Leadbeater’s Possum

To better survey species that spend most of their lives in trees, ARI developed novel arboreal camera trapping methods that have now been widely adopted by DEECA  . The method involves ARI ecologists working with arborists to install cameras in trees, using creamed honey as a lure.

Cameras are set on tree trunks at varying heights (up to 47 m), targeting areas of well-connected vegetation, such as wattle foliage, where possums are most likely to be moving or foraging.

Because the arboreal camera trap survey method has proved highly reliable for detecting Leadbeater's Possums, it has been applied in other DEECA programs including the previous Forest Protection Survey Program (now discontinued) and the modernisation of the Victorian Regional Forest Agreements (Landscape Scale Surveys),   as well as by our project partners.

The refinement of survey techniques has allowed us to develop a more accurate picture of where Leadbeater’s Possum populations occur. This in turn allows for more informed assessments of the impacts of bushfires, fire management activities and other disturbances, such as severe storms.

Publications

• Nelson, J.L., Durkin, L.K., Cripps, J.K., Scroggie, M.P., Bryant, D.B., Macak, P.V. and Lumsden, L.F. (2017) Targeted surveys to improve Leadbeater’s Possum conservation. (PDF, 1.7 MB) Arthur Rylah Institute for Environmental Research Technical Report Series No. 278. Department of Environment, Land, Water and Planning, Heidelberg, Victoria. (accessible version (DOCX, 4.2 MB)
• Nelson, J.L., Lumsden, L.F., Durkin, L.K., Bryant, D.B., Macak, P.V., Cripps, J.K., Smith, S.J., Scroggie, M.P. and Cashmore, M.P. (2015) Targeted surveys for Leadbeater's Possum in 2014-15. Report for the Leadbeater's Possum Implementation Committee. Arthur Rylah Institute for Environmental Research. Department of Environment, Land, Water and Planning, Heidelberg, Victoria.

An arborist inspecting a tree-mounted camera trap. Photo by ARI.

ARI has surveyed nearly 500 sites using the arboreal camera trapping method to locate colonies, identify their habitat and to inform the establishment of the previous timber harvesting exclusion zones. Sites were selected using sophisticated predictive modelling and targeted areas where the species was most likely to occur.

Leadbeater’s Possums were detected at 46% of sites, contributing to thousands of hectares of further protected habitat up until January 2024  , when the Victorian Government announced that commercial native timber harvesting would cease in Victoria’s state forests. Clusters of protection zones were formed to create possum ‘neighbourhoods’. These protections were significant during the period when native timber harvesting occurred in the species’ habitat.

The findings from this study were used extensively in a review of the effectiveness of establishing timber harvesting exclusion zones around Leadbeater’s Possum colonies.

As part of the Regional Forest Agreements (RFA) update, ARI surveyed for Leadbeater’s Possums in atypical habitats to inform the Habitat Distribution Model (HDM). Surveys were conducted in forests on the edge of ash forest habitat within the species’ core range, and in areas with suitable habitat that were outside the known range. This work resulted in a range expansion northeast of the core population area.

Publications

• Macak PV, Nelson JL, Durkin LK, Cripps JK, White MD, Emerson LD, Lumsden LF. (2024) Short range extension delineating the north-eastern limit, and use of atypical habitat by highland Leadbeater’s possum. Australian Mammalogy 46, AM23003. https://doi.org/10.1071/AM23003
• Eyre AC, Harley DKP, Briscoe NJ, Lumsden LF, McComb LB, Lentini PE. (2025) A possum’s cautionary tale: targeted surveys in north-eastern Victoria fail to detect Leadbeater’s possum in remnant forest within its historic range. Australian Mammalogy 47, AM24030. https://doi.org/10.1071/AM24030

Leadbeaters Possum habitat distribution map as on NatureKit (DEECA).

ARI examined the recolonisation of burnt Leadbeater’s Possum habitat following the 2009 bushfires. The presence of unburnt habitat (refugia) positively influenced the occurrence of possums. Additionally,  habitat that remained unburnt in 2009, but where fire or timber harvesting had occurred before then, was also found to have higher Leadbeater’s Possum occupancy.

