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Arboreal folivores are particularly vulnerable to the impacts of extreme climate change-driven heatwaves and droughts as they rely on leaf moisture to maintain hydration. During these increasingly frequent and intense weather events, leaf water content may not be enough to meet their moisture requirements, potentially leading to large-scale mortality due to dehydration. Water supplementation could be critical for the conservation of these animals. We tested artificial water stations for a threatened arboreal folivore, the koala (Phascolarctos cinereus), as a potential mitigation measure during hot and dry weather in New South Wales, Australia. We provided ground and tree drinkers to koalas and investigated changes in use with season, environmental conditions and foliar moisture. Our study provides first evidence of the regular use of free water by koalas. Koalas used supplemented water extensively throughout the year, even during cooler months. Time spent drinking varied with season and depended on days since last rain and temperature. The more days without rain, the more time koalas spent drinking. When temperature was high, visits to water stations were more frequent, indicating that in hot weather koalas need regular access to free water. Our results suggest that future changes in rainfall regimes and temperature in Australia have the potential to critically affect koala populations. Our conclusions can be applied to many other arboreal folivorous mammals worldwide which rely on leaves for their nutritional and water requirements. Artificial water stations may facilitate the resilience of vulnerable arboreal folivores during heat and drought events and may help mitigate the effects of climate change.

Predators attack and plants defend, so herbivores face the dilemma of how to eat enough without being eaten. But do differences in the personality of herbivores affect the foraging choices of individuals? We explored the ecological impact of personality in a generalist herbivore, the brushtail possum (Trichosurus vulpecula). After quantifying personality traits in wild individuals brought temporarily into captivity, we tested how these traits altered foraging by individuals when free-ranging in their natural habitat. To measure their responses to the dual costs of predation risk and plant toxin, we varied the toxin concentration of food in safe foraging patches against paired, non-toxic risky patches, and used a novel synthesis of a manipulative Giving-Up-Density (GUD) experiment and video behavioural analysis. At the population level, the cost of safe patches pivoted around that of risky patches depending on food toxin concentration. At the individual level, boldness affected foraging at risky high-quality food patches (as behavioural differences between bold and shy), and at safe patches only when food toxin concentration was low (as differences in foraging outcome). Our results ecologically validate the personality trait of boldness, in brushtail possums. They also reveal, for the first time, a nuanced link between personality and the way in which individuals balance the costs of food and fear. Importantly, they suggest that high plant defence effectively attenuates differences in foraging behaviour arising from variation in personality, but poorly defended plants in safe areas should be differentially subject to herbivory depending on the personality of the herbivore.

Chlamydiosis is a significant disease affecting Eastern Australian koalas ( Phascolarctos cinereus ), contributing to the decline of some koala populations, necessitating investigations into appropriate management strategies to address chlamydiosis in wild koala populations. The aim of this study was to investigate the effect of a Chlamydia pecorum recombinant Major Outer Membrane Protein (rMOMP) vaccine as a potential strategy for managing chlamydiosis at a population level. This study comprised a blinded, randomised placebo-controlled trial, encompassing different koala populations where chlamydiosis is having differing effects. Wild koalas were recruited into a vaccination or a placebo treatment group and followed for 12 months, with recapture and resampling at 2, 6 and 12 months post vaccination. Vaccination stimulated a significant plasma anti-MOMP IgG response and greater IL-17 and TNFα mRNA fold change from rMOMP stimulated leukocytes, however, did not boost pre-existing immune responses, from natural infection, in koalas. The observed immunological stimulation did not translate to any effect on chlamydiosis or chlamydial shedding in our study populations. These findings highlight the necessity of improving our understanding of what constitutes a protective immune response in koalas to guide the development of a more effective vaccine. This study evaluated the estimated effect of vaccination necessary to achieve management outcomes predicted by modelling studies. It is possible that vaccination has a more modest effect and could benefit koala populations with a lower disease prevalence or be useful in conjunction with additional management strategies.

