Rob Suisted

Making birds

What would happen if city suburbs as well as offshore islands enjoyed freedom from introduced predators? Is it possible for New Zealand to eliminate them all—stoats, ferrets, weasels, possums, and three species of rat?

Written by       Photographed by Rob Suisted

1. The wild laboratory

The helicopter carrying Al Bramley, chief executive of Zero Invasive Predators (ZIP), and me swoops low over the Garden of Eden Ice Plateau, near the spine of the Main Divide. The plateau’s smooth white snowfields are tattooed with crevasses—a forbidding, yet tempting, landscape. Its named features riff on the biblical theme: Adam’s Col, Eve’s Rib, the Abel and Cain Glaciers, the Devils Backbone. We are heading for the Perth River catchment in South Westland, where Bramley and his team are looking to return Aotearoa to something approaching the ecological Garden of Eden it once was—a place untouched by mammalian predation, where wondrous creatures flourished.

In the hinterland of the Southern Alps, research and development agency Zero Invasive Predators has been trialling techniques for a “remove and defend” model of predator eradication in large wilderness landscapes. After two 1080 treatments in the Perth River catchment this year, an array of motion-activated cameras has detected only “four lonely rats and three possums” that survived, says ZIP chief executive Al Bramley.

ZIP takes its name from its mission. In July 2016, the government announced that New Zealand would aim to be predator-free by 2050. ZIP was formed to research how such a dream might become reality. The Perth Valley is its first large proving ground.

One of the peaks here has an apt name for the project happening below it: The Great Unknown. For all its long history of use, the toxin 1080, when dropped in pellets from the air, has never been shown to reduce possum and rat populations to zero. A few per cent, but not to zero. ZIP believes it can achieve zero, and the Perth Valley is the place where it aims to prove it.

That’s ZIP’s great unknown, and it should have the answer by the end of 2019. One 1080 drop has taken place two weeks before my visit in early May; the second is due in July.

The Perth site was chosen in collaboration with local hapū Kati Mahaki ki Makaawhio.

“We offered them three sites with similar technical attributes and asked, ‘Where would you like us to work?’” Bramley tells me. The sites needed to be large—of the order of 10,000 hectares. This early phase of the predator-free mission is about proving that the kind of predator eradication that has been successful on islands (more than 130 in New Zealand alone) can work at the scale of large landscapes. The Perth site is 12,000 hectares.

ZIP also went to Federated Mountain Clubs (FMC), because part of the area it needed to work in is a wilderness area, where human structures are prohibited. Without the ability to cut tracks and have staff living in huts, the project would not be possible.

“FMC fought hard for the establishment of wilderness areas, and its leaders were not keen to see a wilderness area used as a test site,” says Bramley. “They put it to their membership, which sparked a debate around how much value a wilderness area has if its biodiversity is in decline. In the end, they decided that restoring biodiversity should be a high priority, and if putting temporary infrastructure in enables that to happen, then they would support the work.”

Having the local hapū and the tramping community on side is not something that’s incidental to the predator-free mission. Several managers and researchers told me that the social side of the mission is at least as important as the technical side. Arguably more so.

For Makaawhio, as for many hapū, a clinching argument was ZIP’s confidence that predators in a large landscape cannot just be suppressed, but eradicated. Suppression means predator control in perpetuity. Killing without end. Eradication signifies an end to killing. ZIP says it wants to offer communities a pathway so they’ll never need to use 1080 again.

On Mahia Peninsula, Kaya Cooper of Ngati Rongomaiwahine inspects a range of devices being trialled by Predator Free Hawke’s Bay, including an automatic lure dispenser and a wireless self-reporting leghold trap. Velcro on the bait station even samples the fur of visitors to discern between rats and possums.

There’s an economic logic, too. A standard 1080 operation in a landscape like the Perth costs between $30 and $40 a hectare, says Bramley. ZIP is budgeting for complete eradication for a little over $100 a hectare.

“That figure will likely fall as we get better at it,” he says. “But even at three times the cost, that’s three 1080 cycles, and the job’s done. You think, ‘That didn’t take long to pay for itself, did it?’”

Bramley expects biodiversity to go ballistic—to the level it is on offshore islands. What would that mean for the country in terms of ecological resilience, he asks, let alone tourism and other economic benefits?

“If you build a better mousetrap, the world will beat a path to your door,” said American philosopher Ralph Waldo Emerson. Many New Zealand inventors and engineers are devising and manufacturing better traps.

It’s one thing to reduce a population to zero, another to keep it there. Most of the experimentation and innovation within the predator-eradication community tackle the problem of reinvasion. If you can’t protect your gains, you’re back to square one.

One of the obvious strategies is defending boundaries. In ZIP’s work in the Perth, that means identifying geographic features that can serve as barriers to reinvasion: rivers and mountain ranges. Neither is considered impermeable. There will always be times of low river flow, or a tree might fall across a narrow gorge, providing a bridge, or a particularly hardy animal might decide to go for an alpine trek. (The highest rat ZIP has recorded in the Perth was at 1240 metres.)

What’s important, says Bramley, is knowing how long it takes for rats and possums to disperse once they breach a barrier, and how far they can penetrate a ‘clean’ area—one from which all predators have been removed.

“What we’re testing here is the ‘overlap-and-go’ strategy. If we treat an area with 1080 and come back the following year to push on to the next piece, how much would we need to overlap?”

