Secret population of polar bears found in unexpected habitat

A team of biologists announces that they have isolated a secret population of polar bears in eastern Greenland. All these animals live in a habitat that does not offer most of the year no sea ice shelves on which these predators usually hunt. The threat of climate change remains, but this new discovery suggests that at least a small number of these bears may survive longer as the Arctic warms.

Polar bears (Ursus maritimus) are the most iconic predators of the Arctic. Until now, there were nineteen known subpopulations of these animals in the region. One of them, which extends over a stretch of 3,200 kilometers from the east coast of Greenland, has recently been the subject of a genetic study. Thirty-six years of tracking data from bears tagged with GPS collars finally found that this population was splitting into two very distinct subpopulations. One lives southeast of Greenland and does not pass above a latitude of 64 degrees north, while the other moves north, not crossing the same line in the other direction.

This southeastern Greenland subpopulation is home to at least three hundred individuals. Genetic comparisons suggest that they have been isolated from the northeastern population since about two hundred years. Thus, this new work published in the journal Science shows that there are not nineteen, but twenty polar bear subpopulations in the Arctic. However, this is perhaps not the most surprising.

An unusual environment

Polar bears usually rely on sea ​​ice to feed onself. These platforms usually form on the surface of the ocean in the fall before melting in the spring. The rest of the time, bears tend to dip into their fat stores. Unfortunately, global warming increasingly reduces the amount of ice available, and thus also the hunting ground of animals. Sea ice also melts earlier and freezes later.

Here, the fjords within which these “new” polar bears evolve are located at the southern limit of the Arctic Circle. Consequently, the region is more free of sea ice (more than 250 days per year). These conditions are those predicted for the rest of the Arctic by the end of the 21st century based on recent studies. However, it was thought until now that such an environment could not support polar bears.

It is clear that these animals seem to be doing well.

A southeastern polar bear. Credits: Kristin Laidre/University of Washington

A lifeboat

Researchers believe these bears take advantage of chunks of ice that break off from fjord glaciers and flow into the sea. The bears likely use these freshwater patches in the same way they use sea ice to hunt. . The fact that this region is also difficult to access also protects these animals from human threat.

However, the region is also not a paradise for bears. The steep slopes of the fjords limit their movement. Moreover, the birth rate among the new population is very low compared to other populations. Researchers suspect this is because potential mates find it difficult to come together. However, this new discovery suggests that this type of environment could ” serve as climatic refuge hitherto unrecognized“, note the authors.

According to the study, two individuals from the northeast also appear to have grafted onto this southern population, eventually adapting to their new surroundings. This suggests that other populations may be able to follow suit as sea ice conditions deteriorate in other regions. The researchers also identified other areas where similar conditions could support polar bears in northern Greenland and Svalbard.

However, although the study offers a glimmer of hope for some bears, the researchers insist that not everyone can enjoy it.

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