Effects of Group Perturbation on Herd Dynamics in the Domestic Horse (Equus caballus)

Abstract

Animal societies are shaped by interactions between individuals. Understanding animal societies is valuable for understanding the evolution of behavioral strategies and for informing animal management and conservation efforts. Assessing changes in associative and aggressive interactions in response to a change in group composition can help researchers evaluate how well the group is able to respond to change, as well as which individuals have the greatest impact on their society and which are most heavily impacted. Social network analysis is a powerful tool for quantifying social metrics and putting together a coherent understanding of a herd’s dynamics at various points in time. This study investigates individual and group-level responses to group perturbations in a herd of domestic horses (Equus caballus) in order to better understand the roles of dominance and centrality in the resilience of a herd. Resilience, the capacity to respond to new pressures, is important for understanding how animal societies respond to challenges such as environmental change and human interaction. The results show that herd dynamics are context dependent and that an individual’s removal and reintroduction does not necessarily yield the same behavioral consequences upon repeat experimentation. The results do not suggest that the dominance or centrality of the focal individual correlates with a certain set of changes in the herd’s dynamics. Examining changes in association and aggression during the removal phases of the experiments is important for understanding the various mechanisms that drive change during the reintroduction phases. Additionally, the study investigates equine exploratory behavior in the social context. Although there is no clear correlation between social status and curiosity, the results show that horses differ in the frequency, intensity, and type of explorations they perform.