A large-scale stoat eradication programme on d'Urville Island can no longer go ahead because of problems with land access.
The d'Urville Island Stoat Eradication Charitable Trust said it had run out of avenues to try to gain land access and had no option but to put the project into hibernation. Photo: Supplied / Tamzin Hendersom Driftwood Ecotours
Predator Free 2050 has withdrawn $900,000 in funding for the Rangitoto Birdsong project to remove stoats from d'Urville in the Marlborough Sounds.
The project was paused late last year when it could not secure access to all private land on the island.
D'Urville Island Stoat Eradication Charitable Trust chair Rupert Wilson said every attempt was made to keep the project going but it had run out of avenues to try to gain land access for predator control and had no option but to put the project into hibernation.
The trust was established 17 years ago with the aim of removing the predators and returning birds to the island, Wilson said.
"Stoats are really the only major pest on d'Urville. The island is remarkably free a lot of the other standard pests like ship rats, Norway rats, possums and rabbits."
But little spotted kiwi, yellow-crowned kākāriki and South Island kākā were no longer found on the island and Wilson said stoats were the number one killer of birds.
D'Urville is also home to a rare population of South Island long-tailed bats/pekapeka which are preyed on by stoats.
The island has about 45 permanent residents, with ownership a mix of 80 private landowners and public conservation land, including the 5869ha d'Urville Island Scenic Reserve.
Wilson said the eradication programme needed to cover the entire island in order to succeed, but there were several blocks the trust was not able to access.
It had spent the last year trying to resolve the access issues with landowners without success.
The total project cost was just over $3 million and the Rātā Foundation, Marlborough District Council, the Department of Conservation had also committed funding, but without the support of Predator Free, Wilson said they would no longer support an eradication project.
At almost 17,000 hectares, d'Urville is New Zealand's eighth largest island and is about 15 times bigger than other islands previously cleared of stoats.
Wilson said it was disheartening for those that had put time and effort over the last 17 years to achieve what would have been the largest ever stoat-eradication project.
"We hope that one day things will change and access will be possible to all of the island and at that stage we would certainly like to get the project going again, but that may be some years away."
Predator Free New Zealand acting chief executive Brett Butland said it was disappointing to withdraw the funding, but it was important the whole island was accessible for the project to succeed.
"Without it there are potentially large pockets on the island where stoats can reside so the potential for success at this stage is much diminished."
Predator Free contributed $975,000 towards the $3 million project budget. Around $70,000 was spent by the trust in the early stages and in setting initial traplines and the remainder had been withdrawn.
Butland said the project would have included a trapping system on the mainland, within 5km of the island to protect the investment.
"One of the challenges with this island is there are sites where re-invasion can occur, so the potential for stoats as good swimmers to come back has been high and that's possibility at least one of the reasons why it hasn't been previously eradicated."
It was not known what the density of stoats were on d'Urville.
"One stoat has potential to have a significant impact so in an eradication project, you're after the very last animal, which makes it quite different to a suppression project where you're after the next animal."
Butland said if the issues around access on the island could be resolved, Predator Free was in the position to refund the project but in the meantime, it enabled the company to look at other initiatives to support.