In the eucalypt canopies of Sugarloaf, in the western Lower Hunter, a koala population appears to have slipped past one of the species' most feared diseases. A University of Newcastle-led report estimates some 2,337 koalas across a 23,900-hectare landscape, and the animals examined showed no sign of active chlamydia, a disease that has spread through other nearby colonies. The quiet good fortune carries a shadow, because the same long isolation that may have kept infection out has narrowed the population's genetic inheritance, leaving its future to depend on protecting the habitat and watching
Sugarloaf Koalas Show No Sign of Chlamydia, But Isolation Poses Long-Term Risk
The same isolation that may have shielded the koalas could count against them
Mark
Why is a clean result from 27 koalas such big news?
Mimi
Because chlamydia is confirmed in neighbouring populations. Finding no active infection nearby, in an estimated 2,337 animals, is unusual enough that the researchers say it may be one of only a few such populations in NSW.
Luke
Twenty-seven is a small sample against that estimate, though. Dr Witt himself says you can't prove every koala is disease-free.
Mimi
Right, and he words it carefully: chlamydia is either absent or at very low levels. That's the claim, not a guarantee.
Mark
So the isolation helped?
Mimi
He says it may have helped limit the spread of chlamydia. The same isolation seems to have left the koalas closely related, with low genetic diversity.
Luke
Note the hedge, though. It's a 'may have'. The report doesn't establish that isolation is the reason the disease is absent.
Mark
What does the report want done?
Mimi
Protect more core habitat, improve fencing and crossings, and set up long-term monitoring.
Luke
Worth saying what's unknown: how the genetic risk will play out, and whether the disease stays away. The monitoring recommendation is really an admission of that.
Der Puls
- A disease that can blind, sterilise and kill koalas has been confirmed in neighbouring populations, but not among the 27 wild animals tested here.
- Thermal-imaging drones were used to locate the koalas, turning a hard-to-reach canopy census into a careful search for signs of infection.
- Researchers are steering the population toward resilience, urging core habitat protection, wildlife fencing, crossings and long-term monitoring.
- Low genetic diversity from prolonged isolation is the looming threat, and the koalas' current health may not last without sustained intervention.
In the eucalypt canopies of Sugarloaf, in the western Lower Hunter, a koala population appears to have slipped past one of the species' most feared diseases. A University of Newcastle-led report estimates some 2,337 koalas across a 23,900-hectare landscape, and the animals examined showed no sign of active chlamydia, a disease that has spread through other nearby colonies. The quiet good fortune carries a shadow, because the same long isolation that may have kept infection out has narrowed the population's genetic inheritance, leaving its future to depend on protecting the habitat and watching it closely.
In the tree canopies of Sugarloaf, in the western Lower Hunter, researchers have found a koala population that seems to have avoided chlamydia, one of the species' most damaging diseases. A University of Newcastle-led report estimates about 2,337 koalas across a 23,900-hectare area that includes Sugarloaf and Stockrington state conservation areas, Watagans National Park and surrounding forests.
The team tested 27 wild koalas, located with thermal-imaging drones, and found no sign of active infection. Chlamydia can cause blindness, infertility and death, and it has been confirmed in neighbouring populations, so the result may place Sugarloaf among only a few known New South Wales koala groups free of the disease. Dr Ryan Witt, the report's lead researcher, called it extraordinary, while stressing that no one can prove every koala is disease-free.
The finding comes with a catch. The koalas show low genetic diversity and high relatedness, a sign of long isolation. That separation may have kept the disease out, but it also limits the population's genetic resilience over time. The report recommends protecting more core habitat, improving fencing and crossings, and establishing long-term monitoring. Sugarloaf's koalas may be in better shape than many elsewhere, but keeping them that way will take sustained work.
Among the tree canopies of Sugarloaf, in the western Lower Hunter, researchers have found a koala population that appears to have avoided one of the species' most damaging diseases. A University of Newcastle-led report estimates that about 2,337 koalas live across the region, and that the animals tested around Sugarloaf and Stockrington showed no evidence of active chlamydia.
The estimate covers a study area of 23,900 hectares. That area takes in the Sugarloaf and Stockrington state conservation areas, Watagans National Park, adjoining state forests and the habitat surrounding them.
To check for disease, the team tested 27 wild koalas. The animals were located using thermal-imaging drones, and none showed signs of active infection. Chlamydia can cause blindness, infertility and death in koalas, and it has been confirmed in neighbouring populations. Researchers say this may make the Sugarloaf group one of only a small number of known koala populations in New South Wales where the disease has not been detected.
Dr Ryan Witt, a University of Newcastle conservation scientist and the report's lead researcher, called the result extraordinary. He was careful about its limits, though. It is impossible, he said, to prove that every koala in the population is free of disease. What the results suggest is that chlamydia is either absent or occurring at very low levels. In his view, the findings show why healthy koala populations need protecting before problems emerge.
There is a catch. The researchers found low genetic diversity and high levels of relatedness among the koalas, which suggests the population has been isolated for an extended period. Dr Witt said that isolation may have helped keep chlamydia out, but it has also reduced the population's genetic diversity. The same separation that may have shielded the koalas could count against them over the longer term.
The report makes three recommendations: protect more core habitat, improve wildlife fencing and crossings, and establish long-term monitoring. Researchers say Sugarloaf's koalas may currently be in better shape than many populations elsewhere, but keeping them that way will take sustained work.
Bemerkenswerte Zitate
Finding no evidence of chlamydia in the koalas we tested is an extraordinary result.— Dr Ryan Witt, University of Newcastle conservation scientist
The isolation may have helped limit the spread of chlamydia into the population, but it has also reduced genetic diversity.— Dr Ryan Witt
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