For the remaining intact habitat patches, possum presence was not affected by how close they were to unburnt areas outside the fire perimeter. This suggests that populations are recovering primarily through animals surviving within the burnt landscape, rather than by recolonisation from surrounding unburnt habitat.

Publications

• Durkin, L. K., Moloney, P. D., Cripps, J. K., Nelson, J. L., Macak, P. V., Scroggie, M. P., ... & Lumsden, L. F. (2024). Unburnt refugia support post-fire population recovery of a threatened arboreal marsupial, Leadbeater’s possum. Forest Ecology and Management, 551, 121487.

The shortage of tree hollows is a major barrier to Leadbeater’s Possum recovery. Many suitable hollows had developed in old fire‑killed trees (‘stags’) following the 1939 bushfires. However, many of these are now collapsing. Native timber harvesting has further reduced hollow availability. An ongoing decline in suitable hollows remains one of the most direct and acute threats to the species.

ARI has helped design supplementary tree hollows that can be carved by arborists using a chainsaw. These carved tree hollows have a large internal diameter and a smaller entrance, characteristics that Leadbeater’s Possums favour in natural hollows. The possums complete the final touches by bringing shredded bark into the hollow to form a nest.

As part of a trial, 132 hollows were carved and have been monitored since 2015. Of these, 66% have been used by Leadbeater’s Possums throughout the year, including for breeding, with little impact on tree health.

These carved hollows have proved more effective than nest boxes, which are more vulnerable to storm damage, have higher predation risks, less stable internal microclimates and require frequent maintenance, whereas carved hollows require maintenance only every five years  .

The design and implementation of the novel artificial hollows are helping Leadbeater’s Possum colonies establish after disturbance events. They provide a management option to supplement habitat in areas where there is a shortage of suitable nesting hollows.

Publications

• Griffiths, S. R., Robert, K. A., & Jones, C. S. (2022). Chainsaw hollows carved into live trees provide well insulated supplementary shelters for wildlife during extreme heat. Wildlife Research, 49(7), 596-609.
• McComb, L. B., Lentini, P. E., Harley, D. K. P., Lumsden, L. F., Eyre, A. C., & Briscoe, N. J. (2022). Climate and behaviour influence thermal suitability of artificial hollows for a critically endangered mammal. Animal Conservation, 25(3), 401-413.

Strategic fuel breaks are strips of land where vegetation has been permanently removed or thinned in an attempt to reduce the rate of spread of fire, and to assist fire control.

ARI evaluated the effectiveness of mitigation measures used during upgrades to a strategic fuel break in the Port Phillip region. As part of this, trees deemed hazardous or that may impede fire control operations were removed  , many within habitat used by Leadbeater’s Possums.

Mitigation measures, including exclusion zones, habitat retention areas, wildlife corridors and rope bridges, were established and monitored over three years at twelve sites.

ARI research showed that detection rates were slightly higher in wildlife corridors and near rope bridges, compared to exclusion and retention zones. Rope bridge monitoring suggested that there was frequent possum activity, with detection rates of 70- 76% at the two monitored bridges, although full crossings could not be confirmed.

Overall, the findings indicate that these mitigation measures supported the persistence of Leadbeater’s Possums despite habitat disturbance. The study highlights the importance of targeted habitat protection strategies.

With the increased use of strategic fuel breaks as a tool to help manage the impact of large-scale bushfires, our research is helping identify which mitigation methods are effective at minimising impacts on Leadbeater’s Possum populations.

Publications

• Rodriguez-Malagon M.A., Macak P.V. and Nelson J.L. (2024). Strategic Fuel Breaks: Mitigations Effectiveness for Leadbeater’s Possum - Yarra Ranges National Park. Unpublished Client Report for the Forest, Fire and Regions Group. (PDF, 3.98 MB). Arthur Rylah Institute for Environmental Research, Department of Energy, Environment and Climate Action, Heidelberg, Victoria