Variation in self-directed behaviors prior to acting offers insights into decision-making and social style in wild Tibetan macaques

An ability to recognize individuals and effectively manage social relationships is critical for species living in a complex social environment. Here, we used a focal sampling method to record and analyze rates of self-directed behavior (hereafter SDB, an indicator of anxiety, frustration, and stress that includes self-scratching) in wild Tibetan macaques (Macaca thibetana) prior to approaching another group member. Our goal was to examine the ability of Tibetan macaques to retain and use information on rank and kinship in social decision-making. Specifically, we examined the five minute period prior to approaching a conspecific in order to determine (1) whether individuals who make a decision to approach a conspecific were characterized by an increase in SDB compared to individuals who did not approach a conspecific; (2) the degree to which rank, sex, and kinship had an effect on making a decision to approach, and (3) whether individuals who waited longer to make a decision to approach were characterized by an increase in SDBs. Our results indicate that: (1) individuals who approached a conspecific were characterized by higher rates of SDBs compared to social settings in which a Tibetan macaque did not approach another group member; (2) prior to approaching a higher-ranking group member of the same sex, both the males and females exhibited higher rates of SDBs than when approaching a lower-ranking group member; (3) Females showed no differences in the rate of SDBs prior to approaching a female close kin (sister or mother/daughter) compared to approaching an unrelated or distantly related female; (4) lower-ranking adult males were found to exhibit higher rates of SDBs before approaching a receptive female than did higher ranking males; (5) adult females did not exhibit increased rates of SDBs during the first four minutes prior to approaching a higher-ranking female regardless of kinship, however, their rate of SDBs did increase significantly in the last minute (minute 5) prior to an approach. These results indicate that the social decision-making in both adult male and female Tibetan macaques is associated with a increase in rates of SDBs. Given differences in patterns of social decision-making it appears that Tibetan macaques have sex-specific social styes, with males exhibiting a moderately despotic social hierarchy and females exhibiting a moderately tolerant social hierarchy.