Dogs, traps, poison bait stations and cameras are being used by Pest Free Banks Peninsula to protect the biodiversity of Banks Peninsula Te Pātaka o Rākaihautū through the eradication of all animal pests by 2050.
Video / Frank Film
Documents released under the Official Information Act reveal an “urgent” staffing situation jeopardising the operation just days before the stoat was caught
Department of Conservation reports offer a fascinating insight into the stoat’s behaviour and movements, including chasing a rare kiwi along the beach, frequently playing near the hut where DoC staff were staying, and turning its favourite meals into tucker trophies
August 2022. A standard field trip on Chalky Island reveals a set of incriminating footprints. The remote and isolated place in the southwestern corner of the South Island has been predator-free since 1999, but no more.
The presence of a stoat is an immediate threat to this href="https://www.nzherald.co.nz/nz/parakeets-take-off-on-fiordland-island/DD2BM3K5BW4L5HRYSBR5FS2QJM/" target="_blank">haven for threatened or endangered species, including saddlebacks/tīeke, little spotted kiwi, a distinct species of skink, and kākāpō in particular.
Within a few weeks, the threat is confirmed after a stoat-detecting dog and handler finds “the biggest pile of [stoat] scat I have ever seen”, according to a report released to the Herald under the Official Information Act.
The hoped-for sprint becomes “a marathon” after several months without success, with officials scratching their heads for innovative ways to lure the stoat into a trap. This includes rubbing different scents - “otter, meerkat, ferret, cat, freshly shot whole rabbits” - all over different kinds of trap boxes, and even discussing trying to get it hooked on mayonnaise.
It will take eight months before the stoat is found dead in one of the 256 trap boxes used in the operation.
Chalky Island, Fiordland
By then it had left a trail of poo all over the island as well as neighbouring Passage Island, indicating repeated swims almost a kilometre long between the islands.
The stoat also had a fondness for playing right under DoC’s nose, ultimately one too many times; it was found dead in a trap box under the solar panels next to the DoC hut on the island.
And not a moment too soon. The staffing of the field operation had reached a critical point just days earlier, potentially jeopardising the mission, had it dragged on into the following months.
Following five clear sweeps of the island to confirm that it was predator-free, the overall bill came to just under half a million dollars: $483,260 - more than a third of which was for helicopter flights. Conservation groups said it was money well spent.
A further $210,000 was spent on more surveillance systems and biosecurity planning to help keep the island predator-free.
There was thankfully no evidence of the stoat eating any of the 30-odd kākāpō on the island, one of only three kākāpō populations on offshore islands (the others are on Anchor and Whenua Hou islands, which are also at constant risk of a predator incursion).
Once a stoat gets a taste for something, said DoC Te Anau operations manager John Lucas, it tends to hunt that particular thing, and it tends to kill more than it needs to eat.
“If we’d found the stoat was targeting kākāpō, we probably would have made the decision to capture and remove the birds because the risks were just too great. The old adage ‘don’t put all your eggs in one basket’, well, we’ve only got three baskets.
“When you reduce that to two, it starts to get into a really risky situation. It does create risks to the survival of the species.”
The Chalky Island stoat, papped by a remote camera near the Department of Conservation Hut on the island in March 2023. Source: DoC
The stoat appeared, at times, to be “toying with us, thumbing its nose at us”. It was hard to explain why a stoat would play on top of a trap box for months without entering it, and then one day decide to go inside.
“It was frustrating. It was a long, challenging incursion response, which is why we had to have an open mind to different ways [of catching it].
“But we knew eventually the stoat would make a mistake - and it did.”
‘Biggest pile of scat I’ve ever seen’
Brad Windust and his stoat-trained dog Wero started roaming the island in September 2022, within 10 days of the footprints’ discovery.
Signs of the stoat were everywhere. Some of its poo had yellow feathers in it, perhaps the remains of one of its favourite meals: a mohua/yellowhead.
In another spot, a dead tui was on a “display pad”, prompting the team to set up a remote camera there. It’s a favourite site; when Windust returned a few days later, he found “a massive pile of stoat scat outside a den with what looked like yellow brains s**t. I’ve seen it once before outside a den - I think it’s like a trophy.
“My gut feeling is that there’s more than one stoat on the island. I hope I’m wrong, and we will soon know but 25 stoat scat and three dens, one cache site and a display pad is way too much sign for one stoat,” Windust wrote in his report.
