Direct and indirect impacts of beaver ecosystem engineering have mixed effects on bats across feeding guilds.

Abstract

Research Highlight: Moser, V., Capitani, L., Zehnder, L., Hürbin, A., Obrist, M., Ecker, K., Boch, S., Minnig, S., Angst, C., Pomati, F., & Risch, A. (2025). Habitat heterogeneity and food availability in beaver-engineered streams foster bat richness, activity and feeding. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.70136. Ecosystem engineers increase habitat heterogeneity, altering abiotic and biotic resources and are key to effective nature recovery. Reintroductions of Eurasian beavers (Castor fiber) in Europe have indirectly benefitted multiple taxonomic groups, aquatic and terrestrial, as their activities result in wetland restoration and diversification of vegetation composition and structure. Bats have been found to be positively impacted by beaver activity, yet the causal drivers were unknown. In a recent study, Moser et al. (2025) monitored bat species richness, activity and foraging activity at beaver pools and control beaver-free sites in Switzerland, finding significant increases in all three measures. Importantly, this study is the first to show significant positive impacts on bat foraging at beaver-engineered sites, and increases in species richness included red-listed species of conservation concern. By testing causal links of the impact of direct (increased canopy heterogeneity and standing deadwood density) and indirect (increased arthropod prey abundance) impacts of beaver engineering on bats, the authors found mixed responses at the foraging guild level. Edge-hunting aerial hawkers benefitted most from beaver engineering, and increased standing deadwood density was shown to have the strongest impact on bats. This study provides key evidence for the positive outcomes of beaver reintroductions on local biodiversity, highlighting the value of ecosystem engineers for nature recovery strategies.