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A secret population of polar bears in Greenland has been discovered in a seemingly impossible habitat – one that for most of the year lacks the floating platforms of sea ice that the beasts use to hunt. The unusual group, which scientists once thought were part of another nearby population, has been hiding from view for hundreds of years.
The bears live on the steep slopes surrounding fjords — long and narrow coastal inlets where glaciers meet the ocean — and hunt on a patchwork of glacial ice that breaks up in these inlets. The new discovery suggests that some polar bearsat least, can potentially adapt to the disappearance of sea ice climate change worsening, the study suggests.
Still, this isn’t a silver bullet for the species as a whole.
“Glacial ice may help a small number of polar bears survive longer under global warming, but it is unavailable to the vast majority of polar bears,” said lead researcher Kristin Laidre, wildlife scientist at the University of Washington Polar Science Center. said Live Science in an email. That’s because this type of glacial ice is only found near a small fraction of other polar bear populations.
Related: Why are there no polar bears in Antarctica?
Until recently, scientists had identified 19 known polar bear subpopulations (Ursus maritimus) live in the Northern polar circle. One of these populations covers a 3,200 km stretch of the east coast of Greenland. However, when the researchers looked more closely at this group to monitor their numbers, they found that the bears actually consisted of two entirely separate populations.
The researchers analyzed 36 years of tracking data from bears fitted with GPS collars and found that bears from southeast Greenland did not pass above a latitude of 64 degrees north, and bears from the northeast did not pass the same line into the other direction passed. Genetic samples from individual bears confirmed that the southeastern bears differed from their northeastern neighbors.
“We present the first evidence of a genetically distinct and functionally isolated group of polar bears in south-east Greenland meeting [the] Criteria for recognition as the world’s 20th polar bear subpopulation,” the researchers write in their new study, published June 16 in the journal Science (opens in new tab).
The new southeastern population numbers about 300 individuals, although pinpointing an exact number is difficult, the researchers said. The newly discovered group is the most genetically diverse of all 20 populations in the Arctic, and genetic comparisons suggest they’ve been isolated from the northeastern population for about 200 years, the researchers said.
Polar bears are considered critically endangered The International Union for Conservation of Nature (IUCN) Red List. (opens in new tab), and there are around 36,000 individuals left in the wild. However, some studies suggest the species might disappear at the end of the century due to the effects of climate change.
Although polar bears are the world’s largest land carnivore, they are actually listed as marine mammals because they are predominantly aquatic and consist primarily of seals. But to hunt for food, the snow-white bears rely on sea ice as a platform to stalk their prey from above. Unfortunately, the rising temperatures caused by climate change are reducing the amount of sea ice available and shrinking their natural habitat.
Sea ice extent increases and decreases in the Arctic. The temporary ice sheets form on the sea surface in the fall and then melt away in the spring. Polar bears typically survive between 100 and 180 days without food as sea ice disappears in summer. But warming temperatures in the Arctic are causing sea ice to melt earlier and freeze later, driving polar bears to the brink of starvation.
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The fjords, home to the southeastern polar bears, lie on the southern edge of the Arctic Circle, giving the region more than 250 days of sea ice per year. Those sea-ice conditions mimic those projected for the rest of the Arctic through the late 21st century, based on previous studies, which should make the fjords uninhabitable for polar bears, the researchers said. But the southeastern bears seem to do surprisingly well without the sea ice.
The researchers believe that the bears exploit the glacial mélange, or pieces of ice that break off the fjords’ glaciers into the sea. The bears likely use these patches of freshwater ice for hunting in the same way as sea ice, allowing them to feed during the long periods when sea ice is absent in the region. “This suggests that sea-end glaciers may serve as previously unrecognized climate refugia,” the researchers wrote.
The southeastern population also lives far from human populations and the area is believed to be too difficult to reach for most hunters, providing an extra layer of security for the bears. However, the steep slopes of the fjords can also be quite difficult for polar bears to traverse, which can limit their movement. The birth rate in the new population is also very low compared to other populations, which the researchers suspect is because potential mates have trouble reaching each other.
In the new study, the researchers used genetic data to identify two individuals who may be immigrants from the Northeastern population. These migrant bears appear to have adapted very well to hunting glacial mélange, suggesting that other populations may be able to follow suit if sea ice conditions deteriorate in other areas. The researchers identified other similar locations where polar bears in northern Greenland and Svalbard could be supported by glacial conditions. However, relocation to these locations may not be feasible for the majority of bears.
Though the study offers some polar bears a glimmer of hope, the researchers insist it doesn’t make climate change any less dangerous for Arctic predators. “The loss of Arctic sea ice is still the greatest threat to all polar bears,” Laidre said. “This study doesn’t change that either.” Sea ice will continue to decrease in the Arctic, which will reduce the chances of survival for most polar bears, she added.
Originally published on Live Science.