As the sun sets at a pond in Canberra's north, a cackling, drill-like sound starts. It's the call of the Peron's Tree Frog.
Other species of frogs soon join the chorus. There's the guiro sound of the Common Eastern Froglet and the staccato machine gun call of the Spotted Grass Frog.
The Eastern Banjo Frog, or the Pobblebonk, then starts to punctuate the chorus every few seconds with its banjo-like call.
By the time it's dark a whole choir has joined, it's mating season and these frogs are looking for, well, a mate.
It's a nightly occurrence in spring, most prominent after rain, but on this particular night Australian National University students Isabella Howard and William Jaggers will be capturing their sounds in the name of science.
They have chosen a perfect night, it's balmy and recent rainfall has filled ponds, meaning there will be an abundance of frog calls to record.
Listening to frog sounds provides information on how populations of species are tracking but it also helps to determine a whether an environment is healthy. Each October, hundreds of volunteers such as Ms Howard and Mr Jaggers take part in FrogWatch ACT and Region's annual frog census.
The annual census provides invaluable data that helps to measure the health of wetlands in Canberra. It can also help protect frog species in the territory.
Climate change has wreaked havoc on frogs, as well, the deadly chytrid fungus has wiped out populations of species.
Frogwatch ACT and Region coordinator Anke Maria Hoefer has compared the frogs' future to the extinction of dinosaurs.
The citizen science project sees volunteers sign up to monitor a site and they have to visit their chosen site at least twice. Ms Howard and Mr Jaggers are responsible for monitoring wetlands in Macgregor, where they usually start around 7.30pm.
"Usually when we get here we'll have a quick wander around the pond and then we'll make note of the weather, water depth, vegetation and the stuff around the pond," Ms Howard said.
"Then we will take the air temperature and the water temperature and then we sit and have a listen.
"We monitor four ponds, usually it takes us about three hours to do them all but we do take our time and see if we can see any frogs as well as listening to them."
By the time The Canberra Times joins them, Ms Howard and Mr Jaggers had been frog watching three times. By the fourth night they had become accustomed to differentiating between different frog sounds - but it can be tough to identify frog species in the Macgregor wetlands.
"Sometimes certain species drown out other species and there are different rates of calling, so it can be difficult, it's definitely a skill to pick up," Mr Jaggers said.
Over the four weeks they have identified about eight or nine species.
"The Common Eastern Froglet we hear quite a lot, as well, the Plains Froglet and my personal favourite, the Pobblebonk frog," Ms Howard said.
Both got involved with the program, which has been running since 2002, through a biodiversity conservation course at university.
"It's a nice thing to do, after a day of uni you come out to the pond as a group you catch up, meet up, have a chat and sit down and record some observations about frogs," Mr Jaggers said.
"It's also nice to be able to contribute to a good citizen science project."
Ms Howard agreed.
"I love citizen science programs, I think they are such a fantastic way to get everyone involved," she said.
"FrogWatch is a long-term and quite broad study that can be used for so many different things, whether it's policy or conservation so I was definitely keen to get involved."