Introduced house mice as a conservation concern on Gough Island
House mice have previously been identified as a significant threat to both species and ecosystems on Southern Ocean islands. To date, these impacts have been quantified on several sub-Antarctic islands, but the role of house mice on more temperate islands is poorly known. On South Atlantic Gough Island, non-commensal house mice (Mus musculus L.) were probably introduced in the early 19th century and are now extremely abundant. To assess the likely impacts of mice on the fauna and flora at Gough Island we examined the diet of this population from September 1999 to July 2000 using conventional snap trapping techniques. The population has a single breeding season from September to March and mean body mass is notable in being amongst the largest reported for non-laboratory M. musculus. At low elevations (<250 m above sea level [a.s.l.]), avian carrion was the most prevalent dietary item during September and October. From November to February, plant material constituted the bulk of stomach contents and from March to July lumbricid worms were the most common food item. Indigenous invertebrate matter contributed little to mouse diet, independent of season. At altitudes greater than 500 m a.s.l., larvae of endemic brachypterous moths made up a significant proportion of stomach contents. In light of studies elsewhere, these data suggest that mouse predation may pose a significant threat to these species. However, it is not clear whether conservation action, such as an eradication attempt, is warranted. Further assessments of the impacts of mice are required, and in the interim every effort should be made to prevent introductions of other potentially harmful invasive species.