Resistance to anticoagulants in rodents

The present status of anticoagulant‐resistant populations of Rattus norvegicus and Mus musculus in Britain is elaborated and special reference is made to evidence of the practical consequences of resistance for rodent control. A short review is given of genetical and toxicological aspects of resistance and it is predicted that continued dependence upon the anticoagulant rodenticides will lead to the development of new resistance problems. The failure of schemes for the eradication or containment of resistant rat populations by local use of alternative rodenticides is discussed and an approach based more soundly upon the principles of ecological genetics is indicated. It seems in practice, however, that the continued spread of resistance to anticoagulants in Britain is now inevitable and that the development of improved alternative rodenticides will be necessary in order to avoid a decline in the standard of rodent control.