No bears. He spots a tuft of white fur snagged on an alder branch. "They're around here, for sure," he says. He points to the chewed bark. "They like to stand and bite the tree just to say to ...

(Courtesy: Jenny E Ross) In the teeth of the Arctic winter, polar-bear fur always remains free of ice – but how? Researchers in Ireland and Norway say they now have the answer, and it could have ...