The predator-free movement has spawned thousands of community trapping groups across the country, most of which operate without close contact with each other. When father-and-son Kaitake Range trappers Peter and Robby Morgan (brown and blue tops) met with Oakura coastal trappers Clive Saleman and Libby Baker, they wasted no time in sharing tips and techniques, from the best brand of peanut butter to use as a lure to the finer points of positioning and setting a stoat trap.

ZIP’s approach to defence emphasises detection of invaders over prevention of an invasion. The reasoning is that, short of erecting a predator-proof fence, boundary crossings are inevitable. But they only become a problem if the invading animal or animals produce offspring, and thus re-establish a population.

ZIP performed a bold experiment to test its ability to remove invaders. After clearing an area of rats, it reintroduced a rat family into the centre, surrounding it with detection devices. The mother rat raised her seven young, and when the juveniles left the nest, ZIP caught five of them, plus the mother. The pup that travelled furthest was caught 675 metres from where it started.

“We worked out the total area of dispersal,” Bramley tells me, “and the result was 60 hectares in 60 days.”

That’s a frightening thought for a project manager. But it’s ameliorated by the fact that it takes 151 days for the first generation of rat offspring to bear young of their own, and catching them before then returns the population to zero.

“Tactically, we think we’ve got roughly 100 days after treatment to detect any survivors and catch them.”

That may sound like a tolerable window for response, but what makes the predator-free mission especially challenging is that you have to be thinking about several species at once.

Not all locations have the seven target predators—Norway, ship and Pacific rats, stoats, ferrets, weasels and possums—but where they do occur together, each needs an eradication strategy. It’s like playing seven games of chess simultaneously.

In the Perth, ZIP has to contend with just three species: ship rats, stoats and possums. So, each of the questions it’s posing has to be asked three times, once for each
species: What’s our chance of removing the species completely using 1080? What’s our chance of defending the site against reinvasion? If we get an incursion, how fast can we detectit in order to prevent a population re-establishing?

Bramley takes me through the thought process: “What’s our likelihood of removing possums completely with 1080? Pretty high, but we don’t really care if we leave one or two behind because they’ll start roaming, looking for friends—and we’ve done radio-tracking work on this, and a lonely possum roams about 100 hectares every seven days. To intercept those animals, we’ll be putting a leghold device about every 25 hectares. That’s probably overkill by a factor of two at least, but we’re trying to make sure we can pick up any surviving possums.

“Stoats roam even further. We’ve radio-tracked stoats at low density roaming 5000 hectares. But you can’t necessarily count on them travelling such long distances. Some animals seem to just give up. They shrink their home range down to a bare minimum. We won’t bother chasing those. They’ll die out.”

[Chapter Break]

2. The quest for the last possum

Part of ZIP’s mission is to invent new tools and bring them to market. A promising example is an automated lure dispenser that slowly squeezes a dribble of egg mayonnaise from a syringe mounted in a stainless-steel housing. A motor with an extremely high gearing puts constant pressure on the plunger. By adjusting the dispensing rate, lure can be produced continually for up to a year, offering an enticing snack to roving possums, stoats and rats, who then have a greater likelihood of being caught in nearby traps, or of eating a toxic form of the lure.

The dispenser Bramley is showing me near the Perth River has an unexpected hue for egg mayo: it’s magenta. The colour comes from a biomarker, rhodamine B, which makes a rat’s whiskers fluoresce under UV light, allowing researchers to figure out whether the lure is attracting rodents. Of 39 rats caught in a month over three kilometres of riverbank, 32 had traces of the dye. Bramley says this gives them confidence that the dispensers will help them lure and trap rats after the initial knock-down.

Bramley’s background is geotechnical engineering. Love of the outdoors led him to launch an adventure guiding company, and to work on technical development at DOC. He and fellow engineer John Wilks invented a device for digitally gathering data on nesting kiwi, simply by tuning into radio transmitters from an aircraft. It revolutionised kiwi conservation work, slashing the amount of time rangers had to spend tracking the birds on the ground.

Killing predators isn’t rocket science, but eradicating them entirely from New Zealand has been described as “our moon shot”. On Mahia Peninsula, the Rocket Lab spaceport occupies the southern tip of the peninsula. Predator eradicators are working sequentially northward, clearing predators with ground-based pesticides and then deploying detection devices to check for recalcitrant animals which have avoided the toxic baits.
To monitor the effectiveness of an aerial 1080 operation in the Kaitake Ranges, Towards Predator-Free Taranaki placed radio collars on a representative number of possums, so it could track the fate of those animals. Project manager Toby Shanley uses a telemetry antenna to listen for signals from those animals. A moving animal produces a different signal from a stationary (presumably deceased) one.

Bramley’s team is using the same approach of digital monitoring in the Perth, but with cameras and artificial intelligence. In our hut high in the Perth Valley, Bramley outlines a possible scenario.

“One of the cameras detects an animal taking lure from a dispenser, and sends an alert, effectively saying, ‘I’ve just seen a stoat. What do you want to do about it?’ We then instruct a nearby dispenser to release a toxic version of the same lure. We could potentially have hundreds of these devices connected by LoRa—low-powered radio. LoRa is a game-changing technology for backcountry work. It means I can have a trap on the ground here and talk to it from 30 kilometres away. Not in one hit—each device has a communication range of about 200 metres, but we can bounce a message from device to device. Each LoRa module runs off a tiny battery for five years, so I can talk to every device every day for five years. As well as receiving alerts, I can ask, ‘Do you need any more lure? How’s your battery life?’”

