Self-Directed Behaviors Prior to Approaching Conspecifics in Wild Tibetan Macaques (Macaca thibetana)

Abstract

Self-directed behaviors (SDBs) are commonly used as reliable indicators of anxiety, frustration, and stress in nonhuman primates. These behaviors are typically observed in stressful situations, such as being in close proximity to dominants or during post-conflict. However, there is limited evidence on whether individuals increased their SDBs before engaging in potentially risky behaviors. In this study, we used a focal sampling method to record and analyze SDB rates in wild Tibetan macaques (Macaca thibetana) before approaching another group member (as a proxy for potentially risky behavior). Specifically, we examined the 5-min period (selected from focal samplings) before approaching a conspecific to address two main questions: (1) how rank and kinship affect SDB rates before approaching behavior, and (2) when individuals exhibit the highest anxiety, as indicated by peak SDB rates. Our results show that: (1) both males and females exhibited higher rates of SDBs before approaching a higher- than a lower-ranking group member of the same sex; (2) females showed no difference in SDB rates before approaching a female kin (sister or mother/daughter) compared to approaching a non-kin; (3) lower-ranking males exhibited higher SDB rates when approaching a receptive female, but not when approaching a non-receptive female; (4) females showed the highest SDB rates in the last minute (minute 5) before approaching a higher-ranking female. These findings suggest that Tibetan macaques increase their SDBs before engaging in potentially risky behaviors, providing an insight into the psychological state of an individual who is about to engage in a social interaction.