As Dr Brendan Casey sits at his desk, the beautiful and eerie calls of the Growling Grass Frog coming from his computer take him back to the banks of the Merri Creek where he spent childhood days exploring with wonder. The passion born from those early days drives him through the laborious process of manually working through 20,000 frog call recordings gathered over three years of research.

Brendan grew up near the Merri Creek, at a time when native frogs – including Growling Grass Frogs – were abundant. Several decades later, with the Growling Grass Frog listed as vulnerable at both national and state levels, Brendan returned to the area to undertake a monitoring project that would lead to improved understanding of the environmental conditions that affect the frogs’ call activity.

 

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Brendan’s research and support of our monitoring programs for this precious frog has significantly increased community knowledge of the Growling Grass Frog, according to Julia Cirillo, from Merri Creek Management Committee.

“Brendan has generously contributed his time and expertise as a teacher, mentor, volunteer and researcher. His lifetime of passion and knowledge for this frog is a gift to organisations like ours, as well as our member councils, who are working to protect the populations of Growling Grass Frogs in our patches and across the landscapes we love.”

“As a child, I played in Merri Creek a lot,” says Brendan. “It was a really interesting, nice place. There wasn’t the same access as there is today with paths and tracks – you’d just walk over the paddocks to get to the creek. There were no weeds and there were animals everywhere.”

 

Play video: Growling Grass Frog Appeal

Watch our video to hear the Growling Grass Frog's evocative call.

A love of nature ran in Brendan’s family. He remembers his older brother Peter, who was always out roaming around Merri Creek, bringing lizards home to show him. “I thought they were creatures from another world,” laughs Brendan. “That was what initially prompted me to go down to the creek and have a look myself. It was very special having the chance to see Merri Creek at that time when it was so undisturbed.”

As an adult, Brendan maintained his connection with the area and was an active volunteer with the Friends of Merri Creek community group. While he eventually had to step away, his longstanding love for the creek was rekindled in 2018 when he began a PhD at RMIT, on bioacoustic monitoring of frogs (which entails learning about animals by studying the sounds they make).

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Over the years, Brendan had noticed that Growling Grass Frogs often call very intensively, but then stop quite suddenly. Sometimes when they stop, it’s just for a couple of hours, whereas at other times, it might be for days or even weeks. (Listen to one of Brendan's recordings here – jump to 1.58 to hear the call.)

“There is this pattern of on-off calling and I really wanted to try and work out why that was,” he explains. “I set up acoustic recorders to collect frog calls at three different places. I was trying to determine whether there was any connection between the call behaviour and environmental conditions like air and water temperatures. It was quite intense data analysis, but the sounds of the frogs calling made me think of my childhood, so I enjoyed it."GGF Brendan Casey

One of the strongest pieces of statistical evidence Brendan collected was from a pool in Merri Creek in Somerton. At this site, he discovered that Growling Grass Frogs wouldn’t call immediately before, during, or after a rain event. They would only call once the rain had passed and the water level had stabilised or started to drop.

Brendan also believes that water chemistry plays an important role in the health of the frog populations and that management options to address that could include establishing more off-stream water bodies, and increased treatment and filtering of stormwater before it is discharged into the creek.

While further work is required to address some of the knowledge gaps that exist around the Growling Grass Frogs behaviour, Brendan’s research has provided crucial information that will help with protecting the species. Merri Creek Management Committee (MCMC) has now developed plans to monitor water quality and improve the habitat for the Growling Grass and is calling on the community to get behind these efforts.

“Merri Creek Management Committee have already made some really important discoveries, especially about the Growling Grass Frogs moving into the constructed habitat at the Moomba Park Wetlands,” says Brendan. “That’s a huge step forward and a massive victory.”

“I’m also pleased MCMC is actively seeking to involve the local community with their goal to consistently monitor the water quality over a long period – that is a very good idea. They can’t do it without the community’s support. The fortunes of the Growling Grass Frog have waxed and waned over the years but knowing that they are still living in and near Merri Creek is great cause for optimism. With a little bit of help, maybe they’ll stay there a lot longer.”

Join us in our vision for the Growling Grass Frog – help us ensure that children playing by the Merri Creek in the future can delight in hearing the remarkable call, just like Dr Brendan Casey did as a child. 

Donate now.

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Story by Ruth Dawkins / Images by Dr Brendan Casey

We thank Melbourne Water and Merri-bek Council for generously funding the creation of Growling Grass Frog habitat at Moomba Park Wetlands.