Two new ‘loud’ frog species have been found along the east coast of Australia

It’s time to mark up your guide book because it turns out what we know as the bleating tree frog is actually three different species.
By Australian Geographic November 23, 2021 Reading Time: 3 Minutes Print this page

Meet the slender bleating tree frog (Litoria balatus) and screaming tree frog (Litoria quiritatu), two new Australian tree frog species.

Genetic analyses, as well as examination of their calls and differences in appearance have given scientists enough evidence to officially declare that the bleating tree frog (Litoria dentata) is, in fact, three different species.

The findings of their research have been published today in the journal Zootaxa.

Australian Museum Frog biologist Dr Jodi Rowley was in charge of analysing the calls. She’s also the lead scientist for FrogID, an app that gives citizen scientists the ability to submit frog calls from around Australia. Calls submitted through the app have been used to confirm the new species.

“It’s really painstaking going through those calls, even counting the number of pulses in the calls… they have up to 100 pulses sometimes,” Jodi says. “It’s the less glamorous side of science where we’re converting these audio recordings, counting the pulses and measuring things. Frogs are exquisitely in tune with their own calls, but us humans are not really adapted to telling the small differences.”

While it may be difficult for the average person to tell the difference between the species by their call, there are also marked differences in their physical appearance. The screaming tree frog has a bright yellow vocal sac (the part of the frog that puffs out when the frog calls), the bleating tree frog has a brown vocal sac and the slender bleating tree frog is, Jodi says, the “stretch limousine version of the other two” and sports a black vocal sac.

From left to right: the screaming tree frog, slender bleating tree frog and the bleating tree frog. The slender bleating tree frog’s lives in Queensland and the screaming tree frog occurs from the mid-north Coast of NSW to Victoria. (Image credit: Jodi Rowley)

“Once you look at them side by side you can definitely see the difference but if you haphazardly looked at them you’d just think yep, that’s a bleating tree frog.”

News of the new species comes on the back of FrogID week (12-21 November), which resulted in the collection of almost 20,000 recordings of frog calls. Since 2017, 321,109 frog calls have been recorded through the app and nine scientific papers have been published based on the recordings.

“It’s helping contribute to increasing the scientific literature on frogs and it shows you can contribute to science relatively easily. There’s an idea out there that citizen science can’t be trusted and it’s not professional, but FrogID has made it easy for people to make a contribution,” Jodi says, adding that the recordings also help with frog conservation.

“When something is very widespread you don’t have to worry about it hugely, but now that this breaks one species up into three species with smaller ranges, so we need to be more concerned. We’re not worried about the three species now, but it does make things more vulnerable when they are in a smaller area.”

The addition of the slender bleating tree frog and screaming tree frog takes the total number of new Australian frog species discovered for 2021 to five. Previously the most recent discoveries were Gurrumul’s toadlet and the Wollumbin pouched frog, both described in October.

“Globally, more than 100 new frog species are named a year, but in Australia our average is probably only 1 to 2 new species, but some years are bumper years,” Jodi says.

“It’s actually not that rare to find new species of Australian frog, which is actually pretty alarming because our frogs are in a lot of trouble. The fact that we don’t even know what species of frog we have is kind of ridiculous.”

That the new species managed to slip under the radar is “amazing” according to South Australian Museum evolutionary biologist and co-author of the paper, Stephen Donnellan.

“I’m still amazed that it’s taken us so long to discover that the loudest frog in Australia is not one but three species,” he says.

“How many more undescribed species in the “quiet achiever” category are awaiting their scientific debut?”