Northern Bats Research Articles

Relative importance of the environmental factors at site and landscape scales for bats along the riparian zone

To conserve and manage the bat population in an agricultural landscape, we investigated the relative importance of environmental factors on their occurrence and abundance in riparian zones at site and landscape scales. From May to October 2003, four bat species (Myotis daubentonii, M. frater, Plecotus auritus, and Eptesicus nilssonii) were mist-netted at 26 sampling sites in five streams in the Tokachi plain in central Hokkaido, northern Japan. The environmental factors of the two scales were measured at each sampling site. To clarify the most suitable landscape scale for bats, we also compared three spatial extents (250, 500, and 750 m) at each site. Generalized linear mixed models revealed that the occurrence and/or abundance of all four species, except for M. frater, was positively correlated with the percent cover of broadleaved deciduous forest and the height of bank-side tree canopy. Additionally, according to variation partitioning, although the value of the pure effect varied among species and measurement types, the site scale had a relatively larger pure effect than the landscape scale in many cases. However, in three of the five combined models, the proportion of confounding effect was much larger than that of the pure effect at the respective scales. Our study demonstrated that streams adjacent to a well-developed broadleaved deciduous forest are important for night habitats of many bat species in an agricultural landscape. Although focusing on the site scale may be important for bat conservation, we strongly stress the necessity for conservation and management plans at multiple scales.

Bat habitat requirements – implications for land use planning

Knowledge of the habitat requirements of bat species is needed in decision making in land use planning. Bats’ hibernation requirements were studied both in Estonia and in southern Finland. In both countries, the northern bat and the brown long-eared bat hibernated in colder and drier locations, whereas Daubenton’s bat and Brandt’s/whiskered bats hibernated in warmer and more humid locations. In Estonia, the pond bat hibernated in the warmest and most humid conditions, whereas Natterer’s bat hibernated in the coldest and driest conditions. Hibernacula were at their coldest in mid-season and became warmer towards the end of the season. The results suggest that bats made an active choice of colder hibernation temperatures at the seasons end. They minimised the negative effects of hibernation early in the hibernation season by hibernating in warmer locations and energy expenditure late in the hibernation season by hibernating in colder locations. The use of foraging habitats was studied in northern and southern Finland. The northern bat used foraging sites opportunistically. Daubenton’s bat foraged mainly in water habitats, whereas Brandt’s/whiskered bats and the brown long-eared bat foraged mainly in forest habitats. In northern Finland, Daubenton’s bats foraged almost exclusively on rivers and typically together with the northern bat. Daubenton’s bats and Brandt’s/whiskered bats were found only where there were lower ambient light levels. One of the most important things in the management of foraging areas for them is to keep them shady. Hibernacula in Finland typically housed few bats, suggesting that hibernation sites used by even a small number of bats are important. Bats typically used natural stone for hibernation suggesting that natural underground sites in rocks or cliffs or man-made underground sites built using natural stone are important for them. The results suggest that appropriate timing of surveys may vary according to the species and latitude.

Overlap in Roosting Habits of Indiana Bats (Myotis sodalis) and Northern Bats (Myotis septentrionalis)

Roosts are an integral habitat component for species of bats and may affect their survival and fitness. Conversion of forests to agricultural and urban areas may decrease available roosting habitat for the endangered Indiana bat (Myotis sodalis). Furthermore, the effects of habitat loss could be exacerbated if sympatric species favor and compete for similar roost-sites. We used radio-telemetry to study roosting habits of two species of Myotis in northeastern Missouri. We did not directly test for competition between these species for maternity roosts; rather, our goal was to determine if similarities in roost site characteristics were strong enough to warrant further investigation into competition for maternity roosts. Of 118 roosts located throughout the study, 79 were used by Indiana bats and 39 by northern bats (M. septentrionalis). Differences in roost structure (natural vs. manmade), tree status (live vs. snag), roost type (bark vs. cavity/crevice) and canopy coverage indicate that subtle, but biologically important differences exist in roost selection. Northern and Indiana bats both relied heavily on trees as roosts sites; however, Indiana bats roosted in trees with lower canopy cover and less often in cavities and live trees than northern bats. Our results suggest that niche separation in roost selection exists between northern and Indiana bats.

