Polar Bears Suffering From 'High-Energy, High-Fat Lifestyle' Amid Changing Climate

Posted February 02, 2018

"(The camera) gave a perspective right underneath the bear's chin". 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.

Anthony Pagano, a research wildlife biologist with the U.S. Geological Survey and the lead author of the study, says this is the first time a group of polar bears has been studied this intensely.

Polar bears rely nearly exclusively on a calorie-loaded diet of seals. 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.

"We found that they were really dependent on their ability to catch seals", Mr. Pagano said.

While those Arctic ocean bears need ice in order to hunt for food during the spring, global warming is dwindling the blanket of ice across the locale.

Receding sea ice only threatens to compound the problem as polar bears move northward over deeper water that's less conducive to hunting seal.

The ice cover in the Arctic grows in the winter and melts in the summer. "And it appears to be related to changes in sea ice that are occurring". By fall, however, young seals are older and wiser, and the bears can not catch as many of them.

They collared nine adult female polar bears on the sea ice of the Beaufort Sea in Alaska with a Global Positioning System video camera and observed the bears for discreet time periods over three consecutive years.

They attached high-tech collars to the bears to record their activity and captured them twice in 11 days to test their blood and urine. One bear had moved 155 miles away by that time.

It turns out in the extreme conditions of their Arctic home, polar bears have a "high-energy, high-fat lifestyle" to survive.

Previous studies estimate the mortality of male polar bears would increase from 6 per cent to 48 per cent if fasting periods increased from 120 days to 180 days.

Four other bears lost up to 10 percent of their body mass over the same period, the result of not catching seals.

According to recent measurements, the extent of Arctic sea ice is decreasing at a rate of about 14 percent in every 10 years, which can significantly reduce polar bears' access to seals. This bear even leapt into the sea in a failed attempt to catch a seal swimming by.

"I hope we will have an awakening, but we haven't really done much to save polar bears over the past decade", said Amstrup.

"As sea ice becomes increasingly short-lived annually, polar bears are likely to experience increasingly stressful conditions and higher mortality rates", lead author Anthony Pagano said. That's despite the study taking place during the time when bears normally have their most successful hunting. And yet they are uniquely vulnerable in their nearly total reliance on one prey species.

Pagano said it would be hard to say how widely these results might apply across the Beaufort Sea.

Researchers have been studying bears in the Beaufort Sea since the 1980s and studies have shown the population there has decreased by some 40 percent during the last decade.

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". Five populations are thought to be stable and there's not enough known about the others to judge.

In other areas, like the Hudson Bay in northeastern Canada, most polar bears travel onto land when the sea ice retreats.

Andrew Derocher, a polar bear biologist at the University of Alberta, warned that there is wide variability between bears and different times of year.

"Pretty much every component they've found was largely confirmatory in nature", Derocher said. In addition, five of the nine bears in the study lost their body mass, suggesting that they were unable to catch enough fat-rich mammal prey to meet their energy demands. Eventually they start losing muscle, hurting their chances of hunting success, which can lead to a downward spiral. "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".