A similar system is already operating for possums at ZIP’s test site at Bottle Rock in the Marlborough Sounds.

“I have 1000 leghold traps that work 24/7 in Bottle Rock,” says Bramley. “Every morning, I look at the status of them on my phone. I was checking them over breakfast in Franz Josef this morning.”

Nothing had happened last night, but the night before, at node 900 on the D2 leghold line, a trap was sprung at 7.40 and cleared by a ranger at 11.20 the next morning. This system frees humans from the grunt work of checking traps.

“Without LoRa, a ranger can look after a maximum of 200 legholds a day, if that’s all they do,” says Bramley. “So, we would need five people full time managing the legholds at Bottle Rock, walking the lines and going, ‘Nothing, nothing, nothing, nothing, got one’—usually one or two hits a day.”

The challenge of drawing possums from inaccessible refuges on the steep cliffs of Otago Peninsula prompted local electrical engineer Tony Pepers to build a sonic lure that plays the call of a distressed joey. It seems to work: footage from a trail camera shows a possum trying to get at the loudspeaker in the unit.

After the system was automated, the 1000 traps at Bottle Rock went from requiring five full-time employees to 0.1 employee—or four hours a week of maintenance rather than 200.

Animal welfare law stipulates that capture traps such as leghold traps (as opposed to kill traps) must be inspected daily, so that trapped animals are not held for more than 24 hours. When ZIP first approach the Ministry for Primary Industries (the relevant regulatory body) for permission to use electronic instead of human inspection, the agency said no.

“The law says ‘inspection’, and when the law was written, that meant with human eyes,” Bramley tells me. “We had to argue through the DOC legal team that the principle of the living law applied—the law should reflect the new digital context. It took nine months to get over that regulatory hurdle.”

The law has now been amended to allow the use of electronic monitoring systems, and ZIP has been busy perfecting a new leghold trap with a lockable mechanism. Bramley shows me one located a few hundred metres from the hut. A wooden ramp leads up to the trap, which stands about a metre off the ground to keep it away from non-target animals, such as weka. The ramp angle has been calculated to be too steep for an inquisitive ground bird but just right for an inquisitive possum. In fact, having a ramp increases the catch rate by 20 per cent. “We’re trying to make it the lazy route to the thing the animal wants to look at,” says Bramley.

That thing is a piece of white powder-coated aluminium nailed to the tree trunk exactly 600 millimetres above the trap. It doesn’t seem like much of an attraction, but possums are highly curious about bright objects. The height above the trap is calculated to ensure that for a possum to reach the aluminium lure, it has to put its foot into the trap.

In Wellington, Predator Free Miramar organiser Dan Henry explains the vision to students of Worser Bay School. The kererū outfit reinforces the message; killing pests is making nests.

The traps are programmed to be locked during the day, so that no daytime birds (such as an inquisitive kea fiddling with the mechanism) can set them off. An hour after dark (or whenever programmed), a motor activates, unlocking the trap. If the trap is sprung during the night, the motor cannot relock the trap next morning, and sends a message via the LoRa network to alert the monitoring team.

It’s all very impressive, but I wonder why leghold traps are still being used for possums. Their method of action—trapping an animal by a limb—seems to be a throwback to less humane times.

“I’d personally like to get out of legholds,” agrees Bramley, “but they’re still our best capture tool by a factor of two. It’s because of trap shyness. Most of the kill traps that are available are what we call ‘head-in-the-hole’ traps. The predator has to stick its head into something to activate a trigger. You’re asking an animal to do a lot in order to get caught.

“Kill traps are really effective at taking out about a third of the population—the bold, the curious and the stupid. Then there’s the other two-thirds—the cautious and the clever—which are much harder to catch. In our game it’s about catching every individual, not just most of them, and legholds are our best tool for catching those cautious, clever animals.”

Automated trap monitoring is just the tip of the electronic iceberg. Artificial intelligence (AI), including facial recognition of predators, is opening new horizons. Bramley foresees a time when cameras become the main tool to monitor landscapes for predator invasions.

“The next step for us is that all of our legholds will be locked down until the AI camera says, ‘I’ve just seen a possum’.”

The camera system ZIP is developing uses thermal, as opposed to visual, imaging. Thermal cameras, which detect the heat signature of an animal, produce less false reporting than visual cameras, and can operate day and night, whereas visual cameras require light to make an image. ZIP’s thermal cameras are smaller than an ice cube and can record about six minutes of video per day for a year without a battery change. When deployed, they will be able to communicate their status every day via the satellite network.

“Every image of a possum on our cameras’ SD cards gets fed into a recognition program, so that the accuracy keeps getting better and better,” says Bramley. “We don’t even know what it’s recognising. We don’t tell it what to look for. We just say, ‘That’s a possum’, ‘That isn’t a possum’, and the program does the rest.”

Coupling digital recognition to increasingly sophisticated traps and toxin-delivery devices that can be switched on or off remotely offers great promise—for the eradication of predators and the protection of everything else.

The next step is to adapt the technology from the wilds of South Westland to city parks and farmers’ paddocks, where there’s an eighth species to take into account: humans.

[Chapter Break]

3. The city that began trapping

No city has embraced the predator-free ethos the way Wellington has. More than 40 suburbs have a predator-free community hub, providing traps, bait and advice for a populace that has adopted backyard trapping as part of the modern urban contract with nature.

