Individual study: Avoidance feeding behaviour in European badger Meles meles following application of food-based chemicals to pelleted food, Wytham Woods, Oxfordshire, England
Baker S.E., Ellwood S.A., Watkins R., & Macdonald D.W. (2005) Non-lethal control of wildlife: using chemical repellents as feeding deterrents for the European badger Meles meles. Journal of Applied Ecology, 42, 921-931
European badgers Meles meles are opportunistic omnivores; in the UK they are estimated to annually cost the agricultural industry £6.5-12.5 million in crop damage. Further controversy surrounding their potential involvement in the spread of bovine tuberculosis has also served to heighten negativity towards them. This level of hostility conflicts heavily with the current high level of protection afforded to the species by the Protection of Badgers Act 1992. Consequently badgers make an ideal model on which to test the conflict ameliorating capabilities of chemical repellents, as opposed to lethal (culling) control.
A study was undertaken in Wytham Woods, southern England, to assess the efficacy of three food-based repellents (capsaicin, cinnamamide and ziram) in deterring feeding of badgers using remote video surveillance to monitor individual behaviour.
Study site: The study took place in Wytham Woods in Oxfordshire, southern England, and was conducted over a period of 124 nights between the months of July and November in 1996. An area covering 6.5 x 8 m of rough pastureland within Wytham Woods was selected for the repellent trials on the basis that it was located at the convergence of three separate badger social group home ranges. Seven known badgers were observed at feeding stations established for this study, and individual information regarding weight, sex and identity was obtained by collaborating with a parallel badger population study.
Bait preparation: Beta puppy 1-6 months TM pelleted food (Nestlé UK Ltd., Croydon, UK) was chosen as the substrate on which preparations of the three repellents (capsaicin, cinnamamide and ziram) were applied evenly using an industrial mixer. Previous work involving these repellents was consulted to identify relevant concentrations for each chemical (see Table 1, attached). Control baits were left untreated.
Bait presentation: A 'cafeteria-style' experiment was adopted: six concrete paving slabs (45 x 45 cm) were arranged hexagonally to serve as the feeding patches. Each slab was divided into four quadrats so that a total of 24 bait positions were available. Before dusk on each night of the experiment, 50 g of treated/untreated bait depending upon experiment phase (see below) was placed into each quadrant. A water bowl was provided in the centre of the hexagon.
The experiment was split into two phases:
1) a 68 night pre-trial phase during which untreated bait was placed onto each quadrant of each feeding patch every night.
2) a 56 night trial phase during which each patch offered a choice of baits treated with each of the three repellents and a pile of untreated bait.
To rule out effects of seasonality within the trial phase, treatment and control nights were alternated. Furthermore, within treatment nights positioning of bait was randomised for half of the trial to check that badgers were not predicting the positions of treatments.
Behavioural observations: Remote video surveillance of feeding behaviour on each feeding patch was recorded under infra-red illumination (wavelength 880 nm). Badger behaviour was analysed from the moment bait was presented until all feeding had stopped. On treatment nights first choice responses were recorded separately for each bait type using three behavioural events: if bait was sniffed or tasted but no actual eating was observed a 'sample' event was recorded; if a badger fed at the quadrant but did not finish all of the bait an 'eat part' event was recorded and if all of the bait pile was completely finished an eat 'all' event was recorded.
If a badger was observed to move onto a completely different feeding patch after either sampling or eating part of a bait pile then this was recorded as a 'bait patch rejection' meaning the particular repellent received a point referring to its ability to alter normal feeding behaviour.
Bait consumption: After all feeding had ceased any remaining pellets on each quadrat were collected, counted and weighed. On treatment nights, each of the 24 bait piles were assigned a rank depending on the order in which they were completely eaten. Ranks were then totalled for each of the four treatment types on each night.
First choice responses: Eat all events were recorded for the control bait on 77-93% of first choice occasions. All repellent treated baits were only ever sampled i.e. sniffed or tasted, on 94-100% of first choice occasions. Interestingly, no first choice responses towards ziram treated bait involved actual eating – piles were instead sampled by either licking or sniffing.
Bait patch rejection: Rejection associated with each of the three repellents was 20-85 times greater than that associated with untreated baits. Ziram was the most significantly powerful repellent in triggering bait patch rejection events. Patch rejection peaked at 'treatment night 7' by which time badgers had most probably developed conditioned taste aversion towards ziram, possibly as a result of negative post-ingestional effects.
Bait consumption & preference: During the first and second treatment nights, all treated and untreated bait piles were eaten. Untreated, capsaicin-treated and cinnamamide-treated bait continued to be eaten throughout the entire trial. In contrast the consumption of ziram treated bait began to decline on 'treatment night 3', and reached zero consumption by 'treatment night 9'. Only 26.5% of ziram coated pellets were eaten over the whole of the trial phase. Crucially, behavioural observations showed that odour detection through sniffing is a key behaviour for detecting ziram at a distance, thus evading the need for bait sampling.
Untreated control bait was eaten preferentially before each of the three types of repellent treated bait on all but the first treatment night. No difference in preference was found between capsaicum and cinnamamide treated bait. Ziram was either eaten last or not eaten at all.
Conclusions: Ziram in this study, was effective in deterring feeding of European badgers through conditioned aversion to its odour. Badgers were shown to clearly discriminate between food piles that contained ziram and piles that did not, a behaviour that is rarely exhibited by such an opportunistic omnivore. Although capsaicin and cinnamamide did not prove promising in acting as deterrents at the concentrations tested, this does not rule out follow up work using higher concentrations as both have proved successful in deterring grey squirrel Sciurus carolinensis, wood mouse Apodemus sylvaticus and house mouse Mus musculus. A whole range of food-based chemicals exist that have so far remained under-exploited for use as deterrents.
Using chemicals as a non-lethal method of deterring mammals from feeding on crops has the potential to resolve the conflicting interests of agriculture and conservation, however further trials on a much larger, field scale, with potential repellants applied around target crops, are required to test the true efficacy of repellants such as Ziram. If such repellants are proven to be effective, they could also work towards reviving the image of the badger and thus assist in its conservation.
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