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Sprawling urban development is fragmenting the landscape and native wildlife habitats on the Australian east coast. The impact of this rapid urbanization on wildlife health is largely unknown. This study surveyed the health of a high-density (5.4 individuals per ha) population of eastern grey kangaroos (Macropus giganteus) affected by urban encroachment and prolonged drought. Blood parameters (hematological and serum protein), trace element and heavy metal concentrations, and parasite counts (fecal worm egg counts, ticks, and mites) are reported for a sample of ≤ 54 kangaroos at Look at Me Now Headland, New South Wales, Australia. These parameters were compared to lower density kangaroo populations from other sites in New South Wales. We found the health and welfare of this population to be severely compromised, with nonregenerative anemia and nutritional deficiencies evident. Our results indicate that high-density kangaroo populations isolated by urban encroachment are at significant health risk. To prevent further decline in this population’s health, we discuss management strategies that could be employed, concurrent with ongoing health and disease monitoring, to mitigate the poor health outcomes in this population. We conclude that it is essential to retain habitat connectivity when altering land use in areas with resident kangaroo populations if managers are to maintain healthy populations.

Testosterone has a dualistic effect in males by promoting sexual ornamentation at the cost of immune defence. This trade-off has been demonstrated in several taxa, such that males often host a greater parasite burden compared with female conspecifics. We suppressed testosterone in wild male eastern grey kangaroos (Macropus giganteus) for 10 weeks using a novel gonadotropin-releasing hormone (GnRH) vaccine, Bopriva. We evaluated the impact of testosterone suppression on testes width, parameters of health, tick and worm burden in kangaroos using a before-after-control-impact (BACI) experimental design. Given the potential impact of animal movement on parasite burden, core area use of a subset of males was also determined. Bopriva significantly reduced testosterone in male kangaroos as well as reducing the combined size of testes by 9.6% (P = 0.01). There was no detectable effect of testosterone suppression on parasite burden and core area use in Treated kangaroos compared to Control (placebo) and Before treatment animals. Our results suggest that a duration of suppression longer than 10 weeks may be required to observe changes in parasite burden. Overall, this study provides a suitable framework for future studies to test whether reproductive hormones influence energy allocation, parasitism, and reproductive strategies in marsupials.