Bushfire Survivors: What Determines Whether A Koala Recovers

Australia’s “Black Summer” bushfires of 2019–2020 were among the most destructive in the country’s recorded history, burning more than 1.5 million hectares in the southeastern state of Victoria alone. Around 91% of the burned area was native forest, and more than 300 species had at least 40% of their habitat affected. In the months that followed, thousands of wild animals were assessed and treated by veterinary teams. Koalas were among the most visible casualties, as their tree-dwelling habits and relative inability to evade fire make them particularly vulnerable.

Researchers aimed to identify which clinical factors at the time of initial assessment were associated with survival in koalas rescued during this event. Better understanding of these prognostic factors could help future responders make faster, more objective decisions about which animals are most likely to recover — and allocate limited treatment resources accordingly.

The study was a retrospective analysis of veterinary records from three field triage stations established in Victoria in early January 2020. Over 52 days, teams assessed 259 wild animals from 35 species, with koalas making up 77% of all animals presented. For koalas subsequently transferred to wildlife hospitals, more detailed clinical and treatment records were also reviewed.

The analysis focused on 126 koalas with complete records and tracked their outcomes at six months after initial presentation. Tooth wear was used as a proxy for koala age, with more wear indicating an older individual. Body condition was scored on a scale of one to five, where five was excellent. Burns were graded on a scale of zero to three, with three being the most severe. Statistical models were used to identify factors associated with survival (still in care or released) versus death or euthanasia.

Across all 126 koalas assessed, three factors were consistently associated with survival: age, body condition, and how soon after the fire a koala was presented at the triage station.

Older koalas were significantly more likely to die or be euthanized, with each one-unit increase in age class more than doubling the odds of a negative outcome. Each one-point drop in body condition score was associated with more than seven times greater odds of death or euthanasia. Koalas presented in the earliest days after a fire also fared worst. For each additional week that passed before a koala was presented at the triage station, the odds of a negative outcome reduced by one-third. The researchers note this likely reflects a survivorship effect: the most severely injured animals either die in the field or are the first ones encountered.

Two-thirds (66%) of koalas assessed had burn injuries, with the feet being the most commonly affected body part. For these animals, burn severity and the extent of toe burns were important additional predictors of survival, on top of age and body condition.

Koalas with only minor burns survived at a rate of 85%, while survival dropped to 31% in koalas with at least one burn rated as moderate or severe. The number of toes burned was also a critical factor. Koalas with more than 10 toes burned had only a 12% survival rate, compared to around 69% survival in koalas with 10 or fewer toes burned.

A statistical model combining these factors illustrated the pattern clearly. Koalas with moderate to severe or severe burns had only 12% survival regardless of other factors. Among those with less severe burns (minor, minor to moderate, or moderate), young koalas had a 92% survival rate, while for older koalas, body condition played a role. Of older koalas with less severe burns, 75% in good body condition survived compared to only 20% in poor body condition.

As a retrospective study, the research relied on clinical records that varied in detail and terminology across different treating clinicians. Burn assessments in particular lacked standardized language, requiring the researchers to reclassify descriptive notes into a consistent scoring system. The study also excluded koalas who were euthanized immediately in the field on humane grounds, meaning the findings apply specifically to koalas who survived long enough to be transported to a field station. The subgroup transferred to wildlife hospitals was small (just 29 koalas), which limited conclusions about the effects of specific intensive treatments like fluids, antibiotics, and pain relief.

For organizations involved in wild animal rescue and rehabilitation in Australia, this study offers some of the most detailed prognostic guidance to date for bushfire-affected koalas. Field responders can use age, body condition, burn severity, and toe involvement as practical triage criteria, helping to direct intensive veterinary care toward the animals most likely to recover.

The authors are clear that clinical prognosis is only one part of a complex decision. There are many other factors to weigh, including the stress of prolonged captivity on animals, the economic costs of their rehabilitation, the state of the habitat they’re going to be released back into, and the mental health of the people caring for them. For animal advocates, this points to the importance of supporting investment in wildlife-specific veterinary training, standardized data collection, and rehabilitation infrastructure before fire seasons begin — not only during the response itself. The welfare of individual wild animals caught in disasters deserves as much attention and preparation as the population-level conservation concerns that more often drive funding and policy.

This summary was drafted by a large language model (LLM) and closely edited by our Research Library Manager for clarity and accuracy. As per our AI policy, Faunalytics only uses LLMs to summarize very long reports (50+ pages) that are not appropriate to assign to volunteers, as well as studies that contain graphic descriptions of animal cruelty or animal industries. We remain committed to bringing you reliable data, which is why any AI-generated work will always be reviewed by a human.