Gestural Sequences in Wild Spider Monkeys (Ateles geoffroyi)

To date, research on gestural communication in species other than great apes has been quite limited, especially in their natural habitat, although including a broader range of species in different settings is essential for identifying evolutionary patterns and determining whether some of the fundamental characteristics of human communication are widely shared across primates. In this study, we specifically aimed to explore the use of gestural sequences in Geoffroy's spider monkeys (Ateles geoffroyi), a species for which research on gestural communication remains scarce. To this end, we conducted behavioral observations, recording focal video samples of a wild group of 54 individuals. From the videos, we coded all gestures (N = 709), of which 182 occurred alone and 527 occurred within 125 sequences, which mostly consisted of 2-4 successive gestures. The odds of producing gestural sequences rather than single gestures were higher in the contexts of play, aggression and sexual behavior. In contrast, there was no significant effect of signaler's sex and age on the odds of producing a gestural sequence rather than a single gesture. Only three sequences (i.e., embrace-pectoral sniff, push-present climb, grab-grab pull) occurred more than twice and were not mere repetitions of the same gesture type. Our results show that gestural sequences are used by platyrrhines in several different contexts, although more studies are needed to understand their function.