Gestural communication in wild spider monkeys (Ateles geoffroyi)

Gestures play a central role in the communication systems of several species, including primates. In this study, we provide a first assessment of the gestural systems of a Platyrrhine species, Geoffroy’s spider monkeys ( Ateles geoffroyi ). We observed a wild group of 52 spider monkeys, and assessed the distribution of visual and tactile gestures in the group, the size of individual repertoires, and the intentionality and effectiveness of individuals’ gestural production. Our results showed that younger spider monkeys were more likely than older ones to use tactile gestures, despite no inter-individual differences in the distribution of visual gestures. Repertoire size did not vary with age, whereas the probability of accounting for recipients’ attentional state was higher for older monkeys than for younger ones, especially for gestures in the visual modality. Using vocalizations right before the gesture increased the probability of gesturing toward attentive recipients and of receiving a response, although age had no effect on the probability of gestures being responded. Overall, our study provides first evidence of complex gestural communication in a Platyrrhine species, and confirms this taxon as a valid candidate for research on animal communication.