Seasonal variation in the diet of the serotine bat (Eptesicus serotinus): A high-resolution analysis using DNA metabarcoding

Bats play an important role as predators of insect populations but are threatened by a variety of factors, including the loss of foraging habitat and insect declines. Knowledge on trophic interactions, foraging strategies, and hunting areas is key to understanding the ecology of bat species, to assess their impact on ecosystems and to optimize conservation strategies. We investigated seasonal trends in the diet of two nursery colonies of the serotine bat, Eptesicus serotinus, from an intensively farmed agricultural landscape in Germany. Using DNA-metabarcoding of food remains in bat droppings collected from May to July 2018, we identified 254 taxa of 13 arthropod orders to species or genus level, including numerous pest species. Our results indicate an equal use of Coleoptera, Diptera, and Lepidoptera, contradicting previous morphological dietary analyses that had shown beetles to be the most frequent prey. The dietary composition was seasonally highly variable and mainly determined by prey phenology. Dietary richness significantly increased throughout the sampling period, reflecting increasing insect activity with progressing season. Our findings demonstrate that E. serotinus is a generalist forager, linking different habitat types through trophic interactions.