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Stress, wildlife health and the conservation of a critically endangered marsupial, the woylie

Hing, S. (2016) Stress, wildlife health and the conservation of a critically endangered marsupial, the woylie. PhD thesis, Murdoch University.

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Effective wildlife management requires an understanding of how animals cope physiologically with stress. When stressors are encountered, the hypothalamic pituitary adrenal (HPA) axis is activated releasing glucocorticoids, which can alter immune function and infectious disease dynamics. Investigations have suggested that stress associated immunosuppression and exacerbation of infection (particularly by Trypanosoma spp. of haemoparasite) may play a role in the decline of the woylie (syn. brush-tailed bettong, Bettongia penicillata), a critically endangered marsupial. This thesis aims to investigate the relationship between stress, immune function and parasite infection dynamics in woylies.

Woylies were trapped from wild populations, reserves and captivity with faecal and blood samples collected from over 300 individuals. Parallel parasitological and non-invasive endocrine analyses were performed to quantify endoparasites and faecal cortisol metabolites (FCM), end-products of HPA axis activation. I also adapted an assay developed in human infants to assess innate immunity in woylies. The novel results suggest that stress physiology and Trypanosoma infection status influence innate immunity.

Collecting longitudinal field data, I identified proximate factors that influenced woylie stress physiology, including season, sex, parasite status and body condition. I also explored woylies’ response to translocation and a major bushfire that unexpectedly occurred at a field site. After translocation, FCM was significantly higher than before or at the time of translocation. However, the variation in FCM was not related to short-term changes in parasite infection dynamics. FCM was not significantly higher immediately after the fire, nor were there corresponding changes in parasite load or body condition compared to the months preceding the fire. I suggest that woylies can maintain homeostasis at least in the period immediately after a fire provided they are managed appropriately. Thus this thesis provides new knowledge on woylie stress physiology and highlights the value of innovative tools to advance woylie conservation as they continue to face stressors in the future.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Godfrey, Stephanie, Thompson, Andrew and Narayan, Edward
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