Trends in Rescue and Rehabilitation of Marsupials Surviving the Australian 2019-2020 Bushfires.

The 2019-2020 Australian bushfire season had a devastating impact on native wildlife. It was estimated that 3 billion native animals were impacted by the fires, yet there are few estimates of the number of animals that were rescued and rehabilitated post-fire. Focusing on the state of New South Wales (NSW) and Kangaroo Island, South Australia, we used a case study approach to determine the number of marsupials that were reported rescued due to the 2019-2020 bushfires in these areas and analysed species-specific trends in rescue and release success. In NSW, we found 889 reports of fire-affected marsupials in 2019-2020, mostly comprising kangaroos and wallabies (macropods; n = 458), koalas (n = 204), and possums (n = 162), with a smaller number of wombats (n = 43) and other marsupial species. Most reports of fire-affected marsupials occurred 6-8 weeks after fire ignition, and there was no difference in temporal frequency of rescues between marsupial groups. For the three main groups, the probability of survival and subsequent release differed, with macropods having the lowest probability of release after rescue (0.15 ± 0.04) compared to koalas (0.47 ± 0.04) and possums (0.55 ± 0.10). The type of injury was the main predictor of survival during rehabilitation for all three marsupial groups, with those malnourished/moribund or with traumatic injuries less likely to survive rehabilitation. Death or euthanasia occurred on the day of rescue for 77% of macropods, 48% of possums and 15% of koalas. Koalas most often died during rehabilitation rather than on the day of rescue, with 73% either dying or being euthanised between day 1 and 30 post-rescue, representing a potential welfare concern. On Kangaroo Island, koalas were the most frequently rescued marsupial species; most euthanasia cases and deaths occurred in a hospital, whereas other marsupials were mostly euthanised at triage. In both jurisdictions, koalas were over-represented while possums were under-represented relative to baseline population densities and wildlife rescue trends in the years before the 2019-2020 bushfires. These species differences in presentation post-fire warrant further investigation, as do the differences in triage, survival and release outcomes. It is hypothesised that the high intensity and large scale of the 2019-2020 fires impeded marsupial fire evasion tactics, as evidenced by the small number of animals found for rescue, and the differing rates of presentation relative to underlying population densities for the main marsupial groups. Based on our findings, there is a need for detailed record keeping and data sharing, development of consistent and evidence-based triage, treatment and euthanasia guidelines and deployment of trained wildlife emergency rescue teams with advanced search techniques to minimise animal suffering where safe to do so.

Olfactory misinformation provides refuge to palatable plants from mammalian browsing.

Mammalian herbivores browse palatable plants of ecological and economical value. Undesirable neighbours can reduce browsing to these plants by providing 'associational refuge', but they can also compete for resources. Here we recreated the informative odour emitted by undesirable plants. We then tested whether this odour could act as virtual neighbours, providing browsing refuge to palatable eucalyptus tree seedlings. We found that protection using this method was equivalent to protection provided by real plants. Palatable seedlings were 17-20 times more likely to be eaten by herbivores without virtual, or real, neighbours. Because many herbivores use plant odour to forage, virtual neighbours could provide a useful practical management approach to help protect valued plants.

Grow up, be persistent, and stay focused: keys for solving foraging problems by free-ranging possums.

Individuals within a species often vary in both their problem-solving approach and ability, affecting their capacity to access novel food resources. Testing problem-solving in free-ranging individuals is crucial for understanding the fundamental ecological implications of problem-solving capacity. To examine the factors affecting problem-solving in free-ranging animals, we presented three food-extraction tasks of increasing difficulty to urban common brushtail possums (Trichosurus vulpecula). We quantified two measures of problem-solving performance: trial outcome (success/failure) and time to solve and tested the influence of a range of potential drivers, including individual traits (personality, body weight, sex, and age), mechanistic behaviors that quantify problem-solving approach (work time, functional behavior time, behavioral diversity, and flexibility), and prior experience with the puzzles. We found that mechanistic behaviors were key drivers of performance. Individuals displaying greater persistence (higher work and functional behavior time) were more likely to solve a food-extraction task on their first attempt. Individuals also solved problems faster if they were more persistent and had lower behavioral flexibility. Personality indirectly affected time to solve one of the three problems by influencing time allocated to functional behaviors. Finally, adults solved the most difficult problem faster than juveniles. Overall, our study provides rare insight into the drivers underlying the problem-solving performance of wild animals. Such insight could be used to improve management strategies and conservation efforts, such as food or bait deployment, tailored to suit the innovative foraging abilities of target individuals in new and changing environments.

To eat, or not to eat: a phantom decoy affects information-gathering behavior by a free-ranging mammalian herbivore.

