Abstract
Populations of Queensland koalas are rapidly declining, and the driving force behind this is habitat loss. This study analyzed reports (N = 50,858) made to three wildlife- focused veterinary clinics within the South-East Queensland Wildlife Hospital Network for assistance relating to a sick or injured wild koala between 1997 and 2019. Using descriptive and inferential statistics, a nominal logistic regression was performed to test the effect of key independent variables (age, sex, and etiology) on the outcome of each koala (released, deceased, euthanized) after being reported. Results found that the most common outcome for both sexes, most etiologies, and all ages was euthanasia. A comprehensive understanding of the primary risks affecting endangered species, and how these risks affect the likelihood of survival, is essential to inform species conservation policies and extinction risk assessments. We hope this study can provide an indispensable basis for future koala conservation strategies.
Biodiversity, the flora and fauna which make up a habitat, is rich in Australia and tied closely to its unique cultural identity (Satterfield et al., 2013). Close to half (46%) of avian species, 69% of mammalian species, 94% of amphibian species, and 93% of reptilian species that inhabit Australia are endemic to it (Cresswell & Murphy, 2016). This high level of endemism is attributed to Australia’s geographic isolation, stability of tectonic plates, and the effects of a unique pattern of climate change on the soil and flora over geological time (Cresswell & Murphy, 2016). After European colonization in 1788, more species have become extinct in Australia than in any other country on Earth (Australian Government Department of Agriculture Water and the Environment, 2022). There are currently 556 species listed on Australia’s Environmental Protection and Biodiversity Conservation Act, with 216 being vulnerable or conservation dependent, 181 being endangered, 91 being critically endangered, and 68 being extinct (Australian Government Department of Agriculture Water and the Environment, 2022).
The primary driving forces behind animal extinction in Australia are habitat loss (clearing and fragmentation), invasive species, anthropogenic climate change, altered fire regimes, grazing, and changed hydrology (Cresswell & Murphy, 2016). It is the cumulative and interacting effects of many of these driving forces that amplify the threat to biodiversity (Cresswell & Murphy, 2016). According to the most recent State of the Environment Report, the rate of habitat loss in Australia has decreased between 2015–2019, compared to the previous 5 years (Williams et al., 2021). However, even if habitat loss stabilized, the legacy of past clearing and fragmentation continues to cause negative ripple effects on biodiversity (Cresswell & Murphy, 2016). A 2016 inter-governmental report detailing the state of global ecosystems concluded that without drastic action to conserve habitats, up to one million plant and animal species worldwide will become at risk of extinction (Acosta et al., 2016). The report found that global species loss is occurring 1,000 times faster than the natural rate of extinction, with these mass extinctions also predicted to undermine human wellbeing (Acosta et al., 2016).
The koala (Phascolarctos cinereus) is an arboreal, herbivorous marsupial native to Australia and can be found on the east coast of the continent, including in Queensland, New South Wales, the Australian Capital Territory, Victoria, and South Australia (Woinarski & Burbidge, 2020). Wild koala distribution and abundance is entirely dependent on the availability of eucalypts with the correct foliar chemistry (Callaghan et al., 2011; Moore & Foley, 2005) and spatial structure (Moore et al., 2010). The koala was listed as “vulnerable to extinction” until as recently as February 2022, when its conservation status was elevated to “endangered” within New South Wales, Queensland, and the Australian Capital Territory (Australian Government Department of Agriculture Water and the Environment, 2022). Population estimates are uncertain for wild koalas, as they are a cryptic species who are difficult to detect (Youngentob et al., 2021). There is also no single technique or widely accepted method to survey wild koalas, so it is difficult to distinguish between a lack of detection and true absence (Youngentob et al., 2021). Despite exact population estimates being unknown, wild koala populations are decreasing, and the driving force behind this is habitat loss through land clearing and habitat fragmentation (Rhodes et al., 2017).
