The work of a six-legged team has revealed it is "highly unlikely" stoats are living in the Orokonui Ecosanctuary.
Department of Conservation senior technical support officer Scott Theobald and his terrier, Crete, spent 12 hours during the past two days carrying out surveillance throughout the ecosanctuary.
Ecosanctuary conservation manager Elton Smith said it was "fantastic" the pair did not find anything, as it meant it was "highly unlikely there are any stoats in there".
"I think it's another good endorsement for the project. We are starting to be recognised as one of the best biodiversity facilities in the country," he said.
It was the first time a stoat-dog had gone through the area and it was great to have Mr Theobald and Crete visit because it "takes the attack to the animals".
"It's quite a flimsy structure, the [predator-proof] fence, against the hoards on the other side," Mr Smith said.
Dogs are "one of the tools" used in the eradication of pests, alongside predator-monitoring tracks and traps.
Crete is one of 15 predator dogs in New Zealand, which search for rats, and mustelids such as stoats, ferrets and weasels.
Mr Scott said he trained Crete with live animals from about the age of 2.
Dogs were used to identify predators, not control them, and each dog gave unique signals when it had found indications of its target.
It was a "team effort" as the human had to know where predators might be and take the dog to the area for confirmation.
He said they had enjoyed their time at Orokonui, and the weather was perfect for tracking.
"Not all of these places are as good as this one."
By Ellie Constantine