund, there are between 22,000 and 31,000 polar bears left in the world.
The research team used seven years of data collected in the region, as well as 30 years of historical data. For the new data, the team connected with local hunters and used tissue samples taken from hunters’ prey to sequence the bears’ genomes. They also used fieldwork, satellite data — which also allowed them to study the region’s geographic and sea ice conditions — and tracking collars to get an idea of the bears’ movements.
“There’s a very large collection of data here,” Twila Moon, co-author of the paper and deputy principal scientist at the National Snow and Ice Data Center, told Ars. “It took a lot of time on the pitch. This is a very remote region that requires difficult, time-consuming and demanding conditions for field work. »
Southeast Greenland is quite poorly studied. This is due to its rugged, mountainous terrain and unforgiving climate, which includes heavy snowfall. These difficulties also probably explain why the bears are isolated. The region is surrounded by mountains, the Greenland Ice Cap and the Denmark Strait.
Most polar bears use sea ice for hunting, but this is a limited option for bears in southeast Greenland. The region only sees sea ice between February and May. However, movement data suggest that bears display different behaviors from their fellow bears. They probably walk on the glacial ice that flows into the fjords and up the mountains to reach other fjords in search of food, often seals.
“We found that sea ice rarely existed for more than four months a year – in some fjords in some years even much less than that,” Moon said.
According to samples collected and sequenced, the bears are genetically quite different from others of the same species. There are 19 other populations of polar bears observed and their genomes are relatively similar to each other; this isolated subpopulation stands out. According to research, this is the most genetically isolated population of polar bears on Earth, and they may have been in this area of Greenland for hundreds of years.
A bear of a problem
As climate change continues to reduce sea ice levels, bears in other regions may adapt to live like the population in southeast Greenland. However, Moon suggested not to get too excited about the possibility. “There is perhaps a tendency to want to feel that it gives a [feeling of] “Polar bears are saved,” she said. “Unfortunately, there are very [few] places that provide a lot of glacial ice that way… For many arctic polar bears, that type of ice is not available.
This means that many populations of polar bears will not have the opportunity to adapt to life on the ice as the population in southeast Greenland did. The numbers of these Greenland bears are also quite low – only a few hundred individuals – perhaps due to the difficulties the terrain poses when the bears try to find mates. As such, areas like southeast Greenland may not be able to support large groups of bears. Another problem: the Greenland ice cap, which provides the glacial ice that bears use to hunt, is also melting. This is true for other glaciers around the Arctic, Moon said.
Bears in southeast Greenland, however, have a head start in their difficult habitat. As the Greenland Ice Sheet loses ice, it does not retreat by the same amount everywhere around the coast. Southeast Greenland gets a lot of snow in the winter, which helps feed the glaciers. The researchers also note that the region could act as a small-scale climate refuge, a place where the species could survive for some time if sea ice continues to decline. The paper also notes that a few similar habitats exist in other parts of the Arctic, such as Svalbard, a Norwegian territory, and other parts of Greenland.
“This coastal ice, we don’t expect it to retreat from its current location as quickly as the ice sheet areas, for example, on the west or southwest coast,” Moon said. “It’s a nuanced environment.”
Science, 2022. DOI: 10.1126/science.abk2793 (About DOIs)