Hobart's 'platypus whisperer' Pete Walsh forages for help

Pete Walsh faced a challenge when he was diagnosed with a brain injury. He found solace by the Hobart Rivulet, where he met a platypus which was named Zoom by his partner Vonna Keller because she zoomed to him with a distinctive bill waggle when he arrived.

"She's bonded with him in some silent way because every time he comes and sits in the creek she just literally zooms across to him and climbs up on the rock and has a big look at him," Vonna said.

It all began when Pete noticed the platypuses in the rivulet were spending more time in public spaces.

"They're kind of like your buddies," he said. "It's a really sweet, kind of peaceful world."

But after finding Zoom tangled in plastic, Pete realised they were in trouble.

With the help of experts, he explored the rivulet's health and got to know the platypus population, discovering intimate details about their lives.

When bulldozers and a flash flood on the rivulet caused Zoom to disappear, Pete launched a grassroots conservation effort to engage the community and save his platypus friends before it's too late.

It's now the subject of a stunning new film, The Platypus Guardian, which captures unique, never-before-seen footage of one of the world's weirdest animals, revealing a secret magical world that exists in the shadow of the city and Pete's race against time to save it.

Hobart Lord Mayor Anna Reynolds describes the film as a call to action.

"This extraordinary film ... should galvanise the entire community into taking greater action to protect Hobart's platypuses and the rivulets they call home," she said.

"Every weekend our Bushcare volunteers are calling out for more hands on deck to help plant and protect native habitat along the Hobart Rivulet and in our bushland reserves.

"We need more eyes on the ground alerting us to contaminants entering our rivulets so that City of Hobart waterways staff can take action.

"We need more people picking up rubbish before it enters our waterways and threatens our platypuses. It's as simple as seize it, snip it, bin it."

The city recently released its first-ever report into the ecological health of Hobart's four major rivulets.

It revealed that while the rivulets are in excellent health in their naturally forested headwaters, water health drops off as they hit the urban fringe.

The report identified the presence of invasive willow trees as potential culprits behind a clear drop in ecological health in Guy Fawkes Rivulet, a tributary of the Hobart Rivulet.

"The State of Our Rivulets report reinforced the need for the City of Hobart to continue sensitively removing invasive willows from the banks of our rivulets and replacing them with native canopy," Ms Reynolds said.

She said the city is in the process of designing a better litter trap to prevent rubbish from McRobies Gully Waste Management Centre from ending up in the Hobart Rivulet.

It also developing a tree canopy strategy to provide cover for platypuses from predators and to regulate water temperature.

"Our staff are working more closely with industry to help educate them about how their activities can impact on waterway health and tracking pollutants from a variety of sources including concrete wash, sewer leaks and fertiliser run-off," Ms Reynolds said.

"We face many challenges in caring for the natural world around us, especially where it meets the urban interface, but very often real change is led by the community and individual members of our community.

"Pete Walsh has shown us that to protect the incredible natural world around us we must all be platypus guardians."

The Platypus Guardian can be viewed on ABC iview.