In 2020, the Queensland Government launched the “South-East Queensland Koala Conservation Strategy 2020–2025” (State of Queensland, 2020). The primary vision for this strategy was to halt the decline of wild koala populations in South-East Queensland, and secure their long-term survival (State of Queensland, 2020). This strategy proposes three ways to stabilize wild koala population numbers: Firstly, by producing a net gain in the area of core wild koala habitat; secondly, by commencing rehabilitation strategies to restore 10,000 hectares of wild koala habitat; thirdly, by initiating ten programs in threat priority areas to support at least a 25% reduction in disease and injury, which contribute to mortality (State of Queensland, 2020). Disease and injury are significant risks for populations exposed to habitat loss, and wildlife affected by these often require rescue and rehabilitation (Pyke & Szabo, 2018). Wildlife rehabilitation has been described as the treatment and temporary care of injured, diseased, and displaced indigenous animals, and the subsequent release of healthy animals to appropriate habitats in the wild (Miller, 2012). Unfortunately, the effectiveness of wildlife rehabilitation is largely unknown, as despite vast numbers of wild animals undergoing rehabilitation, their fate often remains undetermined after release (Cooper & Cooper, 2006). This challenge arises because post-release monitoring is typically limited by time and financial constraints, and because animals often disperse from their original release site (Mullineaux, 2014).
Over a period of 22 years (1997–2019), 50,858 reports were made to three wildlife-focused veterinary clinics within the South-East Queensland Wildlife Hospital Network for assistance relating to a sick or injured wild koala. The information from these calls is captured in a dataset within the Open Data Portal owned by the Queensland Government Department of Environment and Science. This dataset has been previously used to identify the seasonal and temporal risk factors associated with causes of morbidity and mortality in koalas (Gonzalez-Astudillo et al., 2017). Male koalas and adult koalas often present to veterinary clinics at a higher rate than female koalas and younger koalas (Charalambous & Narayan, 2020; Gonzalez-Astudillo et al., 2017; Griffith et al., 2013), with Chlamydia pecorum being the most common disease present when they arrive (Charalambous & Narayan, 2020; Gonzalez-Astudillo et al., 2017). Therefore, we anticipate that the outcome of a wild koala after being reported to a veterinary clinic would be dependent on their sex, age, and the reason they were admitted. This study aimed to outline the primary threats for wild koalas within South-East Queensland who are reported to veterinary clinics, and how these threats affect the likelihood of each koala being released, euthanized, or found dead on arrival.
Methods
Data Acquisition
This study used an open-access dataset called “Koala Hospital Data” which is owned by the Queensland Government (Queensland Department of Environment and Science, 2022). The dataset contains records of wild koalas sighted by members of the public and/or admitted into one of three wildlife-focused veterinary clinics within the South-East Queensland Wildlife Hospital Network. This network is a group of three specialist wildlife veterinary clinics (SWVCs) in South-East Queensland: Australia Zoo Wildlife Hospital, which covers the Sunshine Coast Region; Currumbin Wildlife Hospital, which covers the Gold Coast Region; and RSPCA Queensland Wildlife Hospital, which covers the Brisbane Region.
In Queensland, when sick or injured wildlife are observed, members of the public are encouraged to call their closest SWVC or fauna rescue group who liaises with SWVCs. Once alerted to a wild koala report, a SWVC or fauna rescue group will record the estimated location including latitude, longitude, suburb, and council area. A representative of the SWVC or rescue group will then attend the location recorded. If the koala is deemed as needing to be caught, and can be caught, they will be admitted into a SWVC where a physical examination is then conducted by a veterinarian. The koala’s estimated age according to tooth wear is recorded, as are any injuries or other relevant clinical signs. Each SWVC periodically sends this information to the Queensland Government Department of Environment and Science, which is then collated and uploaded to the dataset “Koala Hospital Data.”
Data Preparation
On download, the initial dataset contained 37 columns and 50,875 rows. Columns that were superfluous to the aims of this study were removed (such as information specifically pertaining to the SWVC such as animal “name” and record number), and the remaining data was manually validated using the sort and filter function in Microsoft® Excel (2019). Each column was checked to ensure all entries were plausible, with duplicates and incorrect data removed (e.g., latitude and longitude coordinates that were invalid or reflected places outside of Australia). The final dataset resulted in 28 columns and 50,858 rows. Each row represented a report made to a SWVC or fauna rescue group, and each column contained information for each report such as the date and location, the koalas’ demographic information such as estimated age and sex, any injuries or other clinical signs, whether a joey was present, and finally, the outcome for the koala, whether they were released, and if so, when and where this occurred.