Koalas (Phascolarctos cinereus) face many threats, with one of them being the disease chlamydiosis caused by the bacterium Chlamydia pecorum, a cause for infertility and one of the main causes of population decline. In New South Wales, Queensland, and the Australian Capital Territory, the koala is an endangered species, but in Victoria, koalas are widespread and overabundant in some areas. The koala populations in the You Yangs Regional Park (YYRP) and Brisbane Ranges National Park (BRNP) in Victoria are reported to be in decline, although there have been no studies looking into population density or disease. The aim of this study was to investigate the presence of C. pecorum in the koala populations of the YYRP and BRNP to understand whether disease may be a cause of concern. DNA was extracted from scats, and qPCR was used to detect the presence and load of C. pecorum. C. pecorum was found in 12/18 (66.7%) scat samples. Clinical signs of disease, age, and sex did not affect infection shedding load. These results confirm the presence of chlamydiosis within the YYRP and BRNP koala populations. More detailed studies are recommended to quantify prevalence of the disease in these populations and to understand the consequences of chlamydiosis in these areas.

Chlamydiosis is a significant disease affecting Eastern Australian koala ( Phascolarctos cinereus ) populations, impacting individual animal welfare and fecundity and therefore influencing population dynamics. The aim of this study was to investigate the effect of a synthetic peptide vaccine based on 4 components of the Chlamydia pecorum major outer membrane protein (MOMP), over an 18-month period in a koala population severely impacted by chlamydiosis. Wild koalas were recruited into a vaccination or a placebo treatment group on a random allocation, then followed through a period of 18 months, with recapture at 6 monthly intervals. Vaccination did not alter clinical disease expression or chlamydial shedding from the ocular or urogenital sites. Vaccination did not stimulate a significant plasma anti-MOMP IgG response, when compared to the placebo group. There was no significant effect of vaccination on IFN-γ and IL-17A mRNA expression of peripheral blood lymphocytes when stimulated with rMOMP. We have demonstrated that a synthetic peptide vaccination against chlamydiosis is not an effective management tool in a koala population with a high prevalence of C. pecorum infection and related disease. The lack of antigenic response found in this study suggests that further research utilising a larger, full-length antigen is an avenue worth investigation if we are to consider vaccination as a part of a management strategy in diseased koala populations.

The koala ( Phascolarctos cinereus ) is an endangered species in parts of Australia, in part due to chlamydial infections. Treatment is difficult due to the hepatic metabolism of the koala, and the critical reliance on a gut microbiota for survival. This study aimed to identify new compounds for treatment of Chlamydia infections by screening a drug re-purposing library. Screening was conducted using an in vitro cell culture model prior to in vivo mouse infection model testing of two candidates identified from the in vitro screen. One lead, bisoprolol fumarate, showed an impact on chlamydial infection and burden in vitro and in vivo. Whilst the mechanism of action may not support progressing this lead further, the approach to screening the library and list of candidates may enable identification of other new koala treatments. This study demonstrates the potential to apply drug re-purposing to koala treatment and presents a list of candidates that could be explored further.

The giving-up density (GUD) framework provides a powerful experimental approach with a strong theoretical underpinning to quantify foraging outcomes in heterogeneous landscapes. Since its inception, the GUD approach has been applied successfully to a vast range of foraging species and foraging scenarios. However, its application is not simple, as anyone who has tried to use it for the first time might attest. Limitations of the technique were noted at its conception, yet only the artificiality of the patches, the appropriateness of the food resource, and the possibility of multiple visiting foragers were identified. Here we show the current uses of GUD and outline the practical benefits as well as the often overlooked limitations of the technique. We define seven major points that need to be addressed when applying this methodology: (1) the curvilinearity between harvest rate and energy, (2) the energetic state of the forager, (3) the effect of group foraging, (4) food quality and substrate properties, (5) the predictability of the patch, (6) behavioral traits of the forager, and (7) nontarget species. We also suggest how GUD experiments can be enhanced by incorporating complementary methods (such as cameras) to better understand the foraging processes involved in the GUD itself. We conclude that the benefits of using GUD outweigh the costs, but that its limitations should not be ignored. Incorporating new methods when using GUD can potentially offer novel and important insights into the study of foraging behavior.

