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.
For this study, the scientists put trackers on nine female polar bears in the Beaufort Sea region.
When the team recaptured the bears 8 to 11 days later, changes in the ratio of isotopes in their blood gave a measure of metabolic rate.
In an average, the metabolic rates of the monitored polar bears were over 50 percent higher than previously predicted by other studies. At the same time, five of the bears in the study were not able to catch enough seals to supply their energy needs. In fact, four of them lost at least 10 percent of their weight in the span of about 10 days.
HEART-WRENCHING VIDEO: STARVING POLAR BEAR ON ICELESS LAND This video, published in December, ignited debate about what's happening to the world's polar bears. A new study shows some polar bears in the Arctic are shedding pounds during the time they are supposed to be beefing up.
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Unfortunately, with the rapid environmental changes occurring in Arctic sea ice, the specialisation that once allowed polar bears to live in this challenging habitat has painted the animals into a physiological corner and led to devastating consequences."This and other studies suggest that polar bears aren't able to meet their bodily demands like they once were".
A polar bear rests on a chunk of sea ice in the Arctic. They were living on the sea ice of the Beaufort Sea, off the northern coast of Alaska. These large changes in body mass over such a short period of time were striking demonstrations of how heavily polar bears rely on an energy-dense diet of seal blubber.
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.
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The researchers hypothesize that the bears' lazy hunting style - when it works - allows them to conserve energy, helping them survive through the summer months when food is scarce. These trackers included accelerometers and GPS-equipped video cameras to document the bears' activities. "They need to be catching a lot of seals", he said. In contrast, the four bears that actually caught and ate ringed seals gained nearly 10 percent of their body mass.
In this April 15, 2015 photo provided by the United States Geological Survey, a polar bear wearing a Global Positioning System video-camera collar lies on a chunk of sea ice in the Beaufort Sea.
Lead scientist, Anthony Pagano, does note that the findings of the Beaufort Sea shouldn't necessarily be expanded to the other 18 circumpolar populations of bears where he says, conditions can differ for each group.
The video collar data was essential for monitoring the bears' hunting behavior and foraging success.
"To us, it really stressed the feast-or-famine lifestyle that these bears have", Pagano said.
Although it's just a 10-day snapshot, the study confirms that polar bears aren't made for walking, said Andrew Derocher, Canada's leading polar bear expert and a professor at the University of Alberta. During that time the bear crossed into Canada, having walked almost 270 miles (430 kilometers) since her collar had been applied.
While the recent study might be bad news, it doesn't automatically mean the end for polar bears, comments Jörns Fickel, a evolution geneticist at the Leibniz institute for Zoo and Wildlife Research in Berlin.