Dominance hierarchy and social network in a captive group of white-lipped peccary males: what happens after the alpha male leaves?

Abstract

Dominance hierarchies are typically stable, with dominants occupying central positions in social interaction networks. However, system perturbations, such as the removal of individuals, may cause instability, which varies according to the group’s resilience. If the hierarchy undergoes a restructuring, this can occur through a dynamic process of self-organization (Social Dynamics hypothesis) or through the influence of individuals’ attributes (Previous Attributes hypothesis). We analyzed the resilience of the white-lipped peccary hierarchy after the alpha’s death and observed how the rise of a new dominant occurred. Additionally, we evaluated the validity of these two hypotheses in the restructuring of the system. We observed the group of white-lipped peccary males of the Municipal Zoo of Curitiba, PR, Brazil, from May to October 2018. We recorded and analyzed the agonistic and affiliative interactions, and we collected data from the attributes: weight, testicle size, testosterone serum and age, before and after the dominant’s death (August). Due to this perturbation, the hierarchy started to show instability, but proved to be resilient. There was an increase in agonism and more than one individual pleading for the new dominant position, which was occupied by a subordinate male. Affiliative interactions were also important in the rise of the new alpha. The hierarchy was well ordered by the social dynamics among individuals, but weight and testicular volume were also correlated with the status of the individuals before, and with the serum testosterone after the alpha’s death. Thus, both hypotheses affected the restructuring of this system.