Who goes there, friend or foe? The hippos knows! Scientists studying hippos at a nature reserve in Africa say the distinctive honks enable the large mammals to tell friend from foe. Professor Nicolas Mathevon, from the University of Saint-Etienne in France said, "In their call, there is information about the identity of the individual -- so they have 'voices' -- and they are able to recognize each other by their voices.” "This recognition ability supports the social relationships between individuals." He also said this knowledge might assist with conservation as wild hippos are sometimes moved from one location to another to keep local populations healthy. Making recordings can allow local hippos to get used to the voice of new ones before they arrive.