Brush-tailed pests are being killed by the thousand near Christchurch, with spectacular results.
With his fruit trees, veggie garden, and native bush getting frequently munched, Toni Williams turned to trapping and hunting possums.
The Fire and Emergency New Zealand staffer – who works in Christchurch but lives in Akaroa, where he’s also a volunteer firefighter – owns what he calls a small property, of about “6000 squares”, up Purple Peak, perched above the harbourside town.
“I got a fair share of them,” Williams says of the possums. “But I could never get on top of them. As quick as you took one out, more came in.”
A couple of years ago, community organisation Pest Free Banks Peninsula knocked on Williams’ door, explaining its ambitious goal of eliminating possums across 23,000 hectares, or 21 percent of the peninsula/Te Pātaka o Rākaihautū.
It wanted permission to kill the animals – which eat plants, bird eggs, chicks, and, occasionally, adult bird species – from Williams’ property. He was all for it: “We’re quite into native birds.”
What were his expectations? “Excuse the French, but I thought they were pushing shit uphill.”
Williams hasn’t seen or heard a possum at his place for a year. “It’s quite amazing.”
What’s the difference?
Ōnuku rūnanga chair Rik Tainui, who sits on the project’s oversight group, says there’s no visible difference around the marae. The difference is audible. “You just have to walk up the road and listen to the birds.”
Department of Conservation Mahaanui operations manager Andy Thompson says: “It’s a real dream come true to see if we can have a real impact there.”
Since 2019, entrepreneur Grant Ryan has tested thermal cameras for his Cacophony Project in the backyard of his Akaroa property, near Stanley Park “but right up the top”.
Early on, the cameras would detect the movements of several possums each day. Now there are none.
An analysis of 24,000 recordings, over 1100 monitoring nights, reveals possum numbers starting to drop in 2023. In 2024 there was one recording of the brush-tailed critters, and so far, this year there have been none.
“The Banks Peninsula team are probably applying the very best set of tools in New Zealand for the sort of environment they’re in,” Ryan says. “They’re doing a fantastic job.”
Pest Free Banks Peninsula programme leader Sarah Wilson is thrilled to have independent verification, by Ryan’s thermal camera, of its work in and around Akaroa.
“That is what we’re finding,” she says. “We’re now removing the last possum in and around that town.”
She reckons her team has killed tens of thousands of possums since operations began in late 2022.
“We’re not actually that interested in how many we’ve killed. We’re interested in how many are left, which needs to be zero.”
The possum eradication project is nearing an important milestone.
“We have largely cleared – not to the last one yet, we’re working on that right now – but we have significantly cleared about 10,000 hectares of Banks Peninsula,” Wilson says.
“We’ve been funded to undertake 20,000 hectares so we’re about halfway there, and we’re learning a lot as we go. We’re speeding up. We’re getting faster.”
Next year, though, the group has its own hill to climb: How to secure more money.
Work on the wild side
Killing pests for the good of the environment has happened for years across Banks Peninsula, which is blessed with natural gems like the 1250-hectare Hinewai Reserve, and Pōhatu Marine Reserve, home of the at-risk/declining little penguins, or kororā.
The work has taken Wilson’s team – “the coalition of the willing for the killing” – from sea level along the rugged coast to the sub-alpine, wind-swept hilltops, paying particular attention to the gnarliest areas, like steep gullies and sea cliffs, to flush out the furry pests.
The Banks Peninsula Conservation Trust, an idea hatched in 2001 by a handful of farmers, is now a hub for disparate community groups pursuing ambitious goals in a landscape peppered with private landowners.
In 2018, then-conservation minister Eugenie Sage, who lives in Lyttelton, announced a memorandum of understanding to remove pests – like possums, goats, pigs and hedgehogs – from the peninsula. More than a dozen groups signed, including the trust, Department of Conservation, Christchurch’s city and regional councils, and Ngāi Tahu rūnanga.
The work was split in two. In the peninsula’s south-east, known as the extended wildside, possums would be eliminated, while mustelids (weasels, stoats and ferrets), and feral cats would be knocked back to low levels.
Meanwhile, the operation at Kaitōrete Spit, between Te Waihora/Lake Ellesmere and the Pacific Ocean, would remove hedgehogs, mustelids, possums and cats across 5500ha.
In 2020, the peninsula’s pest-free bid got a cash injection – $5.11 million by Predator Free 2050, under the Jobs For Nature programme, which brought its total budget to $10m, after grants from local councils. (Predator Free 2050 had $76m earmarked for community projects, and the Banks Peninsula money was its 10th large landscape project.)
