During Canberra's annual frog census, more than 200 people note the assorted croaks with interest, to better identify the species living in a range of places.

"The main thing is to train volunteers to go out and listen to frog calls," said ACT Frogwatch co-ordinator Anke Maria Hoefer.

"The challenge and the beauty is that this is done at night."

Ms Hoefer said the frog census illustrated "Citizen Science at its best", with the volunteers contributing to the ongoing research by monitoring the amphibians and recording the water and air temperatures.

"Frogs are an environmental indicator species," she said. "We try to pinpoint what makes a wetland good or not so good for frogs."

Ms Hoefer said the group assessed 30 sites and she added there were reasons why frogs loved certain areas.

She had noticed the calling behaviour of the frogs seemed to be altering with climate change and said that, with Canberra's "less predictable spring rains", they seemed to be breeding earlier than in the past.

On Friday night, the Frogwatch team ran a fieldtrip at the Jerrabomberra Wetlands, an event supported by the Woodlands and Wetlands Trust.

Lori Gould, the trust's program manager, was part of the group and she said the frog sounds had changed "almost overnight".

Nick Bakker, who is doing a Masters' degree in Environmental Management at the University of Tasmania, was interested in waterway health assessment and how the frogs provide clues to the water condition.

"Frogwatch volunteers come from all walks of life," Ms Hoefer said, mentioning they ranged in age from 86 to a baby in a pouch.

Young Kelly Bateup enjoyed helping with the census because "there's lots of nature around you".

Frogwatch is holding a training session on Tuesday, October 13 and a field trip on Friday, October 16, both at the Strathnairn Gallery in Holt.

To find out more, phone 6278 3309 or email frogwatch@ginninderralandcare.org.au.