Housed in a lodge: occurrence of animal species within Eurasian beaver constructions in Central Italy

Eurasian beavers Castor fiber are important ecosystem engineers, able to modify freshwater environments and influence local biodiversity. Beaver activity affects not only aquatic ecosystems but also terrestrial habitats and organisms. In recent times, beaver populations have been detected in Central Italy. In this work, we determined the use of beaver lodges and dams by native animal species in Central Italy through intensive camera trapping between March 2021 and May 2022. Saproxylic beetles were searched by sight in spring and summer on lodges, dams, and gnawed trunks on river shorelines. We collected 132 records belonging to at least 17 species on beaver dams and lodges, several of them of conservation concern (e.g. the European bittern Botaurus stellaris and the endemic water vole Arvicola italicus). The most detected species within beaver structure was the yellow-necked field mouse Apodemus flavicollis, with 67 independent videos. Despite being confirmed as a nocturnal species, in our study area, A. flavicollis showed an activity peak on bright moonlight nights. The lodge may thus be used as a protection site from predation risk for small rodents, which may benefit from the beaver presence. By building dams and lodges, Eurasian beavers can increase habitat heterogeneity, thus promoting biodiversity increase and improvement. The potential expansion of beaver populations into these ecosystems may serve as a biotic restoration strategy.