Bleating or screaming? Two new, very loud, frog species described in eastern Australia

With the help of vital FrogID audio, two new species of frog, each with a call as loud and piercing as each other, are described as new to science.

The Bleating Tree Frog (Litoria dentata) is a familiar frog to many residents of eastern Australia. The frog has one of the loudest calls of any Australian frog, and it’s been described as almost painful to listen to - sounding like an incredibly loud, high-pitched screech. Previously, this frog was thought to be widely distributed from southeast Queensland in the north to just across the border into Victoria. However, recent collaborative research, including analyses of recordings submitted to the Australian Museum’s FrogID Project, has revealed that the species is actually not one, but three species. Although similar in appearance, and in their piercing calls, the frogs are genetically very different, and two new species are now scientifically recognised in Australia.

The “original” species of Bleating Tree Frog, now coined the Robust Bleating Tree Frog (Litoria dentata) only occurs from northeastern NSW to around the NSW/Queensland border. The newly described Slender Bleating Tree Frog (Litoria balatus) is present in Queensland, including Brisbane, while the Screaming Tree Frog (Litoria quiritatus) occurs from around Taree in NSW to just over the border in Victoria, including Sydney. The fact that we’ve discovered two new species to science, each of which occurs in such large cities, is remarkable, and demonstrates just how much we still have to learn about our frogs!

The three species vary subtly in appearance. The Slender Bleating Tree Frog, as its name suggests, is slender in appearance, has a white line extending down its side, and males have a distinctly black vocal sac. The Screaming Tree Frog isn’t nearly as slender, doesn’t have the white line extending down its side, and males have a bright yellow vocal sac. In the breeding season, the entire body of males of the Screaming Tree Frog also tend to turn a lemon yellow. The Robust Bleating Tree Frog is most similar in appearance to the Screaming Tree Frog, but males have a brownish vocal sac that turns a dull yellow or yellowish brown when fully inflated.

To understand how different the calls of these frog species were, we drew upon the thousands of call recordings of the species submitted to the FrogID project and picked some of the clearest to analyse. Our examination revealed that their calls differ slightly in how long, how high-pitched and how rapid-fire they are. The Slender Bleating Tree Frog has the shortest, most rapid-fire and highest pitched calls.

Thankfully, the three closely-related species are relatively common and widespread. They are also all at least somewhat tolerant of modified environments, being recorded as part of the FrogID project relatively often in backyards and paddocks, as well as more natural habitats.

This new research highlights how much we still have to learn about Australia’s frogs. The scientific recognition of these two frog species brings the total number of native frog species known from Australia to 246. In fact, they’re the third and fourth species of frog recognised as new to science in the last few weeks, behind Gurrumuls’ Toadlet and the Wollumbin Pouched Frog. This research also highlights the valuable contribution that everyone can make to better understanding and conserving our frogs. By using the free FrogID app to record frog calls you might help discover Australia’s next ‘new’ frog species!

Dr Jodi Rowley, Curator, Amphibian and Reptile Conservation Biology, Australian Museum & UNSW Sydney. Lead Scientist, FrogID.