Dan Henry, a director of the television programme Country Calendar, is the organiser of Predator Free Miramar. He takes me for a drive around the peninsula, a wedge of land to the east of the central city and joined to it by the narrow Rongotai isthmus, across which lies Wellington Airport. Henry says that in the two years he’s been doing this work he’s become as knowledgeable of his local streets as a London cab driver is of the British capital’s. “I know every cul-de-sac in Miramar,” he says.

Our first stop is to drop off a trap—trap #1298—to Rachel Coronno, in Strathmore. She tells us her cat was bringing “little rodent prezzies” to the doorstep. She saw a Predator Free Wellington ute and thought, That’s what I need. She found the Miramar group online, made contact, and here we are. Henry shows her how to set the trap and where to put it. “Rats like fences,” he says, walking the few steps from the front door to the boundary to position the trap box. He gives her some homemade bait: a mix of peanut butter and rolled oats with a slug of cinnamon. “We were given 96 kilograms of peanut butter from Fix & Fogg—seconds from when they test a new roast or grind,” he tells me.

“You’ve made my day,” Coronno says as we leave.

Henry and I drive towards the tip of the peninsula to check traps in a community garden and on council land near the derelict Mt Crawford prison. Henry tells me about Daryl Wilson, who has become something of a local hero to a dozen or so of his neighbours. “Daryl called me and said, ‘I heard about your rat thing. We’ve got rats in the house. Can you help us out?’ We gave him a trap and, long story short, he killed 21 rats in a week, without even going outside. He’d clear the trap, set it, close the door of the hot-water cupboard and before he’d even got back to his chair, he would hear it go off. He and his partner hadn’t been able to sleep for the scratching in the roof. It was driving them bananas. Word got around, and Daryl got back in touch to ask if he could have some more traps because his neighbours wanted him to trap for them. He’s currently running 14 traps around his neighbourhood, and sends me a weekly text with the kill numbers. Last week, he caught 29 rats in three days. Daryl’s found a calling.”

Henry says the community uptake and enthusiasm amaze him.

When Brian Lunt and Vivienne Crawshaw saw a stoat when they were clearing a bank, they called Te Korowai o Waiheke. Operations manager Jo Ritchie brought a stoat trap to the property, and showed the family (included son Jack) how it worked. Community approval and support is seen as crucial for the predator-free mission to succeed, and Te Korowai tracks metrics such as trap deployment and predator kills on an online dashboard, in foreground.

“Some people are initially diffident. They say, ‘I might have to get my husband to set it and clear it.’ A week later, they’re catching with impunity. You see them online saying to their friends, ‘You’re going to love it. You’re going to get addicted’. Early on in the project, I was the cheerleader. Any time someone would catch something and post it on Facebook, I would chime in with a comment saying, ‘Well done’. Now I don’t need to. That encouragement is coming from all quarters.”

He shows me a Facebook post from Rebecca, who has been running six traps on council land over her fence that is overrun with blackberry: “So excited. Just saw a kererū land on my roof in Miramar. Beautiful.”

He pulls up an email with a photo of a harlequin-patterned lizard. The message reads: ‘You won’t believe this, but a friend of mine found this on the outside of her car this morning in Athens St. Is it native to NZ?’

Henry’s reply: ‘Wow. Yes. It’s a Raukawa gecko. Raukawa is the Māori name for Cook Strait.’

That dividend—seeing wildlife returning to the suburbs—is tangible, and motivational. But the community predator movement goes much deeper, says Henry. “It’s a reward in and of itself, and I don’t think anyone would have anticipated that. The neighbourhood enhancement. The social capital. Neighbours making contact who wouldn’t previously have had a reason to. Plus a little friendly competition—57 and 59 Miramar North Road are battling it out as to who’s got the biggest rodent tally.

“What’s the reward? For Rebecca, it’s a kererū landing on her roof. For Daryl, it’s being able to sleep at night, and a sense of being able to contribute something valuable in his community. For a couple who run a shop in Miramar village, it’s knowing that a rat won’t chew through their dishwasher pipe again and cost them $1200 to fix water damage to their kitchen.

For some people, it’s simply, ‘Oh my God! I’ve got rats. That’s horrifying!’ They feel tainted in some way. I would say that for most people, it’s about the birds and also about doing something tangible that makes a difference. There are so many things we feel powerless about.”

Across the bay, Ian Robertson of Predator Free Mt Vic agrees that social outcomes have been as important as ecological ones. Robertson, a photographer, told me about a presentation he had given at the Tararua Tramping Club, which meets near his home. Next day, he was phoned by a member of the audience. “He said, ‘I got one of your traps at the beginning of the year but I’ve had a stroke and I can’t set it any more. Would one of your members be able to help me out?’ I put the call out on Facebook and a woman came straight back and not only squared him up with the trap but helped with a couple of other things around the house and sorted out the watering system in his garden.

“I had another chap phone up who was blind. He’d lived in Upper Hutt, and there was a lot of birdlife up there, and then he moved here and noticed there wasn’t as much to start with, but it was increasing, and he was keen to do his bit to assist. I went to his place next to a reserve at Oriental Bay and set out chew cards [hollow plastic-coated cards filled with peanut butter]. I popped round a few days later and gave him the chew cards to feel—they were absolutely shredded by rats. He now has a self-resetting trap that he can easily manage.”