This financial year, Pest Free Banks Peninsula, a coalition of 20 groups governed by the conservation trust, received $160,000 ($100,000 specifically for controlling pigs) from the Christchurch City Council, with another $616,000 from the regional council, ECan.
Wilson, the pest-free group’s boss, says about $3 million has been spent on the wild side operation targeting possums. Out of an overall team of 23, nine work on the wild side, and five on Kaitōrete.
Every kind of threat
Possums, brought across from Australia and established in Southland in 1858, are voracious eaters, and can cause the collapse of forest canopies, says Te Ara, the online encyclopedia. “In New Zealand they consume an estimated 21,000 tonnes of vegetation a night.”
They’re drawn to succulent fruit and flowers, starving birds of food and halting forest regeneration. Possums also eat insects, reptiles, bird eggs, chicks, and sometimes adult native bird species.
As they carry bovine tuberculosis, they’re a threat to farming.
Destroying the animals helps forests rebound, Wilson says, and dramatically increases the success of bird breeding.
What’s the strategy?
Wilson says her group started in the south-east corner of Banks Peninsula, keeping the water at their backs, and headed towards Akaroa. “Possums are not going to head out to sea.”
Ollie Rutland-Sims, the wild side operations coordinator, says the operation has four main phases.
First is the knock-down, an intensive, tight-knight network of toxin stations or traps – depending on the landowner’s preference – to try and kill 95 percent of possums. This lasts three to five months.
Then there’s a “passive mop-up” over a period of months, using AT220 traps at a density of about one per 20 hectares.
“There’s always pockets in the landscape where things get missed on that first wave that come through – really steep gullies, sea cliff areas, little pockets in the landscape.”
Lincoln University research published last August showed, on one particular block with bait stations loaded with toxins brodifacoum and feratox, possum-triggered camera interactions dropped from 482 in the first week to zero by week eight. Re-invasion occurred in week 16, when one possum interaction was recorded.
A surveillance network is the next phase, using track cameras, and community observations, including an online pest reporting system. Possum dogs are brought in to root out elusive stragglers.
The fourth and final phase is defence.
“We can’t detect any possums,” Rutland-Sims says, “but we’re leaving a layer of monitoring equipment in there so that if something does crop up we can be aware of it – and then think about what we might need to do there.”
Prep work can be tough and time-consuming. Within Hinewai Reserve, where they’re working now, the team has cut 37 kilometres of new access tracks. “It’s all on foot, right?”
‘There were thousands of the little furry buggers out there‘Mark Thomson, Children’s Bay Farm
Rutland-Sims pulls out some numbers.
Knock-down, across the operational “front line”, is happening across 357 hectares, about 6800ha are in passive mop-up, another 1400ha is under surveillance, and properties spanning 950ha are in defence, without a possum being detected. That’s a total of 9507ha.
Reinvasion is always a risk, especially when juvenile males can travel tens of kilometres each week.
“It’s bloody rewarding,” says Rutland-Sims, who returned to the peninsula and fell into the job after Covid-19 lockdowns jolted him from his university training in tourism. “We’re in this really cool phase at the moment of proving a concept that hasn’t been done elsewhere in the country.”
(The team’s expertise is acknowledged by the department’s Thompson, who says conservation staff initially provided technical advice. “To be honest, the pest-free team are probably ahead of us in terms of their knowledge and skills now, because they’re out there doing it every day.”)
News of the project’s success has spread.
Rutland-Sims says they’ve approached private landowners wondering if they’ll be asked, why would I want you in my backyard? But what they’re often asked is: “When are you going to be in my backyard?”
British couple Jack and Charlotte Gibbs own a 235-hectare sheep and beef farm, with almost 1000 breeding ewes, above Ōnuku Marae.
Jack, whose background is in farming, forestry and finance, became a trustee of Banks Peninsula Conservation Trust in 2019.
Possum eradication started on the Gibbs’ farm in January 2023, and they were almost possum-free within a year. That’s a far cry from when the pair moved to live full-time on Banks Peninsula in 2013.
Charlotte says: “We had possums all over the roof nearly every night. We were catching them in Timms traps around the garden, along the fences.
“They ate every plant, every rose, every everything. They were absolute nightmare for us, to the extent that we thought, ‘What on earth have we done?’”
The couple got serious. They established a trapping network, and Charlotte was licensed to handle cyanide pellets, called Feratox.
Those first few years they killed about 4000 animals, and afterwards, about 200 a year.
“Once we started on that, you saw the immediate benefits to biodiversity,” Jack says. “But they have been nothing in comparison to the benefits that we have seen from the total removal of the possum in the last 24 months … the jump in biodiversity has been spectacular.”
