The impacts of an introduced mammalian predator (Mus musculus) on tree weta (Hemideina trewicki) and skinks (Oligosoma polychroma, Oligosoma infrapunctatum and Oligosoma lineoocellatum) in Cape Sanctuary, Hawkes Bay

The introduction of exotic species, particularly predators, into new ecosystems is one of the biggest causes of loss of biodiversity across the globe. Understanding the impacts that introduced species have on native species is crucial in conservation management, particularly for those species that are conservation-reliant. I examined the impact that an introduced mammalian predator (Mus muscularus) had on native prey populations of common (Oligosoma polychroma), speckled (Oligosoma infrapunctatum) and spotted (Oligosoma lineoocellatum) skinks and Hawkes Bay tree weta (Hemideina trewicki). I conducted a mark-recapture study using pitfall traps to examine the impact of mice on skink populations. I conducted a mark-recapture study through manual counts to examine the impact of mice on tree weta. I also examined occupancy of weta refuges while in the presence of mice. There were no captures of spotted skinks, and very low captures of common skinks. There was no significant change in capture numbers for speckled skink, however observed numbers did decline from November 2013 to November 2014. There was a significant decline in capture rates for tree weta over the course of my study. It was difficult to establish mice as the sole cause of any observed changes, however it is likely that they are a limiting factor for skink and weta populations, and have the potential to be a major factor in the observed decline in the tree weta population. My results highlight the importance of monitoring native populations, particularly those that are small and are in the presence of introduced predators. By monitoring native populations conservation management can make better informed decisions to work towards populations not being ‘conservation-reliant’.