Individual recognition in a wild cooperative mammal using contact calls

Many of the mechanisms advanced to explain the evolution of intraspecific cooperative behaviour, such as reciprocity or social prestige, hinge on an animalʹs ability to recognize individual group members. However, ‘true’ individual recognition, between adult group members, has never been demonstrated in a cooperatively breeding bird or mammal species. We tested whether a wild cooperative mammal, the dwarf mongoose, Helogale parvula, could recognize individual group members from their vocalizations. We provided test subjects with a large, desirable food item and then simulated the approach of another group member using playbacks of its contact calls. Mongooses were more vigilant after hearing the calls of individuals of higher rank than themselves (that could steal their food) compared with individuals of lower rank than themselves (that could not). We showed that the mongooses were not simply responding to age-related cues that conveyed potential information on rank, and provide some evidence that they were associating the unique characteristics of the call with an individually specific characteristic of the caller (i.e. its relative rank). We conclude that dwarf mongooses exhibit ‘true’ individual recognition, and this finding supports the potential validity of mechanisms that rely on individuals monitoring the behaviour of others to explain the evolution of cooperative behaviour.