Potential impacts of poison baiting for introduced house mice on native animals on islands in Jurien Bay, Western Australia

Abstract

Context House mice (Mus domesticus) are present on Boullanger and Whitlock islands, Western Australia, and could potentially threaten populations of the dibbler (Parantechinus apicalis) and grey-bellied dunnart (Sminthopsis griseoventer) through competition for resources. A workshop in 2007 recommended a study to assess the feasibility of eradicating house mice from the islands by using poison baits and of the risk posed to non-target native species. Aim We aimed to assess the risk to non-target native species if poison baiting was used to eradicate house mice on Boullanger and Whitlock islands. Methods Non-toxic baits containing the bait marker rhodamine B were distributed on Boullanger Island and on the mouse free Escape Island to determine the potential for primary poisoning. Acceptance of baits by mammals was measured through sampling and analysis of whiskers, and by reptiles through observations of dye in faeces. To determine the potential for secondary exposure to poison, the response of dibblers to mouse carcasses was observed using motion-activated cameras. Bait acceptance was compared using two methods of delivery, namely, scattering in the open and delivery in polyvinyl chloride (PVC) tubes. A cafeteria experiment of bait consumption by dibblers was also undertaken using captive animals held at the Perth Zoo. Ten dibblers were offered non-toxic baits containing rhodamine B in addition to their normal meals; consumption of bait and the presence of dye in whiskers were measured. Key results Bait acceptance on the islands was high for house mice (92% of individuals) and dibblers (48%) and it was independent of bait-delivery technique. There was no evidence of bait acceptance by grey-bellied dunnarts. Dibblers may consume mice carcasses if available; however, no direct consumption of mice carcasses was observed with movement sensor cameras but one dibbler was observed removing a mouse carcass and taking it away. During the cafeteria experiment, 9 of 10 captive dibblers consumed baits. Conclusions This investigation demonstrated that dibblers consume baits readily and island populations would experience high mortality if exposed to poison baits. Poison baiting could effectively eradicate mice from Boullanger and Whitlock islands but not without mortality for dibblers. Implications Toxic baits could be used to eradicate mice from Boullanger and Whitlock islands, provided that non-target species such as dibblers were temporarily removed from the islands before the application of baits.