A polar bear plunges into the icy Arctic waters in search of firmer ice; its world, which was once a sea of white, is melting beneath its paws. ‘Research has documented declines in polar bear populations in some regions of the Arctic’, says Anthony Pagano from the US Geological Survey, explaining that the bears now have to roam further on the receding ice to locate the seals upon which they dine. And, to make their predicament worse, measurements in the 1970s and 1980s suggested that polar bears consume more energy than other similarly sized animals because they have to generate heat to remain warm in the frigid environment and walk long distances to catch food. Knowing how much energy polar bears use just to remain alive is essential if we are to understand how the animals will survive in their dwindling environment, so Pagano and colleague Terrie Williams from the University of California, Santa Cruz, embarked on an ambitious programme of measuring how much energy polar and grizzly bears consume as they amble along. The scientists publish their discovery that polar bears and grizzly bears walk efficiently, consuming the same amount of energy while walking as other large animals, in Journal of Experimental Biology.