Williams et al. - Consumption of rodenticide baits by invertebrates as a potential route into the diet of insectivores - field data and pilot data

European hedgehogs (<i>Erinaceus europaeus</i>) continue to experience a notable long-term decline across the UK. A key threat they face is exposure to anticoagulant rodenticides, however the pathway of exposure is currently unknown. This study aimed to examine whether invertebrate prey are a potential vector for anticoagulant rodenticides in the diet of the European hedgehog. A field study measured the uptake of rodenticide baits in invertebrates across a variety of habitats and locations. Uptake was negligible in captured insects, however 20.7% of slugs and 18.4% of snails captured showed uptake of bait. Both the percentage of and total number of molluscs showing uptake of bait significantly decreased with distance captured from the bait boxes, and increased with proximity to buildings. Maximum temperature had a significant negative impact on the percentage of molluscs showing uptake of baits, but no effect on the total number. The presence of copper tape significantly decreased the number of molluscs entering the bait boxes. Based on these data it seems likely that molluscs pose a significant threat to European hedgehogs via secondary rodenticide poisoning. This research has provided a more comprehensive idea of which prey items pose an exposure risk to hedgehogs and which environmental factors influence this; knowledge which has the potential to aid the development of effective mitigation measures. Further investigation into using mollusc repellents around bait boxes should be considered.