DOI 10.1515/mammalia-2012-0104 Mammalia 2014; 78(1): 85–91 Viesturs Vintulis* and Gunārs Pētersons Root cellars are important winter roosts for brown long-eared bats (Plecotus auritus) and northern bats (Eptesicus nilssonii) in Latvia Abstract: Small human-used root cellars are the most widespread bat hibernacula in Latvia, but their impor- tance was hitherto underestimated. We compared bat species diversity and numbers of individuals in root cel- lars 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 cel- lars as hibernacula. The maximum population size of bat species hibernating in root cellars in Latvia was esti- mated 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. Keywords: Baltic State; cellars; Chiroptera; hibernacula; Vespertilionidae. *Corresponding author: Viesturs Vintulis, Faculty of Biology, University of Latvia, Kronvalda bulv. 4, LV-1010 Riga, Latvia, e-mail: viesturs.vintulis@lu.lv Gunārs Pētersons: Faculty of Veterinary Medicine, Latvia University of Agriculture, Helmana Street 8, LV-3004 Jelgava, Latvia Introduction Insectivorous bats in the temperate zone spend the winter in hibernation, and the availability of roosts with appropriate microclimate is presumably crucial for their survival. In the northeastern part of Europe, bats hiber- nate mainly in underground or semi-underground roosts (Masing 1982, Pauza and Pauziene 1998, Siivonen and Wermundsen 2008). Caves, mines, and other large man- made underground structures are sometimes regarded as the most important hibernacula for bats in this part of Europe because they sometimes harbor several thou- sand bats (Demjanchik and Demjanchik 2000, Lutsar et al. 2000). However, the counts of hibernating bats in underground roosts for some bat species are much lower than those from nursery roosts in summer (Racey 1998, Dietz et al. 2009). Large hibernacula are generally rare, and for many bat populations in Europe the winter roosts are not known. There are few natural underground hibernation sites containing large numbers of bats in northern and north- eastern Europe and the Baltic Sea region in particular. This is mainly for geological reasons because cave-form- ing limestone is relatively scarce. Presumably, hibernating bats depend on artificial shelters. The largest hibernacula, some of which contain thousands of bats, in this region are found in fortifications, large cellars, and mines (Masing 1990, Urbanczyk 1990, Pauza and Pauziene 1998, Demjan- chik and Demjanchik 2000, Lutsar et al. 2000, Siivonen and Wermundsen 2008, Masing et al. 2009). However, these hibernation sites are distributed irregularly and they may only be practically accessible for species that make long- or medium-distance seasonal movements (Hutterer et al. 2005). For example, the brown long-eared bat Pleco- tus auritus (Linnaeus, 1758) may often be excluded from such sites because its seasonal movements are usually shorter than 20 km (Hutterer et al. 2005). However, an alternative type of hibernaculum is root cellars, which in some north European countries, including Latvia, are widely used by rural human populations to store veg- etables and other agricultural products during the winter (Masing 1980, Busha 1984, Lesiński et al. 2004). Despite all the literature concerning bat hibernation, there are few articles on bats in root cellars. Studies on similar types of hibernacula have been carried out in Estonia (Masing 1980, 1982), southern Sweden (Rydell 1989), and Poland (Lesiński et al. 2004, Lesiński 2009). In Latvia, root cellars have been investigated since the 1970s. On the basis of a survey of 71 cellars, Busha (1984) found that such sites were important for brown long-eared and northern bats Eptesicus nilssonii (Keyserling et Blasius, 1839). Over the last 30 years, the number of recorded bat- inhabited root cellars has increased 10-fold, and now extends throughout the country. The aims of this study were (1) to investigate bat species diversity and abundance in root cellars and to compare it with other types of underground roosts, and Brought to you by | University of Southern California Authenticated | 68.181.176.15 Download Date | 4/9/14 8:06 PM