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Polar Bear Secrets: Starvation is Inevitable, Say Experts

Jul 20, 2015 12:31 AM EDT
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Conservationists and wildlife biologists alike are bound to be disappointed. A new study has determined that 'walking hibernation' - a fabled adaptation that could help some bear species survive in unwelcoming environments - just isn't possible for polar bears. As a result, there is even less faith that these critically endangered creatures will ever survive a warming world.

It's no secret that polar bears populations are not in good shape. Thanks to gradually warming seas, the duration of the Arctic sea ice season is growing shorter and shorter, even as the ice continues to thin at worrying rates. Some have even estimated that the flux of the sheet will stop entirely within our lifetime, leaving polar bears with nowhere to hunt.

To make matters worse, environmental pollutants are also wreaking havoc on their reproduction, kicking a declining population when it's down.

In light of this, experts have already estimated that unless polar bears pull off one heck of a hat trick, they will be gone before 2100.

A Polar Bear Pipe Dream

One hope was that a theoretical adaptation called "walking hibernation" - where bear species turn on what can best be described as an 'energy-saving mode' while staying mobile - would allow polar bears to simply move with the retreating ice. (Scroll to read on...)

(Photo : Rune Dietz / Aarhus University)

In a small way, this is already what polar bears are doing, with recent surveys finding that the animals are traveling further than ever before to chase the changing ice seasons and find new food sources. If they could also ensure that only a minimal amount of energy was used when taking up this nomadic lifestyle, it was thought polar bears may be able to persevere.

However, according to a study recently published in the journal Science, walking hibernation just isn't going to happen. After tagging, tracking, and recording the body temperatures of more than two-dozen wild polar bears, researchers found that during long iceless seasons, these animals just starve.

"We found that polar bears appear unable to meaningfully prolong their reliance on stored energy, confirming their vulnerability to lost hunting opportunities on the sea ice," study lead John Whiteman said in a statement. "This suggests that bears are unlikely to avoid deleterious declines in body condition, and ultimately survival, that are expected with continued ice loss and lengthening of the ice-melt period."

Why Polar Bear Popsicles Don't Happen

Still, it's not all bad news. While polar bears might not be the ideal walking nomads that researchers had hoped they were, they are actually surprisingly prepared for long-distance swimming. One consequence of a shorter sea-ice season is that many polar bears become stranded, surrounded by only water after their icy stepping-stones melt away. Bears too far from shore often wind up drowning. (Scroll to read on...)

 

(Photo : Kathy Crane/NOAA)

What's interesting is that few of these drowned bears die from freezing. That may sound a little silly to say. Of course they didn't freeze! They're polar bears. However, even the most well insulated animal can freeze if left in frigid water long enough.

So how are they pulling it off? The researchers found that to protect their body heat, the bears purposely cool their outermost tissues to form an insulating shell - a phenomenon called regional heterothermy.

"This regional heterothermy may represent an adaptation to long-distance swims, although its limits remain unknown," the researchers wrote. One bear, for instance, was able to pull off a stunning 400-mile, 9-day swim. Her cub, however, did not survive the experience.

Now we wait with bated breath to see which of this pair - the stubborn survivor or the mourned cub - the species will inevitably share its fate with.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

 - follow Brian on Twitter @BS_ButNoBS


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