One reason Wellingtonians have embraced the predator-free ethos so enthusiastically is that they see its results daily in the form of native birds repopulating the city—especially the large, charismatic ones such as kererū, kākā and tīeke, or saddlebacks. In large part, this is because Zealandia, the fenced ecosanctuary behind Karori, is serving as an avian maternity ward. Chicks that hatch in that predator-free environment grow into birds that fly over the fence to occupy surrounding areas in an ever-expanding ecological halo.


Polhill Reserve, up the Aro Valley, was one of the first places to experience the Zealandia spillover. Paul Ward, a backyard trapper who now has his sights set on re-establishing kiwi around the city fringes, meets me at the entrance, and we take a path down into the reserve.

“Ten years ago, this was unremarkable scrub infested with every weed on the list,” he says. “Two things changed it. Mountain bikers built trails all through here, opening it up for recreational use. And then, in 2014, for the first time in human memory, tīeke nested in the wild on the mainland again, right here. There were two chicks. The friendlier one disappeared, and the other one lost all its tail feathers—a classic sign of a cat attack—but it made it through to independence. So, we had a singular proof of concept.”

He stops mid-sentence, hearing a piercing, high-pitched call.

“That’s tīeke now,” he says. “If we’re lucky we’ll see some.”

Soon enough, we do. The svelte black body spattered with orange, two bubblegum-pink wattles at the base of the bill, shaped like a pair of apostrophes.

“In Auckland I have to take a boat to Tiritiri to see tīeke,” I tell him. “All you have to do is go for a walk in the park.”

What’s happened at Polhill, and right across the city, is testimony to the power of behaviour change, says Ward.

“Five years ago, if someone’s cat brought in a funny-looking blackbird with a bit of orange on its back, that’s all it would have been, whereas now, most of the people in the community around here would think, ‘Shit, it’s a saddleback. It’s a taonga’.

“Five years ago, every dog would have been off lead in here—and that would have been true of every park in Wellington. We realised that if manu like kākāriki, tīeke, toutouwai were going to have any chance of surviving in here, we had to shift the behaviour of dog owners. We worked with Garage Project brewery on a campaign called ‘Take the Lead’. If you posted a photo on social media with your dog on a lead or turned up at our food truck with your dog on a lead, you got a doggie bag with a free beer, a free mashbone dog biscuit, which they make from leftover hops, and an SPCA voucher. It wasn’t about waving the big stick, it was being inclusive and saying these are shared community spaces. We now have three-quarters of dogs on leads. Like trapping, it’s seen as part of being a good citizen. You recycle, you don’t use disposable coffee cups, you take cloth bags to the supermarket, you set your trap. It’s just something you do to look after your wild backyard.”

For the city’s mountain bikers, checking traps and planting trees are now part of the normal recreation experience. The Polhill Protectors describe their kaupapa as “birds, bikes and beer”.

“Twenty years ago, being an off-roader or mountain biker probably didn’t have much overlap with conservation, but now they’re the ones doing the work,” says Ward. “As a result, the birdsong we’re listening to now is better than what you hear in most national parks.”

When the Polhill Protectors group was formed in 2013, traps were hidden away from the tracks, to prevent them being tampered with, and to avoid having the unpleasantness of killing things in public view.

“We decided we should be upfront about the work it takes to look after our wildlife,” says Ward. “We made them obvious, and the traps became an advertisement for change.”

Deep public support for ecological recovery in Wellington encourages Ward and others to aim for the big prize: kiwi living among people once again. Kiwi have been missing from the wild in Wellington for more than a century. The Capital Kiwi project aims to eradicate predators and reintroduce the birds across a swathe of 23,000 hectares of farm and scrubland on the city’s western doorstep—the “Western front”, as Ward calls it. The area is roughly from Porirua to Red Rocks, using the city fringe as the eastern barrier and State Highway 1 as the northern. It’s the size of Abel Tasman National Park.

Ward says the initial target will be stoats. To start with, they will use only traps, roughly one every five hectares—a density that has successfully eradicated stoats on Fiordland islands. It hasn’t yet been done on the mainland.

From a high point on Terawhiti Station, west of Wellington, Paul Ward and Jamie McNaught, organisers of Capital Kiwi, contemplate the task of cutting tracks and laying stoat traps over an area of 23,000 hectares—the size of Abel Tasman National Park. From the windswept ridge to Wellington Harbour in the far distance, this landscape will be “new kiwi habitat for as far as the eye can see,” they say.
The predator-free mission knows no age restrictions. In Oakura School’s outdoor classroom, a conservation area of native plantings and nest boxes, 13-year-old Samuel Salisbury shares his predator-trapping knowledge with his fellow students. As well as being an expert in the ways of predators, Salisbury is an official ambassador for Lake Rotokare, near Eltham, a wildlife sanctuary within a predator-proof fence.

Right now, though, the project that’s being watched—its outcome eagerly and nervously awaited—is the attempt to eradicate rats, stoats and weasels from Miramar. (Possums were eradicated from the peninsula in the early 2000s.) If successful, it will be the world’s first large-scale urban eradication of rats and stoats. The outcome should be known by Christmas.

