Upward Trends in Some Bat Populations from Central Poland between 2000 and 2023 Revealed in Small Hibernacula.

Results of a long-term study conducted in large bat hibernacula of central Europe showed upward trends in populations of many species over the last three decades. This study was aimed to check if similar changes in numbers could be observed in smaller underground winter roosts of bats. Surveys were made in three military shelters near Warsaw between 2000 and 2023 (once a year in February). These roosts hosted relatively small number of hibernating individuals (up to 38). Six bat species were recorded: Myotis nattereri, Myotis daubentonii, Eptesicus serotinus, Plecotus auritus, P. austriacus and Barbastella barbastellus. The species preferring cold sites for hibernation (P. auritus and B. barbastellus) predominated in the studied roosts, representing together over 86% of the recorded individuals. The numbers of the two most abundant species and of all bats showed statistically significant upward trends. [ABSTRACT FROM AUTHOR]