This article relates to ongoing debates on Australian Rural & Regional News: Open for Debate: Koalas; Open for Debate: Bushfires, Logging, Burns & Forest Management

Comment on research article, An 8-year long retrospective analysis identifies the major causes of morbidity and mortality in rescued koala joeys, by Harsh Pramila Pahuja and Edward Jitik Narayan. Australian Rural & Regional News has sought a response (see below) from the authors and also Danielle Clode from Flinders University, who has responded below.

“Wildlife rescue and rehabilitation centres aid millions of species worldwide.” I think not. Perhaps millions of animals. The koala is a species suffering disease, dog attacks and vehicle injuries because there are too many. When this naturally rare species first irrupted in plagues a century after Europeans arrived, the humane and economic response was to shoot the malnourished and diseased animals and use their valuable skins.

Most young animals of any species do not survive. That’s why populations remain relatively stable. Numbers are limited by food. Habitats have a carrying capacity which cannot be exceeded in the long term. This study showed an “exceptionally high mortality rate of koala joeys with renal disease”.

The study area was suburban Adelaide and adjacent bushlands, where even the Koala Industry admits that numbers are increasing. A logical scientific hypothesis is that kidney disease is a sign of joeys suffering from a bad diet because they’re denied access to the essential food resource of soft young eucalypt shoots. That resource is controlled by the already overabundant adults.

Koalas in natural low-density sub-populations have chlamydia but not chlamydiosis. The disease is a consequence of poor nutrition in dense populations. There haven’t been any studies of the naturally high mortality of joeys in healthy forest. It’s a fact of life.

Healthy eucalypts forests have a very low carrying capacity because soft young shoots are ephemeral and solitary koalas move around large ~ 100 ha home ranges consuming them wherever they arise. Koalas have large noses to sniff them out. Forests get sick in the absence of maintenance by mild fire. Sick trees turn over large quantities of soft young shoots and koalas rapidly increase until trees and koalas crash in extreme droughts.

Dense undergrowth commonly develops under sick trees. Sick forests explode in uncontrollable fires when ignited by lightning, accident or arson in extreme weather during drought. Many koalas are killed. But the massive regrowth after drought-breaking rains starts the next cycle of irruption in koala numbers. Lock It Up and Let It Burn ‘conservation’ polices, dense koala populations and destructive wildfires go together.

But academics don’t see the big picture of forest ecology and management. Blinkered specialists focus on trees or koalas or understorey plants or ‘fuels’. There’s been several recent studies of ‘eucalypt dieback’ near Adelaide.

We are told that “the rapid increase of renal disease … warrant[s] the attention of future conservation policy developers [and] the severely high mortality rate of koala joeys due to renal disease warrants improving treatment protocols and any measures that can help reduce the mortality rate of this disease in koala joeys”.

In fact this is an animal welfare issue – nothing to do with conservation. The scientific solution would be to reinstate frequent mild burning in the bush. That is to restore a healthy, safe and diverse landscape with a naturally low carrying capacity for koalas and increased carrying capacity for the truly endangered species whose habitat is being choked out by scrub. In the meantime, the ethical solution to the animal welfare problem would be to euthanase sick and badly injured joeys and export healthy and rehabilitated joeys to wildlife parks. Of course, the multinational, multi-million-dollar Koala Industry won’t allow that. 

Responses sought by Australian Rural & Regional News

Australian Rural & Regional News has sought and welcomes a response to this article from the authors of the research article, Harsh Pramila Pahuja and Edward Jitik Narayan, and also Danielle Clode from Flinders University who has written about abundant koala populations in South Australia.

In particular, a response is sought to the proposition that the paper does not:

• take into account the natural attrition of joeys even in healthy environments;
• consider any correlation between koala health and the health of the eucalypt forest in which they live;
• consider any correlation between koala health and population density;
• consider the carrying capacity and sustainable density of the particular eucalypt forest the habitat of the diseased koala joeys being studied;
• recognise that the focus of more effective and sustainable koala conservation efforts might be proper land management to maintain healthy forests which would in turn better support sustainable levels of healthy koala populations.

Responses will be included here once received.

Danielle Clode has responded as follows (14 December 2023):

“Thank you for inviting me to comment on this review of an eight year study of the major causes of death in rescued koala joeys in South Australia. This academic research paper has been published in a respected scientific journal ’Wildlife Research’ and would have been rigorously peer-reviewed by a number of experts in the field of koala and wildlife health prior to being accepted for publication. I am not an expert in koala health, but I am a biologist who specialises in animal behaviour, science writing and communication and have a broad knowledge of the current state of koala research and history as well as bushfires, having recently published,  ‘Koala: A Life in Trees’ as well as ‘A Future in Flames’. I found this paper to be a solid, well-written piece of research with a sound methodology and analysis yielding results that are carefully discussed in full recognition of the limitations of the data and scope of the findings.  It’s a very useful and interesting paper showing that most rescued koala joeys are orphaned or heat stressed and just need a bit of TLC before being returned to the wild, and identifying the major health factors as renal disease (common in SA), heat stress, chlamydia and injuries by other animals and vehicles.

One of the most interesting findings was that renal disease, heat stress and chlamydia all increased between 2014 and 2021. While the causes of heat stress and chlamydia are well understood, the causes of renal disease as a factor in SA koalas (but not NSW and Qld populations) is still poorly understood and further studies are needed to understand the links between genetics, maternal stress and drought in this disease. The factors regulating koala populations across Australia are incredibly complex and variable (which is why it took me a whole book to understand and explain these issues, synthesising the results of hundreds of papers like this one). Understanding how these factors operate in different areas and ecosystems is important in developing appropriate policies to protect and manage koalas nationally. This study makes an important contribution to that knowledge.

In relation to the article published by Vic Jurskis in Rural and Regional News about the koala joey mortality paper, I feel this review misrepresents the original article and does not present a fair, coherent or well-supported argument. While some of the personal opinions presented relate to the broader debate about koala management and conservation generally, they are just not relevant to the animal welfare paper being reviewed and I think it is unfair to call for responses to propositions that fall well outside the scope of the paper being reviewed.”

Vic Jurskis responds

“Dear Editor,

Dr. Danielle Clode’s response ignores your propositions about a recent paper on kidney disease in koala joeys. Her reply contains many apparent misrepresentations and factual errors.

My “review” of the paper was a brief comment. The “eight year study” was a desktop analysis of other peoples’ data carried out during 2022. It clearly wasn’t “rigorously peer-reviewed”. The first sentence in the paper was “Wildlife rescue and rehabilitation centres aid millions of species worldwide”.  Critical review would have identified this error.

Dr Clode says that “One of the most interesting findings was that renal disease, heat stress and chlamydia all increased between 2014 and 2021”. So did koala numbers. She claimed that “The factors regulating koala populations across Australia are incredibly complex and variable (which is why it took me a whole book to understand and explain these issues, synthesising the results of hundreds of papers like this one)”.

But Clode didn’t address your basic propositions on these factors. She says that my “personal opinions” which were peer-reviewed and published as a research article in the same CSIRO journal six years earlier “are just not relevant to the animal welfare paper being reviewed”. The “animal welfare paper” sought to influence conservation policy as well as animal welfare protocols. Hence my brief comment.”