A single male stoat continues to evade capture on previously predator free Chalky Island in Fiordland.

The stoat has been seen on-camera, but so far has avoided the 100 stoat traps set by Department of Conservation field staff, since stoat footprints were spotted in August.

The island had been free of stoats since 1999.

On Resolution Island to the north, two rats were found in traps in July during a standard stoat trap check. While the island has mice and very few stoats and deer, it is free of possums, and up till now was one of New Zealand’s largest islands without rats.

Since then, DoC traps have caught 11 rats on the island.

Work to stamp out the predator incursions on both Te Kākahu-O-Tamatea / Chalky Island and Mauīkatau/Resolution Island is top priority this summer, says DOC Southern South Island Director Aaron Fleming.

Field staff will be flying and sailing to and from the islands in tight rotations, and a New Zealand-wide network of staff is supporting logistics, planning, mapping, and dog handling to remove invading predators, in a response that began in winter.

"We can’t afford to slow our efforts on these unique island havens that provide habitats for some of our most critically endangered species, such as kākāpō," Fleming says.

"The response to these predator incursions is bigger than DOC and involves help from government Jobs for Nature projects, RealNZ and Pure Salt.

"We are working together to ensure the biodiversity gains we’ve made on these islands over the years are not lost. This work is critical to protecting some of our most precious taonga."

Resolution Island looking over Anchor Island, Dusky Sound. Photo: Department of Conservation / Tim Raemakers

Eradicating the stoat and rats is proving challenging and the teams’ approach is continually being adapted to meet the changing situations on the islands, Fleming says.

"Teams of expert trappers, dog handlers and staff on the ground haven’t been able to catch all the rats on Resolution Island so a small aerial operation has been undertaken over almost 600 ha to help with the eradication effort.

"The response has also involved creative thinking with the support team recently sourcing 500 metal tea strainers which are perfect for holding peanut butter (much loved by rats) inside the traps. The strainers stop mice nibbling the bait."

Chalky and Resolution islands are home to kiwi, Te Kākahu skink, kākāpō, Fiordland skinks, geckos and giant land snails.

"Protecting these vulnerable species and their ecosystems is critical and will continue to have our highest priority," Fleming says.