An unexpected polar bear population could bring hope to the species

Image of a polar bear on drift ice

In the southeast corner of Greenland, scientists have discovered an unexpected population of polar bears. This population has developed different habits for surviving in their strange – as far as polar bears are concerned – habitat, and the bears’ genomes are very different from those of many of their conspecifics. Aside from the novelty these animals represent, new research suggests they could also help inform scientists how more traditional bears will fare in a warming Arctic.

Several things distinguish this group of bears. For much of the year they survive by chasing ice that falls into the ocean after breaking off a Greenland glacier. the ice floats in the fjords 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 worldwide.

The research team used seven years of data collected in the region along with 30 years of historical data. For the new data, the team connected with local hunters and used tissue samples taken from the hunters to sequence the bears’ genomes. They also used field research, satellite data – which also allowed them to study the region’s geographic and sea-ice conditions – and tracking collars to get a feel for the bears’ movements.

“There’s a really big collection of data here,” Twila Moon, co-author of the paper and associate principal scientist at the National Snow and Ice Data Center, told Ars. “It took a lot of time in the field. This is a very remote area that requires difficult, time-consuming and challenging fieldwork conditions.”

Alienated

Southeast Greenland is pretty poorly explored. This is due to its rugged, mountainous terrain and unforgiving weather, which includes heavy snowfall. These difficulties also probably explain why the bears are isolated. The region is surrounded by mountains, the Greenland ice sheet and the Denmark Strait.

Most polar bears use the sea ice for hunting, but this is a limited option for the south-east Greenland bears. Sea ice is only present in the region between February and May. However, movement data suggests that the bears exhibit some behaviors that differ from their relatives. They are likely to walk on glacial ice flowing into the fjords and travel 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 much less,” Moon said.

According to the samples collected and sequenced, the bears are genetically very different from other bears of the same species. There are 19 other observed polar bear populations, and their genomes are relatively similar; this isolated subpopulation stands out. According to the research, they are the most genetically isolated population of polar bears on Earth, and they may have lived in this area of ​​Greenland for hundreds of years.

A bear of a problem

As climate change continues to shrink sea ice, bears in other regions could adapt to life like people in south-east Greenland. However, Moon suggested not to get too excited about the possibility. “There may be a tendency to want to feel like this is something [feeling of] ‘The polar bears are saved,'” she said. “Unfortunately there are very [few] Places that provide a lot of glacial ice in this way… For many arctic 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 glacial ice like the population in Southeast Greenland has. The numbers of these Greenland bears are also quite small – only a few hundred individuals – possibly because of the difficulties the terrain presents when the bears try to find mates. As such, regions such as south-east Greenland may not be able to support large groups of bears. Another problem: The Greenland ice sheet, which provides the glacial ice that the bears use for hunting, is also melting. This is true of other glaciers in the Arctic, Moon said.

However, the bears of southeast Greenland have an edge in their difficult habitat. As the Greenland Ice Sheet loses ice, it is not retreating equally along the coast. Southeast Greenland gets a lot of snow in winter, which helps feed the glaciers. The researchers also note that the region could function as a small-scale climate refuges, a place where the species could survive for a time if sea ice continues to disappear. The paper also notes that some similar habitats exist in other parts of the Arctic, such as B. Svalbard – a Norwegian territory – and other parts of Greenland.

“We don’t expect this coastal ice to recede from its current position as quickly as, for example, areas of the ice sheet on the west or southwest coast,” Moon said. “It’s a nuanced environment.”

Science, 2022. DOI: 10.1126/science.abk2793 (About DOIs)