A koala colony in Brisbane on the brink of collapse has not only recovered but more than doubled through a painstaking new way of managing the endangered species.
When University of Queensland (UQ) researchers started the project in 2019, chlamydia was rampant and had infected 60 per cent of the colony.
There was just one healthy breeding female across the 95-hectare Belmont Hill Reserve.
"The population was crashing," head researcher Sean FitzGibbon said.
"Now, we've got numerous females that are reproducing ... and there's now the likelihood that the colony will exist long into the future."
Dr FitzGibbon led a team of three, including two ecologists and a wildlife vet, to develop the new management approach.
They hope to roll it out to at least a dozen colonies in steep decline, but the approach is costly and time consuming.
What are they doing differently to save koalas?
Dr FitzGibbon said while a huge amount of time, money and effort went into treating sick koalas around Australia, efforts were largely "fingers crossed", opportunistic and ad hoc.
For example, usually a member of the public would call in a sick or injured animal. It is then treated at a hospital and released back into the wild, where there was a high level of disease.
"Really, what have we achieved in doing that?" Dr FitzGibbon said.
"Their prospects of getting infected with chlamydia again hasn't changed."
The UQ team, funded by Brisbane City Council, took what they believed to be the first "systematic" approach to wiping out the sexually transmitted infection and reviving the population.
First, they took weeks searching every tree, craning their necks for at least 15 minutes on each one.
When a koala was found, it was fitted with a GPS tracker and vet Amber Gillett gave each a health assessment in the bushland.
Thirteen koalas were assessed.
Five were healthy and released, six were euthanased and two were taken to hospital and released back about two months later.
"Some of them needed to be euthanased straight away, they were even having trouble climbing down a tree they were so unwell," Dr Gillett said.
"Unfortunately that's the chlamydial diseases story for koalas.
"No matter what treatment you throw at them, you cannot reverse the disease process. It's pretty nasty."
Despite the colony plummeting to just seven since the program's start, with successful breeding in the wild, and the injection of four healthy koalas rescued from other areas, the population has reached 15.
"Although it looks like you have a drop in growth, the overall output has increased," Dr Gillett said.
"Over one to two generations of breeding, you start to get an acceleration, as you don't have those infertile animals impeding the population growth.
"We don't want to claim we've wiped chlamydia out entirely, but we may have.
"There's always the possibility that there is another koala out there that we haven't found."
Where else would this be successful?
The Belmont Hill Reserve is almost a closed colony, hemmed in by suburbia, a motorway and a busy thoroughfare.
Dr FitzGibbon said their project would work in other populations that were similarly closed off, therefore almost negating the risk that chlamydia would be re-introduced.
The program would not be successful in a sprawling national park.
The research also examines if there are areas in the reserve that the koalas gravitate to, if and when they cross roads, and a koala's travelling range and therefore how much bushland would be needed to sustain one.
Brisbane City Council invested about $500,000 into the four years of research running until 2023.
To do it across Brisbane alone, Dr FitzGibbon said it would cost millions of dollars "because it's just so time consuming".
"We're calling on the Queensland government and local councils to work together to get koala survey teams to go out and do this and take a more strategic approach to treating sick koalas and conserving populations," he said.
Dr Gillett said it was normal for ecologists survey koalas but having a vet do on-site assessments was one of the key's to the program's success.
"We can detect disease, even at low levels," she said.
While some koalas just harbour the bacteria and transmit it, a large proportion can get conjunctivitis and become blind.
Others get painful bladder infections and constantly dribble urine, or the bacteria can spread to the kidney and reproductive tract, leading to infertility.
Will governments put in?
Federal Environment Minister Sussan Ley said there were a number of grants that will become available in coming months to improve koala health and the practical application of research outcomes.
"While not a part of this research, we will closely monitor the findings and are always open to considering new approaches that maximise health outcomes and strategies for the koala health," she said.
A Brisbane City Council spokesperson said the program successfully re-established a healthy population "that was at immediate risk of local extinction".
"We have demonstrated it can be done and we hope the program can be extended further and replicated across south-east Queensland and Australia.
"We hope that we can not only stop the decline of koalas but increase their numbers."
The state government has been contacted for comment.
