At the southeastern tip of Greenland, scientists have discovered an unexpected population of polar bears. This population has developed different habits to survive its strange habitat, as far as polar bears are concerned, and the genomes of bears are quite different from many of their relatives. Beyond the novelty these animals represent, they could also help inform scientists about how the more traditional bears will fare in a warming Arctic, according to new research.
Several things distinguish this group of bears. For much of the year, they survive by hunting ice that falls into the ocean after breaking a Greenland glacier; the ice floats in the fjords that these bears call home. This is unlike most other polar bear populations, which require sea ice for hunting. 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, along with 30 years of historical data. To obtain the new data, the team connected with local hunters and used tissue samples taken from the killers of the hunters to sequence the genomes of the bears. They also used fieldwork, satellite data, which also allowed them to study the geographical conditions and sea ice of the region and tracking collars to get an idea of the movements of the bears.
“There’s a big data collection here,” she told Ars Twila Moon, co-author of the paper and assistant chief scientist at the National Snow and Ice Data Center. “It simply came to our notice then. This is a very remote area that requires difficult conditions, which are time consuming and challenging for fieldwork. “
Strange
Southeast Greenland is poorly studied. This is due to its rugged, mountainous terrain and its relentless weather, which includes heavy snowfall. These difficulties also explain why bears are isolated. The region is surrounded by mountains, the Greenland ice sheet and the Strait of Denmark.
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 exhibit different behaviors from their relatives. They probably walk on the icy ice that flows into the fjords and climb the mountains to reach other fjords in search of food, often seals.
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“We were finding that sea ice rarely existed for more than four months a year, in some fjords in a few years, even much less,” Moon said.
According to the samples collected and sequenced, bears are genetically quite different from others of the same species. There are 19 other polar bear populations observed, and their genomes are relatively similar to each other; this isolated subpopulation stands out. According to research, they are the most genetically isolated polar bear population on Earth, and may have been in this area of Greenland for hundreds of years.
A bear of a problem
As climate change continues to lower sea ice levels, bears from other regions could adapt to living as the population of southeast Greenland. However, Moon suggested not getting too excited about this possibility. “It simply came to our notice then [feeling of] “Polar bears are saved,” he said. “It simply came to our notice then [few] locations that provide a lot of glacial ice this way … For many Arctic polar bears, this type of ice is not available. “
This means that many polar bear populations will not have the opportunity to adapt to life on glacial ice as the population of south-east Greenland has. The number of these bears in Greenland is also quite small, only a few hundred individuals, possibly due to the difficulties of the terrain when the bears try to find a mate. As such, regions such as southeast Greenland may not be able to sustain large groups of bears. Another problem: the Greenland ice sheet, which provides the glacial ice that bears use to hunt, is also melting. That’s true for other glaciers around the Arctic, Moon said.
However, the bears of south-eastern Greenland do have a leg up in their difficult habitat. As the Greenland ice sheet loses ice, it does not retreat the same amount across the coast. Southeast Greenland receives a lot of snow in the winter, which helps fuel glaciers. Researchers also point out that the region could act as a small-scale climate refuge, a place where the species could survive for a while if sea ice continues to decline. The document also notes that some similar habitats exist in other parts of the Arctic, such as Svalbard, a Norwegian territory, and other parts of Greenland.
“We don’t expect this coastal ice to withdraw 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 DOI)