The Eastern grey kangaroo in coastal NSW: reproduction, genetics and behaviour

The environment an animal inhabits directs the inheritance of traits that improve fitness, with genes that aid survival being selected for each generation. Furthermore, sexual selection plays a role directing the inheritance of traits that enhance individual reproduction. As such, the presence of particular traits exhibited by animals within different environments can provide insights into species or population level social and mating systems. The overall aim of this thesis was to examine long-standing evolutionary assumptions surrounding reproductive ecology, and male life history, in the Eastern grey kangaroo (Macropus giganteus). Specifically, the impacts of genetic relatedness on social and behavioural aspects of free ranging kangaroos, as well as the influence of sexually selected traits on male reproductive success, were investigated. Initial investigations identified correlations among genetic relatedness, social affiliation and geographic home range. Females were found to be more related to one-another than males were, males exhibited larger home range overlap and more social affinity than females, and socially affiliated males and females were more related than expected by chance. Further investigations elucidated several male attributes that were correlated with reproductive success at two geographically isolated sites, namely body size parameters, including weight and testes size. While larger males generally sired more offspring, other smaller successful males appeared to engage in alternative reproductive strategies, including extensive roaming habits. The findings of this study enhance our understanding of the complex interplay between intrinsic and extrinsic factors that influence male reproductive success in a free ranging polygynous marsupial species, including the notion that site-specific factors likely influence the relative importance of these attributes.