Diversity and Abundance of Bats (Chiroptera) found in Bat Boxes in East Lithuania

Bat diversity and abundance was investigated in thirteen areas in east Lithuania in 2009. A total of 504 bat boxes of four models were checked in each area (30–60 bat boxes per area). The bat boxes were checked six times during the warm season of the year: in May, June, July, August, September and October. Six bat species, namely the Nathusius’ pipistrelle (Pipistrellus nathusii), soprano pipistrelle (P. pygmaeus), pond bat (Myotis dasycneme), brown long-eared bat (Plecotus auritus), noctule (Nyctalus Noctula) and northern bat (Eptesicus nilssonii), were found in bat boxes. The Nathusius’ pipistrelle and soprano pipistrelle clearly dominated in the bat assemblage (accordingly, 79.3% and 18.4%). The breeding colonies of Nathusius’ pipistrelles and soprano pipistrelles were found in standard and four/five-chamber bat boxes. The breeding colonies of bats were constituted of approximately 30–150 individuals. Multichamber bat boxes in Lithuania were erected for the first time.

Response of Northern Bats (Myotis septentrionalis) to Prescribed Fires in Eastern Kentucky Forests

Prescribed fire is becoming a common management tool for restoring forests of North America; however, effects of prescribed fire on forest-dwelling bats remain unclear. During 2006 and 2007, we monitored prey availability, diet, foraging behavior, and roost selection of adult female northern bats (Myotis septentrionalis) before and after 2 prescribed fires in dissected terrain of the Red River Gorge on the Daniel Boone National Forest in eastern Kentucky. Size of home ranges and core areas did not vary between bats radiotracked before and after fires. Bats foraged more often in the vicinity of pine stands than hardwood or mixed stands, and along ridges and midslopes than lower slopes, regardless of burn condition. Home ranges were closer to burned habitats following fires than to unburned habitats. Abundance of coleopterans, dipterans, and all insects combined captured in blacklight traps increased following prescribed fires. Fecal samples of bats demonstrated lepidopterans, coleopterans, and dipterans to be the 3 most important groups of insect prey, with consumption of dipterans increasing after burning. Bats chose roosts that were taller in height and in earlier stages of decay than random snags, and after prescribed fires chose roosts in trees with a greater number of cavities and a higher percentage of bark coverage. More roosts were observed in burned habitats (74.3%; n = 26) after fires than in unburned habitats (25.7%; n = 9). The results of this work suggest that northern bats are tolerant to prescribed fire on the landscape pattern and scale observed in this study. Northern bats responded to habitat alterations resulting from prescribed fires through shifts in the location of foraging areas as bats tracked changes in insect availability, and through shifts in the selection of roost trees by occupying trees and snags possessing more potential roosting microsites.

Mitochondrial DNA relationships among North Palaearctic Eptesicus (Vespertilionidae, Chiroptera) and past hybridization between Common Serotine and Northern Bat

Interspecific hybridization was proposed as one of the explanations for the lack of differentiation between mtDNA of the morphologically divergent bats Eptesicus serotinus and E. nilssonii. However, only West European populations of these species were examined so far. The cytochrome b mitochondrial gene sequences of E. serotinus originating from Russia were compared with those of other North Palaearctic Eptesicus. Common serotines from the Caucasus, Central and South Russia constitute a separate monophyletic group, distinct from western E. serotinus populations, E. nilssonii, and also from E. isabellinus. Only a common serotine from Kaliningrad region proved to be a member of the West European clade. According to these results one may suppose that most of Russian population of E. serotinus escaped the hybridization event that led to fixation of alien mitochondrial genome in the West European populations. Given that (i) preliminary nuclear data support the distinction between E. serotinus and E. nilssonii and (ii) E. serotinus appears morphologically homogeneous throughout the European part of its range, we consider that this past mtDNA introgression has no direct taxonomic implications. For the first time included in a molecular phylogenetic analysis, E. gobiensis was shown to be a full species, related to E. nilssonii. From our mtDNA phylogenetic tree, the taxonomic validity of the subgenus Amblyotus appears doubtful.

Meta-analysis of Summer Roosting Characteristics of Two Species of Myotis Bats

We compared roost site characteristics of the Indiana bat (Myotis sodalis) and northern bat (M. septentrionalis), which form maternity colonies in cavities and beneath bark of dead (snags) and living trees in eastern North American forests. We used published data (n = 28 sources; n = 1145 roost trees) from studies completed where the distributions of the two species overlap and evaluated a suite of habitat features that might affect roost selection and interspecific competition between these two congeners. We found no differences between these species in average height of roost aboveground, density of snags in the vicinity of roosts, selection of live trees versus snags or relative elevation. Populations of northern bats were more likely to choose roosts in crevices or cavities (88.9%) than Indiana bats (30.0%; P < 0.1), and roosted in trees that averaged smaller in diameter (30.0 ± 5.4 cm) than trees selected by Indiana bats (41.4 ± 2.4 cm; P < 0.1). Northern bats demonstrated greater variability than Indiana bats in height of roosts aboveground and in stem diameter of roost trees. Existing data indicate northern bats exhibit greater plasticity in choice of summer roosts than Indiana bats, explaining, in part, why northern bats are more widely distributed and more common in forests of eastern North America than are Indiana bats.

