Polar Bears Are Swimming Themselves To Death As Sea Ice Melts


"Activity and movement on the sea ice strongly influenced metabolic demands", the researchers summarized in the abstract of their paper.

Polar bears are listed by the U.S. government as a threatened species but the Trump administration has reversed measures that tackle climate change, with the president himself seemingly unaware of the situation in the Arctic.

The report, published Thursday in the journal Science, uncovers the physiological factors that have led to observed declines in polar bear populations.

"We've been documenting declines in polar bear survival rates, body condition and population numbers over the past decade", said Anthony Pagano, a PhD candidate at the University of California, Santa Cruz, who led the new study.

When the team recaptured the bears 8 to 11 days later, changes in the ratio of isotopes in their blood gave a measure of metabolic rate. They also used metabolic tracers that helped them determine how much energy the bears were expending.

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. "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".

Polar bears in the wild have substantially higher metabolic rates than previously thought, and melting Arctic sea ice is forcing them to travel much greater distances in an attempt to catch sufficient amounts of prey, researchers have discovered.

Every year in the Beaufort Sea, the sea ice begins to retreat north in July.

Even though the Arctic should be flush with seal pups in the month of April, the researchers found numerous bears were spending more energy chasing down prey than they consumed.

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Most of the time the bears tracked in the study did use the "sit and wait" technique.

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.

The Polar bears are facing a fast-paced decline as they are unable to find enough seals to eat, under the harsh weather conditions.

But as their hunting grounds melt away, their chances of catching the seals they need to sustain themselves, diminish.

During spring, polar bears mostly prey on recently weaned ringed seals, which are easier to catch than adult seals. That helps the bear to gather a lot of fats and help them to survive more a long time without any foods.

"It's thought that bears might catch a couple per month in the fall, compared to five to 10 per month in the spring and early summer", Pagano said.

A study of polar bear metabolism conducted near Alaska's Prudhoe Bay has provided more reason to worry about the future of these massive predators that prowl the Arctic.

The polar bear popular in the Beaufort Sea is estimated to have plummeted by about 40 per cent over the past decade.

Dr Megan Owen, a researcher at the San Diego Zoo Institute for Conservation Research who participated in the study, added: "The rapid pace at which sea ice losses are mounting means that we must work together to develop a science-based understanding how polar bears will be impacted by climate change".

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