When foraging, making appropriate food choices is crucial to an animal's fitness. Classic foraging ecology theories assume animals choose food of greatest benefit based on their absolute value across multiple dimensions. Consequently, poorer options are considered irrelevant alternatives that should not influence decision-making among better options. But heuristic studies demonstrate that irrelevant alternatives (termed decoys) can influence the decisions of some animals, indicating they use a relative rather than absolute evaluation system. Our aim was to test whether a decoy influenced the decision-making process-that is, information-gathering and food choice-of a free-ranging mammalian herbivore. We tested swamp wallabies, Wallabia bicolor, comparing their behavior toward, and choice of, two available food options over time in the absence or presence of the decoy. We used a phantom decoy-unavailable option-and ran two trials in different locations and seasons. Binary preferences (decoy absent) for the two available food options differed between trials. Irrespective of this difference, across both trials the presence of the decoy resulted in animals more likely to overtly investigate available food options. But, the decoy only shifted food choice, weakly, in one trial. Our results indicate that the decoy influenced the information-gathering behavior during decision-making, providing the first evidence that decoys can affect decision-making process of free-ranging mammalian herbivores in an ecologically realistic context. It is premature to say these findings confirm the use of relative evaluation systems. Whether the foraging outcome is more strongly affected by other decoys, food dimensions, or ecological contexts, is yet to be determined.

Efficacy of a synthetic peptide Chlamydia pecorum major outer membrane protein vaccine in a wild koala (Phascolarctos cinereus) population.

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 ethics of intervening in animal behaviour for conservation.

Conservation behaviour is a growing field that applies insights from the study of animal behaviour to address challenges in wildlife conservation and management. Conservation behaviour interventions often aim to manage specific behaviours of a species to solve conservation challenges. The field is often viewed as offering approaches that are less intrusive or harmful to animals than, for example, managing the impact of a problematic species by reducing its population size (frequently through lethal control). However, intervening in animal behaviour, even for conservation purposes, may still raise important ethical considerations. We discuss these issues and develop a framework and a decision support tool, to aid managers and researchers in evaluating the ethical considerations of conservation behaviour interventions against other options.

Patch quality and habitat fragmentation shape the foraging patterns of a specialist folivore.

Research on use of foraging patches has focused on why herbivores visit or quit patches, yet little is known about visits to patches over time. Food quality, as reflected by higher nutritional quality and lower plant defenses, and physical patch characteristics, which offer protection from predators and weather, affect patch use and hence should influence their revisitation. Due to the potentially high costs of moving between patches, fragmented habitats are predicted to complicate foraging decisions of many animals. We aimed to determine how food quality, shelter availability and habitat fragmentation influence tree reuse by a specialist folivore, the koala, in a fragmented agricultural landscape. We GPS-tracked 23 koalas in northern New South Wales, Australia and collated number of revisits, average residence time, and average time-to-return to each tree. We measured tree characteristics including food quality (foliar nitrogen and toxic formylated phloroglucinol compounds, FPCs concentrations), tree size, and tree connectedness. We also modeled the costs of locomotion between trees. Koalas re-visited isolated trees with high leaf nitrogen disproportionately often. They spent longer time in trees with high leaf nitrogen, and in large trees used for shelter. They took longer to return to trees with low leaf nitrogen. Tree connectivity reduced travel costs between patches, being either individual or groups of trees. FPC levels had no detectable effect on patch revisitation. We conclude that food quality and shelter drive koala tree re-visits. Scattered, isolated trees with nutrient-rich leaves are valuable resource patches for koalas despite movement costs to reach them.

A new conceptual and quantitative approach to exploring and defining potential open-access olfactory information.

All organisms emit odour, providing 'open-access' olfactory information for any receiver with the right sensory apparatus. Characterizing open-access information emitted by groups of organisms, such as plant species, provides the means to answer significant questions about ecological interactions and their evolution. We present a new conceptual framework defining information reliability and a practical method to characterize and recover information from amongst olfactory noise. We quantified odour emissions from two tree species, one focal group and one outgroup, to demonstrate our approach using two new R statistical functions. We explore the consequences of relaxing or tightening criteria defining information and, from thousands of odour combinations, we identify and quantify those few likely to be informative. Our method uses core general principles characterizing information while incorporating knowledge of how receivers detect and discriminate odours. We can now map information in consistency-precision reliability space, explore the concept of information, and test information-noise boundaries, and between cues and signals.

The Olfactory Landscape Concept: A Key Source of Past, Present, and Future Information Driving Animal Movement and Decision-making.