James Willcocks, who is directing the project, meets me one July morning at its headquarters, which was also the filming location of the 2014 vampire flick What We Do in the Shadows. Miramar’s predators will likely meet their death by night, but there is nothing shadowy about how Predator Free Wellington has gone about winning the support of the suburb. Three thousand individual permissions from homeowners were needed for the desired eradication grid—50 metre by 50 metres for bait stations, and traps every 100 metres by 100 metres across the peninsula. It involves some 7000 devices in total.

“The trust people have shown is amazing,” Willcocks tells me, “because it’s not just ‘Can we put a trap or bait station on your property?’ but ‘Can we visit it every week for 26 weeks?’”

Willcocks shows me around the yard, where there are stacks of trap boxes with a stencilled message: “Rats, stoats and weasels: please come in! Humans: do not touch!”

Inked paw prints track across the lid. A storage room has sacks of cereal baits with a strawberry fragrance.


Although the eradication, one of five landscape-scale projects funded by Predator Free 2050, isn’t being carried out by community volunteers (see sidebar), Willcocks says the social momentum has come from the backyard trapping movement that started with Kelvin Hastie in Crofton Downs in 2014.

“Today, we have predator-free groups in 49 suburbs,” says Willcocks. “It’s gone from a fringe thing to front and centre of people’s minds. In the latest survey, 80 per cent of Wellingtonians were either already involved or wanted to be. Predators are not being perceived as an external problem for some agency to fix. It’s about us defining the kind of city we want to live in. Ten years ago, to see a kākā I would have had to walk into Pureora Forest for three hours. Today, our kids get to see them every day at the bus stop.”

Willcocks was a DOC ranger, then the department’s national manager for volunteering, but nothing he has seen matches the energy, ingenuity and commitment of Wellington’s predator-free movement.

“It’s the collective approach that’s most impressive,” he says. “We get refugee families being welcomed to Miramar by neighbours with a batch of muffins, a pot plant and a trap. People get together over the weekend with a few beers to build trap boxes. For newcomers, we put out leaflets in multiple languages, from Samoan to Arabic: ‘No rats, free service’. The free service is our staff coming around to service bait stations and traps.”

Willcocks says Predator Free Wellington has tried to avoid imposing institutional confines around what is at heart an organic movement.

“One of the things we’ve learned is not to dictate how people can be involved. As a result, we’ve seen some cool innovation. A group of ex-Vic uni students gave themselves the name Traplordz to tackle rat-infested student flats. We provided trap boxes, which they stacked into a wall and got a street artist to paint a mural on them, so that each box is like a piece of a jigsaw puzzle. Which is exactly what the project is about: each of us contributing a piece of the puzzle.”

I ask him about the challenges of using toxins, given people’s concern about poisons in the environment.

“We’ve been upfront from the start that we’re using a combination of traps and toxin,” he says. “We’re using toxin—in this case brodifacoum—because we know we have to. That’s the tool that’s proven. But we don’t want perpetual reliance on toxins. Deciding to go on a journey of eradication and not control sets us on a different path. Do it once, do it quickly and cleanly, and we won’t have to go there again. That resonates with people. They understand that they’re not signing up for killing in perpetuity. Rather, that at some point it switches from an eradication phase to a defence phase.”

Defence is where the urban setting provides the project with its biggest asset: thousands of eyes and ears for monitoring, surveillance and detection. They will be sorely needed. When Willcocks describes the multiple ways a rat could invade, maintaining predator freedom seems a formidable task.

“We’re working with waste management companies,” he says. “We don’t want rubbish trucks full of rotting food coming on to the peninsula. We’re working with the supermarkets in terms of how freight comes on to the peninsula. Also ferries, wharves, jetties. And what if one of the 29,500 residents who live out here decides to tow a caravan that’s been parked up on a property in Coromandel for two years back to their yard in Miramar, and there’s a family of rats living in the ceiling? We’ve got the airport. We’ve got international film studios. This is a city where people work and play, so we can’t go around creating barriers to people’s movement. We have to adapt to our context.”

He admits that the project team is “building the aircraft as we’re flying it”. There is no template for urban eradication. There are a lot of nights when the complexities and uncertainties swirl around in his head. “Also, there’s a weight of public expectation. We’ve done a huge amount of work to switch people on, to get them to participate and buy into this vision. And they naturally expect us to deliver. That’s huge. It plays on one’s mind.”

[Chapter Break]

4. The farmers and their difficult terrain

While Miramar’s target is rats and stoats, on Otago Peninsula the predator team lives and breathes possums. The Otago Peninsula Biodiversity Group aims to have the peninsula possum-free within 5 years. Across the harbour, another group is working to enhance the halo of native species spilling out from Orokonui Ecosanctuary. The two rural jaws of the pincer are joined by an urban eradication effort. Together, they form another of Predator Free 2050’s landscape-scale projects: Predator Free Dunedin.

In the rural landscape of the peninsula, the team, mostly volunteers, is using a combination of traps and bait stations. Unlike at Miramar and Mahia, they are not using brodifacoum, but another toxin, cholecalciferol, which, curiously, is the same chemical compound known as vitamin D3. That a dietary supplement can also be a predator toxin reflects the fact that sometimes the only difference between what is therapeutic and what is toxic is the dose.

Kākā have become become a symbol of the resurgence of native species as mammalian predators are knocked out of the ecosystem. Whether in cities (Wellington), rural landscapes (Otago Peninsula) or islands (Waiheke) they have been welcomed as harbingers of a new ecological regime—one where introduced predators no longer rule the roost.

