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

Abstract

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. 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.