Social bonding in horses : linking physiology, behaviour & reproductive success.
Thesis DisciplineBiological Sciences
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Social bonding, reproductive success and communication are important for social mammals, and enhance the multiple benefits of forming social groups. Usually social bonds are seen between close relatives but in some species, like equids, strong bonds form between un-related individuals. The adaptive value of social bonding has been shown in many species such as primates, elephants and wild horses but the proximate mechanisms which drive and maintain social groups are poorly understood, particularly in non-kin social relationships. Oxytocin is implicated as a hormonal link in social relationships and can have a physiological calming mechanism on mammals, but few studies have experimentally tested its role in the development of social bonds. I address this shortcoming in a highly social mammal, the horse. This thesis experimentally tests whether intra-nasal oxytocin mediates social bonding in a population of domestic horses, both in terms of dyadic horsehorse relationships, and horse-human relationships. Results indicate that oxytocin changes a suite of affiliative and aggressive behaviours, and induces a physiological calming mechanism. I also test if social relationships generally benefit unrelated individuals in social groups in a wild population of horses, and show that the strength of social bonding between one preferred partner is more important for wild horse reproductive success than having multiple bonds. I discuss the implications of this work for understanding social bonding in wild and domestic mammals in terms of both evolutionary advantages and the underlying proximate mechanisms that drive these interactions in individuals.