Using haematology and biochemistry to investigate the health and evolutionary biology of eastern grey kangaroos (Macropus giganteus)

Abstract

Land clearing has detrimental and long-lasting impacts on natural ecosystems and biodiversity, yet land clearing is accelerating world-wide. The eastern grey kangaroo (Macropus giganteus) is a large common macropod that can reach high densities on cleared land. Despite their apparent success, kangaroo populations are susceptible to food shortages and increased disease risk. Developing a broad understanding of the drivers of kangaroo health is required to establish a benchmark to study poor health. This thesis aimed to develop an evidence-based tool that characterises kangaroo health. Species-specific haematological reference intervals (RI) were developed using blood samples collected from up to 245 animals from four sites across New South Wales and the Australian Capital Territory. Results showed that abiotic factors are critical determinants of kangaroo health outcomes. A health investigation was then performed, utilising the developed RIs, on a population of kangaroos in which health and welfare issues. This kangaroo population was from Look At Me Now Headland (LAMN) in NSW and was found to have widespread disease (parasitism and non-regenerative anaemia) and nutritional deficiencies stemming from a high population density, prolonged drought and reduced grazing habitat. The risk factors associated with parasitism were explored by examining potential selection pressures driving the evolution of kangaroos. An experiment was done to examine the influence of testosterone suppression on health parameters, parasite burdens and movement patterns in male kangaroos. While there was no effect of testosterone on these factors during the ten-week suppression period, a trend for reduced parasite burdens in kangaroos with supressed testosterone was evident. The findings of this thesis emphasise that regional planning must consider habitat connectivity for kangaroo populations to prevent overabundance and enhance positive outcomes for the health and welfare of the species.