There are many theories why animals play but none have jet been proven. During observation on Canids, play seems to be important when they learn to control the intensity of the bite and to facilitate the social structure within a group. When dogs play they perform behaviours that otherwise are used during hunting, reproduction and aggression that in another context would be for example hostile. The dog is one of the species that we humans have domesticated and they have been exposed to an intense and concentrated breeding so they can function in different areas, for example herding and hunting. This breeding has resulted in that the pure bred dogs can be very different between the breeds.