Adhesive traps for suppressing pest insects represent a serious threat to bats across Europe

The use of biocides is one of the main threats to biodiversity worldwide, representing a significant driver of decline for several taxa. Mechanical devices for the control of pest insect populations are commonly considered as less impacting, and yet may also represent a serious threat to wildlife. Among such mechanical devices, adhesive traps meant to control pest insects are especially widespread, and anecdotal evidence suggests that several vertebrates are at risk of being trapped by adhesive traps as bycatch. Specifically, we here focus on bats as potential bycatch of adhesive traps across Europe, conducting a literature review and community science data collection to describe and quantify bat mortality due to such devices, followed by a trait-based approach to highlight potential biases in the frequency of bycatch. We retrieved 222 cases of bats caught by adhesive traps, involving 17 species, with the brown long-eared bat Plecotus auritus being the most heavily affected. Among European bat species, probability of being caught by adhesive traps is significantly trait- biased, with the risk of getting caught being higher for species featuring smaller size, a gleaning hunting style, and being associated with anthropogenic habitats. Our results shed light upon a so-far overlooked risk posed by mechanical remedies meant to control insect pests upon bats, and the ecosystem services they provide. Our findings thus clearly indicate that the use of such devices should be avoided, especially in proximity to important roosts of rare or sensitive species, besides providing insights into the risk of “eco-friendly” remedies in organic agriculture.