Why this newly discovered group of polar bears is so special | National Geographic

Indigenous hunters in Greenland have long claimed that polar bears live in the fjords around the island’s southern coast all year round. When the Greenland government commissioned a study of the distribution of the species, Ledry and her team relied on maps drawn by the Inuit. Leader said local fishermen worked with the team and were “invaluable in the investigation.” The maps showed an unexplored group of bears living at the foot of the glaciers, near a very remote settlement in the southeast of the island: Skjoldungen-Timmiarmiit.

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In new research published this week in the journal Sciences, has been presented DNA analyzes showing that the approximately 100 polar bears living in the region are so different from the approximately 26,000 other polar bears in the world that they can be considered as twenty subpopulations. A subpopulation is a group of animals within a single species that has become genetically and geographically isolated. Additionally, satellite data from 27 roaming bears fitted with collars and transmitters showed that this subpopulation could live without ice packs for three months longer than scientists thought possible.

In light of this data, it’s tempting to view the study as a hopeful sign that polar bears have learned to survive on less ice, but the study’s authors stress that the conclusion is incorrect: polar bears are no better against climate change. . Instead, they believe, polar bears are choosing places like southeast Greenland, where glaciers off the mainland are making up for the loss of the ice pack at sea, as their last resort.

A daunting task

Together with Fernando Ugarte of Grønlands Naturinstitut and a large number of international researchers, Laidre combed through 36 years of data and DNA analysis to find out what makes this group of bears different from other populations. To their surprise, they found in the data that polar bears live north of 64e The latitude has been living there for a long time and the East Antarctic bears only moved south of this dividing line without there being much contact between the two groups.

Heartbreaking video: A polar bear is starving on land without ice | National Geographic

While its likes in northeastern Greenland roamed nearly six miles a day over vast expanses of ice packs, southerners stayed near shore to fish in a series of fjords—long bays carved past by glaciers that descended from the sea. Greenland to the sea. In the summer months, large chunks of ice fall from these glaciers, creating so-called ‘ice mixes’ just off the coast, a mixture of rafts that can be so densely packed that polar bears can walk and hunt on them.

Lidri found that some polar bears continued to hunt for a long time in one fjord or a few fjords, sometimes covering a hunting area of ​​up to eight to fifteen square miles. This is a postage stamp compared to the regions of the Northeast Group, where the average polar bear roams over the ice for more than 1,400 km each year.

Polar bears on the beach

Lidder said analysis of the DNA material — collected in the field by Lidrey’s team, collected in previous studies and provided by indigenous hunters — shows that the southeastern animals are “the most genetically isolated polar bears on Earth.” In short, they are less closely related to their neighboring subpopulations than are the nineteen other – officially recognized – subpopulations of the world that are related to their neighbours’ populations.

But why did both groups of polar bears become so isolated from each other? According to the researchers, there is evidence of a “founder effect”, which means that the southeastern population arose far from a larger group by a small number of individuals, after which the descendants of these polar bears interbred. Genetic analyzes show that all of the eastern Antarctic bears from which tissue samples were sampled share a modern common ancestor that lived about two hundred years ago.

The most likely cause of polar bear stranding in these fjords is the East Greenland Current, a huge ocean current that flows south at high speed along the east coast of the island. The current actually creates a belt of floating ice, which forms on the northeast coast and then splits into smaller buoys as it drifts south.

According to Ugarte, a handful of eastern arctic bears are transported south every year in this way, to about Cape Farewell, the southernmost tip of Greenland. The surviving polar bears are animals that reach the southwest coast, where they can migrate north and then west to reach Canada. The less fortunate polar bears drown.

“What’s really interesting and special about these new residents is that they know how to handle their situation,” Ugarte says. Offshore currents swept 11 polar bears that were tracked by a transmitter and swept an average of 188 kilometers on ice in two weeks. But within a month or two, they all managed to find their way back to their “fjords” by swimming through icy waters or taking trips along the coast.

temporary asylum

University of Alberta biology professor Andrew Desrocher, who has researched polar bears in the Arctic for more than 40 years and was not involved in the new study, said the study is “elegant” and brings together “some interesting findings.”

He notes that a number of polar bears were previously created to search for glacial ice in the absence of an ice pack. A well-documented example is the Spitsbergen range in the Norwegian archipelago, where researchers have discovered polar bears occupying very small hunting grounds on glacial ice.

Scientists predict that Arctic glaciers that pass through the fjords will remain intact longer than the region’s ice pack during climate change, which could make them temporary refuges for problem species elsewhere, such as polar bears that rely on ice packs for hunting.

But that doesn’t mean “save the polar bear,” says Stephen Amstrup, chief scientist at the environmental group Polar Bears International. Amstrup was director of polar bear research at the USGS in Alaska for 30 years.

Although the Arctic may appear to be full of glaciers, the vast majority of the region is made up of tundra, which are treeless plains with permanently frozen subsoil called permafrost. “In the Arctic, you’ll find huge reservoirs of glacial ice only in Greenland and Spitsbergen, and then some as far north as Canada,” Ledri says. So ice mixes are not as widespread as you might think, and can only support small numbers of polar bears.

Amstrup hopes the research will lead scientists and conservationists to assess what other places in the Arctic polar bears can take refuge on the glacial ice so they can stay there longer.

“Anyway, this study is another example of the fundamental relationship between polar bears and floating ice,” he says. Do polar bears really care whether they hunt on saltwater ice or icy freshwater ice? Probably not, as long as there were seals under it.


The authors of the new study believe that Greenland’s southeastern bears should be considered the 20th subpopulation of arctic polar bears due to genetic differences and geographic isolation from the northeastern major group.

Ultimately, this is a problem that should be evaluated by polar bear experts at the International Union for Conservation of Nature (including Laidre and Derocher). In doing so, they will take into account factors such as the number of polar bears within the subgroup – a number that has not yet been precisely established – and whether it would be beneficial to the animals if managed as a separate group.

The authors view the genetic isolation of the populations in the Southeast as something special that must be protected. Derocher and Amstrup are no different, but they do have caveats.

“I think we’re dealing with a small, isolated population that has a lot of inbreeding,” Derocher says. “We know from other studies of large carnivores that such populations are susceptible to inbreeding depression.” [de algehele verzwakking van de populatie door erfelijke aandoeningen]Diseases and accidental demographic events.

“From an evolutionary perspective, isolated populations are usually most vulnerable,” Amstrup also says. “As populations of smaller and smaller polar bears take refuge in increasingly isolated areas, we are likely to see such genetic isolation and fragmentation more frequently,” Derocher says.

This article was originally published in English at nationalgeographic.com

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