Polar bears are natural loners, but they transform into social, playful creatures when it comes time to find a mate. In this excerpt from the BBC’s ‘Life Story’ series, a male polar bear tracks the scent of a female over several weeks before she engages him in a rigorous test of fitness. The test, it turns out, is all about play – rolling in the snow, clambering up steep, slippery slopes and chasing each other about. When the male tires, the female has a few flirty tricks left to entice him back to his feet.