Australian frogs are no exception to the threats currently impacting amphibian species globally. The disease chytridiomycosis, climate change, habitat destruction, and developments that harm natural ecosystems are just a few of the pressures causing frog declines. The Littlejohn's Tree Frog (Rawlinsonia littlejohni, formerly Litoria littlejohni) is one such species: a rare amphibian endemic to the Australian state of New South Wales. This mid-sized, curry-scented, brown frog is found in only three isolated regions: the Woronora Plateau, the Blue Mountains, and the Watagan Ranges. The fragmented nature of these habitats has led to poor gene flow between populations and high rates of inbreeding.
Much of what we know about this frog has been uncovered in the last decade, primarily through work by conservation researchers at the University of Newcastle (UoN). Recent ecological studies have prompted an upgrade of the species' IUCN (International Union for Conservation of Nature) conservation status from 'Vulnerable' to 'Endangered', following more accurate population estimates and accounting for its limited geographical range. Currently, within the University's Centre for Conservation Science, a multidisciplinary team of researchers is managing a 'Saving Littlejohn's Tree Frog Project'. Blending ecological and biological practices, the Amphibian Integrated Conservation Unit (ICU), led by Dr Alex Callen, Dr Kaya Klop-Toker, and Dr Rose Upton, aims to combine ecology, habitat restoration, reproductive science, and citizen engagement to bolster the species' chances of survival.
Project Successes
In the field, the Amphibian ICU worked with State Forest and National Parks to construct new breeding ponds within the Watagan Ranges, with the aim of boosting reproduction and population size. The other goal of these ponds was for them to act like stepping stones, helping frogs move across the landscape. Population genetics research by Dr Nadine Nolan during her PhD found that frogs living in ponds only 2 km apart were not intermixing, and that two small sub-populations with increased rates of inbreeding were forming. It was hoped that placing 'stepping-stone' ponds along this 2 km corridor would link these sub-populations and increase genetic diversity. These ponds were quick to see success, with breeding occurring within three months of pond construction. Ongoing field surveys have seen clutches of eggs develop all the way through to metamorphosed frogs, and follow-up genetic analysis has shown increased rates of genetic mixing: a promising step forward for growing the gene pool in the region.
In the lab, more wins have occurred within the University of Newcastle's amphibian facility, with the first ever successful breeding event of the Littlejohn's Tree Frog in a captive setting occurring in winter 2025. Being a cool-climate breeding frog, captivity has not been as straightforward as it may be for other species. Littlejohn's Tree Frogs prefer cool, temperate heath forests and slow-flowing pools, with breeding often triggered by heavy rainfall, and the challenge for UoN researchers has been replicating this natural habitat in a captive setting. The extremely sensitive tadpoles also require carefully balanced water chemistry and temperature for successful growth through the vulnerable metamorphosis stage. The team has gained critical knowledge of the species over the course of the project, and their success follows years of persistence and refinement. As further insurance for the species, the team is also improving sperm cryopreservation techniques for biobanking: a method to preserve valuable genes for use in future IVF projects.
UoN's Amphibian ICU has recently partnered with Aussie Ark and WILDLIFE Sydney Zoo (WLSZ), transporting over 50 Littlejohn's Tree Frogs to the two zoos' new custom-built breeding facilities. The combined efforts are clearly paying off, with a second wave of successful captive breeding occurring in April 2026 at WLSZ, only three days after the frogs had moved into their new homes. This breeding success marked another key milestone for the project, as it was the first successful pairing of animals from the Blue Mountains with those from the Watagan Ranges, the first time animals from these different regions have been crossbred. The overall fitness, reproductive health, and immune markers of the offspring are now being assessed, allowing researchers to examine the viability of crossbreeding populations to combat the effects of inbreeding. The research team is hopeful that these genetically diverse offspring will be better equipped to fight threats such as disease and environmental change.
The Threat of the Hunter Transmission Line Project
Despite these conservation wins, a newly proposed transmission line development in the Watagan forest threatens to reverse all this headway. The Hunter Transmission Line project, which will help support the future use of renewable energy in the region, currently proposes to clear an 80 to 140 m wide corridor right next to the newly created breeding habitat, with a 5 ha switching station to be built on top of key historic breeding ponds. UoN's researchers have been tirelessly fighting the proposal in an attempt to save the Littlejohn's Tree Frog's habitat, urging government to build the project further from known breeding ponds, or to find alternative routes that do not cut through 50 km of native forest. The key environmental dilemma affecting countries globally is striking a balance between developments intended to reduce carbon emissions and the protection of critical ecosystems. This conflict is particularly difficult when it applies to areas already receiving active conservation attention. In this case, the research team is raising animals to release back into the wild, but does not yet know whether there will be any habitat left to release them into.
Looking Forward
The Amphibian ICU team is hopeful for the preservation of the habitat, but through their multidisciplinary approach, their insurance plan serves as an important backup. The ambitious project aims not only to increase population size but to restore lost genetic diversity, through selective crossbreeding in captivity, ecological fieldwork involving pond construction and monitoring, and reproductive biology using IVF from cryopreserved sperm. If the last few years have taught the team anything, it is that these projects certainly deliver their fair share of challenges, but that securing healthy populations of frogs in the wild is worth the effort.