Chelsea Harvey
under the Endangered Species Act.
Scientists worry that their populations will suffer worse declines in the future as sea ice continues to melt.
Having more information about the bears’ activity can help scientists develop more accurate models about how they will withstand food deprivation and what will happen to their populations, says Whiteman, the lead author. When producing these models, scientists now know to plug in a normal metabolic rate for the bears rather than assuming they may go into walking hibernation.
It’s worth noting that while polar bears didn’t show any signs of walking hibernation, the study did produce evidence for another kind of special adaptation that may help bears survive under stressful conditions.
The data suggests that when bears swim in the Arctic water for extended periods of time — longer than a few minutes, according to Ben- David — they can cool down the outer parts of their body cores so less body heat is lost to the frigid water.
“This is an exciting new finding and something we didn’t know about the bears,” Whiteman says. And it may be increasingly useful in the future when retreating sea ice forces bears to swim for longer periods of time to get between the ice and the shore.
But it’s not to say they can swim forever. One of the bears being tracked swam for nine days and amazingly survived the journey, but lost nearly a quarter of her body mass by the time she came out of the water.
When it’s all said and done, the results of the study confirm that polar bears aren’t superheroes — they’re susceptible to the same kinds of stresses, including food stress, that other animals are.
But while the paper gives us some deeper insights into the bears’ physiological responses to tough times, Whiteman cautions that there’s still a lot left to learn.
“We’re not looking at any quantitative predictions for what will happen to the bears in the future in terms of climate change,” he says. “There still are some fundamental aspects of polar bear biology that we have yet to understand.”