New investigations of the mechanisms involved in kin discrimination showed effects of genetic factors, as well as social environment, on mandrills vocalizations and that mandrills are able to discriminate their (unknown) kin based on their voices alone.
Few words about the kin selection theory …
The theory of kin selection has been proposed in 1964 by William Donald Hamilton to explain altruism or cooperative behavior within animal societies. Indeed, related individuals (sharing high genetic proximity) tend to be more altruist with each other compared to unrelated individuals. Kin selection theory suggests that these behaviors allow to increase inclusive fitness.
Kin selection is possible if mechanisms of kin discrimination have evolved to allow identifying related peers. These mechanisms are, however, still poorly understood. Within the framework of the Mandrillus Project, the possible implication of vocal signatures in phenotype matching processes have been investigated.
Use of vocalizations to discriminate your family's members ?
New results on two captive and a wild mandrill's populations show that the acoustic structure of contact calls is influenced by both genetic similarity between calling individuals and their social experience (familiar individuals share common acoustic features). Moreover, playback experiments showed that actor mandrills respond more intensely to vocalizations from genetically related speakers (their kin), regardless of the familial environment and origins. To conclude, kin-biased behavior observed in these animals are explained by the so-called "phenotype matching" mechanism, using vocal cues.
Levréro F, Carrete-Vega G, Herbert A, Lawabi I, Courtiol A, Willaume E, Kappeler PM, Charpentier MJE. 2015. Social shaping of voices does not impair phenotype matching of kinship in mandrills. Nature Communications 6: 7609. [PDF]