<I>Mus musculus</I>

Antipodes Island is part of New Zealand’s World Heritage subantarctic region and hosts special biodiversity values and significant species endemism. Invasive house mice were the only introduced mammal and detrimentally impacted invertebrate and native bird communities. Eradication of mice from Antipodes Island was undertaken in 2016 and confirmed in 2018. We present the monitoring used to confirm eradication of mice and the ecological outcomes measured over the 6 years since the eradication.

Auckland Island, the fifth largest island in New Zealand, is the only island in New Zealand’s subantarctic region where introduced mammalian pests remain (pigs, Sus scrofa; mice, Mus musculus; cats, Felis catus). The island has unique biodiversity and is a key site for progressing New Zealand’s goal to be free of several introduced predators by 2050. Recent island eradication successes have rekindled interest in eradicating pests from Auckland Island, and for the first time considering all three pests in one project.

The house mouse (Mus musculus) is considered the most difficult rodent species to eradicate from islands. Eradication projects require careful planning and execution of an ‘over-engineering’ approach to ensure every individual of the targeted population is encountered and removed. Aerial broadcasting of rodenticides has been the method of choice for island rodent eradications since the 1990s and the methods and parameters continue to be refined.

House mice (Mus musculus) are highly invasive mammals and can cause extensive ecosystem damage on islands where they are the sole mammalian pest species. Capability to eradicate mice has improved in recent years. Mouse eradication has been achieved on large islands where mice cohabit with other rodents and islands where mice are the sole mammalian pest. As the islands targeted for eradication become larger and more challenging, reduced toxic cereal bait application rates can reduce both complexity and cost, and ultimately make currently unachievable operations feasible.

House mice (Mus musculus) are an invasive species on Auckland Island in the New Zealand subantarctic and planning for their eradication is underway. Mast seeding events cause rodent populations to irrupt, though little is known about this phenomenon in snow tussock grass (Chionochloa spp.) systems on Southern Ocean islands. The aim of this study was to understand population fluctuations of mouse abundance on Auckland Island for the 2 years following a mast event, and with which tools to monitor abundance, to inform planning of bait application for eradication.

Mesopredator and competitor release can lead to population increases of invasive house mice (Mus musculus) after larger introduced mammals are controlled or eradicated. In New Zealand, mammal-resistant fences have enabled multi-species mammal eradications in order to protect indigenous species. When house mice are the only mammals remaining in these biodiversity sanctuaries, they may reach a high population density, with potential consequences for their indigenous prey.

We used a long-term replicated before-after control-impact (BACI) sampling design to monitor the effect of aerial 1080 possum-control operations on common forest bird populations. Paired treatment and non- treatment sites in the Rolleston Range (East Coast, South Island) and Alexander Range (West Coast, South Island) were monitored once before 1080 treatment during winter 2012 and for three successive summers afterwards. Mammals (possums Trichosurus vulpecula, rats Rattus spp.

Vertebrate pest management on Macquarie Island has removed five vertebrate species since 1988; weka (Gallirallus australis scotti), cats (Felis catus), rabbits (Oryctolagus cuniculus), ship (black) rats (Rattus rattus) and house mice (Mus musculus). The latter three were eradicated in a combined eradication operation that commenced in 2006 and was declared successful in 2014. Eradication planning for removal of rabbits, rats and mice took about five years, with implementation another three years.

Ecological research into rodents in New Zealand commenced in the late 1940s with the creation of the Animal Ecology Section, Department of Scientific and Industrial Research (DSIR). Field surveys of rodents were backed by study skins and skeletal material. Supplemented by specimens from the Wildlife Service and the public, these accrued over the next 45 years laying the foundation for our present knowledge of rodent distribution. In 1951, J. S. Watson joined the DSIR from the Bureau of Animal Population, Oxford, and brought much needed experience in rodent biology and control.

The eradication operations to remove stoats (Mustela erminea) from islands in Fiordland provided an opportunity to assess the diet of stoats in areas with no rodents or with only mice (Mus musculus) available as mammalian prey. The carcasses of stoats trapped on Chalky Island in 1999, Secretary Island and the adjacent mainland in 2005, and Resolution Island in 2008 were collected and their gut contents analysed. On rodent-free Chalky Island, most of the stoats had consumed birds, mostly passerines.