New population of polar bears survives on glacier slush instead of sea ice

July 28, 2022

By all accounts, there shouldn’t be polar bears in southeastern Greenland—but apparently no one told the polar bears.

Although excellent swimmers, polar bears are fundamentally land animals that subsist almost entirely on marine life. To accomplish that, the massive creatures make a living as ambush predators, lying in wait next to cracks and holes in the sea ice that seals use to breathe.

But in southeastern Greenland, the sea ice season is less than four months—“too short for polar bears to survive,” says Kristin Laidre, a University of Washington scientist who researches Arctic animal ecology in collaboration with the Greenland Institute of Natural Resources. What, then, explains the presence of bears there?

Research, published today in the journal Science, presents DNA evidence that roughly a few hundred bears in this part of Greenland are different enough from their neighbors to be considered the 20th subpopulation—a group of animals within the same species that are genetically and geographically separated—of the 26,000 polar bears in the world.

Tracking data from satellite radio collars on 27 bears also confirmed that this population survives without sea ice for three months longer than scientists had thought possible.

While their cousins in northeastern Greenland roam an average of six miles a day on sheets of sea ice, the southeasterners stay close to shore in a series of fjords—long, narrow inlets carved by glaciers fed by Greenland’s ice cap. In the summer months, pieces of ice calve into the ocean, creating what scientists call a freshwater glacier mélange, a chunky slush that can pack tightly enough for polar bears to walk—and hunt—on.

Laidre found that some bears stayed in a single fjord or a couple of adjacent fjords for years at a time, occupying a home range of as little as five or six square miles. That’s a postage stamp compared to the home ranges of the northeastern population, where a typical bear traveled more than 900 miles a year across the sea ice.

Source - https://www.nationalgeographic.com/animals/article/why-this-newly-identified-polar-bear-subpopulation-is-so-special