# Retrospective Analysis of Triage and Hospitalisation Records for Bushfire-Affected Koalas (Phascolarctos cinereus) and Other Wildlife Species from Victoria, Australia, 2019–2020

## TL;DR

This study analyzed veterinary records of bushfire-affected wildlife in Victoria, Australia, focusing on koalas to identify factors affecting survival and guide treatment decisions.

## Contribution

The study identifies specific prognostic factors for koala survival after bushfires, including age, body condition, and burn severity, to guide resource allocation in wildlife rehabilitation.

## Key findings

- Older koalas, those in poor body condition, and those rescued early after the fire had higher odds of death or euthanasia.
- Koalas with moderate or severe burns had significantly lower survival rates compared to those with minor burns.
- Burns affecting more than 10 digits were strongly associated with poor survival outcomes in koalas.

## Abstract

Following bushfires (also known as wildfires), impacted free-living wildlife may be captured and presented for veterinary assessment. This study was an in-depth investigation of the records of veterinary assessment and treatment of 259 animals in Victoria, Australia, impacted by bushfire in late 2019 and early 2020. The animals assessed included 35 different species, most commonly koalas. Further evaluation of the 6-month post-rescue outcomes for koalas presented for assessment was undertaken to understand the likelihood of survival for koalas with health impacts of fire exposure including injuries. The koalas least likely to survive were older koalas, koalas in poor body condition, and those rescued and evaluated in the first days after the fire. Two thirds of the koalas had burn injuries, and in addition to age and body condition, those with more severe burns and burns to many toes were least likely to survive. These findings can support veterinarians in understanding the likely medical outcomes for bushfire-affected koalas in the future and thus also assist in the appropriate allocation of treatment and rehabilitation resources to those animals most likely to recover.

Following bushfires (also known as wildfires), impacted free-living wildlife with welfare or conservation concerns are captured and presented for veterinary assessment where possible. This study represents an in-depth retrospective analysis of the veterinary records of 259 animals in Victoria, Australia, impacted by bushfire in 2019–2020. In total, 35 different species were assessed, including 196 koalas. Multivariable analyses of 126 koalas with complete medical records identified several clinical prognostic factors affecting 6-month survival outcomes. Increased odds of negative outcomes (death or euthanasia) were associated with increasing age (tooth wear class; odds ratio 2.70 for one unit increase), lower body condition score (one-unit decrease OR 7.27), and the earlier animals were presented after the fire event (OR 0.94 for each passing day). In 83 koalas with burn injuries, negative outcomes were also associated with burns more severe than minor (85% survival for minor burns only, compared to 31% survival with moderate or severe burns), and burns to more than 10 digits (12% survival). In burnt koalas, the combination of burn severity and digital involvement appear to be important prognostic factors for long-term outcomes. These findings can support veterinarians to more accurately evaluate prognosis for bushfire-affected koalas during initial assessment and will facilitate the strategic allocation of limited treatment and rehabilitation resources to the animals most likely to recover. The scope of this study was limited to the consideration of health outcomes, with the recognition of health as just one of many factors that must inform decisions about rehabilitating injured wildlife.