The trap set under solar panels next to the Department of Conservation hut on Chalky Island is where the stoat was eventually found dead. Photo / DoC
“It is likely one female stoat has got here and dropped her kit, this time last year. If so, none of the female’s [sic] will be pregnant. If this is not the case, the females will be pregnant, and about to den. The numbers will explode exponentially.”
If that were the case, DoC would need to “evacuate all nationally critical, endangered, vulnerable and nationally increasing birds and lizards off the island”.
Windust suggested a number of ways to lure the stoat or stoats into a trap, including using dead ones. “Rubbing their smell about traps really helps. Discuss whether it’s possible to use a judas stoat.”
He also found two old stoat poos on Passage Island to the north, making the presence of a stoat there “highly probable”.
He stressed the importance of a team of good trappers, but a DoC summary report on October 26 said they were of “very limited availability”.
At this stage the cost of the operation - involving 20-plus staff on two-week rotations - was just over $14,000, but it ballooned to over $50,000 a week later, and then to over $80,000 a further week later. By this time, the costs were high enough to warrant a no-surprises policy: a heads-up was required when daily operational costs exceeded $10,000.
The red markers indicate the places where a DoC worker, with a stoat-trained dog, found stoat poo and scent on Chalky Island. Photo / DoC
Chasing kiwi
A different dog-and-handler team - Angela Newport, with Macca - spent 10 days on Chalky Island just before the operation shut down for three weeks over the 2022 Christmas break.
She found tracks in the sand on a beach where the stoat was ”quite clearly following kiwi prints as I followed them up the dune system from the beach high tide line”, and onward towards an area known for a dense population of titi/muttonbirds.
“It seems that the stoat has changed its behaviour a little since mid-October. It is no longer engaging with traps and fake dens and has only been picked up on camera fleeting past, mostly along the edge of [the] frame too,” Newport’s report said.
In a twist, she found no sign of a stoat on Passage Island after a five-hour hunt.
The first post-Christmas DoC summary report showed the costs running at just under $125,000. There had been no motion-detecting camera shots of the stoat for over a month, though it was common for stoats to “disappear for a while and be detected again” much later.
More than four months had passed since the initial footprints were found. “Aim to innovate and develop new idea/s to roll out - what we are doing now has not had any result,” DoC’s January 2023 report said.
Footprints on a beach on Chalky Island indicated that the stoat had chased a little spotted kiwi. Photo / Sallie Bassett
Right under DoC’s nose
Windust and Wero returned in late January, finding two poo samples on Passage Island and 15 on Chalky Island, the “most promising” on the wooden frame of the solar panels by the helipad.
This was right next to the DoC hut where the workers sleep.
Portentously, Windust said the site appeared to be a favourite, making it a good place for trapping as “happy stoats playing accidentally run into traps”.
“The scent and scat was fresh as fresh. It is the perfect play site, which make [sic] the best places to catch them,” he wrote in his report.
The team set up a camera - one of 36 used in the operation - and two different traps among the framing.
“Curiosity could kill the stoat. Using pulses of different scents, otter, meerkat, ferret, cat, keep trying different things. Getting freshly shot whole rabbits to rub along the ground making trails to traps, and rub over traps and then bait with large chunks,” he said.
“Also using a couple of the ZIP MotoLure mayonnaise lure dispenser with cameras to see if you can get it hooked into eating mayonnaise then set trap with mayonnaise bait.”
Some financial reprieve arrived by late February from Air New Zealand - $6000 for a travel fund - but this was only a tiny fraction of the running price tag of $175,000.
The team was under new management by then, with four new management staff, though capacity remained an issue; a trip to the island for mid-March was cancelled due to “limited capacity in operations to organise, brief and support the trip”.
With the success of the operation under pressure, DoC pencilled in starting a poison drop in July.
The Chalky Island stoat caught on trail-cam footage checking out a fake den in October 2022. Photo : DoC
Playing all over and around traps - but not in them
The camera under the solar panels papped the stoat on the night of March 28, 2023 - seven months after the initial footprints were found.
Windust and Wero choppered in the following day to find fresh stoat poo, again, on the framing of the panels - but no stoat. The camera had been moved, too, as if the stoat wanted to play with all the equipment employed to catch it, while roaming as close to the DoC hut as possible.
The stoat seemed to have favourite bits of moss as well as favourite play spots; he repeatedly defecated on some moss in a spot near a different camera.
“You could just make out yellow feathers in it, which I found interesting because there’s a lot of young titi (muttonbirds) at the moment, yet he’s still hunting mohua (yellowheads),” Windust said in his report.