Data Analysis
This dataset was analyzed using the spatial mapping software ArcGIS Pro version 2.7.0 (ESRI, 2020) and statistical programming software R version 4.1.1 (RCoreTeam, 2022) with RStudio version 2021.09.0 (RStudioTeam, 2019). To produce maps using ArcGIS Pro, the dataset was uploaded to the base map “world topographic map.” Most entries within the dataset contained the latitude and longitude of the estimated sighting location for each wild koala, which could be used directly in ArcGIS. For those which did not (N = 933), the latitude and longitude of the center of the suburb in which each koala was sighted was recorded instead. This information was combined within the map using a spatial join, and each coordinate was represented as a red dot within the map.
Descriptive statistics and inferential statistics were both performed using R with RStudio. Total counts and proportions were calculated and combined in contingency tables for each variable before being displayed in a bar chart using the ggplot2 package (Wickham, 2016). A nominal logistic regression was then performed using the nnet package (Venables & Ripley, 2002) to test the effect of key independent variables (age, sex, etiology; note: etiology refers to the set of causes leading to a disease or condition) on the outcome of the koala (e.g., released, deceased, euthanized). Each known etiology (exposed to bushfire, attacked by a dog, fallen from a tree, hit by a motor vehicle, clinical signs of chlamydia disease, and found in an unsuitable landscape) was included as a binary variable, as these were not mutually exclusive. Therefore, some koalas had more than one etiology (e.g., attacked by a dog and hit by a motor vehicle). It should be noted that some koalas had no known etiology (“unknown”) and so this was used as the reference category. Using the lmtest package (Zeileis & Hothorn, 2002), independent variables were tested in a stepwise process with likelihood-ratio tests used to determine if the inclusion of an independent variable led to a significantly improved model; however, all explanatory variables were influential and were included in the final model. Coefficients from the final model were converted into risk ratios with 95% confidence intervals.
Results
A total of 50,858 reports were made to the three SWVCs within the South-East Queensland Wildlife Hospital Network for assistance relating to a sick or injured wild koala between 1997 and 2019. The three SWVCs within this network include Australia Zoo Wildlife Hospital, Currumbin Wildlife Hospital, and RSPCA Queensland Wildlife Hospital. Reported koala locations were dispersed across South-East Queensland with clusters on the Sunshine Coast, the Gold Coast, and Brisbane (Figure 1).
The estimated location of each koala report made to the South-East Queensland Wildlife Hospital Network between 1997 and 2019
Citation: Society & Animals 2025; 10.1163/15685306-bja10220
Outcomes included 32,278 koalas being admitted into SWVCs where they were either euthanized or released into suitable habitat, and 18,580 koalas with other outcomes, including being found deceased, being left alone in their habitat, being unable to be captured or located, being caught and relocated to an alternative habitat, or unknown (Table 1).
Outcome of each koala reported to the South-East Queensland Wildlife Hospital Network between 1997 and 2019
Citation: Society & Animals 2025; 10.1163/15685306-bja10220
Of the reports made, 17,549 were of male koalas, 16,720 were of females, and 16,589 were of koalas of unknown sex. In terms of age, 42,624 reports were made for adult koalas (> 3 years), 4,346 were for sub-adult koalas (1–3 years), 2,764 were for young koalas (< 1 year), and 1,124 were for koalas of unknown age (Table 2).
Outcome of each koala reported to the South-East Queensland Wildlife Hospital Network between 1997 and 2019 as raw numbers dased on sex and age
Citation: Society & Animals 2025; 10.1163/15685306-bja10220
The year with the highest number of reports made to the three SWVCs within the South-East Queensland Wildlife Hospital Network between 1997 and 2019 was 2009, and the year with the lowest number of reports was 2017 (Figure 2a). The number of koalas admitted into and either released from or euthanized within veterinary clinics each year fluctuated but followed an overall trend of growth in terms of percentage of reports (Figure 2b).