Charlotte adds: “We now have so many tūī and bellbirds. It’s just an explosion.”
Rutland-Sims, of Pest Free Banks Peninsula, reckons Akaroa now has one of the best dawn choruses of birds in the South Island, if not the country.
“The food source in the forest is just blooming, and with that comes extra habitat for our native birds. A lot of holes in the trees that possums would den in are also holes that native birds would normally make homes in.”
He recalls one warm night, having left his bedroom window open, getting grumpy at being woken early by birdsong. “It hit me a couple days later: That’s the whole point!”
Williams, who lives up Purple Peak, says he notices the lack of roadkill on the Akaroa side of State Highway 75, after cresting the highest point, Hilltop.
The Gibbs’ farm is still under camera surveillance for possums. That last animal is very smart, Jack says – it doesn’t like poisons, and it’ll run away if it spies a dog. “So you have to get smarter and smarter.”
(Rutland-Sims says leaps in camera technology have led to huge improvements, and the project adapts every week because of what they’re seeing in the field. “I’d hate to think what version of our operational plan we’re up to.)
‘Thousands of the little furry buggers’
A few weeks ago, the Pest Free team went to check on a 240-hectare Angus cattle breeding farm at Children’s Bay, between Takamatua and Akaroa, owned by prominent Christchurch businessman Humphrey Rolleston, and wife Debra.
Farm manager Mark Thomson says about 80ha is “shut up” – fenced off to allow native bush to regenerate. They’ve done plenty of new planting, too.
But the possums would raid the farm in spring, in particular, and wipe out new growth on native trees. In places, possum tracks wore through to the dirt.
“So the trees are taking a lot longer to establish, really, because the possums just kept on eating them. There were thousands of the little furry buggers out there.”
The possum-killing operation has made a big difference, he says. He noticed changes to the look of whitey wood/māhoe and five finger/whauwhaupaku last spring.
“It’s just the colour,” Thomson says. “It’s a lighter green, and the hills were just covered with it compared to previous years.”
(The other Thompson, the department boss, says there’s clear evidence killing possums is positive but the department is still working to quantify ecological improvements. Questions he’s interested in answering are: “Can we cover the landscape in a cost-effective way that guarantees an elimination strategy, and then can we defend it?”)
Some people like the possum-killing operation and some don’t, says Thomson, the farm manager. The ones who don’t tend to be those living near farms with pets, he says.
“I think it’s great. I mean, the possums never were here [before being introduced], so why should they still be here?”
More than just ‘killing stuff’
The operation has had its challenges.
Tainui, of Ōnuku rūnanga, says it’s hard to keep good staff, and it’s tough work. “There’s a lot involved, aside from killing stuff – that’s the thing I’ve learned.”
Thompson says: “It takes a special kind of dedication to be walking up a hill with a big pack on a wet day, pushing through the scrub.”
The pest-free project is a community adventure, says Gibbs, who lives above Ōnuku Marae. “The longer-term benefits, which it will take a while for people to wake up to, is really the creation of jobs and GDP for the region.”
Rutland-Sims, the operations coordinator, says he’s one of five people working on the project who attended the local high school. Two of them did work experience and then, after finishing school, got jobs.
But an existential crisis looms.
Work could come undone
Wilson, Pest Free Banks Peninsula’s programme leader, says the Predator Free 2050 money runs out at the end of June next year.
Her team is pushing hard towards its 20,000ha target, but it doesn’t want to achieve just the suppression of pests.
“We actually want to achieve elimination, and then guard that and put in a buffer to protect that. We also want to keep moving forward. We have a lot of support from our community, in terms of rates [money], as well as direct support from landowners.”
Thompson says he’s concerned the project might not be able to be maintained, or expand. “We’ve been thinking in five-year time frames. But actually, we really need to be thinking in 25-year, 50-year timeframes.”
Tainui, of Ōnuku, says he’s hopeful funding will be found. “How do we make sure that all the work they’ve done doesn’t come undone because of lack of funding?”
A Predator Free 2050 discussion document, released on May 5, proposed retaining the current list of national target species, which includes possums. The document said: “With several effective tools available, the possum’s relatively slow reproductive cycle and dispersal, eradicating possums from the New Zealand mainland is considered plausible.”
There are no promises for Pest Free Banks Peninsula, however, or any other groups funded by Predator Free 2050. Submissions close on June 30.
Wilson says her team would love to have central government support to continue.
“It doesn’t make any sense to stop. We don’t want to build a fence – that’s just dumb. We want to move forward.”