Narrandera’s koala population is contributing to a major scientific study led by the NSW Government in partnership with the University of Sydney, Taronga Conservation Society and other universities. The researchers from the Koala Sentinel Program have been back in the Riverina for its final round of fieldwork. 

The Riverina is one of six Sentinel sites being studied across NSW as part of the most comprehensive assessment of koala health ever undertaken.

Professor Mark Krockenberger from the University of Sydney’s Koala Health Hub in the Sydney School of Veterinary Science said: “Disease is a major threatening process for koalas in the wild, the Koala Sentinel Program is providing a unique opportunity to collect disease data for a range of populations. This will be critical to our understanding of disease in the wild.”

Narrandera in the Riverina was chosen because of its unique history. After severe population declines caused by hunting and habitat clearing in the early 1900s, koalas were re-established in the area in the 1970s. Today, the region supports one of the densest koala populations in NSW, within rare river redgum habitat.

Researchers in the Sentinel Program are investigating factors such as health, disease, genetics, nutrition, habitat and ecology across six different landscapes across the state, from the subtropical Northern Rivers to the semi-arid Riverina.

Professor Carolyn Hogg in the School of Life and Environmental Sciences and the Australasian Wildlife Genomics Group at University of Sydney said: “Maintaining genetic diversity is essential for any species to be able to adapt to a changing environment. Understanding genetic diversity and how it affects the overall health of koala populations is vital to their future health in the wild.”

Genetic variation at the six sites

Professor Hogg said data from the Sentinel site in the Riverina shows Narrandera has the second highest genetic diversity of any of the studies populations, second only to the Richmond Ranges in northern NSW.

The study found Narrandera’s koala population has portions of its genome that are homozygous (they do not have much genetic variation).

“This is likely a remnant of the Victorian koalas that were released there as it takes a number of generations to break up these long runs of no variation. We expect them to improve with time,” she said.

“Narrandera has the second highest effective population size, meaning we believe them to be at lower risk of extinction from a genetic point of view than other populations.”

Specialist teams are building on two years of detailed field surveys, using heat-sensing drones to locate koalas before dawn and conducting health checks in a mobile veterinary field unit. Each koala is safely returned to the same tree after samples are collected, measurements taken and GPS collars fitted to track movement.

Research team leader Tim Jessop from the NSW Department of Climate Change, Energy, the Environment and Water said: “We know that to better protect koalas, we need better information about where they are and how they’re surviving in the wild.

“This landmark study is the largest and most comprehensive of its kind. The findings from this intensive program will provide the evidence we need to guide future koala population management and inform the next phase of conservation action across NSW.”

Findings from Narrandera will be compared with results from the five other Sentinel populations to help build the first statewide picture of what supports healthy koala populations in the wild.

The research is led by the NSW Department of Climate Change, Energy, the Environment and Water, in partnership with the Taronga Conservation Society Australia, and major universities including the University of Sydney, Western Sydney University and the Australian National University. An initial statewide report is due in mid‑2026.

What is the Sentinel Koala Program?

The Koala Sentinel Program is a long‑term scientific study examining koala health across six populations in NSW.

By collecting consistent data on genetics, disease, habitat and movement, scientists can better understand why some koala populations are thriving while others are under pressure.

Early findings highlight the need to assess koala health at a population level, rather than individual animals.

The findings will help guide future koala population management and conservation action across NSW.