The importance of ponds for the conservation of bats in urban landscapes

Ponds have an important role in the ecology of urban areas, as they provide essential habitats to aquatic species, as well as fundamental resources to terrestrial wildlife. Artificial water sites such as urban ponds provide foraging and drinking resources to synurbic wildlife, among which bats stand out as an important group. Availability of water sources may thus strongly influence the persistence of animal populations in urban habitats. Pond characteristics, as well as landscape structural patterns in the surrounding area, may modulate the use of such water sites by bats. We investigated bat species richness and activity levels in a pond archipelago within the city of Rome, one of the largest urban areas in Italy. We hypothesized that the presence of woody vegetation and hedgerows affects activity rates over ponds and that bat responses to habitat and landscape structures as well as artificial illumination are species-specific. Bat species richness was mainly influenced by the availability of wooded vegetation within 1000 m around ponds, with minor effects of the amount of bank habitat, while bat activity was affected by different habitat features in a species-specific way. All species responded positively to pond proximity to linear landscape elements such as hedgerows and to the amount of bank habitat. The presence of natural banks, the amount of woodland and that of open green areas positively influenced the activity of different species at different scales, while distances between ponds and artificial lights had a species-specific effect direction. Our results highlight the importance of key factors characterizing ponds and the surrounding habitat in urban landscapes whose appropriate management may improve the viability of synurbic bat populations.