Signals use by leaders in Macaca tonkeana and Macaca mulatta: group-mate recruitment and behaviour monitoring
Résumé
Animals living in groups have to make consensus decisions and communicate with each other about the time, or the direction, in which to move. In some species, the process relies on the proposition of a single individual, i.e. a Wrst individual suggests a movement and the other group members decide whether or not to join this individual. In Tonkean (Macaca tonkeana) and rhesus macaques (Macaca mulatta), it has been observed that this Wrst individual displays speciWc signals at departure. In this paper, we aimed to explore the function of such behaviours, i.e. if these behaviours were recruitment signals or only cues about the motivation of the Wrst departed individual. We carried out temporal analyses and studied the latencies of the Wrst departed individual's behaviours and of the joining of other group members. We also assessed whether the social style of a species in terms of dominance and kinship relationships inXuenced the patterns of signal emissions. We then analyzed how the Wrst departed individual decided to make a pause or to stop it according to the identities of group members that joined the collective movement. Results showed that Tonkean macaques and rhesus macaques seemed to use back-glances to monitor the joining of other group members and pauses to recruit such individuals. This was especially the case for highly socially aYliated individuals in Tonkean macaques and kin-related individuals in rhesus macaques. Moreover, back-glances and pauses disappeared when such individuals joined the Wrst departed individual. From these results, we suggested that such behaviour could be considered intentional. Such Wndings could not be highlighted without temporal analyses and accurate observations on primate groups in semi-free ranging conditions.