Play behaviors and signals during playful interactions with juvenile conspecifics are important for both the social and cognitive development of young animals. The social organization of a species can also influence juvenile social play. We examined the relationships among play behaviors, candidate play signals, and play bout termination in Tibetan macaques (Macaca thibetana) during juvenile and infant social play to characterize the species play style. As Tibetan macaques are despotic and live in groups with strict linear dominance hierarchies and infrequent reconciliation, we predicted that play would be at risk of misinterpretation by both the individuals engaged in the play bout and by those watching, possibly leading to injury of the players. Animals living in such societies might need to frequently and clearly signal playful intent to play partners and other group members to avoid aggressive outcomes. We gathered video data on 21 individually-identified juvenile and infant macaques (one month to five years of age) from the Valley of the Wild Monkeys, Mt. Huangshan, China. We used all-occurrence sampling to record play behaviors and candidate play signals based on an ethogram. We predicted that play groups would use multiple candidate play signals in a variety of contexts and in association with the number of audience members in proximity to the players and play bout length. In the 283 playful interactions we scored, juvenile and infant macaques used multiple body and facial candidate play signals. Our data showed that juvenile and infant Tibetan macaques use a versatile repertoire of play behaviors and signals to sustain play.

Social play in animals has long intrigued ethologists, and current research in this field, especially pertaining to primates, has revealed that the behavioral lives of juveniles in particular are rich and behaviorally and socially complex. It is widely acknowledged that play contributes to the biological, social, and cognitive growth of juveniles, but the impact of this growth on fitness, future adult social relationships, or general social group experiences remains unknown. Comparative social play research can enhance our understanding of how play influences these variables critical to juvenile development and fitness. Comparisons across taxa with varying social organizations, e.g., Macaca spp., can further this understanding. In this chapter, we introduce the 2017 social play network of Yulingkeng A1 infant and juvenile Tibetan macaques (Macaca thibetana) and discuss how social play is organized in this species.