Bridge structures as habitats of bats (Chiroptera): species and spatial diversity

In 2000–2021, 150 various types of bridge structures were examined in different regions of Ukraine, where 742 individuals of 13 bat species were found: Myotis dasycneme, Myotis daubentonii, Myotis brandtii, Myotis mystacinus, Myotis aurascens, Myotis nattereri, Nyctalus noctula, Plecotus auritus, Plecotus austriacus, Pipistrellus pygmaeus, Pipistrellus nathusii, Pipistrellus kuhlii, and Eptesicus serotinus. The occupancy rate was 30.7%. M. daubentonii and P. auritus were observed in most of the studied regions. The frequency of observations of M. daubentonii was 50% of inhabited bridges (n = 23) and almost 65% of the number of individuals, with a concentration of localities in the western and north-western parts of the country. P. auritus (frequency 32.6%) dominated the bridges of the Dnipro Lowland and the Western Polissia. M. aurascens (Azov Sea region), M. mystacinus and M. brandtii (Western Polissia), P. austriacus (Black Sea region), and P. kuhlii (Azov Sea region) were found singly or only in some regions. Nursery colonies of M. daubentonii were found in the Western Polissia, Volynian–Podolian Upland, and Dnipro Lowland, N. noctula in the Dnipro region, P. auritus in the Western Polissia and the Black Sea region, and M. aurascens in the Azov Sea region. In a geographical aspect, the number of species in bridges is the highest in the regions of Western Polissia and Azov Sea (7 species each), and slightly lower in the Dnipro Lowland (n = 6), and Azov Sea (n = 5). The highest percentage of inhabited bridges (64.3%) was found in the Dnipro Lowland; in other regions it was 37.8–10.5%. Bridges play an important role as summer roosts for bats (both for single individuals and breeding colonies), as well as in late summer–autumn (after the disbandment of breeding colonies) and as spring roosts (during seasonal migrations). Bridge structures can be important for the settlement of bats in regions with no underground cavities of natural or anthropogenic origin. We assume that this is the reason why the maximum number of species and abundance of bats in bridges was found in the Western Polissia and Dnipro Lowland, which are characterised by flat topography and lack of abundant and various underground cavities.