Number of koalas reported to the South-East Queensland Wildlife Hospital network between 1997 and 2019 as raw numbers (2a) and as percentages based on their outcome (2b)
Citation: Society & Animals 2025; 10.1163/15685306-bja10220
Of the reports made, 15,197 were male adult koalas, compared to 14,054 female adult koalas (Table 2). Of all the adult koalas, there were more males who were released than females, but almost the same number of males and females were euthanized. Overall, the most common outcome for male and female adult koalas was euthanasia. The sex of 13,373 adult koalas was unknown or not recorded.
Additionally, 1,547 were female sub-adult koalas, compared to 1,144 male sub-adult koalas. Of those sub-adult koalas, there were more females both released and euthanized than males, and the most common outcome for both males and females was euthanasia. The sex of 1,655 sub-adult koalas was unknown or not recorded.
Lastly, of the reports made, 1,101 were young male koalas, compared to 981 young female koalas. Of those young koalas, there were more males both released and euthanized than females, and the most common outcome for both males and females was euthanasia, closely followed by released. The sex of 682 young koalas was unknown or not recorded.
The most frequent occurring etiology from the reports made was “Unknown,” followed by “Symptoms of Chlamydia Disease” and “Hit by a Motor Vehicle” (Table 3). The most frequent outcome from the reports made was euthanasia, followed by being left alone, and then release (Table 3). For the etiologies “Exposed to Bushfire,” “Attacked by a Dog,” “Fallen from a Tree,” “Hit by a Motor Vehicle,” and “Symptoms of Chlamydia Disease,” the most frequent outcome was euthanasia, followed by release. In contrast, the most frequent occurring outcome for the etiology “Found in an Unsuitable Habitat” was release, followed by relocation.
Outcome of each koala reported to the South-East Queensland Wildlife Hospital Network between 1997 and 2019 as raw numbers based on etiology
Citation: Society & Animals 2025; 10.1163/15685306-bja10220
All tested explanatory variables (sex, age, and etiology) had a significant effect on the outcome of a koala. The reference group used for this analysis was an adult male with an unknown etiology whose outcome was release back into the wild. This reference group was chosen because an adult male was the normative default, and a koala with no known etiology was most representative of a healthy koala.
Sex
Compared to males, female koalas were more likely to be euthanized (Relative Risk = 1.69) or found deceased (Relative Risk = 1.60) than released (Table 4).
Nominal logistic regression showing the association between independent variables (dex, Age, and Etiology) and the dependent variable (Outcome) as per each report made to the South-East Queensland Wildlife Hospital Network between 1997 and 2019
Citation: Society & Animals 2025; 10.1163/15685306-bja10220
Age
Compared to adults, sub-adult koalas were less likely to be euthanized (Relative Risk = 0.60) or found deceased (Relative Risk = 0.63) than released (Table 4). However, young koalas were less likely to be euthanized (Relative Risk: 0.49) than released, but more likely to be found deceased (Relative Risk = 1.11) than released.
Etiology
Koalas who had clinical signs of chlamydia disease were more likely to be euthanized (Relative Risk = 1.96) than released, but less likely to be found deceased (Relative Risk = 0.14) than released (Table 4). This was similar for koalas who had been exposed to bushfire, as they were less likely to be found deceased (Relative Risk = 0.66) than released, although the likelihood of being euthanized (Relative Risk = 1.02) versus released was not significantly different. On the other hand, koalas who had been attacked by a dog were more likely to be euthanized (Relative Risk = 1.92) or found deceased (Relative Risk = 2.60) than released. Koalas who had fallen from a tree were also more likely to be euthanized (Relative Risk = 1.86) or found deceased (Relative Risk = 1.63) than released. Likewise, koalas who had been hit by a motor vehicle were more likely to be euthanized (Relative Risk = 2.72) or found deceased (Relative Risk = 4.07) than released. Finally, koalas who had been found in an unsuitable landscape were less likely to be euthanized (Relative Risk = 0.17) or found deceased (Relative Risk = 0.08) than released (Table 4).
