Multi-kill, gas-powered traps are boosting hopes our rarest duck can be saved from extinction.
The whio is elusive, endemic, endangered - and the only duck in the world to whistle instead of quack.
The rare whio, or blue duck, lives in the Ruahine Ranges and is a national icon, featured on our $10 note.
But it's not money that's saving these ducks. It's the efforts of volunteers trapping stoats, rats and weasels.
Ruahine Whio Protectors Trust chairwoman Janet Wilson has dedicated the past 10 years to bringing the duck back from the brink of extinction.
She said recent innovations in traps had proved heartening for those having to tramp deep into the ranges to reset traps.
"This trap kills. It can go on killing rather than those box traps ... which can only kill once until someone comes along and takes the dead thing out of it.
"These are fantastic."
Last week, Wilson took a few volunteers into the Oroua River valley, northeast of Apiti in the Manawatū - to reset traps and find the whio in its natural habitat.
Wilson said there were fewer than 3000 whio in the country and it was far more endangered than the kiwi.
"It's specially adapted to live in these rivers," she said. "It has a rubbery bill that can get under rocks and find the invertebrates ... they're fiercely territorial and cover up to 1.5km of river."
Although the whio in the Ruahine Ranges spent the majority of their time living on the fast flowing and pristine headwaters, to reproduce they have to lay eggs on the river banks where predators await.
Wilson said stoats, rats and weasels could not resist the smell and taste of them, and there was graphic video evidence of rodents attacking a nest and killing a mother.
Wilson hoped more volunteers would join the fight against the whio predators.
"You've got to be committed and strong enough to handle the sometimes-harsh elements of the Ruahine Ranges," she warned.
Rangiwahia residents Steve and Mary Bielski regularly reset several traps along a 15km loop which starts at the Rangiwahia Hut carpark.
Steve Bielski said the walk was a wonderful experience, and it was rewarding to give the ducks a chance, but the trapping also gave other birds in the Ruahine a chance to bounce back.
The efforts were now being multiplied.
Contact the Ruahine Whio Protectors www.rwp.org.nz or find them on Facebook.