Until recently, polar bears were thought to primarily survive on ice-covered waters. Not only do they tend to breed and rest on sea ice, but they also prey on seals that use cracks and holes in the ice to breathe.
A new discovery in southeastern Greenland where sea ice season tends to be shorter than four months, however, has found that some polar bears don’t seem to need as much ice as originally thought. The findings, published in the journal Science, suggest that a genetically different subpopulation of polar bears has adapted to life off ice.
With the help of indigenous hunters that have long believed that polar bears live in the southern parts of Greenland all year around, the team of researchers found around a few hundred bears living at glaciers near Skjoldungen-Timmiarmiit. DNA evidence suggests that these bears are so genetically and geographically different to their ice neighbours that they make up the 20th subpopulation of the 26,000 polar bears in the world. It was determined that this subpopulation is the world’s most genetically isolated population after being cut off from other polar bears for several hundred years.
By tracking 27 of these bears with satellite radio collars, the researchers also found that this distinctive population survives approximately three months longer without sea ice than previously thought possible.
But this finding doesn’t mean that polar bears are more resilient to climate change, as Kristin Laidre, lead author of the study and University of Washington polar scientist pointed out: “They survive in fjords that are sea-ice free more than eight months of the year because they have access to glacier – freshwater – ice on which they can hunt. This habitat, meaning glacier ice, is uncommon in most of the Arctic.”
“Loss of Arctic sea ice is still the primary threat to all polar bears. This study does not change that,” she added.
Beth Shapiro, evolutionary molecular biologist and study co-author explained: “They are living at the edge of what we believe to be physiologically possible. These bears are not thriving. They reproduce more slowly, they’re smaller in size. But, importantly, they are surviving. It’s hard to know yet whether these differences are driven by genetic adaptations or simply by a different response of polar bears to a very different climate and habitat.”
According to the study, the population roams sea ice and glaciers in spring, while the individual bears are able to survive in primarily open water with floating glacial ice pieces in summer. Laidre added: “I do think they can teach us something about where rare, small numbers of polar bears might be able to hang on in an ice-free Arctic.”
While polar bear numbers are on the decline globally due to climate change, the findings offer a small glimmer of hope nevertheless as the region’s conditions are said to be similar to the climatic conditions expected in the northern Arctic at the turn of the century if global warming can’t be stopped.
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Photography courtesy of Unsplash.