Ever wondered why dogs roll on their backs, or sniff each other's behinds? These behaviours help teach dogs the social rules of interacting with other dogs, as well as helping them play! Subscribe: bit.ly/BBCEarthSub #Dogs #BBCEarth #PetsWildAtHeart Watch more: Planet Earth bit.ly/PlanetEarthPlaylist Blue Planet bit.ly/BluePlanetPlaylist Planet Earth II bit.ly/PlanetEarthIIPlaylist Planet Dinosaur bit.ly/PlanetDinoPlaylist Pets: Wild At Heart We may think of our pets like another member of the family - but they exist in a secret world that we would hardly recognise. In this series new filming techniques reveal our pets' wild behaviour and natural abilities. Using the latest filming techniques, from spycams to thermal imaging and moving x-rays, this series reveals why just a small select group of animals have the perfect characteristics to become human companions. The first episode shows how our pets use play to get in touch with their wild sid...