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Polar bears going hungry

Researchers have attached tiny cameras to polar bears for a bear's-eye view of them hunting on the sea ice, one of a suite of high-tech tools providing what could be the closest look yet at how the iconic animals are coping with a rapidly changing Arctic.

"This study was designed trying to get a much more detailed understanding of what the bears were actually doing on the ice," said researcher Anthony Pagano of the University of California in Santa Cruz.

He and his colleagues studied nine bears in the Beaufort Sea over the course of about a week during three successive Aprils from 2014 to 2016. They equipped the bears with GPS-enabled video cameras as well as with instruments to measure the speed and distance they travelled, how quickly they burned energy and how much time they spent in the water.

One big conclusion is that polar bears need a lot more food than previously thought. Scientists have believed that because bears hunt mostly by waiting for a seal to pop through a blowhole, they don't use much energy. Others theorized the bears were able to lower their metabolism during those waits.

Wrong, said Pagano. His study concludes bear metabolism is about 60 per cent higher than previous estimates, meaning the animals need to eat that many more seals to maintain weight.

The cameras recorded footage of bears catching seals and hauling them out of the ice, as well as of bears wrestling with large seals in frigid waters.

"It was quite fascinating and really exciting to watch," said Pagano.

Ominously, he found that five of his nine bears lost weight during the study, up to 10 per cent of their body mass. That's despite the study taking place during the time when bears normally have their most successful hunting.

The Beaufort Sea has seen dramatic losses in sea ice. Its population of polar bears is known to be in decline.

Pagano cautions the conclusions of his study are tempered by its small sample size and limited time span.

Andrew Derocher, a polar bear biologist at the University of Alberta, warned that there is wide variability between bears and different times of year.

Still, he said, the study backs up others looking at how polar bears are coping with shrinking sea ice, their favourite hunting platform.



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