Odor is everywhere, emitted across the landscape from predators, prey, decaying carcasses, conspecifics, vegetation, surface water, and smoke. Many animals exploit odor to find food, avoid threats, and attract or judge potential mates. Here, we focus on odor in terrestrial ecosystems to introduce the concept of an olfactory landscape: real-time dynamic olfactory contours reflecting the patchy distribution of resources and risks, providing a key source of information used by many animals in their movement and decision-making. Incorporating the olfactory landscape into current frameworks of movement ecology and animal behavior will provide a mechanistic link to help answer significant questions about where, why, and when many animals move, and how they do so efficiently in both space and time. By understanding how animals use the olfactory landscape to make crucial decisions affecting their fitness, we can then manipulate the landscape to modify ecological interactions and, ultimately, ecosystem consequences of these interactions.

Validation of an Enzyme Immunoassay to Measure Faecal Glucocorticoid Metabolites in Common Brushtail Possums (Trichosurus vulpecula) to Evaluate Responses to Rehabilitation.

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.

A Possible Link between the Environment and Cryptococcus gattii Nasal Colonisation in Koalas (Phascolarctos cinereus) in the Liverpool Plains, New South Wales.

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.

A systematic review of factors affecting wildlife survival during rehabilitation and release.

Millions of native animals around the world are rescued and rehabilitated each year by wildlife rehabilitators. Triage and rehabilitation protocols need to be robust and evidence-based, with outcomes consistently recorded, to promote animal welfare and better understand predictors of wildlife survival. We conducted a global systematic review and meta-analysis of 112 articles that reported survival rates of native mammals and birds during rehabilitation and after release to determine intrinsic and extrinsic factors associated with their survival. We assessed survival during rehabilitation and in the short- and long-term post-release, with the hypothesis that survival will vary as a function of species body size, diel activity pattern, trophic level and study location (region of the world). We aimed to determine the direction of effect of these factors on survival to assist in decision-making during triage and rehabilitation. Results showed that mammals and birds were equally likely to survive all stages of rehabilitation, and survival rates varied between locations. Birds in North America had the poorest survival rates post-release, particularly long-term, as did diurnal and carnivorous birds in the short-term post-release. Anthropogenic factors such as motor vehicle collisions and domestic or feral animal attack contributed to morbidity and post-release mortality in 45% (168 of 369) of instances. The reasons for rescue and associated severity of diagnosis were commonly reported to affect the likelihood of survival to release, but factors affecting survival were often species-specific, including bodyweight, age, and characteristics of the release location. Therefore, evidence-based, species-specific, and context-specific protocols need to be developed to ensure wildlife survival is maximised during rehabilitation and post-release. Such protocols are critical for enabling rapid, efficient rescue programs for wildlife following natural disasters and extreme weather events which are escalating globally, in part due to climate change.

Behavioural drivers of survey bias: interactive effects of personality, the perceived risk and device properties.

Detecting small mammal species for wildlife research and management typically depends on animals deciding to engage with a device, for instance, by entering a trap. While some animals engage and are detected, others do not, and we often lack a mechanistic understanding of what drives these decisions. As trappability can be influenced by traits of personality, personality has high potential to similarly influence detection success for non-capture devices (chew-track cards, tracking tunnels, etc.). We present a conceptual model of the detection process where animal behaviours which are detected by different devices are grouped into tiers based on the degree of intimacy with a device (e.g., approach, interact, enter). Each tier is associated with an increase in the perceived danger of engaging with a device, and an increase in the potential for personality bias. To test this model, we first surveyed 36 populations of free-living black rats (Rattus rattus), a global pest species, to uniquely mark individuals (n = 128) and quantify personality traits. We then filmed rat behaviour at novel tracking tunnels with different risk-reward treatments. As predicted, detection biases were driven by personality, the bias increased with each tier and differed between the risk treatments. Our findings suggest that personality biases are not limited to live-capture traps but are widespread across devices which detect specific animal behaviours. In showing that biases can be predictable, we also show biases can be managed. We recommend that studies involving small mammal sampling report on steps taken to manage a personality-driven bias.

Testing transgenerational transfer of personality in managed wildlife populations: a house mouse control experiment.

Pest species control operations are most effective if every individual in a population is targeted. Yet, individual personality drives variation in animal responses to devices such as traps and baits. Failing to account for differences in behavior during control operations may drive a selective removal, resulting in residual animals with biased expressions of personality. If these biased traits are passed onto offspring, control operations would become increasingly problematic. To test if biased trait expressions in founding populations are passed on to offspring, we quantified personality traits in wild-caught house mice (Mus musculus) and created founder populations selected for biased (high, low) or intermediate expressions of activity. We released the behaviorally biased populations into outdoor yards to breed to the F1 generation and, 10 weeks later, removed the mice and quantified the personality traits of the offspring. Despite the strong personality bias in founder populations, we observed no transgenerational transfer of personality and detected no personality bias in the F1 generation. Our results provide reassuring evidence that a single intensive control operation that selects for survivors with a personality bias is unlikely to lead to a recovering population inherently more difficult to eradicate, at least for house mice.

