Agriculture shapes the dietary spectrum of Myotis emarginatus, a bat species originally foraging under dense vegetation cover.

Insectivorous European bats, being effective generalist predators, have long been suggested to reduce agricultural damage by consuming many crop pest species. However, few, if any, data corroborates bats regulation of pest species harmful to trees or livestock, despite their high economic relevance. Here, we thus focused on a bat species foraging in closed or semi-open habitats, while also opportunistically visiting cowsheds, Myotis emarginatus. Using DNA metabarcoding, we described two COI markers within 195 bat fecal pellets collected across 5 localities in Belgium and during 3 sampling sessions along the breeding season, to characterize the bat dietary spectrum and evaluate the incidence of forest and cattle pests. We detected 65 potential pest species, from all sampling localities, across all sessions and in 97% of the analyzed samples. While 60% of these species belonged to the Lepidoptera, the most consumed pests (frequency of occurrence >60%) were the Diptera Stomoxys calcitrans and Musca domestica, which, by disturbing feeding and their ability to transmit pathogens, reduce milk and meat production. As flies’ consumption increases along the breeding season, prevention in farms should be reinforced during the summer. In addition, 76.9% and 38.9% of pest species targeted, respectively, forest and fruit trees. Our results highlight bats role as natural samplers and regulators of pest entomofauna and thereby their importance as allies of both forest managers and farmers.