A new study finds polar bears in the wild have higher metabolic rates than previously thought, and as climate change alters their environment a growing number of bears are unable to catch enough prey to meet their energy needs.
In December previous year, a video of a dying polar bear rummaging in trash and eating styrofoam, assumed to be starving, went viral on social media.
Biologists at the University of California, Santa Cruz, monitored the behaviour, hunting success and metabolic rates of adult female polar bears without cubs as they hunted for prey on the sea ice of the Beaufort Sea, in the Arctic Ocean, in the spring.
The researchers attached high-tech collars to the bears to record locations, video and activity levels over a span of 8 to 11 days.
But the scientists found the bear's metabolic rate was 1.6 times greater than previously thought - akin to that of other carnivores. Despite what you may have heard, the sea ice that makes up their hunting grounds has been diminishing by about 14 percent a decade, and the ice that does form freezes later and melts earlier. They're not efficient walkers, but thanks to their high-energy diet of seals they can roam an area as large as 95,000 square miles, Derocher said in an interview. 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.
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". This causes them to expend more energy during the summer, when they are fasting until the ice returns to the continental shelf in the fall.
"In the Beaufort Sea we are seeing that the ice is retreating much further to the north than it had historically", Mr Pagano said.
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Although capable of swimming long distances, polar bears burn far more energy doing so than walking, a recent study published in Polar Biology found.
Bears can lose weight fast but also gain it back quickly if they can catch seals. As sea ice continues to decline, frequent and timely monitoring of polar-bear subpopulations across Canada will be necessary to ensure co-management boards can make informed decisions.
Experts estimate the total polar bear population at between 22,000 and 31,000.
Polar bears are listed as Vulnerable on the International Union for Conservation of Nature's (IUCN) Red List of Endangered Species and listed as threatened by the US Endangered Species Act.
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.
The study found that for one polar bear to sustain its energy level it would require an intake of 12,325 calories a day, usually one adult ringed seal every 10 days. "Activity and movement on the sea ice strongly influenced metabolic demands", the researchers summarized in the abstract of their paper.
Best estimates say there are 20,000 to 30,000 polar bears in 19 different groups or populations scattered across the top of the U.S., Canada, Greenland, Norway, and Russian Federation. Even though the findings are based on only a few female polar bears, the result will be same for the polar bears of other areas.