Case of Apparent Resistance of Rattus norvegicus Berkenhout to Anticoagulant Poisons

Abstract

OVER a period of two months, a heavy rat population on a farm in the west of Scotland was treated with two anticoagulant poisons, ‘Diphacinone’ and ‘Warfarin’. Although the treatments were properly conducted, and the rats ate the poison bait freely, little impression was made on the size of the population. There was no evidence of recruitment from outside, and the conclusion drawn was that this population was more than normally resistant to these anticoagulants. Cage tests on 28 animals trapped on the farm to confirm this gave the results shown in Table 1.