Unexpected polar bear populations can give some hope for the species

Picture of a polar bear on liquid ice

In the southeastern corner of Greenland, researchers have discovered an unexpected population of polar bears. This population has developed distinct habits to survive in its strange – when it comes to polar bears – habitat, and the bears’ genome is quite different from many of their relatives. In addition to the news these animals represent, they can also help inform researchers about how more traditional bears will fare in a warmer Arctic, according to new research.

Several things separate this group of bears. For large parts of the year, they survive by hunting from ice that falls into the sea after being broken by a Greenland glacier; the ice floats in the fjords these bears call home. This is in contrast to most other populations of polar bears, 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 spent seven years with 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 ‘killings to sequence the bears’ genomes. They also used fieldwork, satellite data – which also enabled them to study the geographical and sea ice conditions in the region – and tracking collars to get a sense of the bears’ movements.

“There is a very large collection of data here,” Twila Moon, co-author of the paper and assistant principal researcher at the National Snow and Ice Data Center, told Ars. – It required a lot of time in the field. This is a very remote area that requires difficult, time-consuming and challenging conditions for fieldwork. “

alienated

The southeastern part of Greenland is quite poorly studied. This is due to the rough, mountainous terrain and the unforgivable weather, which includes heavy snowfall. These difficulties probably also explain why the bears are isolated. The region is surrounded by mountains, by the Greenland ice sheet and by the Strait of Denmark.

Most polar bears use sea ice to hunt, but this is a limited alternative for the southeastern Greenlandic bears. The region only sees sea ice between February and May. However, movement data suggest that the bears show somewhat different behavior than their relatives. They probably walk on glaciers that flow 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 of the year – in some fjords for a few years, even much less than that,” said Moon.

According to the samples collected and sequenced, the bears are genetically quite different from others in the same species. There are 19 other observed polar bear populations, and their genomes are relatively similar; this isolated subpopulation stands out. According to research, they are 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 can adapt to living like the population in Greenland’s southeast. Moon, however, suggested not to get too excited about this opportunity. “There may be a tendency to want to feel that this gives one [feeling of] “The polar bears are saved,” she said. “Unfortunately, it is very [few] places that give a lot of ice this 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 southeastern Greenlandic population has. The number of these Greenland bears is also quite small – only a few hundred individuals – possibly due to the difficulties the terrain poses when the bears try to find mates. As such, regions such as southeastern Greenland may not be able to sustain large groups of bears. Another issue: The Greenland ice sheet, which gives the ice the bears use to hunt, also melts. This is true for other glaciers around the Arctic, Moon said.

However, the bears in Southeast Greenland have a bone in their difficult habitat. As the Greenland ice sheet loses ice, it does not retreat as much everywhere around the coast. Southeast Greenland receives a lot of snow in the winter, which helps to feed the glaciers. The researchers also point out that the region can function as a small-scale climate refuge, a place where the species can survive for a time if sea ice continues to decline. The article also notes that a few similar habitats are found in other parts of the Arctic, such as Svalbard – a Norwegian territory – and other parts of Greenland.

“That kiss ice we expect will not retreat from its current location as quickly as areas of the inland ice, such as the west or southwest coast,” Moon said. “It’s a nuanced environment.”

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