The Aussie Green Tree Frog’s disappearing act from Sydney

FrogID reveals that Green Tree Frogs, once common throughout Sydney, are now few and far between.

Australian Green Tree Frogs (Litoria caerulea) are an Aussie icon. These large, bright green and permanently happy-looking frogs are widely distributed across much of Australia and commonly associated with human settlements. This species was once common throughout Sydney, but for decades there have been reports of the species’ decline in the area. For the first time, thanks to the national citizen science project, FrogID, we now have the first evidence of this decline. Citizen scientists used their smartphones and the free FrogID app to record Green Tree Frogs across Australia, but the tell-tale calls of the species were noticeably absent from most of Sydney. We hope that FrogID and its users will help us understand the reasons for this decline, and give the Green Tree Frog a helping hand in the Sydney area.

The Australian Green Tree Frog was widely distributed throughout the Sydney area in the late 1800s and early 1900s. It was reported from many central Sydney suburbs, including Sans Souci, Botany Bay, Randwick, Waverley, Bondi, Mosman and Curl Curl. In 1922, Launcelot Harrison noted that the species was “very generally distributed both in gardens and in the bushland surrounding them” in Mosman, with “perhaps a hundred frogs” observed on a night (Harrison 1922, p. 21).

For decades, there have been murmurings amongst frog biologists and nature-lovers across Sydney that the Green Tree Frog is no longer as common as it once was. The Green Tree Frog is large and easily recognizable. It is also rather bold, often moving in with us humans (there’s a reason its affectionately called the Dunny Frog), and males have a distinctive call that can be heard from far away. So, it’s not surprising that people noticed something was amiss. Several scientific reports have noted the apparent decline of the Green Tree Frog in Sydney, however there has been no real evidence of this decline - until now. Thanks to FrogID, a national citizen science project, and thousands of people recording the calls of frogs across Sydney, we finally have enough data for the first compelling evidence of the disappearance of the Green Tree Frog from most of Sydney.

In the first year of the FrogID project (November 2017-November 2018), we received 7,000 FrogID records from the Greater Sydney area (extending from the Central Coast to Bargo and past Katoomba). Only 52 of these were of the Green Tree Frog, and most were from outside Sydney itself. No Green Tree Frogs were recorded from any of the inner Sydney suburbs with historical records.

Elsewhere, even in urban areas, Green Tree Frogs were heard loud and clear. Country-wide, Green Tree Frogs were the seventh most common species identified from recordings submitted to FrogID, with over 2000 records of the species. Indeed, the Green Tree Frog was the most common frog species recorded in Darwin, and the third most common species recorded in the Brisbane area. Given how loud and distinctive their call is, their absence from most of Sydney is likely to truly reflect their decline throughout much of the Greater Sydney area.

FrogID is a citizen science project aimed at understanding and conserving one of the most threatened groups of animals on the planet, frogs. The project has already dramatically increased our understanding of the distributions, breeding seasons and habitats of frogs, and has revealed the severe decline of an Aussie icon, the Green Tree Frog, from Sydney. We hope the information we gain through FrogID will help us understand the reasons for this loss and prevent the species declining even further. With a little luck, this unique frog will be heard again throughout the suburbs of Sydney.

Dr Jodi Rowley
Curator, Amphibian & Reptile Conservation Biology, Australian Museum & UNSW Sydney

Timothy Cutajar
Research Assistant & Honours student, Herpetology, Australian Museum & UNSW Sydney