In many places around the world, discovering a rat in your garden would barely register a second thought.

But in parts of New Zealand, a single rat, possum or stoat can trigger an urgent response, as the country embarks on a world-leading project to eradicate introduced predators by 2050 to save its unique wildlife from further decimation.

Wellington resident Davin Hall knows first hand. In March he noticed large tunnels cutting through the compost bin at his home. He suspected a rat and after two weeks of trying to catch the pest, he called in the cavalry: a team of pest-catchers who will try all methods possible to hunt down and kill a single rat.

“It’s kind of like this idea of Ghostbusters,” says James Willcocks, project director at Predator Free Wellington, which hunts down pests in the New Zealand capital.

“If we get any intel from the public that might be a suspected rat then we need to be able to deal with that immediately.”

The team fields roughly five tip-offs a week and each is treated with urgency.

First, they set out to determine whether there is a rat, says Philip Wisker, Predator Free Wellington’s eradication technical officer. Occasionally, people call in with reports of rat faeces in their shed, which sometimes belongs to the wētā – an unusual endemic insect. The difference lies in the smell – wētā poo “smells like nutmeg, spicy”; rat poo smells “quite pooey”, Wisker says.

A dog detector team is then sent out to sniff out signs of rats, followed by the “capture team” who sets up cameras, traps and bait. When they find the rat – and they almost always do – it is promptly sent off for genomic sequencing, to determine if it is local or has travelled into the region.

In Hall’s case, they had success. The intruder was a “giant rat”, 529 grams heavy and 495mm long with a meaty tail and piebald coat. The Norway rat – a species that arrived in New Zealand on European ships in the 1700s – was one of the largest the Wellington team had caught.

A similar response plays out if a stoat is spotted on Waiheke Island, in Auckland’s Hauraki gulf, where just a few remain, and again for possums in Akaroa, near Christchurch, and Otago Peninsula in Dunedin, where they have been eliminated.

In regions where eradication efforts have been successful, or are close to it, locally run predator-free projects are increasingly relying on residents to call in tip-offs to their “hotlines” when they see, or suspect, a predator has returned.

“If we can activate those 20,000 sets of eyes and ears that are a community – or the 212,000 eyes and ears living in Wellington city – then we’ve got the most sensitive detection network anywhere in the world,” Willcocks says.

Who ya gonna call? 0800 NO RATS

New Zealand’s only endemic mammal species are bats and marine mammals. Subsequently, its birds evolved in unusual ways – the country is home to more species of flightless birds, both living and extinct, than any other place in the world.

Isolation from land-based mammals left the country’s birds largely defenceless against introduced predators. An estimated 25m native birds are killed annually by rats, stoats, possums, and cats, and 50 bird species have gone extinct, according to the Department of Conservation.

Predator Free Wellington has, over 10 years, managed to eradicate rats from Miramar peninsula, a 15-minute drive from the city centre. Now it is in phase two of its project – elimination in a number of nearby suburbs before it expands further into the city.

It has achieved this through extensive trapping and monitoring networks, a large volunteer workforce, widespread community buy-in and now, residents calling 0800 NO RATS when they see a pest.

Since the project began in Wellington, the population of native birds on Miramar peninsula has increased by 500%. In Waiheke, populations have increased by 99% since 2020.

Still, the teams refuse to become complacent. Rats can breed multiple times a year and catching a single interloper early can stop it re-establishing a population. Expert dog handler Sally Bain is one of the rat-catchers.

On the Miramar peninsula, she scours the coastline for signs of rats, with her two highly trained dogs, Kimi and Rapu, who lead with their noses to the air.

A rat was recently discovered in a rat trap here, prompting a search of the area. Close to a small construction site, the dogs become animated. Rats regularly hide in cars, cabins and construction materials, Bain says, and the dogs’ interest in the site could either signal there are more rats hiding there, or this was where the dead rat had originated.

Stamping out rats in a city of people is no small task. Day after day, Bain traverses Wellington’s tricky hilly terrain hunting them down. When asked what drives her, Bain says: “Humans weren’t the only ones who suffered when we turned up here.”

“It’s about what you save, not what you kill.”

For Wellington residents like Hall, those efforts and the wider buy-in from the community – from building and setting traps to keeping their eyes open for rats – have been “remarkably successful”.

He says: “We’ve got kererū … pooping on people’s cars and sitting on powerlines, a family of kākā who live in the area and chase each other around. All these native birds have come back and getting rid of the rats means they get to stay.”