I join operations manager Bruce Kyle and three of his team for a walk around a bait station line near Sandymount. Kyle has a zoology degree and spent 13 years at Invermay researching cattle, sheep and deer. He later worked for DOC on pest control of tahr, deer, goats, possums, and other invasive plant and animal species. He started with the peninsula group in 2013.

Kyle tells me they chose cholecalciferol because it doesn’t linger in the environment like other toxins. It acts by raising the calcium level in a predator’s bloodstream to induce a heart attack or renal failure. But because cholecalciferol baits are much faster acting than anticoagulants such as brodifacoum, there is a risk that an animal won’t eat enough to receive a lethal dose, and may subsequently become bait-shy. To avoid this outcome, the team pre-feeds using nontoxic baits to condition the animals to the taste, and uses an additional lure to draw them to the bait stations. Prefeeding also creates a social effect that draws animals in from surrounding habitat.

I step into a shipping container with Frank Pepers, a retired forestry technician. He has the distinction of having New Zealand’s tallest tree named after him—he measured the 80-plus metre mountain ash growing in Orokonui Ecosanctuary in 1982 and after that, it became known informally as “the Pepers tree”.

Pepers is one of four permanent staff who work with Kyle. He shows me the flour-and-icing-sugar concoction they use as a lure. They make it themselves. I smell a strong aroma of aniseed and cinnamon.

“We put a blaze of this stuff on a tree and sprinkle a bit in the bait stations,” he says. Possums can’t help themselves—they have to investigate. It’s death by deception.”

The possums “eat and eat” the pre-feed, and then one day it’s switched for cholecalciferol bait.

Kyle hands me a pair of thermal imaging binoculars he’s trialling. Sol Wogan, a member of the operations team, calls it “the eye of God”. Would that it were. While effective in open terrain, such devices can’t penetrate through the thick canopy of New Zealand vegetation. A drone-operated foliage-penetrating imaging device would be a great means of detecting recalcitrant animals in forest remnants. And perhaps it’s not that far into the future. A Tauranga company receiving innovation funding from Predator Free 2050 has already mastered aerial delivery of toxic baits by drone, and in 2019, it was used to help clear rats from a Galápagos island.

We’re standing above Lovers Leap, on the south side of the peninsula. The land around here is precipitous, often with bush patches notched into ledges and crevices, all but inaccessible to humans.

Social acceptance, even more than technical breakthroughs, will determine whether the Predator Free 2050 mission succeeds. On Waiheke, the predator-eradication team devotes much of its time to the necessary work of planning public engagement programmes, seeking landowner permissions and working alongside external agencies and conservation groups to build a community that will welcome them at the gate.

As with all the project teams, the Otago group think a lot about how to get these last hard-to-reach animals. There are two basic approaches: going to the animals or getting the animals to come to us. Kyle favours the latter. If lures can be made compelling enough, animals can be drawn out of their refuges, rather than people having to scour every nook and cranny of a landscape to find them. Olfactory, sonic and visual lures are all being researched. Kyle shows me a prototype of a possum sound lure that was built by Pepers’ son Tony, an electrical engineer. The device switches on automatically when night falls and plays the distress call of a possum joey. Initial tests look promising.

For more accessible landscapes, it can be hard to beat a dedicated human volunteer who comes to know a place intimately and becomes attuned to it. I follow one of them, John Aldis, on a rough track through dense scrub on a farmer’s property as he checks his possum traps and nails chew cards to trees. Like many of the volunteers, Aldis lives on the peninsula. A tramper for 50 years, he says the thought of losing rock wren, blue duck and other endangered species is unacceptable. He’s been looking after this patch for three years.

Kyle says people like Aldis are worth their weight in gold: “They love being in the outdoors and making a difference, they’ve got an area they come to know well, they understand the terrain, they know where the animal trails and hostpots are, and they get on well with landowners.”

The worry for Kyle has been finding enough volunteer labour as the treatment areas have grown to include the entire peninsula. He’s relying on a human version of the halo effect—people starting to see taonga species in Dunedin city, noticing the increase in birdsong, seeing the forest canopy on the peninsula grow thick and lush, and wanting to be part of the project.

The Zealandia phenomenon is just beginning to happen here. People phone the biodiversity group to say they’ve seen a tūī on their property for the first time in 50 years. Aldis says grizzled farmers who have lived on the peninsula all their lives are remarking on the renewal. The man who owns the property we’re on told him, “It’s marvellous. I’m a grumpy old bugger but I sit in the shed and have my lunch and the fantails join me. I just love it.”

Nathan McNally (camo jacket) and Bruce Kyle check a possum bait station atop 160-metre sea cliffs at Cape Saunders as a freezing southerly front hits Otago Peninsula. The tactical requirements of predator eradication are such that it’s an all-weather operation. Teams can’t take the risk of an animal not receiving a lethal dose of toxin and becoming bait-shy. “To achieve eradication you have to think in a zero paradigm,” Kyle says. No animal left behind.
Waiheke is protected by a wide moat of sea and a halo of predator-free islands, making re-invasion less likely than many mainland sites. Nevertheless, more than a million tourists visit the island every year, along with thousands of recreational boat owners. Once the island is predator-free, keeping it that way will require careful surveillance to ensure that if a pest gets ashore, it is detected quickly and removed.

