Gestural Communication in a Wild Population of Moor Macaques (Macaca maura) in South Sulawesi

Abstract Gestures are one of the key components of primate communication and have been proposed to be important precursors of intentional communication and human language. Understanding how gestural communication varies across primate taxa is therefore important for reconstructing the evolutionary origins of intentional communication and making inferences about its socio-ecological drivers. In this study, we investigated gesture use in moor macaques ( Macaca maura ), a socially tolerant Sulawesi macaque species for which systematic studies of communication remain scarce. We conducted a 5-month observational study of a wild group of 27 individuals, in which we documented the gesture types and modalities (i.e., visual, auditory or tactile) used, the likelihood of accounting for recipients’ attentional states and receiving a response, and the effect of age and context of use on these variables. Moor macaques used a repertoire of 19 gesture types across affiliative, agonistic, play, and sexual contexts, producing gestures predominantly in the visual modality. Age did not significantly predict variation in gesture modality, sensitivity to recipients’ attention, or response probability. Instead, contexts strongly shaped patterns of gestural production. Visual gestures were more likely produced during resting than during activities related to group movement. Moreover, signalers were more likely to account for recipients’ visual attention in affiliative than other contexts, and gestures were more likely to elicit responses during affiliative and agonistic interactions than during sexual ones. These findings suggest that immediate social and ecological contexts may play a central role in shaping gestural production in this species. However, given the relatively limited sample size, these findings should be considered preliminary. Our study expands the comparative database on primate gestural communication and highlights macaques as valuable models for investigating how context might influence communication.