Artificial tunnels of hydroelectric power plants as valuable habitat for European bats

Natural caves play a crucial role in providing habitat for numerous bat species in temperate regions. While the potential of man-made structures to support biodiversity gains attention, there is a lack of information regarding the suitability of artificial tunnels as viable alternatives to natural ones. In this study, we assessed the use of artificial tunnels of hydroelectric power plants by bats in the NE Iberian Peninsula (Spain) during the breeding season for most species. Between 2013 and 2014, we monitored bat activity in 37 individualized tunnel entrances using harp traps and mist nets. To understand factors influencing their habitat use, we built competitive models to assess the effect of surrounding landscape, environment and tunnel factors on the richness and abundance of both cave-dwelling and generalist species, as well as on its suitability as breeding habitat for bats. We captured and identified a total of 738 bats representing 60% of species occurring in the South-West countries of Europe, including three regionally and two globally threatened species. Of the total, 67% of surveyed tunnels were used by bats. Our findings highlight that tunnel characteristics such as tunnel height, absence of grilles, and cover of surface runoff influenced all bat groups. Relative humidity primarily favours richness and abundance of females with pups. When properly designed and managed, man-made tunnels of hydroelectric power plants can play an important role in bat conservation by offering essential roosts and breeding sites; however, other potential ecological impacts of these infrastructures on local ecosystems must be considered.