Bats (Chiroptera) of Transnistrian underground shelters based on results of the 2020–2021 census

This report presents data on the species composition of bats inhabiting underground structures and complexes on the left bank of the Dnister River according to survey results for 2020–2021. Field studies of bats (order Chiroptera) inhabiting underground shelters of the left bank of the middle and lower reaches of the Dnister were conducted from August 2020 to October 2021. In total, we found 26 underground sites and complexes potentially suitable for bats in Transnistria and in 15 of them we counted their number and species composition. Most of the detected underground objects are of anthropogenic origin (former industrial tunnels for limestone mining and manual mining), and only 2 of natural origin — a shallow cave in the village of Rascov, Camenca District and a karst cave in the village of Mikhailovka, Rybnitsa District. The identified objects formed the basis of the first detailed cadastre of underground structures of the left bank of the Dnister and adjacent areas. Each underground facility was mapped with exact GPS coordinates and assigned a corresponding index and serial number. According to the survey results, 8 species of bats were recorded: Rhinolophus hipposideros, Myotis blythii, Myotis bechsteinii, Myotis daubentonii, Myotis dasycneme, Plecotus auritus, Plecotus austriacus, and Eptesicus serotinus. The most widespread and frequently encountered species in the studied area are the lesser horseshoe bat Rhinolophus hipposideros and Daubenton’s bat Myotis daubentonii. The rare species include the brown long-eared bat Plecotus auritus and the grey long-eared bat Plecotus austriacus. The pond bat Myotis dasycneme and Bechstein’s bay Myotis bechsteinii are considered extremely rare, and the latter has never been recorded in Transnistria before. Based on the obtained data and in order to preserve the species diversity of bats, we identified a number of underground complexes as key objects of primary importance in the life of bats during hibernation and their breeding season.