Abstract
House mice (Mus musculus) are a widespread invasive species on islands. Where they are the sole introduced mammal they can have particularly strong negative impacts on recipient ecosystems. House mice impacts have been documented on almost every component of the terrestrial ecosystem on Southern Ocean islands, including plants, invertebrates, birds and ecosystem function. We undertook a comprehensive study to determine the impacts of house mice on Antipodes Island, New Zealand. This study was done prior to mouse eradication to inform monitoring and restoration. We used invertebrate pitfall trapping on the main Antipodes Island and neighbouring mouse-free offshore islands together with mouse stomach contents and stable isotope analyses of mouse livers to examine dietary preferences. We identified directly impacted and consumed invertebrate Orders relative to their abundance and provided a comprehensive picture of resource flow and overlap in the invaded terrestrial ecosystem. The remote terrestrial ecosystem of Antipodes Island was tightly circumscribed with strong resource overlap. Mouse diet varied seasonally with resource availability, dominated by invertebrates and land birds in summer, and plants and seabirds in winter. Invertebrates that were preferentially preyed upon were Amphipoda, Lepidoptera and some species of Coleoptera. These patterns suggest the ecosystem is annually driven by a seasonal bottom-up resource pulse over summer, where mice are a selective predator, differentially preying on invertebrates relative to invertebrate abundance. Mice appear to be exhausting preferred prey as they systematically consume their way through the terrestrial ecosystem. Land bird diet also varied seasonally and some of these birds likely competed with mice for invertebrate prey. Eradication of mice from Antipodes Island should reduce the predation on invertebrates and reduce the effects of competition and predation on land birds. This should have flow-on effects to the abundance of invertebrates and endemic land bird sub-species of pipit and snipe.
Highlights
House mice (Mus musculus) are a widespread invasive species and one of the most commonly introduced rodent species to islands (Moors and Atkinson 1984; Angel et al 2009)
Results from invertebrate pitfall trapping on the main Antipodes Island in summer (January) 2011 and winter (July) 2013 have been described elsewhere (Russell 2012; Elliot et al 2015)
We present the additional pitfall trapping results, collected in association with mouse eradication on the main Antipodes Island, and for the first time, mouse-free offshore islands from winter (June) 2016
Summary
House mice (Mus musculus) are a widespread invasive species and one of the most commonly introduced rodent species to islands (Moors and Atkinson 1984; Angel et al 2009). Invertebrates are a favoured prey item, and mice can contribute to their decline and even extinction (Rowe-Rowe et al 1989; Le Roux et al 2002; Smith et al 2002). Through their predation of invertebrates, mice may compete with insectivorous birds and impact on ecosystem function and trophic links (Huyser et al 2000; Marris 2000; Le Roux et al 2002; Miskelly et al 2006)
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