Behaviour: mammalsWinner: Practice run by Grégoire Bouguereau (France) When a female cheetah caught but didn't kill a Thomson's gazelle calf and waited for her cubs to join her, Gregoire guessed what was about to happen. He'd spent nearly a decade studying and photographing cheetahs in the Serengeti National Park, Tanzania, and he knew that the female s behaviour meant one thing: a hunting lesson was due to begin. The female moved away, leaving the calf lying on the ground near her cubs. At first, the cubs took no notice of it. But when it struggled jerkily to its feet the cubs natural predatory instincts were triggered, says Gregoire. Each cub gaze locked on to the calf as it made a break for freedom. The lesson repeated itself several times, with the cubs ignoring the calf when it was on the ground and catching it whenever it tried to escape an exercise that affords the cubs the chance to practise chases in preparation for when they will have to do so for real Photograph: Gregoire Bouguereau/2012 Veolia Environnement Wildlife Photographer of the Year