The effects of captive management on primate social behaviour and aggression

Abstract

Given the current rapid rates of extinction and habitat destruction, a growing number of species are reliant on human management for survival, both in and away from their natural habitat. An estimated 60% of all primate species for example, are threatened with extinction, 40% of which are currently held in zoos. For captive conservation efforts to be effective, animal managers must understand basic species biology and behaviour, and how they may be influenced by a captive environment. In this thesis, I address these questions, initially by using phylogenetic comparative methods to understand differences in conflict related behaviour in captive and wild primates, before taking a holistic approach to monitor the behavioural, social, and physiological impacts of management interventions on a captive troop of Sulawesi crested macaques (Macaca nigra). In wild primates, rates of conflict are strongly and positively associated with social density, an effect which is particularly evident among female group members (Chapter Two). Surprisingly, captive primates were found to have significantly lower rates of aggression than those in the wild (Chapter Three), although higher rates of aggression were observed at in groups with high male to female sex ratios. In captivity, contraception is frequently used to manage aggression, although efforts are met with mixed success (Chapter Three). Variable effects may result from differences in products, species, and group management, or may result from behaviours that are learnt over time. Alternatively, as one intact male was more effective at managing group rates of aggression than several castrated males in the Sulawesi crested macaque troop, contraception may interfere with natural mechanisms of conflict intervention (Chapter Four). Social network analysis further suggests that intact males may broker social relationships as grooming associations, particularly those among females, became stronger following the introduction of a single, intact male to the troop (Chapter Five). While social networks would suggest that the troop were minimally affected by the removal of several castrated males and an enclosure move, the responses of adrenal 'stress' hormone monitoring and activity budgets would suggest otherwise (Chapter Six). Following the removal of the males, the macaques increased rates of behaviours traditionally associated with stress, such as huddling and grooming and had consistent, group-wide shifts in stress hormones. Given the variation in behavioural, endocrine, and social responses to perturbation however, this thesis highlights that captive management significantly influences the behaviour and physiology of captive animals, and that multiple tools are required to garner a comprehensive overview of animal responses to change. A key aspect for future research is understanding whether these responses have biologically relevant effects on individual fitness.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Susanne Shultz (Supervisor) & Keith Jensen (Supervisor)