Discussion
Total reports made to the South-East Queensland Wildlife Hospital Network between 1997 and 2019 numbered 50,858 with the number of reports fluctuating year to year. As the global human population continues to increase, so too does conflict between humans and wildlife through the destruction, modification, and fragmentation of habitat (Finn & Stephens, 2017; Lowry et al., 2013; McKinney, 2002). Evidence suggests that the major factors driving veterinary clinic admissions of native animals of all taxonomic groups in areas heavily influenced by urban expansion are anthropogenic activities such as car strikes and dog attacks (Taylor-Brown et al., 2019). Increased urban expansion is an expected result of human population growth; in 1996, the population of Queensland was estimated to be 3.36 million, whereas in 2021, the population had grown to 5.17 million (ABS, 2022). It is highly likely that increased anthropogenic activities from urban expansion is the primary driving force behind constant admissions of koalas to the South-East Queensland Wildlife Hospital Network. This study aimed to outline the primary threats for wild koalas within South-East Queensland who are reported to veterinary clinics, and how these threats affect the likelihood of each koala being released, euthanized, or found dead on arrival. We hypothesized that the outcome of a wild koala after being reported to a veterinary clinic would be dependent on their sex, age, and the reason they were admitted. It is important to note that this study only reflects what is happening to koalas within South-East Queensland, and not Australia as a whole. Furthermore, the three SWVCs in this study are not the only SWVCs within South-East Queensland to which koalas are reported; they are however three of the largest most well-known veterinary clinics, which is influential on koala intake numbers.
This study found female koalas were more likely than males to be euthanized or found deceased. Other studies suggest male koalas often arrive to veterinary clinics with terminal injuries which require euthanasia at a higher rate than females (Charalambous & Narayan, 2020; Gonzalez-Astudillo et al., 2017; Griffith et al., 2013). This is likely due to behavioral differences between female and male koalas (Griffith et al., 2013). For example, male koalas spend more time traveling on the ground during the breeding season (Griffith et al., 2013), and doing so increases their risk of encountering anthropogenic threats including cars, dogs, and humans (Narayan & Williams, 2016). However, it is documented that when assessing clinical outcomes for koalas, being a female is a risk factor associated with poorer clinical outcomes when diagnosed with chlamydia (Gonzalez-Astudillo et al., 2017). This is likely due to advanced diagnostic tools that favor females, such as ultrasound of the ovaries, an organ often assessed during a diagnosis of chlamydia (Gonzalez-Astudillo et al., 2017). It is much more challenging to diagnose chlamydia in males, so without overt disease expression, chlamydia can often be underdiagnosed for this sex (Gonzalez-Astudillo et al., 2017). Almost 30% of koalas in this study were diagnosed with clinical signs of chlamydia disease, and this is likely why female koalas were more likely to be euthanized or be found deceased than males. It is important to note that 32% of koalas in this study had an unknown or unrecorded sex.
Furthermore, this study found that sub-adult koalas were more likely to be released, and less likely to be euthanized or be found deceased than adults, while young koalas were more likely to be found deceased, and less likely to be euthanized or released than adults. Research suggests that adult koalas often arrive at veterinary clinics with terminal injuries which require euthanasia at a higher rate than young and sub-adult wild koalas (Charalambous & Narayan, 2020; Gonzalez-Astudillo et al., 2017; Griffith et al., 2013). This increased risk is likely a product of specific selection pressures and temporal fitness requirements (Gaillard et al., 2000). For example, young and sub-adult koalas are highly dependent on their mothers for survival, so are less likely to experience misadventure (Charalambous & Narayan, 2020; Gonzalez-Astudillo et al., 2017; Griffith et al., 2013). Comparatively, adult koalas are independent, and survival becomes harder with increased pressure from anthropogenic threats including cars, dogs, and humans (Narayan & Williams, 2016). Additionally, there was a higher proportion of adults in this study than sub-adult or juvenile koalas. This is because adult koalas comprise a higher population proportion, and are generally much easier to spot in the wild (Gonzalez-Astudillo et al., 2017). For these reasons, it is not surprising that results indicated sub-adults were more likely to be released, and less likely to be euthanized or be found deceased than adults, and young koalas were more likely to be found deceased, and less likely to be euthanized or released than adults.
