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.
So don't give up yet on the powerful polar bear. Without examining the bear in the video-thought to have died-it's impossible to know for sure what ailed that individual, but now scientists have published new findings that shed more light on the risk to the species overall.
"You're talking a pretty wonderful amount of mass to lose", said US Geological Survey wildlife biologist Anthony Pagano, lead author of the study.
That loss of sea ice is a grave problem for polar bears, which rely on the fat-rich seals found in a sea-ice environment.
Of course this presumes that the bears can find the seals in the first place. When a seal surfaces to breathe the bear stands on its hind legs and smacks it on the head with both of its front paws to stun it.
"They need to be catching a lot of seals", Anthony Pagano, a PhD candidate at UC Santa Cruz said. "Every piece of evidence shows that polar bears are dependent on sea ice and if we don't change the trajectory of sea ice decline, polar bears will ultimately disappear".
However, the abundance of sea ice across the Arctic is decreasing at a rate of 14 percent per decade, which is likely reducing polar bears' access to their prey. "And it appears to be related to changes in sea ice that are occurring". Or they stay on land longer, spending the summer and, increasingly, the fall fasting, living off their fat from the seals they caught in the spring.
For his study, Pagano, who is also a wildlife biologist with the U.S. Geological Survey, examined adult female polar bears on sea ice in the Beaufort Sea, off the north coast of Alaska.
As well, the bears were equipped with Global Positioning System collars that also collect video records of activity during daylight.
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. One bear had moved 155 miles away by that time. "This and other studies suggest that polar bears aren't able to meet their bodily demands like they once were". This bear even leapt into the sea in a failed attempt to catch a seal swimming by.
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He says it's become hard to hunt for bears, and when hunters do make it out they see fewer bears while travelling further to try and find them.
But the scientists found the bear's metabolic rate was 1.6 times greater than previously thought - akin to that of other carnivores. The species is categorized as "vulnerable".
Pagano said it would be hard to say how widely these results might apply across the Beaufort Sea.
"Arctic communities are not prepared to deal with such a spill, and when it happens the contaminants will have long-term impacts on important habitat for wildlife, including polar bears, whales and fish", said Paul Crowley, vice president of Arctic conservation for WWF-Canada, in a scorecard that included nation-by-nation evaluations in areas such as management of human and polar bear conflict. Four of these populations are considered to be declining.
The Beaufort Sea has seen dramatic losses in sea ice. Five populations are thought to be stable and there's not enough known about the others to judge.
Retreating ice sheets, a result of climate change, are forcing the bears to travel greater distances to find the food they need.
"Pretty much every component they've found was largely confirmatory in nature", Derocher said. "I've seen a 500-kilogram [1,100-pound] male consume 100 kilograms [200 pounds] of seal in one meal", he said.
During an interview on Sunday, Donald Trump said that "the ice caps were going to melt, they were going to be gone by now, but now they're setting records". Eventually they start losing muscle, hurting their chances of hunting success, which can lead to a downward spiral. But less sea ice means they have to walk or swim more in search of food.
"With the data from this study we can start to quantify what that means for the energy expenditure and how many seals they need to be catching". While the decline has been easy to observe, the causes have been more elusive, given the remote areas the bears inhabit.