Cereal aversion in behaviourally resistant house mice in Birmingham, UK.

In 1986, house mice in a small defined area of inner Birmingham were reported as not taking a variety of rodenticides from bait containers, a phenomenon labelled 'behavioural resistance'. This study investigated behavioural resistance by comparing the food preferences of West Midlands behaviourally resistant (WMBR) mice with those of normal (BC) mice. Nine bait boxes each containing one of nine different foods (cheese, chicken, tuna fish, peanut butter, canary seed, Cat stars, wheat, PCD (MOD) pellets and Non-tox) were introduced to 12 WMBR and seven BC sites (Experiment 1). The experiment was repeated in the laboratory with six pens of WMBR and six of BC mice (Experiment 2), and to investigate whether the preferences had a genetic basis the offspring were similarly assayed (Experiment 3). In each experiment the consumption of each food was measured over 7 days and the droppings around the bait boxes were counted to assess mouse activity. Food neophobia was noted in some populations of BC mice. Tested in the wild and in the laboratory WMBR mice showed an aversion to foods containing cereals, as did their offspring. These results, with other lines of evidence, strongly suggest that cereal aversion in WMBR mice has a physiological/genetic basis. Since cereal aversion allows WMBR mice to survive cereal-based rodenticidal baits, we conclude that WMBR mice have genetically based behaviours that allow them to survive poisoning regimes that kill other strains.