Not all gum leaves are created equal… and koalas know it! But what do we know?
Once abundant in eastern Australian forests that contain Eucalyptus species, koala populations have declined since European arrival1. Protected in all states and territories, koala populations continue to decline, driven by increasing temperatures, fire severity, drought conditions, disease, dog predation and vehicle strike. Habitat loss, degradation and fragmentation is also a key driver of population declines2.
Furthermore, there is quite a lack of understanding and agreement on what koala habitat really looks like2. We do know that a koala diet consists of eucalypt foliage, as well as traces of bark, flower buds and soil. However, what we have long pondered is why koalas prefer some trees over others…
Across a koala’s home range (the space a koala needs to survive in the wild—which tends to vary depending on the quality of the habitat), koalas eat leaves from over 100 eucalypt species4. However, koalas appear to be quite “fussy” over what tree they browse from—observed often to ignore other trees of the same species.
This has long been a question for the team at QKC, and we are so excited to work with fellow leaf enthusiast, Dr Kara, who is really getting to the root of the matter.
Introducing… The Gourmet Gum Leaves Project
At Queensland Koala Crusaders, we have been working with Australian National University researcher, Dr Kara Youngentob, on the fascinating Gourmet Gum Leaves Project, a ANU and Redland City Council collaboration—and it’s changing what we thought we knew about koalas.
Now entering its third year, the research team “aims to boost the long-term viability of koala and greater glider populations by enhancing the nutritional quality of habitats and restoration plantings”3.
For years, it was believed that factors like soil and climate determined why koalas prefer some trees over others. But this research suggests something surprising: it may come down to genetics!
Even more intriguing? The discovery of “mosaic trees” —single trees that produce both high-toxicity and low-toxicity leaves. Koalas will carefully browse only the parts they want, leaving the rest untouched.
Kara and her team are identifying the trees koalas prefer, analysing their nutrients and toxins, and growing new seedlings from those exact trees. Those baby trees are now nearly ready for planting... a huge step forward.
This month, we helped prepare a planting site with the incredible Koala Farmland Fund, getting ready for what could be a game-changer in habitat restoration.
Koala-ty over Quantity
The Gourmet Gum Leaves Project is working to improve how habitat nutritional quality is assessed. Because here’s the key: planting more trees isn’t enough—we need to plant the right trees. If we can restore landscapes with the most nutritious, koala-preferred species, we can dramatically improve survival rates where habitat has been lost.
We aim to stay closely connected to this project, with Kara and her team, supporting them in as many ways as possible.
By Madeleine Coyle, with special thanks to QKC Research Coordinator, Jessie Maclean
Find out more
Gourmet Gum Leaves by Dr Christina Zdenek
Sign up to our email list to stay up to date with QKC
References
1Melzer A, Carrick F, Menkhorst P, Lunney D. and John B.S. (2000), Overview, Critical Assessment, and Conservation Implications of Koala Distribution and Abundance. Conservation Biology, 14:619-628. https://doi.org/10.1046/j.1523-1739.2000.99383.x
2McAlpine C, Lunney D, Melzer A, et al. (2015) Conserving koalas: A review of the contrasting regional trends, outlooks and policy challenges, Biological Conservation, 192:226-236, https://doi.org/10.1016/j.biocon.2015.09.02
3Youngentob K & Marsh K (n.d.) Gourmet Gum Leaves Project - Improving landscape nutritional quality for koala and greater glider conservation and management, Australian National University, accessed 23 April 2026.
4Youngentob K, Marsh K, Skewes J (2021) A review of koala habitat assessment criteria and methods, Australian Government, Department of Climate Change, Energy, Environment and Water, accessed 23 April 2026.