Cryptococcosis caused by yeasts of the Cryptococcus gattii species complex is an increasingly important mycological disease in humans and other mammals. In Australia, cases of C. gattii-related cryptococcosis are more prevalent in the koala (Phascolarctos cinereus) compared to humans and other animals, likely due to the close association that both C. gattii and koalas have with Eucalyptus species. This provides a cogent opportunity to investigate the epidemiology of spontaneous C. gattii infections in a free-living mammalian host, thereby offering insights into similar infections in humans. This study aimed to establish a link between nasal colonisation by C. gattii in free-ranging koalas and the tree hollows of Eucalyptus species, the key environmental source of the pathogen. We (i) detected and genotyped C. gattii from nine out of 169 free-ranging koalas and representative tree hollows within their home range in the Liverpool Plains, New South Wales, and (ii) examined potential environmental predictors of nasal colonisation in koalas and the presence of C. gattii in tree hollows. Phylogenetic analyses based on multi-locus sequence typing (MLST) revealed that the koalas were most likely colonised by the most abundant C. gattii genotypes found in the Eucalyptus species, or closely related genotypes. Importantly, the likelihood of the presence of C. gattii in tree hollows was correlated with increasing hollow size.

Volunteer wildlife rehabilitators rescue and rehabilitate thousands of native animals every year in Australia. However, there is little known about how exposure to novel stimuli during rehabilitation could affect the physiology of wildlife. We investigated this question in a species that commonly enters rehabilitation, the common brushtail possum (Trichosurus vulpecula). We evaluated five enzyme immunoassays (EIA) to determine the most suitable for measuring faecal glucocorticoid metabolites (FGM) as a proxy for evaluating the response of brushtail possums to potential stressors during rehabilitation. An adrenocorticotrophin hormone (ACTH) challenge was conducted on wild-caught possums to determine the best-performing EIA based on the successful detection of FGM peaks in at least two of three possums. While a number of assays met these criteria, the 11-oxoaetiocholanolone (abbreviation: 72a) EIA was selected as it had the largest amplitude of change in response to the ACTH challenge. This assay was then used to measure FGM concentrations in 20 possums during rehabilitation. There was high variation in baseline FGM concentrations and response to captivity between possums. Significant changes in FGM levels were detected in most possums during captivity, but were not reliably associated with potentially stressful events that were identified by rehabilitators. The probability of an FGM peak occurring within five days of a potentially stressful event was about 50%, regardless of the type of event. Our study has demonstrated that injured and orphaned possums show changes in FGMs during captivity and rehabilitation and has identified events that can induce a physiological response in some individuals. We recommend that research now focus on the relationship between these responses during rehabilitation and pre- and post-release survival.

1. Foraging is a three-stage process during which animals visit patches, consume food and quit. Foraging theory exploring relative patch quality has mostly focused on patch use and quitting decisions, ignoring the first crucial step for any forager: finding food. Yet, the decision to visit a patch is just as important as the decision to quit, as quitting theories can only be used if animals visit patches in the first place. Therefore, to better understand the foraging process and predict its outcomes, it is necessary to explore its three stages together. 2. We used the common brushtail possum (Trichosurus vulpecula) as a model to investigate foraging decisions in response to food varying in quality. In particular, we tested whether patch nutritional quality affected the following: (1) patch visits; (2) behaviours at the patch during a foraging visit; and (3) patch quitting decisions (quantified using giving up density—GUD). Free-ranging possums were presented with diets varying in nitrogen content and concomitantly volatile organic compound (VOC) composition at feeding stations in the wild. 3. We found that possums were able to distinguish between different quality foods from afar, despite the location of the diets changed daily. Possums used VOC (i.e. odour cues) emitted by the diets to find and select patches from a distance. High-quality diets with higher protein and lower fibre were visited more often and for longer. Possums spent more time foraging on diets high in nutritional content, resulting in lower GUDs. 4. Our study provides important quantitative evidence that foraging efficiency plays out during all the three stages of the foraging process (i.e. visit, consume and quit), and demonstrates the significance of considering all these stages together in future studies and foraging models. Sensory cues such as food odours play a critical role in helping foragers, including mammalian herbivores, find high-quality food. This allows foragers to make quick, accurate and important decisions about food patches well before patch quitting decisions come into play.