Proceedings of the Vertebrate Pest Conference

Since 1984 pest control operatives in some inner-city areas in the U.K. have found that house mice have become increasingly difficult to control. Mice in these very localised areas have stopped taking rodenticide bait from bait containers, a phenomenon referred to here as behavioural resistance. We report here preliminary experiments designed to characterise the phenomenon more precisely by comparing West Midlands behaviourally resistant (WMBR) populations with non-resistant (BC) populations in Berkshire. We investigated three hypotheses, that compared with non-resistant populations, resistant mice 1) are less likely to enter conventional live-capture traps; 2) have unusual food preferences; and 3) avoid bait boxes. Longworth, Sherman and 'Tichy' traps were all less successful at resistant sites, the Longworth being ineffective and the Sherman almost so. WMBR mice also avoided Longworth traps more than BC mice in small-scale laboratory experiments designed to exclude environmental differences. A field trial showed that resistant mice much prefer peanut butter and Test Food 3 (which cannot be named for commercial confidentiality) to canary seed and Betalard (a proprietary rodenticide), but in this trial bait boxes were not avoided more than bait trays.