The rain has arrived in south-western Australia and researchers are hoping to mobilise citizen scientists to help track the health of local frogs using a smartphone app.

Jodi Rowley, an amphibian researcher at the Australian Museum, told ABC Radio Perth that frogs were extremely difficult to study because they only came out when it rained.

And they can usually be heard but not always seen.

"They are very tricky to study, particularly in the really dry areas," Dr Rowley said.

"I could plan a million field trips, but if it is not the right weather we won't see or hear the frogs; they will be hiding underground."

Jodi Rowley and Paul Doughty are keen to enlist the public to find out where the frogs are. ( ABC Radio Perth: Emma Wynne )

Understanding the health and size of native frog populations is vital and, according to Dr Rowley, frogs are in a lot of trouble.

"Forty-two per cent of all frogs and other amphibians are threatened with extinction," she said.

"In Australia we've lost at least four species already and many of our other frogs we think are in a lot of trouble.

"But one of the biggest obstacles is that we don't know that much about them."

So Dr Rowley wants citizen scientists to download a free app she and her colleagues have developed called FrogID.

The app allows users to find out what frogs sound like.

Users can also record what they hear and submit it to the team at the Australian Museum who will listen to the sound and send an email back explaining which frog it was.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 4 seconds 4 s The sound of the Wotjulum frog (crazy chicken) ( Supplied ) Download 35.5 KB

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 11 seconds 11 s Recognise the sound of the ticking frog ( Supplied ) Download 90.6 KB

"They are actually calling out what species they are," Dr Rowley said of the frog sounds.

"It's male frogs calling and they are calling to attract female frogs.

"They don't want to get it wrong, they don't want the wrong species to respond, so they each have a different call."

West Australians can expect moaning and hooting

Paul Doughty from the Western Australian Museum said right now was a crucial time for people in the state's South West to be listening.

"The moaning frog is endemic to south-western Australia, along with four other species, and they are autumn breeders so this is really the peak of moaning frog breeding time," he said.

"This is the time to get out with the app and see where they are."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 10 seconds 10 s The sound of the moaning frog, which is breeds in autumn in WA ( Supplied ) Download 82.7 KB

Numerous listeners to ABC Radio Perth reported hearing and seeing frogs in their backyards, but some were more welcome than others.

Nel: "We live near the wetlands in Spearwood and in various seasons we hear different frogs. At the moment it's the moaning frogs we're hearing at night, other times it's the banjo frogs and other times the motorbike frogs are more prominent."

Dean: "This year we had approximately 1,500 tadpoles in a large backyard pond in residential Albany. I fed them all the way to frogs and sad to see them leave."

Marnie: "I had a moaning frog a few years ago ... called him Fabio the 'effing' frog. I nearly had to move house. Drove me mad for months."

Deb: "I have a frog in my backyard but for months I thought it was a cricket, it made more of a clicking noise ... It has been in my backyard in a reedy, wet part of the garden."

About one in five recordings submitted to FrogID are of crickets when it is dry, but when the weather is wet the number of frogs submitted increases.

Neil from Armadale submitted this picture of a western banjo frog found in his garden in Perth's east. ( Supplied: Neil )

Local recordings wanted

There are a number of local species the researchers are keen to track.

"Motorbike and slender tree frogs, which are common in Perth backyards, are climbing species so you have the slender tips of the fingers and they will be clinging on trees and grass and the side of your house," Dr Doughty said.

"The hooting frogs are Hills endemic so if you're up in Kalamunda or anywhere along the scarp, they like to breed there.

"They are not very loud but if you want to go and wander with the torch where there are creeks, we'd love people to record them."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 8 seconds 8 s The hooting frog's call ( Supplied ) Download 69.3 KB

The team is hoping the citizen science FrogID push will run for at least five years so they can get a thorough overview of Australia's frogs.

"We want to understand how frogs are changing with a changing climate and environment," Dr Rowley said.

"We would love a recording every night because we really want to understand how frogs respond to weather and climate."