Other curiosities included a stoat nest next to a dead wood pigeon. “My feeling is that it caught it and carried it back to its den but it couldn’t get it down the hole so it camped up beside it.”
He also found some “fresh stoat prints” on a beach in the northeastern corner. “This may be a random play site or an area he often plays ... He then went running, full tit down the beach, then went up into the bushes.”
Windust characteristically suggested trying to catch the stoat on the beach, in case that was also a play spot the stoat might return to.
“Getting creative like wrapping run-throughs [a type of trap] in foam, covering them in sand etc might help. Having a feather dangling from Cotton [sic] in the trap might get his attention.”
Mirrors to make the stoat think he had company were “an awesome idea” to lure him into a trap box.
Stoat incursion on Chalky Island, September 2022. Here the stoat is photographed, in a pattern that would be repeated for several months, right next to a trap box he didn't enter. Photo / DoC
On Passage Island, Windust only found a single scat sample - with mould on it. “I should be finding more scat from a resident stoat, which made me wonder if weka would eat the stoat scat.”
The DoC summary report 10 days later, in April, still indicated two male stoats, one on each island, adding that the operation was “a marathon not a sprint”.
The staffing situation had become critical.
“Field staff resourcing and scheduling for May-June is now urgent ... very few IMT (incident management team) staff in place post April 30. Need to retain or recruit into almost all roles.″
Other operations were tightening the staffing squeeze: an incursion operation on Resolution Island, as well as the ongoing response to Cyclone Gabrielle.
A week later, Windust’s tactics paid off; the stoat was found dead in one of the traps under the solar panels. DoC proclaimed in a press release: “To have it caught in eight months is an achievement”.
The cost of the operation at this stage was less than half of what the total cost would become; several more clear sweeps of the island were needed before a return to business as usual.
The stoat was eventually found dead in a trap under the solar panels, a favourite play place, right next to the DoC hut on Chalky Island. Photo / DoC
A titi killed by a falcon or raped by a kakapo?
Newport and Macca made the first post-capture sweep, in May, of Chalky and Passage islands - no sign of any stoats.
Among items of interest were some headless titi/muttonbird carcasses, though Macca gave no signal that a stoat had been involved in the head-eating.
The stoat appeared to have been roaming both Chalky and Passage islands, Newport said, which would mean repeatedly swimming the stretch of water - called Bad Passage, nearly a kilometre long - between them.
Windust and Wero also found no trace of a stoat in June, except for two “very old” stoat poos on Passage Island. Canine excitement ruined one of the samples: “When I reached to get the ball for his [Wero’s] reward, he leaped forward, and his paw squashed the scat into the ground, and I couldn’t find it to retrieve it. It basically turned to dirt. Sorry!”
He also made a curious discovery: a titi/muttonbird carcass with a cut in the back of its neck. He wrote in his report that maybe it had been a “kākāpō rape victim, falcon kill, or stoat”, though Wero had found no trace of the latter.
He sent a photo to a falcon expert, who said it could well have been the work of a falcon even though he would have expected to see more feathers around the open wound.
“Falcons would bite to severe the vertebrae behind the skull like this, then pluck the immediate area to break into the flesh. It looks like it has just been torn into,” Windust quoted the expert saying. “Interesting that so little was eaten, maybe it was disturbed.”
Asked about a kākāpō raping a titi, DoC operations manager John Lucas told the Herald it wasn’t abnormal for bird species to prey on other bird species.
Asked about a kākāpō raping a titi, DoC operations manager John Lucas told the Herald it wasn’t abnormal for bird species to prey on other bird species.
“It’s not helpful for us to have other native species undoing our good work. When you’re dealing with a species as vulnerable or rare as kākāpō or takahē or kiwi, it is particularly challenging and frustrating. But that’s the natural ecosystem doing what the natural ecosystem does.”
He said kiwi had a tendency to be a “tad clumsy”.
“Often their demise is at their own hand ... falling into a hole and drowning, et cetera. Accidents do happen.”
Three further sweeps of the islands - one each in July, August, and September - found nothing stoat-related.
Lucas said there might be people who think that it wasn’t worth the money to return the island to being predator-free.
“But I think doing this work to safeguard a population of kākāpō and skink et cetera is worth the investment. It is a challenge, but responding to incursions is probably some of the highest priority work we do.
“These islands support significant biodiversity values - species like kākāpō. You can’t put a value on them.”
Derek Cheng is a senior journalist who started at the Herald in 2004. He has worked several stints in the press gallery team and is a former deputy political editor.
