In July 2013 the New Zealand Department of Conservation and University of Auckland jointly led a mid-winter trip to Antipodes Island in the remote New Zealand subantarctic, with support from the National Geographic Society. Four scientists travelled on the 50 ft yacht ‘Tiama’ and researched the terrestrial ecology of the island in preparation for eradication of introduced mice from the island supported by the Million Dollar Mouse campaign.
The main goal of the trip was monitoring a 6 hectare area which the team treated with non-toxic bait containing the biomarker pyranine, simulating what would happen in a real eradication. The biomarker glows under UV light allowing scientists to track bait consumption by animals. The University of Auckland team focused on exhaustively trapping mice throughout the monitored area to estimate mouse density and confirm 100% bait consumption which is required for eradication to be successful. The Department of Conservation team focused on capturing all birds, particularly the endemic parakeet species, to estimate the rate of bait consumption by these non-target species, which should be as close to 0% as possible.
One hundred mice were captured and the rate of bait consumption was 100%. The 2013 winter was the mildest on record for New Zealand and accordingly the density of mice was as high as it has been recorded in summer (previous work from 2011), over 80 per hectare, emphasising the urgency in eradicating mice from this island where they are constantly at plague densities, especially with a warming climate. Thirty-five parakeets were captured and showed no signs of consuming bait, and were held in temporary captivity for observation. The team also continued invertebrate monitoring at five sites to set a baseline for ecosystem recovery after mouse eradication.
Now that the team are back in New Zealand further laboratory work is being undertaken. Over one hundred unidentified bird scats were collected which will be genetically analysed to determine which species they come from. Plant, insect and animal samples will be analysed using stable isotope analysis which estimates their position in the food-web on the island and to determine how all the terrestrial species are interacting with one another.
Meanwhile, the New Zealand Department of Conservation has just appointed Stephen Horn as project manager for the Million Dollar Mouse eradication. He will take up his new role shortly, having just completed a successful stint clearing nearby 13,182 ha subantarctic Macquarie Island of introduced mammals. Antipodes Island should be a breeze after that! With over a year of preparation required, the eradication is planned for winter 2015.