Almost half of the reported koalas in this study had no recorded etiologies, and this can be attributed to several factors. Firstly, 12% of koalas in this study had outcomes including being left alone, relocated, unable to capture, unable to locate, or unknown. In these cases, koalas were not able to be admitted into one of the three SWVCs. Secondly, this database has collected reports since 1997. It is reasonable to assume that the three SWVCs changed the way in which they record and store information on koala admissions, and so data may not be absolutely comparable over time. Third, there have been major advancements in the way veterinarians diagnose koalas who receive clinical care. As a result, this has likely caused some discrepancies in earlier records of unknown etiologies.
The most common specific etiology of koalas admitted into one of the three SWVCs described koalas having clinical signs of chlamydia disease. Studies have shown that chlamydia is the most common disease wild koalas present with on admission into veterinary clinics (Charalambous & Narayan, 2020; Gonzalez-Astudillo et al., 2017). Clinical signs of chlamydia disease include conjunctivitis, blindness, pneumonia, urinary tract infections, and infertility (Quigley & Timms, 2020). Many advancements have been made in understanding and combating this complex, chronic disease by slowing its progression over time, and supporting koalas’ immune response to infection (Quigley & Timms, 2020). For example, antibiotics such as chloramphenicol, doxycycline, and florfenicol are shown to somewhat improve the recovery rate of koalas infected with chlamydia, hence their use as front-line treatments (Budd et al., 2017; Govendir et al., 2012; Phillips et al., 2019; Robbins et al., 2018). However, their rate of failure due to adverse gut dysbiosis outcomes means koalas are often euthanized on the grounds of welfare (Charalambous & Narayan, 2020; Gonzalez-Astudillo et al., 2017; Griffith et al., 2013; Phillips et al., 2020). For this reason, it is not surprising that the results indicated that koalas reported as having clinical signs of chlamydia disease were more likely to be euthanized and less likely to be found deceased than released.
Following clinical signs of chlamydia disease, the second most common specific etiology of koalas admitted into one of the three SWVCs described koalas being hit by motor vehicles. A study of hospital records of wild koalas consistently identified physical trauma in cases where wild koalas were hit by a motor vehicle (Gonzalez-Astudillo et al., 2019). Injuries of this nature are overwhelmingly associated with fractures to the skull and jaw (Henning et al., 2015). It is thought that due to koala gait and conformation, and particularly skull height in relation to the ground clearance of a car, koalas are predisposed to head trauma during a collision with a motor vehicle (Canfield, 1991). This is exacerbated by the fact that when this species moves around at night, they are likely to encounter motor vehicles using their headlights, and koalas are known to freeze when startled by bright light (Canfield, 1991). Previous studies have identified that the recovery rate of koalas with fracture injures is very low (Henning et al., 2015). Head fractures in koalas will often result in dental misalignment, which severely affects their ability to maintain sufficient energy intake (Logan & Sanson, 2002). Due to their poor energy diet of eucalyptus, koalas have no visceral fat reserves and disturbances in energy intake will often result in poor body condition and debilitation (Logan & Sanson, 2002). Unfortunately, the rehabilitation success for koalas who present to clinical care with physical trauma from being hit by a motor vehicle is only 2% (Henning et al., 2015), and for this reason, it is not surprising that results indicated that koalas who had been hit by a motor vehicle were more likely to be euthanized or found deceased than released. Efforts have been made to understand whether koalas use fixed structures such as wildlife corridors. Studies indicate that only 21% of koalas have been found to use wildlife corridors, and male koalas and those under five years of age tend to use them most often, highlighting the need for further research (Dexter et al., 2016, 2018).
