Antipodes Island – mouse free and back on course

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Over a year has gone by. The mice are gone (although final proof won’t come until a revisit in 2018). On Antipodes Island, 760km southeast of Dunedin, 21 species of seabirds and 4 unique species of ground birds, will be preparing to raise their young in an environment completely free of introduced mammalian predators. Hundreds of species of unique plants will be blooming and seeding, providing food for an array of unique insects – and this year neither plants nor insects will be gnawed on by 200,000 mice.

Kākāriki on a grassy area
Antipodes Island Parakeet with boat in the distance. Image credit: J Russell

This year the pink-beaked Antipodean Albatross  will be able to raise their chicks without risk of being molested by mice and the island’s two endemic species of parakeets. will be able to forage safely on the ground for the seeds, berries, invertebrates and occasional carrion that makes up their diet without mice getting to it first. The Antipodes Island snipe will have more invertebrates to eat too now that the hordes of mice are gone.

Mice were the only introduced mammalian pest on the main Antipodes Island. The first published reference to mice on Antipodes Island was in 1909. They may have been introduced from a ship wreck or from one of the many sealing trips to the island following the island’s discovery in 1800. The unique haplotype of the island’s mouse population is not found in NZ but has affinities to Spain.

Years of planning and fund-raising all came to fruition in the winter of 2016, when mouse numbers were likely to be lower than in summer, breeding finished and food scarce. Over a few weeks in June, 65,500kg of cereal-based Pestoff rodent bait specifically targeted for mice, was dropped by 2 helicopters over a total treatment area of 2045 hectares to kill an estimated 200,000 mice. The accuracy and even spread of bait was ensured with the help of the latest GPS flight line display technology.

The highly skilled helicopter pilots were supported by a 3 person ground crew and 13-strong operational team, along with one medic. The team also carried out monitoring work while they were on the island, sampling invertebrate species and banding birds.

The whole operation was made possible by funding from major donors, The Morgan Foundation, World Wide Fund for Nature (WWF) , Island Conservation and an outpouring of donations from the New Zealand public. On August 6, less than 3 months after they left, the eradication team returned safely to the New Zealand mainland.

How different will Antipodes be looking already? After years of devastation, recovery may begin slowly – but it will be beginning and in 2018 a team of scientists will return to check on the island’s progress and make absolutely sure that every single mouse has been eradicated.

So how will we know that every single mouse is gone?

At least two mouse breeding seasons after the eradication attempt, a team of two rodent detection dogs and their handlers  will work with a small team of monitoring staff to search the island for sign of mice. Monitoring tools may also include ink tracking cards, wax tags and chew cards designed to show the presence of mice. It would not be possible to efficiently detect the presence of mice prior to this as the island is difficult to get around and the likelihood of detecting one or two individuals is too low. The eradication is a one off attempt. The result monitoring will show whether it was successful or not and at this stage the result can be declared.

If you are interested in an overview of the project, check out this infographic.