English zoologist Rory Wilson is renowned for developing ingenious ways to track wild animals and record their behaviour without directly observing them. His latest invention, a lightweight electronic logger, can go where satellite-based tracking devices cannot, to observe free-living animals. Rory’s new logger harnesses the laws of physics to accurately estimate the energy expenditure of animals on land, at sea and in the air, and is set to revolutionize research into the behaviour of threatened species, and obtain precious data to help save them and their habitats.