Study shows polar bear metabolic rates are higher than previously predicted

Study shows polar bear metabolic rates are higher than previously predicted

"This study identifies the mechanisms that are driving those declines by looking at the actual energy needs of polar bears and how often they're able to catch seals", Anthony Pagano of U.S. Geological Survey, now a Ph.D. candidate at University of California, Santa Cruz and first author of the paper, said in a statement Thursday. The team was marked them with Global Positioning System collar to record videos of their movements and hunting style.

The scientists also analysed blood and urine samples taken at the beginning and end of each bear's 8-11 day journey across the ice fields to ascertain the animal's metabolic rate.

The bear videos showed researchers all sorts of usually private aspects of polar bear life, including courtship and hunting.

The metabolic rates of the bears were on average more than 50 per cent higher than previous studies had predicted, according to the findings. However, it seems these savings are small at best. The study reinforces the understanding that polar bears are reliant on a diet of fat-rich seals to survive in the energetically-demanding Arctic.

And the bears' challenge to survive is only likely to increase as sea ice coverage continues to decrease.

Until then experts had assumed that polar bears required less energy because they have no natural predators and their hunting method does not involve a lot of physical exertion: They sit on ice floes and wait for seals to emerge.

Though Pagano's study focuses on just, numerous other populations around the Arctic likely face the same challenges, says Derocher.

This research was a collaborative effort led by the USGS and the University of California, Santa Cruz, with contributions by the San Diego Zoo, the Oregon Zoo, Washington State University and Polar Bears International. But later in the year, after the bears' long summer fast, those young seals are older and wiser, meaning polar bears are not able to catch as many.

"Unfortunately, with the rapid environmental changes occurring in Arctic sea ice, the specialisation that once allowed polar bears to live in this challenging habitat has painted the animals into a physiological corner and led to devastating consequences".

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"They are spending so much energy walking to find their prey that the energy gained once they find a seal is not enough to maintain their weight", Williams said.

Polar bears are the iconic animals of climate change.

USGS researchers' most recent estimate of the polar bear population indicates their numbers have declined by 40% over the past decade, but a common problem for researchers is that it has been hard to study polar bear behavior in these harsh environments, Pagano said in a statement.

"That [number] tells us a lot about modelling into the future what's going to happen with the bears". Last month, a video of a starving polar bear went viral, but it is from a different part of the Arctic and unlikely to be related to global warming, Durner said. "Activity and movement on the sea ice strongly influenced metabolic demands", the researchers summarized in the abstract of their paper.

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

Mr Pagano said the next step was to study what happened to polar bears throughout the year, particularly when the ice breaks up and the bears move further north with the ice.

Professor Whiteman said it was important to understand what happens when the bears are fasting. Five populations are thought to be stable and there's not enough known about the others to judge.

"You're seeing everything it is seeing", Durner said.

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