The Predator Free Dunedin conservation collective co-ordinates efforts to eradicate pests from the city’s environment, and has recently received a funding boost. Clockwise from top left: Wendy Wall re-baits a Trapinator possum trap in her garden in the Glen; a well-chewed chew card from Ms Wall’s garden; a Good Nature A24 automatic humane trap for killing rats in Ms Wall’s garden; a possum pest; Di Martin shows an apple tree that has been adversely affected by possums in her and partner Peter McCaskill’s garden in the Glen; City Sanctuary community engagement facilitator Kate Tanner attaches a Trapinator trap to a tree in Mrs Martin and Mr McCaskill’s garden; Otago Peninsula Biodiversity Group member Ben McConnell holds a live capture cage trap; and Jonah Kitto-Verhoeff holds an AT220 rebaiting and resetting possum and rat trap while, behind him, fellow Halo Project members (from left) Kim Miller, Sophie Bond and Conor Houghton hold a stoat trap. PHOTOS: LINDA ROBERTSON & PETER MCINTOSH
Predator Free Dunedin has been working to eradicate stoats, possums and rats from Dunedin since 2018, and with a new funding boost is set to expand its territory. Otago Daily Times reporter Eric Trump visits the frontlines in the war against the city’s pests.
On a recent afternoon, City Sanctuary community engagement facilitator Kate Tanner helped the effort to free Dunedin of predators by "baiting the runway" and "seasoning the box".
The runway, a strip of white Corflute, led inside a wooden box where a T-Rex rat trap waited, its mouth open and toothy.
"The trap should seem like a fancy new restaurant," Ms Tanner said, rubbing a thin icing of peanut butter outside the box.
She found a spot for the trap in the backyard of Di Martin and Peter McCaskill, who lived in the Glen area of Dunedin and were two of more than 300 City Sanctuary trappers.
Mrs Martin pointed to an apple tree in her garden.
"We used to have seven buckets a year.
"Now, because of possums we have seven apples," she said.
Mrs Martin and her partner had been there 50 years and seen traps evolve from steel cages delivering live prey to the swift-kill traps of today.
Ms Tanner next set a plastic possum trap, the Trapinator, which hung from a tree. A powdery blaze of flour, icing sugar and spices led up the trunk to a trap a few metres above ground. Inside was a bait bar with a helping of possum dough, a spicy mix of aniseed and cinnamon. At the tree’s base was a gnawed corflute chew card that identified rats, stoats possums and hedgehogs by their teeth marks. The heavily chewed card meant the trap was in the right place.
City Sanctuary has traps on 8000ha of Dunedin land and has killed 985 rats and more than 1000 possums.
It is a delivery partner of Predator Free Dunedin (PFD), the conservation collective begun in 2018. PFD is composed of 22 organisations working in concert with local farmers and two Dunedin runaka, all of whom would like us to be familiar with the vocabulary and practice of predator elimination, as they seek to free a vast necklace-shaped area, from the Silver Peaks to the Pacific, from Karitane to Brighton, of possums, stoats and rats.
PFD’s three main partners are: City Sanctuary, which monitors city reserves, such as the town belt and the backyards of Dunedin; the Otago Peninsula Biodiversity Group, which stretches from Anderson’s Bay Inlet to Taiaroa Heads; and the Halo Project, which aims to spread a safe halo around Orokonui Ecosanctuary.
Together, they have 6300 traps on the ground and have caught almost 50,000 predators.
PFD recently received $7million in funding that will allow it to expand its operations area by another 37,500ha.
"We are eliminating predators to protect what should be here," PFD communications and engagement director Kimberley Collins said.
What should be here but is not reads like a threnody to biodiversity: the adzebill, South Island piopio, stoat-legged wren, laughing owl, snipe-rail ... nearly half of New Zealand’s vertebrate species have disappeared since mammals arrived, and 4000 species are currently at risk. Humans accelerated the slaughter when possums were imported for fur, the Rabbit Nuisance Bill of 1881 allowed stoats in en masse and acclimatisation societies introduced hedgehogs.
Ms Collins was optimistic about the future. She said New Zealanders were thrifty people always coming up with new ideas.
"We’ll never bring back what we lost. But we can try to keep what we have," Ms Collins said.
With an estimated 25million native birds, chicks and eggs lost to introduced predators a year, and 30million leaf-chewing, egg-drinking possums from Stewart Island to Cape Reinga, that will be a challenge.
