The dynamics of dominance in a ‘despotic’ society

Abstract

Dominance hierarchies are a key feature in the dynamics of animal social groups, playing a crucial role in fostering group stability. Despite often being viewed as static, persistent linear structures, hierarchies are fundamentally dynamic and can change over time due to ecological conditions, demographic changes and ontogenetic development. There are numerous methods used to construct hierarchies and quantify individual dominance rank, but methods to capture the dynamics of a hierarchy across time have only recently been developed. As such, relatively little is known about the longitudinal hierarchy dynamics in many social species, including nonhuman primates, and the timescale at which these hierarchy dynamics play out. Here we consider the longitudinal hierarchy dynamics across a 4-year period in a large group of rhesus macaques, Macaca mulatta. We investigated group and individual level predictors of active rank dynamics, or dynamics that arise from rank reversals. We found that, despite rhesus macaques being considered to have relatively stable hierarchies, there was significant active rank mobility in both males and females, even in the face of limited resource competition. Female rank change was not solely driven by matrilineal structure or demographic processes as females also opportunistically ascended in rank. Furthermore, we found strong links between rank certainty and hierarchy dynamics with periods of high hierarchy instability associated with low mean dominance certainty. Lastly, we found limited evidence of associations between periods of high active rank dynamics and social global network structure. This suggests more localized dynamics during hierarchy instability are at play rather than widescale network reorganization. Together, these results stress the importance of considering social context in rank dynamics, illustrate the dynamic nature of macaque dominance rank and further highlight the opportunistic nature of the species.