Evaluation and cost-benefits of controlling house mice ( Mus domesticus) on islands: an example from Thevenard Island, Western Australia

Abstract

Feral mammals occur on many offshore islands around Australia, but their eradication by poison-baiting requires a careful assessment of the associated costs and long-term benefits. This paper describes a replicated trial program to poison house mice Mus domesticus selectively on Thevenard Island, Western Australia, in the presence of a native species of mouse, and to evaluate whether the eradication of house mice from the island is an achievable and cost-effective goal. It was found the densities and survivorship of house mice declined more on grids with bait stations spaced every 10 m than on grids baited every 20 m when compared to unbaited (control) grids. On one grid baited every 10 m, the abundance of house mice declined by 83% 22 days after baiting commenced. This decline was correlated with an increase in the abundance of short-tailed mice Leggadina lakedownensis on the grid. A total of 55 person days was required to conduct the present poison-baiting trials, and expenses incurred were over $AUS1000 ha −1. Baiting islands for house mice can prove a costly excercise, and management organisations need to assess whether ground-based baiting is an efficacious and cost-effective management option if complete eradication fails.