Within the wider context of endeavours to assess pest damage to crops, the chapter focuses on the contribution made by wartime research to more effective rodent-control, both immediately by way of statutory regulation and through such peacetime reconstruction measures as the Prevention of Damage by Pests Act of 1949. A conspicuous part was played by the leading animal ecologist, C.S.Elton, and his Bureau of Animal Population, both as to the technique and organization of rat and mouse control and more generally to concepts of the management of wildlife populations in the post-war period