Root cellars are important winter roosts for brown long-eared bats (plecotus auritus) and northern bats (eptesicus nilssonii) in Latvia

Small human-used root cellars are the most widespread bat hibernacula in Latvia, but their importance was hitherto underestimated. We compared bat species diversity and numbers of individuals in root cellars with that in other types of bat hibernacula in Latvia over 35 years. Both species diversity and number of bats hibernating in root cellars were significantly lower than that in other roost types. However, two species, Plecotus auritus and Eptesicus nilssonii, extensively used root cellars as hibernacula. The maximum population size of bat species hibernating in root cellars in Latvia was estimated to be from 27,600 to 42,450 individuals for P. auritus and from 7940 to 12,210 for E. nilssonii. We conclude that root cellars are crucial hibernation sites for P. auritus and E. nilssonii in Latvia.