A needy spaniel has proved a powerful weapon in the Hauraki Gulf fight against one of the world's 100 most invasive species.
Rhys Jones, a 4-year-old Welsh springer spaniel, has learned to sniff out Argentine ants, unwelcome invaders which can overwhelm native species by sheer weight of numbers.
The dog has been part of a breakthrough project which, in a New Zealand first, appears to have eradicated the unwelcome ants from part of Kawau Island.
Gulf biosecurity adviser Brian Shields, who looks after Rhys Jones, says the dog is the only one in the world trained to sniff out Argentine ants, or "argies" as he calls them.
The spaniel learned his skill by training on pieces of blotting paper containing ant pheromones.
Argentine ants produce a signature scent, and Rhys Jones is now attuned to it.
In the field, Rhys Jones pauses when he encounters the tell-tale scent.
His nose is sufficiently acute to ignore native ants and only confirm the presence of the invader species.
Effectively he is a mobile laboratory, able to give his handlers the confidence that he has detected the pest.
This week on Kawau he confirmed three nests at Vivian Bay, north of the Schoolhouse Bay site where the ants appear to have been wiped out.
The dog has been trained to Department of Conservation standards to work on islands in the presence of endangered species.
"It means he's not going to take out birds," Mr Shields said.
At his canine finishing school, Rhys was put to the test by Landcare Research.
He had to complete a field trial which required him to pick out Argentine ant samples from a smorgasbord of other ants.
He correctly picked 85 per cent of the 100 baits on offer and like a good wine has improved with time.
Mr Shields: "We're comfortable that Rhys can identify 100 per cent in the field that we've got argies. Without a doubt."
Before settling on a spaniel for the ant task, Mr Shields said he looked carefully at a lot of breeds and spent time with Customs dogs.
He found mailroom sniffer dogs liked to play - "they were pretty hypo" - whereas Rhys was a "needy" animal.
"He loves to be around me and hates it when I'm out of sight. That neediness gave him the ability to do what he requires to please me."
The dog had been part of the team at Schoolhouse Bay in Kawau's Bon Accord Harbour, where monitoring over three years has led Auckland Council biosecurity staff to conclude that the bay is free of Argentine ants.
Senior biosecurity adviser Jeff Cook said encouraging results were now also coming from work to wipe out the ants at Vivian Bay.
Sweeps using Rhys Jones and visual inspections by biosecurity teams indicated that a lot of colonies had been knocked out.
On steep Vivian Bay slopes the antbusting team uses small tubes filled with frozen insecticide called AntDroids, which are fired by slingshots or thrown grenade-style into hard-to-access areas.
Mr Cook said the bait was used carefully, given that it could be toxic to native ants, bees and other insects, as well as kiwi and weka.
Bait was used in a form which the ants carried back to nests where it spread among the colony. It was laid on paths, pipelines, retaining walls, and edges - all places which the ants tended to use.
At Vivian Bay, which Mr Cook and Mr Shields inspected on Tuesday, Argentine ant nests are dying out.
Mr Cook said: "We're not confident we've eradicated every one but we're getting closer to the point where we are struggling to find nests. That's promising considering they were in everyone's gardens, everyone's houses. We're talking millions and millions of ants."
The programme had been supported by locals, who provide accommodation for field staff.
Next month a team of 10 or so will grid-search Vivian Bay and conduct a forensic search for the ants.
Mr Cook now wants to apply the Schoolhouse Bay lessons to a more ambitious and expensive project on Great Barrier Island, where the ant also has become established.
The idea is to keep pests and predators out of all the Gulf islands.
Through a programme called Treasure Islands, run jointly by the Department of Conservation and Auckland Council, Gulf users are encouraged to stop the spread of pests.
Mr Cook said the aim was to change the way people used the Gulf so that these special places could always be enjoyed.
How to stop the spread of Argentine ants
• Submerge potted plants in water for two minutes before moving them.
•Examine soil, bark and building materials before shifting them.
•Use suitable insecticides.