In the southeast corner of Greenland, scientists have discovered an unexpected population of polar bears. These inhabitants have developed distinct survival habits in their exotic habitat – in relation to polar bears – and the genomes of the bears are very different from many of their relatives. In addition to the novelty these animals represent, they can also help inform scientists about how traditional bears cope in the warmer Arctic, according to new research.
There are several things that distinguish this group of bears from each other. Most of the year, they survive by fishing from the ice that falls into the ocean after a glacier broke in Greenland. Ice floats in the fjords that these bears call home. This is in contrast to most other groups of polar bears, 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 area, along with 30 years of historical data. For the new data, the team reached out to local hunters and used tissue samples taken from killing poachers to sequence the genomes of the bears. They also used field work, satellite data – which also allowed them to study the geographical and marine glacial conditions in the area – and tracking collars to learn about the bears’ movements.
“There’s a really big set of data here,” Twila Moon, co-author of the paper and principal deputy scientist at the National Snow and Snow Data Center told Ars. “It required a lot of time in the field. This is a very remote area and it requires difficult and time consuming field working conditions.”
Southeast Greenland is very poorly studied. This is due to its rugged mountainous terrain and harsh weather that includes heavy snowfall. These difficulties also likely explain why the bears are isolated. The area is surrounded by mountains and ice sheets in Greenland and by the Denmark Straight.
Most polar bears make use of sea ice for hunting, but this is a limited choice for bears in southeast Greenland. The area only sees sea ice between February and May. However, locomotion data indicates that bears exhibit some different behaviors than their relatives. They likely walk on icy ice that flows into fjords and travel through mountains to reach other fjords in search of food, often seals.
“We found that sea ice was rarely present for more than four months of the year – in some fjords in some years, it was much less,” Moon said.
According to the samples collected and sequenced, bears are genetically completely different from other species in the same species. There are 19 other groups of polar bears that have been observed, and their genomes are relatively similar to each other; This isolated subgroup stands out from the population. According to research, they are the most genetically isolated group of polar bears on Earth, and they may have been in this region of Greenland for hundreds of years.
As climate change continues to reduce sea ice levels, bears in other areas could adapt to live like populations in southeast Greenland. However, Moon suggested not to get too excited about the possibility. “Perhaps there is a tendency to desire to feel that this gives [feeling of] “The polar bears were saved,” she said. “Unfortunately, there are many [few] Sites that provide a lot of glacial ice in this way… For many polar bears, this 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 glacial ice as the inhabitants of southeastern Greenland did. Greenland’s bear population is also very small – only a few hundred individuals – possibly due to the difficulties that the terrain poses when trying to find mates. As such, regions such as southeastern Greenland may not be able to maintain large populations of bears. Another problem: The Greenland ice sheet, which provides the glacial ice that bears use for hunting, is also melting. That’s true for other glaciers around the North Pole, Moon said.
However, bears in southeastern Greenland have a leg up in their difficult habitat. Because the Greenland ice sheet is losing ice, it does not retreat by the same amount everywhere around the coast. Much snow falls in southeast Greenland in the winter, which helps feed the glaciers. The researchers also note that the area could function as a microclimate hut, a place where species could live for some time if sea ice continues to diminish. The paper also notes that there are a few similar habitats in other parts of the Arctic, such as Svalbard – a Norwegian territory – and other parts of Greenland.
“This coastal ice we don’t expect will retreat as far from its present location as ice sheet regions, for example, on the west or southwest coast,” Moon said. “It’s a delicate environment.”
Science, 2022. DOI: 10.1126/science.abk2793 (about DOIs)