Abstract

Black rats (Rattus rattus) and house mice (Mus musculus) from Lord Howe Island were live-trapped, housed in the laboratory and tested for resistance to the anticoagulant poison warfarin. All rats fed warfarin (0.025% w/w) in their diet died within 4–12 days whereas no rats in the untreated group died. Mice fed warfarin at the same concentration over 21 days all survived. Black rats on Lord Howe Island remain susceptible to warfarin, but house mice appear resistant.