Non-lethal control of wildlife: using chemical repellents as feeding deterrents for the European badger Meles meles.
Abstract
Non-lethal methods of controlling wildlife foraging damage may offer conservation, ethical, legal and efficacy advantages over lethal control. Chemical repellents present a potential non-lethal approach, but have not been adequately researched in natural environments. Many previous studies have been poorly designed and a lack of data on individual behavioural responses has limited the practical development of repellents. We aimed to identify effective repellents for resolving feeding conflict with wild mammals, using European badgers Meles meles as models. The experiment took place on rough pastureland within Wytham Woods, Oxfordshire, UK, from 19 July to 19 November 1996, at the convergence of three separate badger social group home ranges. We tested the relative efficacy of capsaicin, cinnamamide and ziram, in a multichoice paradigm, using remote video-surveillance to obtain detailed behavioural observations of known free-ranging individuals. Treatment nights were alternated with control nights over 56 nights. Badgers discriminated precisely between the four treatments, demonstrating a clear preference for untreated baits, followed by cinnamamide and capsaicin (in no particular order) and then ziram. All untreated baits, and baits treated with capsaicin or cinnamamide, were eaten throughout the trial. Ziram baits were fully consumed on treatment nights 1 and 2. Ziram consumption then declined to zero between treatment nights 3 and 9, this coinciding with a sharp rise in bait patch rejection. This 'learning curve' peaked at treatment night 7. We conclude that badgers developed conditioned taste aversion towards ziram-treated baits at this point. Ziram bait consumption was practically zero over the last 20 treatment nights (40 trial nights) and individuals avoided ziram baits, without sampling, for the last 12-22 treatment nights (24-44 trial nights). Observed changes in badger behaviour suggested that avoidance at a distance was facilitated by odour cues. Synthesis and applications. This study provides proof of the concept that ziram has clear potential for reducing badger feeding damage through conditioned taste aversion to an odour. Our detailed observations allowed us to elucidate the behavioural mechanism involved, crucial for directing future development of this approach, thus demonstrating the importance of studying individual responses in wildlife management research. Second-order conditioning, such as this, might be applicable to managing other wild mammals. The next step will be to develop a strategy for use in wildlife damage situations.