A cutting-edge study of creeks and waterways near Brisbane has delivered a welcome surprise – there are more platypuses than expected.

The environmental DNA study sampled water from 155 sites in creeks in Moreton Bay and found the slippery mammals at 90 locations.

Last year the same study returned 71 positive results.

“Pleasingly, the results from the project to date show that our platypus population is a lot more widespread than we first anticipated,” City of Moreton Bay Mayor Peter Flannery said.

Environmental DNA, known as eDNA, is a revolutionary technique that can tell scientists what has been swimming in the creeks.

All animals leave a trace, whether it’s scales, skin, hair or excrement, and it all ends up in the water.

That water gets filtered through fine mesh and is then tested in a lab, where trace elements are compared to a database that tells scientists what has been present in the water.

Dr Tamielle Brunt from Wildlife Queensland, who has been doing eDNA work in the region for almost a decade, helped launch the Moreton Bay project in 2022.

While her work initially focused on platypuses, it has expanded to other species as part of a new project across 11 south-east Queensland councils.

“Being able to add in full [multiple] species, it really gives us an understanding of the health of our waterways,” she said.

Platypuses, rakali, freshwater turtles, lungfish, frogs, endangered Mary River cod and invisible microorganisms are among the species being monitored at about 250 sites stretching from Noosa to Logan.

Brunt said eDNA changed the way she studied aquatic animals, which she said could be cryptic and tricky to track down.

“Just because you don’t see them doesn’t mean they are not there, so we are picking up the DNA that they leave in the water,” she said.

“It’s quite incredible to be able to go out and sample quite extensively, when traditional methods are quite laborious, like trapping platypuses overnight.”

The project is run by Resilient Rivers South-East Queensland, a body funded by the SEQ Council of Mayors, along with the state and federal governments.

Brunt said the project, which is aimed at cleaning up the region’s waterways, would paint a picture of where priority species live and help identify where money should be spent on conservation and revitalisation.

But she said the results would only provide a baseline for further studies, adding eDNA results could be used as a metric for success of restoration projects down the road.

“Even 250 sites across the south-east Queensland region really isn’t that much when you’re trying to really delve in,” Brunt said.

“This is such a powerful monitoring tool, it just makes sense for Resilient Rivers to be potentially harnessing that for broader waterway health.

“I’m so excited to just get all this data and sift through it.”

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