Following being hit by a motor vehicle, the third most common specific etiology of koalas admitted into one of the three SWVCs described koalas being attacked by dogs. The severity of a dog bite injury is dependent on the ferocity of the attack and the anatomical location of the bite (Dendle & Looke, 2009). For koalas, the main complications of a dog bite injury often include infection and torso fractures (Dendle & Looke, 2009; Henning et al., 2015). There are several recognized zoonotic organisms carried by dogs that, when passed to wildlife, can cause infection (Smout et al., 2017). These include skin infections, respiratory infections and gastroenteric infections, among many others (Smout et al., 2017). Much like treating chlamydia, treating skin, respiratory, and gastroenteric infections is difficult because of the high failure rate of antibiotics due to adverse gut dysbiosis outcomes (Phillips et al., 2020). Apart from transmitting infection, dog bite injuries can result in torso fractures, which is a result of the fragility of ribs combined with the high pressure generated from the canine jaw and the associated ripping and tearing motion (Abrahamian, 2000; Henning et al., 2015; Morgan, 2005). Much like head fractures, torso fractures result in poor body condition and debilitation, however this is the result of severe hemoabdomen and hemothorax from hepatic and pulmonary lacerations (Gonzalez-Astudillo et al., 2019). It is often the case that koalas who are attacked by dogs have no underlying diseases; however, the trauma of a dog attack remains a major contributor to koala mortality (Gonzalez-Astudillo et al., 2017). It is not surprising that victims of this trauma were more likely to be euthanized or found deceased than released. Despite almost 50% of households in Australia having a pet dog, there is limited research on the human management of pet dog and wild koala interactions (Rundle-Thiele et al., 2019). Some efforts have been made to develop this area, but there is a need for further studies to implement human-focused behavior management strategies to prevent dog attacks on koalas (Rundle-Thiele et al., 2019).
Conclusion
We positively hypothesized that the outcome of a wild koala after being reported to a veterinary clinic would be dependent on their sex, age, and the reason they were admitted. We found that all tested explanatory variables (age, sex, and etiology) had a significant effect on the outcome of a koala. Specifically, adults were more likely to be euthanized or found deceased than released, compared to sub-adult or young koalas. Females were more likely to be euthanized or found deceased than released, compared to male koalas. Koalas who had clinical signs of chlamydia disease were more likely to be euthanized than released, but less likely to be found deceased than released. Koalas who were exposed to bushfire were also less likely to be found deceased than released but the likelihood of being euthanized than released was not significantly different. Koalas who had been attacked by a dog, fallen from a tree, and/or been hit by a motor vehicle were more likely to be euthanized or found deceased than released. Finally, koalas who had been found in an unsuitable landscape were more likely to be released than euthanized or found deceased.
We examined three explanatory variables to determine their effect on the outcome of a koala admitted into clinical care. Results illustrate that koalas experience different outcomes based on their age, sex, and etiology. Understanding the distinctive challenges faced by koalas based on these factors is important to inform future conservation policies, as policy action is most effective when implemented alongside informed science. For example, understanding that koalas hit by a motor vehicle are not likely to recover means that targeted conservation policies should be implemented to minimize motor vehicle impacts in the first place. Unfortunately, this study was limited by the fact that the most frequently reported etiology was “unknown,” meaning that no etiology was identified, or the field was blank in the dataset. Additionally, 32% of koalas in this study had an unknown or unrecorded sex. We understand the complexities involved, but we encourage SWVCs to implement better record keeping practices to avoid missing data in the future. Despite the limitations, however, this study was able to provide an updated retrospective analysis for a large proportion of South-East Queensland koalas, over a period spanning more than two decades. The benefits of doing so include an advanced understanding of the primary threats for wild koalas within South-East Queensland. This can provide an indispensable basis for future koala conservation strategies through informed management and conservation policy development.
Acknowledgments
We would like to thank the veterinary staff and volunteers at Australia Zoo Wildlife Hospital, Currumbin Wildlife Hospital, and RSPCA Queensland Wildlife Hospital for contributing data to the South-East Queensland Wildlife Hospital Network. We would also like to thank the staff and volunteers at the Australian Koala Foundation for their assistance and expertise with the program ArcGIS. Finally, we would like to thank the editor and reviewers of SOAN for their valuable feedback to improve this manuscript.
Research was funded by the University of Queensland PhD Scholarship.
With regards to the author contributions: project conceptualization by EJN and RC; data validation by RC; data analysis by KAD and RC; writing by RC; editing by EJN and KAD; project supervision by EJN and KAD.
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