Relative palatability and efficacy of brodifacoum-25D conservation rodenticide pellets for mouse eradication on Midway Atoll

Authors

Peter J. Kappes, USDA APHIS National Wildlife Research Center
Shane R. Siers, USDA Animal and Plant Health Inspection Service (APHIS)Follow
Israel L. Leinbach, USDA APHIS National Wildlife Research Center
Robert T. Sugihara, USDA APHIS National Wildlife Research Center
Wesley J. Jolley, Island Conservation
Jonathan H. Plissner, Island Conservation
Elizabeth N. Flint, USFWS Pacific Islands Refuges and Monuments Office
Kelly L. Goodale, O'ahu/Maui National Wildlife Refuge Complex
Gregg R. Howald, Island Conservation

ORCID IDs

Peter J. Kappes http://orcid.org/0000-0001-6029-5355

Shane R. Siers http://orcid.org/0000-0001-7961-5072

Wesley J. Jolley http://orcid.org/0000-0001-6542-7361

Document Type

Article

Date of this Version

5-1-2022

Citation

Biol Invasions (2022) 24:1375–1392

https://doi.org/10.1007/s10530-021-02714-1

Comments

This is a U.S. government work and not under copyright protection in the U.S.;

Abstract

Invasive mice (Mus spp.) can negatively impact island species and ecosystems. Because fewer island rodent eradications have been attempted for mice compared to rats (Rattus spp.), less is known about efficacy and palatability of rodenticide baits for mouse eradications. We performed a series of bait acceptance and efficacy cage trials using a standard formulation of brodifacoum-based rodenticide on wild-caught mice from Sand Island, Midway Atoll, to help inform a proposed eradication there. Mice were offered ad libitum brodifacoum pellets along with various alternative food sources, and a “no choice” treatment group received only bait pellets. Mortality in the no choice trial was 100%; however, when offered alternative foods, mice preferred the alternative diets to the bait, leading to low mortality (40%). Because there was concern that the bittering agent Bitrex® in the formulation may have reduced palatability, we conducted a subsequent trial comparing brodifacoum bait with and without Bitrex. Mortality in the with-Bitrex treatment group was slightly higher, indicating that the bittering agent was not likely responsible for low efficacy. Laboratory trials cannot account for the numerous environmental and behavioral factors that influence bait acceptance nor replicate the true availability of alternative food sources in the environment, so low efficacy results from these trials should be interpreted cautiously and not necessarily as a measure of the likelihood of success or failure of a proposed eradication.