Modeling social styles in macaque societies applied to a semi-free-ranging group of Macaca tonkeana

The covariation hypothesis (Thierry 2004 ) describes conflict management and variations in social structure observed in macaque societies and arranges these species in four dominance styles or grades ranging from egalitarian to despotic. Using an agent-based model (i.e., A-KinGDom), we obtained a set of measurements to quantitatively define the four social styles in captive or semi-free-ranging conditions. Results showed that intensity of aggression was an important parameter involved in the emergence of dominance styles and its level was critical to defining grade 2 (i.e., the second of the two despotic grades described in macaques). In our simulations, grade 2 only appeared using high-intensity aggression values that reflected the phylogenetic origin of despotic grades. Moreover, comparison between simulation results and the data obtained on a semi-free ranging group of Macaca tonkeana (classified as grade 4, or egalitarian) showed the presence of traits close to despotic societies (for example, an increase of gradient of hierarchy or a decrease of reconciliation behaviors). These results both support assigning grade 4 to this macaque species according to its phylogenetic origins and indicate the presence of intra-group variability in semi-free ranging groups of macaques, which in turn yields valuable information of their current social structure and facilitate the handling of these groups. Significance statement We have developed an agent-based model that drives the emergence of social styles in macaque societies. The results of our simulations suggest that social style in macaques is an emergent behavior and that agent-based models are a good tool for exploring emergent behaviors in silico . Moreover, these models can be used to assess hypotheses on social structure in macaque in semi-free-ranging conditions and report useful knowledge about specific techniques for group handling.