Researchers have found out that polar bears have higher metabolisms than previously thought and are having trouble eating enough food to keep up their weight in the wild. Using GPS-enabled collars affixed with videocameras, researchers watched 9 female polar bears living in the Beaufort Sea forage for food during 3 spring seasons. They also captured the bears to take blood and other samples at the beginning and end of the study. With these data in hand, they measured how fast the large carnivores burn calories and found polar bears need to eat more than 12,000 calories per day minimum. That means they have to eat at least 1 adult ringed seal or the equivalent of nearly 220 Big Macs every 10-12 days. Bears that killed and ate ringed seals during the 8-11 day observation periods, gained or maintained weight, but more than half the bears lost weight and four lost at least 10% of their body weight. It turns out polar bears use a lot of energy when they walk, more than similarly-sized animals. What’s more, the bears they tracked walked a fair amount more than a quarter of the time. This is bad news for these bears. As sea ice continues to collapse, energy demands may outstrip the bears’ ability to find food and ultimately lead to their demise.