I call in to visit Brendon Cross, a sixth-generation farmer on the peninsula and deputy chair of the biodiversity group. He’s in his stockyards, vaccinating sheep with his daughter. He’s been with the group since it started, and says the impulse for setting it up was the thinking that, “We live in a pretty special place; how can we enhance it?” There wasn’t a conscious effort to start targeting pests, he says, but that soon emerged as the most important aspect, with possums the most obvious initial target.

“When we surveyed the community, for larger landowners the main concerns were rabbits and possums, while in the urban environment it was possums and rats. By targeting possums, one, you’re hitting something with confidence. The technology’s there. You could do it tomorrow. Two, you’re taking out something that sits by itself in the food chain. Removing possums isn’t going to affect anything else. Three, it’s something that benefits rural and urban dwellers, so we get both parts of the community on board.”

Though not everyone. Some people have told the group they shouldn’t be getting rid of possums.

“These projects are a hard sell, sometimes, because you’re killing things,” Cross tells me. “It’s not such a hard message for the rural community, because everyone can understand the economic implications and why it’s being done. It’s probably more questionable the closer you get to town. Why would you want to kill something that’s living in your back yard and not affecting you, apart from maybe eating the fruit off your trees? You may not have fruit trees. You’re not seeing chicks in nests killed at night. So why would you set a trap? It surprises me that we still have to do that sell: that yes, it’s a cool animal, an intelligent animal, it’s just in the wrong place. I’ve heard people involved in predator work say, ‘We’re not killing pests, we’re making birds’. That’s a good way to look at it.”

[Chapter Break]]


When the government declared the predator-free goal, it formed a Crown-owned charitable company, Predator Free 2050, to invest in large landscape eradication projects—areas of several thousand hectares—and to obtain philanthropic, business and local government funding for research and development of new tools and methods.

The company has provided co-funding and support for five eradication projects so far—Wellington, Dunedin, Hawke’s Bay, Taranaki and Waiheke—and is working with several more groups to deliver the next round of projects.

One focuses on the Whangarei peninsula, roughly from Pataua to Bream Head, an area of around 9000 hectares. Community support for ecological recovery through predator suppression on the peninsula has prepared the way for mounting an all-out eradication effort.

At a recent Waiheke Walks festival, ecologist Jo Ritchie explains how Te Korowai o Waiheke proposes to rid the island of mammalian predators. Stoats could be gone in as little as four years’ time. With its highly diverse community, ranging from bach owners and alternative lifestylers to winemakers and corporate commuters, Waiheke is seen as a test case for communities around the country. If it can work here, it can work anywhere.

Ed Chignell, chief executive of the Predator Free 2050 company, says it is the combination of local passion and proven capability on the community side, and provision of funding and organisational support by the company, that makes the predator-free vision achievable.

The company’s tag line is ‘Kia uru ora’, ‘Return to life’. Some people may think that’s laying an attractive spin over the ugliness of pest extermination. There are certainly doubters and cynics who see the predator-free mission as misguided, unachievable and even immoral (see sidebar). In a hut book in the Perth Valley I read an unsigned rant that claimed that possums do not eat birds’ eggs, that ZIP is deliberately targeting kea and whio, and that Predator Free NZ is a lie.

Some criticise the initiative for being a government juggernaut rolling across the landscape, crushing individual liberties and community-based initiatives in its path. That’s not what I saw. All of the projects are seeking, and finding, a sweet spot between agency implementation, community ownership and individual action.

“Change happens at the speed of trust,” a predator-control friend of mine likes to say, and trust is the lifeblood of this kaupapa.

It would also be a mistake to think that death to predators is the motivation for this mission. I have not met anyone in this work who takes pleasure in killing animals. Yes, they take satisfaction in seeing predator populations decimated—and hope to see them eradicated—but that’s not the same thing. When I visited Māhia Peninsula, part of the Hawke’s Bay eradication project, I learned from Rongomaiwahine leader Mo Cooper that his iwi sees eradication of introduced predators as just one component in an initiative that looks centuries into the future.

“Our people have been here a thousand years,” he said. “We want an environment that can sustain us for another thousand.”

Predators can swim, but not very far, and not against strong currents, so water—whether the sea, as at Mahia Peninsula, or rivers, in South Westland—offers a natural barrier, enabling the predator-free operation to clear and consolidate an area before moving to the next. Little by little, predators are pushed back. Could we wake up in 2050 to find that they’re gone?

I think most people want to bequeath something better to future generations. The sorrow over extinction is genuine. The worry that there will be further losses is real. If the cause can be removed rather than treated “forever and a day”, as Chignell puts it, so much the better.

Where do things stand? We have 30 years to get the job done. The first round of Predator Free 2050-funded projects represents just under one per cent of the New Zealand landmass. Ninety-nine per cent to go. How can that happen in a mere three decades?

Technology advances and spreads virally, something I learned from Grant Ryan (see sidebar). Seen through this lens, there is time to conceive, develop and refine new tools and methodologies over the coming decades—backing the winners, discarding the losers—and still achieve the 2050 goal.

Physicist and entrepreneur Paul Callaghan famously called predator freedom “New Zealand’s moon shot”. Like the Apollo programme, the predator-free mission is about the audacity of imagination. When I think of it in those terms, there is a similarity between achieving national predator freedom and addressing the climate crisis. Both involve reducing something—predator populations, net carbon emissions—to zero. Both require action and behavioural change at the level of individuals, communities and larger governance structures. Both seem impossible. But perhaps by achieving one impossible goal we will find we can succeed with the other.

More by

More by Rob Suisted