The Koala (Phascolarctos cinereus) is an endemic marsupial inhabiting four states of Australia. Urbanisation, declining habitat, drought and fires are threatening the survival of this flagship species. These threats may cause acute and chronic stress in koalas, which might also be associated with occurrence of infectious diseases in koala populations. Stress may induce an increase in cortisol reflected in increased faecal cortisol metabolite (FCM) values. To be able to use faecal cortisol metabolites to measure stress levels in this species, our aim was to determine baseline values for males and females during breeding and non-breeding season. A total of 351 defecations were collected fortnightly, twice a day, for 12 months from koalas at a wildlife facility in South East Queensland. Samples were analysed with three different enzyme immunoassays (EIAs): a cortisol, 5α-pregnane-3β,11β,21-triol-20-one (37e) and tetrahydrocorticosterone (50c) EIA. The latter, which also reacts with tetrahydrocortisol, the main metabolite in koala faeces, was found to have the highest biological sensitivity and, therefore, is the most suitable EIA to measure stress levels in koalas. Utilising this EIA, we found significant differences (p < 0.05) in FCM values between males and females, breeding and non-breeding season, and between morning and evening samples. Values of faecal cortisol metabolites established in stress-free koalas in this study can serve as a reference for future studies in koalas.

The koala (Phascolarctos cinereus) is an arboreal folivorous marsupial endemic to Australia. Anthropogenic activities and climate change are threats to this species’ survival and are potential stressors. A suitable non-invasive method is needed to objectively detect stress in koalas. Under conditions of stress, the concentration of the hormone cortisol in plasma or in saliva is elevated, and this would provide a convenient measure; however, collecting blood or saliva from wild animals is both practically difficult and stressful, and so likely to confound any measurement. In contrast, measurement of cortisol metabolites in faeces provides a practical and non-invasive method to objectively measure stress in koalas. Unfortunately, the identity of the main faecal cortisol metabolites of koalas is unknown. In this study, we have used both untargeted liquid chromatography–mass spectrometry (LC-MS) and enzyme immunoassays (EIAs) to identify several faecal cortisol metabolites in two koalas, one female (18 months old, 4.1 kg) and one male (4 years old, 6.95 kg) upon administration of hydrocortisone (cortisol) sodium succinate. The LC-MS analysis identified tetrahydrocortisol along with several other isomers as cortisol metabolites. After a survey of five enzyme immunoassays, we found that two metabolites, tetrahydrocortisol and 3β-allotetrahydrocortisol, could be detected by EIAs that used antibodies that were raised against their structurally similar corticosterone counterparts, tetrahydrocorticosterone and 3β-allotetrahydrocorticosterone, respectively. While the 3β-allotetrahydrocortisol metabolite was detected in the faeces of only one of the two animals studied, tetrahydrocortisol was detected in both. These results ultimately indicate that tetrahydrocortisol is likely the main faecal cortisol metabolite in koalas, and we demonstrate that it can be measured by an EIA (50c) that was originally developed to measure tetrahydrocorticosterone.

Thirty Chlamydia-free koalas, Phascolarctos cinereus, were moved from French Island National Park to three forests near Ballarat (Victoria). Chlamydial exposure and infection were monitored by antibody Enzyme-linked Immunosorbent Assay (ELISA), Direct Immunofluorescence (DIF) and Polymerase Chain Reaction (PCR) of swabs; its impact evaluated by clinical examination. Chlamydia was not detected on French Island. At the end of the study, 16 out of 17 koalas were Chlamydia antibody positive, and 11 out of 16 were also positive for the presence of Chlamydia in the uro-genital tract. C. pecorum infected seven out of nine koalas, one out of nine were infected by C. pecorum and C. pneumoniae and one out of nine by C. pneumoniae alone. This translocation trial shows a high incidence of infection of the translocated koalas, suggesting that the movement of Chlamydia-free animals to areas where the status of the disease is unknown, or the movement of infected animals to other sites where koalas are present, should not be considered as a management option without detailed pre-release research. Further studies should focus on ascertaining the longer term impact of the disease on individuals and population dynamic of this species.

Koalas moving across open ground risk dog attacks and collisions with vehicles when crossings roads. Historical records from a resident survey, two regional wildlife carers and a state government department wildlife shelter returns database for Victoria, Australia, were examined to determine the importance of certain admission types. Koala Vehicle Collisions (KVCs) and dog attacks were important contributors to the overall intake of injured koalas. However, KVCs were the most numerous recorded cause of koalas entering a wildlife shelter, and the most frequently assigned cause of death. There were relatively high rates of admission into care, and of death, for male koalas. Furthermore, almost twice as many individuals were admitted during the breeding season; sex ratio was not a differentiating characteristic of road-kills between breeding and non-breeding seasons, or by individual months. Comprehensive, accurate and detailed data gathering are essential for effective evaluation of the success of rehabilitation and release, as well as post release survival rates. This, together with population studies would determine whether admission rates reflect the sex ratio of local populations, and whether the high number of injured or killed females has an impact on their viability. Analyses of wildlife carer databases have great potential for decision making in koala conservation.