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.
Marked sites established around Port Ross in 1973 were re-examined in 1983 to measure changes in the vegetation and assess the impact of goats and pigs. Goats had not increased in numbers, nor extended beyond their earlier range, but they were seen higher on the Hooker Hills. Pigs were scarce, but their sign was seen throughout. Photopoints and numerical methods both showed that Chionochloa antarctica tussock was eliminated or greatly reduced where goats and pigs occurred together, and where only pigs were present it was reduced slightly.