Melting Arctic ice is forcing polar bears to take perilous, long distance swims

AS THEIR habitat dwindles, polar bears are undertaking dangerous long-distance journeys, without rest or food.

Melting sea ice is proving to be a challenging environment for polar bears; one which they’re struggling to adapt to. Source: Supplied

POLAR bears are being forced to undertake increasingly dangerous and long-distance swims in order to find food as Arctic sea ice continues to melt.

A study, recently published in the journal Ecography, tracked 100 bears in Hudson Bay and the Beaufort Sea from 2007-2012 in order to observe their migratory response to climate change.

It found the number of bears attempting life-threatening, marathon swims have increased over the past decade.

Nearly 70 per cent of bears swam at least 49km in 2012, a 25 per cent increase on the number of bears who travelled in 2004. One female bear was recorded swimming more than 400km over nine days in 2009. Her cub perished on the journey however she was spared when she found an ice flow large enough to hold her weight in what is becoming an increasingly common phenomenon.

Canadian biologist, and study co-author, Andrew Derocher told Radio Canada International: “Some of our Alaskan colleagues had seen some very unusual swimming events in the polar bears that they were following. They had one bear that swam almost 700km, and during that swim she lost her cub and she lost over 20 per cent of her body weight.”

While polar bears are capable swimmers, the open ocean is not their preferred habitat. What’s more, not all bears are suited to long-distance swims — especially hypothermia-prone cubs.

Derocher explained, “The issue here is if you are a really young bear — like a young cub that’s dependant on its mother in the first couple of years — those bears are not capable of swimming long distances. They cool down, they run out of energy, they just exhaust themselves and they’re more at risk of dying. And of course at the other end of the age spectrum the older bears, the bears of poor condition, are also at risk.”

“This is an animal that’s evolved to walk on sea ice, not swim in the oceans. It’s not like a seal or a walrus or some other species that’s really well designed for swimming permanently,” he said.

A polar bear on ice; its preferred habitat. Picture: iStock.

The Beaufort population of bears in particular have seen a large decline in their numbers; upwards of 50 per cent in the last decade, Derocher estimated.

Melting sea ice has long been thought the culprit. Not only does it prompt long swims, it’s also given rise to new competition.

Killer whales are now taking advantage of the ice-free passage. They’re venturing into the Canadian Arctic in exponential numbers, on the hunt for ringed seals and bearded seals, the favoured prey of polar bears.

And as polar bears’ habitat and food supply disappears, bear-human run-ins have increased. In 2014 Halloween was cancelled in a northern Canadian town due to polar bear numbers.

Derocher said, “The problem for the bears is the rules are changing, and they’re changing very fast.”

This bear was stranded on land, unable to feed on seals, his normal prey, because the sea ice had melted throughout the region as the result of climate change. Picture: Dylan Coker.

A young male polar bear climbs precariously on the face of a cliff above the ocean in northern Novaya Zemlya in the Russian High Arctic, attempting unsuccessfully to eat eggs in the nests of Brünnich’s Guillemots. Picture: Dylan Coker.