Anticoagulant resistance in wild Norway rats in New York

Abstract

Wild Norway rats (Rattus norvegicus) from several habitats were tested for their susceptibility and resistance to warfarin. Animals were fed 0·005% warfarin in ground oatmeal for periods varying from 1 to 12 days. Rats having no prior exposure to anticoagulants were shown to be susceptible, none having survived a 6-day feeding period. Resistant rats were found on two farms where anticoagulant materials had been used intensively for about 20 years. © 1973, Cambridge University Press. All rights reserved.