The discovery of 60 koalas in the trees around Bootawa Dam near Taree has been soured by the finding that half of them have chlamydia.
“If there's a continued increase in the number of animals within that population that test positive, then our breeding rates will decline, and the population will be at risk,” said MidCoast Council’s senior ecologist Mat Bell.
Strong numbers: MidCoast Council identified the “high-density” koala population around the dam site early last year, using a drone with a thermal camera attached.
Local community groups had been aware of the presence of koalas, but not the size of the population.
The search found one koala for every 2.5 hectares of land, which is seven times higher than the local average.
“In terms of koala densities, it's certainly the highest that we know of on the MidCoast, and it's one of the highest density koala populations anywhere in NSW,” Bell said.
Testing times: Council partnered with the University of Sydney to learn more about the population and why the area was so conducive to a high density of koalas.
However, Bell said during the related health assessments and disease screenings a little over half tested positive for chlamydia.
Why that matters: Chlamydia in koalas is primarily sexually transmitted and can affect their vision - impacting foraging ability - and reproductive system.
It can also be transmitted via physical contact and young koalas can become infected during birth or in their mother’s pouch.
“The really insidious thing about chlamydia is that females develop ovarian cysts, and they quite quickly become infertile,” Bell said.
If the disease takes hold, a population can become “functionally extinct”.
“Populations under severe stress from disease tend to disappear from the landscape because all of those aged koalas reach the end of their lifespan, and there's no sufficient recruitment of young animals into the population,” Bell said.
“There might be a few animals still within the landscape, but they don't function like a viable population.”
Bell said the Bootawa population was not yet at that level and was still breeding.
What next: Council is looking at how it can reduce the spread of the disease within the population and facilitate breeding between healthy koalas.
Chlamydia in koalas can be treated by antibiotics, however these can cause severe digestive system issues.
Bell said recovery rates from treatment “aren't extremely high”. Those koalas that do recover are susceptible to catching the disease again.
A vaccine developed by the University of the Sunshine Coast was approved last year, and a fundraising campaign is underway to support its rollout, which is expected to begin with koalas in captivity before moving to wild populations.
Image credit: Abbey Henry/LLS.