Antipodes Islands declared free of mice

A remote and windswept archipelago in New Zealand's Subantarctic islands has been formally declared mouse free, following one of the most sophisticated pest-eradication projects undertaken anywhere in the world.

The Antipodes Islands, which lie about 760 km south-east of Bluff, on New Zealand's South Island, were once home to around 200,000 mice that preyed on bird chicks and eggs, invertebrates, and plants. The impact was enough to alter the biodiversity of the 2,100 ha island group, recognised as a World Heritage site for its outstanding natural values.

Fears had grown after mice were observed eating large seabird chicks alive in their nests on two south Atlantic islands. It wasn't known whether that was happening on the Antipodes, but this was a behavioural shift that was seen as a risk for all 25 of the bird species breeding there.

However, as of 21 March, that threat no longer exists – the islands have been formally declared mouse-free by the Department of Conservation's Island Eradication Advisory Group.
 

The Endangered Antipodean Albatross is one of 21 species of breeding seabirds that will benefit from the eradication of mice (Jason Zito/Island Conservation).

It was largely thanks to the Million Dollar Mouse project – a fundraising effort in which the public contributed $250,000, WWF NZ provided $100,000, and the Morgan Foundation matched the donations dollar for dollar; the rest of the funding came from the Department of Conservation.

The five-year project involved preparations and hut repairs, a helicopter bait-drop in June 2016 and post-eradication monitoring by teams that searched the island for a month and found no sign of mice.

"The success of this project was built on the lessons and experience from many other island eradications in New Zealand and abroad," project manager Stephen Horn said. "The Subantarctic islands are remote, but the role they play in global conservation as the home for so many unique species can't be overstated."

Conservation Minister Eugenie Sage said its success meant 21 species of breeding seabirds, more than 150 species of insects, 21 uncommon plant species and four unique and endemic landbirds could now thrive.

"This is huge news for conservation both in New Zealand and internationally," said Sage, who recently visited the island aboard HMNZS Wellington. "The successful Antipodes Island mouse eradication is another landmark conservation achievement which underlines the Department of Conservation's technical expertise in pest control and threatened species protection."
 

Recording albatross chicks on Antipodes Island (Jason Zito/Island Conservation).

The project follows other successful large-scale pest eradications on New Zealand islands. Elsewhere in the Subantarctics, Campbell Island was cleared of rats in 2001, rabbits and mice were eradicated from Enderby and Rose islands in 1993 and a small population of goats were cleared from Auckland Island by 1992.

More recently, the Department of Conservation eradicated cats and rats from Great Mercury Island in the Hauraki Gulf in 2014, and eight different mammalian pests were eradicated from Rangitoto Motutapu Islands in 2009, including rats, mice, cats and Stoats. More than 100 of New Zealand's 220 large islands are now pest-free – something the Predator Free 2050 initiative aims to replicate across the mainland by the middle of the century.
 

The Million Dollar Mouse monitoring team (New Zealand Department of Conservation).