However, just as Prime Minister Jacinda Ardern had her "team of fivemillion" resist Covid-19, PFD has its team of more than 1000 paid staff and volunteers, and more than 7000 devices on the ground.
PFD project manager Rhys Millar said whether it was possible to be predator free or not, New Zealand had to try.
"We have one of the highest extinction rates of native species in the world.
"We can’t sit around while more species are lost," he said.
Ms Tanner and Mrs Martin next moved inside to record a kill on Trap.NZ, the national database that shows where traps are and locates predator hotspots so more traps can be set. The computer screen shows New Zealand peppered with red dots, some areas denser than others — a map of predator contact-tracing.
Then, Ms Tanner knocked on neighbour Wendy Wall’s door. She had been a volunteer for only two weeks, but her chew card also showed possum activity.
Another trap, a CO2-powered GoodNature A24 rat and stoat trap, was slung from a tree. It delivered a muted but satisfying concussion when Ms Tanner demonstrated how it worked.
"I can’t wait for my first catch," Ms Wall said.
Ms Tanner said possums were not malignant.
"They didn’t want to come here.
"They’re just trying to survive," she said.
Ms Tanner took care to explain how to set traps and dispose of carcasses, and, above all, that the traps were designed to prevent animal suffering.
"It’s important that PFD find social acceptance," Ms Tanner said.
Tracing Otago Harbor’s eastern curve, you pass through the suburb of Musselburgh. Here, where city meets peninsula, the Guardians, one of many smaller groups PFD embraces, have set up a Maginot Line of traps to protect the peninsula from predators expanding north.
Guardian Marcia Dale ran a trap line on the Chisholm Links golf course.
"We’re already seeing more bird life: kereru, tui, korimako.
"Last week, I had to swerve to miss a skink.
"In 10 years, this will be a different place," Ms Dale said.
Ms Dale was also the community team leader of the Otago Peninsula Biodiversity Group (OPBG) on Portobello Rd, in a building adorned with Happy Hens.
Puku the housedog is celebrated as a reaper of 180 possums. The OPBG itself had taken 20,000 since 2011 and aimed to have the peninsula liberated by 2023.
OPBG planner Micaela Kirby-Crowe explained the organisation targeted possums before rats and stoats.
"When possums are gone by next year, they won’t upset the natural balance.
"If we eliminated stoats first, the rabbit population might explode, so we have to plan carefully," she said.
Ms Kirby-Crowe said local farm owners want to eliminate possums because were the chief spreaders of bovine tuberculosis.
Possums eat an estimated 21,000tonnes of vegetation a night. Ms Kirby-Crowe looked forward to native plant life, such as kanuka, ngaio, ribbonwood and mahoe, returning to the peninsula.
PFD’s third front in the effort to save biodiversity is across the harbour. The Halo Project’s headquarters are in Port Chalmers, though Halo’s heart is Orokonui. Its territory includes Flagstaff, Mt Cargill and Mihiwaka, as well as Aramoana and, because of the new funding, the Waikouaiti and Taieri Rivers.
Quarantine Island lies in Otago Harbour.
"Stoats could swim over there," Halo’s PFD project manager Jonah Kitto-Verhoeff said.
"They could swim across the harbour."
His team muttered admiration for the enemy.
"We all have respect for the animals we trap," Conor Houghton said.
The Halo website refers to stoats as "rock stars", for their short and frenzied lives. A stoat will kill not just one bird, but the entire nest. A male stoat mates not just with the female, but with any female kits in the nest, though they may be only 2 weeks old.
Last year, Halo killed 80 stoats, 978 rats and 476 possums. The project also laid 9000m of fencing as part of the Source to Sea project, which helps private landowners protect waterways. This project has planted more than 16,000 native trees and grasses.
Inside its headquarters are stacks of traps, including the AT220 trap, which attracts possums and rats with mayonnaise. It deactivates during the day. It resets 100 times and can be left in the wild for six months.
"We need to be ingenious because these animals are," Mr Kitto-Verhoeff said.
Ingenuity had created the Spitfire, he said, which could ensure an animal was a predator through a sensor and then spray its abdomen with a toxin to be ingested during grooming.
Getting back to the garden may be impossible. But with PFD and its suite of traps and detection devices, its vigilant volunteers and staff, Dunedin may be able to save the taonga that remain.
