A dose-response trial with ziram-treated maize and free-ranging European badgers Meles meles
Baker SE., Ellwood SA., Watkins RW., MacDonald DW.
There are increasing demands for non-lethal methods of resolving foraging conflict between people and a wide range of wildlife species. Badgers make good models for studying human-wildlife conflict resolution, and they epitomise the circumstances driving research in this field; they cause millions of pounds worth of crop damage each year in England and Wales, and yet they are protected legally from culling. In anticipation of future field conditioning trials, we set out here to identify the minimum concentration of the repellent ziram for inhibiting badger damage to maize. We believe this to be the first study to investigate the dose-dependent effects of a repellent on a wild free-ranging population of mammals. We adapted a multi-choice design to test the acceptability to free-ranging badgers of maize cobs treated topically with a range of ziram concentrations (0-5.3% (w/w)). We used video surveillance to obtain detailed behavioural observations of individually identifiable animals. The seven badgers that ate maize during the trial did not discriminate between treatments on the first night on which they fed. However, on subsequent nights, most of these badgers either failed to return to experimental sites or returned without feeding. These animals may have developed learned aversions to ziram after a single night's exposure. Two individuals visited and fed throughout the study, and demonstrated a clear negative dose-dependent response that reached a plateau at a ziram concentration of 1.3% (w/w). This effect was evident in both individual behavioural data and the proportion of cobs suffering badger damage. Our aim was to identify an optimal (threshold) concentration of ziram for deterring badger feeding on maize; we conclude that maize cobs should be treated at approximately 1.3-1.5% (w/w), by topical application of a 10% (w/v) ziram paste. A field experiment of similar design could provide a model starting point for research with other species, repellents and food substrates.