Polar Bears Don't Slow Down in the Summer: Metabolism Risk in a Warmer Arctic

First Posted: Jul 17, 2015 12:39 PM EDT

Polar bears may be less resilient to ice melt than previously thought. Scientists have found that while polar bears can reduce their energy expenditure a little, it's not enough to make up for current food shortages.

During the summer, ice melts and the hunting territories of polar bears dwindle. This causes the bears to move onto shore, where food is less plentiful. In the past, some scientists have suggested that polar bears forced ashore can compensate by entering a low-energy state called "walking hibernation," which allows them to survive despite the loss of on-ice foraging opportunities caused by climate change.

Scientists decided to see if this was true or not. To evaluate the extent to which polar bears' metabolic rates decline in summer, the researchers used satellite collars and surgically implanted loggers to continuously monitor polar bear's summertime movements and core body temperatures on ice and shore. Bears in both habitats reduce their body temperatures and activity levels below those of bears actively hunting and feeding, but not to levels as low as those observed during energy-saving hibernation.

So what does this mean for the bears? It turns out that the observed declines mirrored those of a fasting animal. This doesn't offer significant energy savings and means that polar bears are, indeed in trouble.

As climate change continues, the habitat and hunting grounds of polar bears are shrinking. With less food available, bears can starve to death, reducing an already dwindling population.

The findings show the importance of taking steps to ensure that the polar bear population remains stable. It seems that even with some reduction in their metabolism, it's simply not enough to cope with shrinking food supplies.

The findings are published in the journal Science.