Polar bears might be worse off than we thought, study finds

Polar bears might be worse off than we thought, study finds

Polar bears are starving during their prime hunting period as Arctic ice melts because of climate change, according to a United States study published Thursday that analysed the animals' metabolism for the first time.

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To analyze these circumstances, Pagano and his team monitored the hunting success, behavior and metabolic rates - the amount of energy used by an animal per unit of time - of nine female bears without cubs as they hunted for prey in the Beaufort Sea in the spring.

It all comes down to metabolism, the rate at which the bears use energy, according to Anthony Pagano, a PhD candidate at U.C. Santa Cruz and lead author of the study.

While scientists were quick to caution that the causes of the animal's condition remain unknown-disease, injury or any number of other factors could potentially have spelled its demise-experts are anxious that starving polar bears may soon become a more common sight as the sea ice they rely on for hunting grounds continues to melt away.

The Beaufort Sea has seen dramatic losses in sea ice. It takes a great deal of calories to sustain that mass and move it around in some of the harshest conditions on the planet and the bears rely on a fat-rich diet of seals to get them through long fasting periods.

As a scientist, he stresses that we shouldn't go off of gut feelings, but rather reliable data - "and for polar bears, those (data) aren't there yet".

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How many seals does a polar bear need to eat to maintain a healthy weight? They also injected the bears with water labelled with stable isotopes of hydrogen and oxygen. By fall, however, young seals are older and wiser, and the bears can not catch as many of them. Bears are also doing a lot more swimming as the sea ice declines, said Derocher.

The problem is that many polar bears can't seem to find enough food to satisfy their high energy requirements.

And they should lobby the global community more to address greenhouse gas emissions, which threaten the polar bears' habitat. However, human-induced climate change reductions in sea ice have caused declines in the number of bears, with young polar bears having a higher mortality rate than adults.

Polar bears are listed as threatened under the US Endangered Species Act and as vulnerable by the International Union for the Conservation of Nature - a designation just short of endangered on both lists. "It shows that polar bears are more like the big cats-lions and tigers- predatory carnivores with high energy metabolisms", Amstrup said. The agency's most recent population estimate suggests the bears have declined by about 40 percent over the past decade.

Researchers at the U.S. Geological Survey have been studying polar bears around the Beaufort Sea since the 1980s. "Activity and movement on the sea ice strongly influenced metabolic demands", the researchers summarized in the abstract of their paper.

"Just to break even they have to capture at least one seal every five to 10 days - and that's just to break even", said study co-author George Durner, a USGS research zoologist. There, Arctic warming means the sea ice is breaking up earlier in the summer and returning later in the fall, forcing bears to spend more time on land.

However, it has been hard for scientists to analyze the behavior and fundamental biology of the bears in this harsh and remote environment, according to Pagano. Today, it is estimated that there are approximately 23,000 polar bears living throughout the Arctic.

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