Climate change diet: As Arctic sea ice thins, so do polar bears

Brandon Parsons
February 2, 2018

Researchers discovered the polar bears have a higher metabolic rate than previously assumed - up to 1.6 times higher - meaning the animals require up to 1.6 times the food energy than previously understood, just to maintain body weight.

One bear lost close to 44 pounds, including her lean muscle, in 10 days.

The problem is that many polar bears can't seem to find enough food to satisfy their high energy requirements. Using collars equipped with video cameras and other high-tech instruments, Pagano was able to monitor the bears over an 8- to 11-day period in the spring, when the bears hunt most actively.

"We've been documenting declines in polar bear survival rates, body condition, and population numbers over the past decade". But the new information on how dwindling sea ice affects the health of female polar bears could be important for conservation efforts.

"This study is a lovely example of how animals are built to live in synchrony with their environment".

It doesn't help that the loss of sea ice means that polar bears have to work harder to stay where the food is, Whiteman pointed out.

The sea ice is "not like it used to be", he said, adding he's observed fewer polar bears in the region and has to travel further to find them.

Five of the nine bears studied lost body mass, indicating they were unable to catch enough prey to meet their energy demands. "Eventually, you run out of gas".

Blaine Griffen, a Brigham Young University biology professor who wasn't part of the study, praised the USGS work, noting that past studies have looked at resting polar bears and polar bears on treadmills in the lab.

The findings, described in the journal Science, reveal alarming facts about the polar bear's unsustainable physiology in the face of ongoing climate change.

If you've ever wondered what it's like to be a polar bear rambling about the freezing areas near the arctic circle, now you can - thanks to this fantastic video captured on a point-of-view camera.

Scientists once thought that polar bears should be able to reduce their metabolic rates when there's not much food available. Global Positioning System video-camera collars were applied to solitary adult female polar bears for 8 to 12 days in April, 2014-2016.

"It's an issue of how much fat they can put on before the ice starts to break up, and then how much energy are they having to expend", Pagano said.

Anthony Pagano, USGS Research Wildlife Biologist, said: 'It's really quite fascinating to learn the basic behaviours of these animals and how they're using the sea-ice environment, and how dynamic the sea-ice environment is and how their behaviour might change from year to year based on the sea ice conditions that they're experiencing'.

In the Beaufort Sea, for example, the polar bears are forced to move much greater distances than they previously did as the Arctic warms and more sea ice melts.

But the report does conclude with one seemingly inescapable conclusion for polar bears facing the same situation as those studied.

Pagano said the working assumption is that as the ice recedes and the bears move further North following receding ice, they will move over deep water that is less conducive to seal hunting.

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.

They have evolved to hunt seals from atop sea ice and it's the only way they can satisfy their massive caloric needs.

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".

The loss of sea ice has a domino effect on the species, which, in 2008, became the first animal listed under the Endangered Species Act due to threats from climate change.

Every year in the Beaufort Sea, the sea ice begins to retreat north in July. There, Arctic warming causes sea ice to break up earlier in the summer and return later in the fall, which forces the bears to spend more time on land.

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