How one group of polar predators is bearing up nicely in the face of climate change

The polar bears were found to be physically and genetically distinct from other species, which researchers believe is because they are hemmed in by mountains, the Denmark Strait, the East Greenland coastal current and the Greenland Ice Sheet.

Body measurements suggest that adult females are smaller than in most regions. They also have fewer cubs, which may reflect the challenge of finding mates in the remote landscape of fjords and mountains.

Unlike other polar bears, the community also prefers to stay in one place, rather than venturing far over sea-ice to hunt. Satellite tracking showed that when 27 bears accidentally floated 120 miles on ice floes caught in a coastal current, they swam to land and walked back home.

“They are the most genetically isolated population of polar bears anywhere on the planet,” said co-author Professor Beth Shapiro, of the University of California, Santa Cruz and investigator at the Howard Hughes Medical Institute.

“We know that this population has been living separately from other polar bear populations for at least several hundred years, and that their population size throughout this time has remained small.”

‘A steady supply of ice’

The landscape means that the south-east Greenland bears have access to sea ice for only four months, between February and late May, but for the remaining two-thirds of the year, they hunt seals from chunks of freshwater ice breaking off the Greenland Ice Sheet.

But researchers say the fact that bears can survive suggests that marine-terminating glaciers, and especially those regularly calving ice into the ocean, could become climate sanctuaries as ocean ice melts.

“Even with rapid changes happening on the ice sheet, this area in Greenland has the potential to continue to produce glacial ice, with a coast that may look similar to today, for a long time,” said co-author Twila Moon, deputy lead scientist at the US National Snow and Ice Data Center.

“These types of glaciers do exist in other places in the Arctic, but the combination of the fjord shapes, the high production of glacier ice and the very big reservoir of ice that is available from the Greenland Ice Sheet is what currently provides a steady supply of glacier ice.”

A separate study by the University of California found that 10 per cent of brown bear DNA comes from polar bears, with researchers suggesting that the breeds may start mating again if climate change pushes their habitats closer together.

The findings were published in the journal Science.


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