Influence of vitamin K-rich plant foods on anticoagulant baiting efficacy in wild House Mice, wild Norway Rats, and wild Black Rats

Abstract

Rodents introduced to islands have caused the extinction of many species of animals. Anticoagulant rodenticides are relied on to eradicate rodents from these islands, but if the rodents are eating plant materials that contain high amounts of vitamin K (the antidote to anticoagulants) anticoagulant rodenticides may not be effective. In a laboratory trial, individually caged Norway Rats Rattus norvegicus, Black Rats R. rattus and House Mice Mus musculus were fed fresh plant material high in vitamin K (Collards [0.62 mg vitamin K per 100 g] and Brussels Sprouts [0.19 mg vitamin K per 100 g]) for a period of 7 days. When presented later with anticoagulant rodenticides (0.0025% brodifacoum pellets or 0.005% diphacinone pellets) along with the diet of plant material, 94% of the rodents died. We conclude from this study that the presence of green feed rich in vitamin K does not reduce the effectiveness of anticoagulant rodenticides. However, we add a word of caution on one of the findings of our study. While we think the low efficacy (75%) we found in the case of brodifacoum and Black Rats was probably an artifact of small sample size in that treatment group, the result warrants further investigation.