An already bleak future for polar bears may have just gotten worse. A study published this week in Science found the endangered species may need much more energy to survive than previously believed. Scientific American reports researchers used radio collars and blood samples to track the energy needs and movements of nine female polar bears in the Beaufort Sea off the coast of Alaska last April. They found the bears' metabolic rates were about 60% higher than scientists had previously assumed. During the study, five of the nine bears lost body mass, and four lost at least 10% of their weight over a span of 10 days or so.
The study is bad news as sea ice continues to disappear—in December it was at its second lowest level since 1979, CNN reports. Polar bears rely on seals for their immense caloric needs—the four bears that lost 10% of their weight didn't catch a single seal during the study and relied on scavenging—and sea ice is pretty much a requirement for polar bears to catch seals. As sea ice recedes, bears will have to travel further and expend more energy to catch seals or resort to scavenging calorie-poor foods. That could explain the 40% decline in polar bear population in the southern Beaufort Sea between 2001 and 2010 as noted by an earlier study. And the authors of the current study predict "higher mortality rates" for polar bears as sea ice continues to disappear. (Read more polar bears stories.)