Leveraging Motivations, Personality, and Sensory Cues for Vertebrate Pest Management.

Managing vertebrate pests is a global conservation challenge given their undesirable socio-ecological impacts. Pest management often focuses on the 'average' individual, neglecting individual-level behavioural variation ('personalities') and differences in life histories. These differences affect pest impacts and modify attraction to, or avoidance of, sensory cues. Strategies targeting the average individual may fail to mitigate damage by 'rogues' (individuals causing disproportionate impact) or to target 'recalcitrants' (individuals avoiding standard control measures). Effective management leverages animal behaviours that relate primarily to four core motivations: feeding, fleeing, fighting, and fornication. Management success could be greatly increased by identifying and exploiting individual variation in motivations. We provide explicit suggestions for cue-based tools to manipulate these four motivators, thereby improving pest management outcomes.

The power of odour cues in shaping fine-scale search patterns of foraging mammalian herbivores.

Foraging by mammalian herbivores has profound impacts on natural and modified landscapes, yet we know little about how they find food, limiting our ability to predict and manage their influence. Mathematical models show that foragers exploiting odour cues outperform a random walk strategy. However, discovering how free-ranging foragers exploit odours in real, complex landscapes has proven elusive because of technological constraints. We took a novel approach, using a sophisticated purpose-built thermal camera system to record fine-scale foraging by a generalist mammalian herbivore, the swamp wallaby (Wallabia bicolor). We tested the hypothesis that odour cues shape forager movement and behaviour in vegetation patches. To do this, we compared wallaby foraging in two odour landscapes: Control (natural vegetation with food and non-food plants interspersed) and +Apple (the same natural vegetation plus a single, highly palatable food source with novel odour (apple)). The +Apple treatment led to strongly directed foraging by wallabies: earlier visits to vegetation patches, straighter movement paths, more hopping and fewer stops than in the Control treatment. Our results provide clear empirical evidence that odour cues are harnessed for efficient, directed search even at this fine scale. We conclude that random walk models miss a key feature shaping foraging within patches.

Acute exposure to urban air pollution impairs olfactory learning and memory in honeybees.

While the ecological effects of pesticides have been well studied in honeybees, it is unclear to what extent other anthropogenic contaminants such as air pollution may also negatively affect bee cognition and behaviour. To answer this question, we assessed the impacts of acute exposure to four ecologically relevant concentrations of a common urban air pollutant-diesel generated air pollution on honeybee odour learning and memory using a conditioned proboscis extension response assay. The proportion of bees that successfully learnt odours following direct air pollution exposure was significantly lower in bees exposed to low, medium and high air pollutant concentrations, than in bees exposed to current ambient levels. Furthermore, short- and long-term odour memory was significantly impaired in bees exposed to low medium and high air pollutant concentrations than in bees exposed to current ambient levels. These results demonstrate a clear and direct cognitive cost of air pollution. Given learning and memory play significant roles in foraging, we suggest air pollution will have increasing negative impacts on the ecosystem services bees provide and may add to the current threats such as pesticides, mites and disease affecting colony fitness.

Needing a drink: Rainfall and temperature drive the use of free water by a threatened arboreal folivore.

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.

Urbanisation and wing asymmetry in the western honey bee (Apis mellifera, Linnaeus 1758) at multiple scales.

Changes in the mean and variance of phenotypic traits like wing and head morphology are frequently used as indicators of environmental stress experienced during development and may serve as a convenient index of urbanization exposure. To test this claim, we collected adult western honey bee (Apis mellifera Linnaeus 1758, Hymenoptera, Apidae) workers from colonies located across an urbanization gradient, and quantified associations between the symmetries of both wing size and wing shape, and several landscape traits associated with urbanization. Landscape traits were assessed at two spatial scales (three km and 500 m) and included vegetation and anthropogenic land cover, total road length, road proximity and, population and dwelling density. We then used geometric morphometric techniques to determine two wing asymmetry scores-centroid size, a measure of wing size asymmetry and Procrustes distance, a measure of wing shape asymmetry. We found colony dependent differences in both wing size and shape asymmetry. Additionally, we found a negative association between wing shape asymmetry and road proximity at the three km buffer, and associations between wing shape asymmetry and road proximity, anthropogenic land cover and vegetation cover at the 500 m buffer. Whilst we were unable to account for additional variables that may influence asymmetry including temperature, pesticide presence, and parasitism our results demonstrate the potential usefulness of wing shape asymmetry for assessing the impact of certain landscape traits associated with urbanization. Furthermore, they highlight important spatial scale considerations that warrant investigation in future phenotypic studies assessing urbanization impact.

Visit, consume and quit: Patch quality affects the three stages of foraging.

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. 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. 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. 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.