Single and group organizations of individual animals in the community of bats (Chiroptera: Vespertilionidae) hibernating in artificial caves of the Samarskaya Luka

The spatial arrangement of individual bats of seven species and their tendency to form groups were studied in artificial caves of the Samara Luka during five winter periods (1999 and 2003-2006). It was demonstrated that formation of dense groups did not depend on the hibernating population size or density and was related to the biological characteristics of the species. Most Myotis brandtii and M. dasycneme (60-80% of the populations) wintered in groups. M. mystacinus, M. daubentonii, Pecotus auritus, M. nattereri, and Eptesicus nilssonii usually wintered singly (87% of the animals). In M. brandtii and M. dasycneme, as many as 78% of individual animals were in conspecific groups, whereas this proportion for the other species was no higher than 11%. All pairs of species exhibited negative assortativeness, which indicated a higher preference of spending winter in conspecific groups than in groups containing representatives of other species. Estimation of the ratios between groups containing animals of one and several species showed that conspecific groups were prevailing in M. brandtii and M. dasycneme, whereas all other species usually formed mixed groups.

Bats hibernating in Kaunas Fortress, Lithuania

INTRODUCTION In areas where long periods of cold occur annually, sedentary bats hibernate. Underground sites like caves and other places with similar conditions provide suitable hibernation sites for bats. In northeastern Europe not many places are known where bats hibernate in great numbers. Probably the reason is that regular ice ages prevented the formation of large natural caves. However, during the last one or two hundred years large man-made underground rooms such as mines, fortification buildings, tunnels etc. have appeared in this area (Strelkov, 1958; Randla, 1969; Masing, 1990; Gustavson, 1993; Racis, 2004). Thus, it is not surprising that bats use these underground sites during winter when outside temperature falls too low for hibernation (Masing & Lutsar, 2007). Underground roosts provide excellent conditions for hibernating bats because they provide a humid and cool microclimate and in these dark sites bats remain often undisturbed (Ryberg, 1947; Kuzyakin, 1950; Ling, 1953; Poots, 1956; Strelkov, 1958, 1971; Randla, 1969; Busa, 1984; Masing, 1984a, 1990; Baranauskas, 2006). In northeastern Europe large hibernation colonies including several hundreds or even thousands of sedentary bats are found in the following places: (1) abandoned sandstone mines at Piusa in southeastern Estonia (Ling, 1953; Poots, 1956; Lutsar et al., 2000); (2) underground tunnels of Peter the Great Sea Fortress and one abandoned mine near Tallinn (Ling, 1953; Randla, 1969; Masing, 1990; Masing & Lutsar, 2007); (3) abandoned sandstone mines in the vicinity of St. Petersburg in Russia (Strelkov, 1958, 1971); (4) natural caves in the Ural Mountains (Strelkov, 1958; Bol'shakov, 1981); (5) abandoned mines at Samarian Luka by the Volga River (Il'in et al., 1999); (6) Kaunas Fortress (Masing & Busa, 1983; Pauza & Pauziene, 1996); (7) an abandoned railway tunnel in Vilnius (Baranauskas, 2006); (8) Daugavpils's Fortress in Latvia (Vintulis & Petersons, 2007). Kaunas Fortress, one of the largest bat hibernation sites known in northeastern Europe, is the remains of a fortress complex in Kaunas, Lithuania. It was constructed and renovated between 1882 and 1915. Forts 1-8 were constructed at the end of the 19th century, while Fort 9 was built at the beginning of the 20th century (Racis, 2004). During World War I, this complex was the largest defensive structure in Lithuania. Today, Kaunas Fortress is a well-known place where bats (Chiroptera) concentrate to hibernate during autumn, winter, and early spring. It consists of nine completed forts, each including several separate underground roosts. At least eight forts have underground rooms suitable for bat hibernation. Additionally, there are a number of separate underground bunkers in Kaunas, which are also used by bats during winter. Systematic counts of hibernating bats have been carried out at these sites since the late 1970s. Thus far the following eight sedentary bat species have been found hibernating in this vast fortress: Barbastella barbastellus (Schreber, 1774), Eptesicus nilssonii (Keyserling & Blasius, 1839), Eptesicus serotinus (Schreber, 1774), Myotis brandtii (Eversmann, 1845), Myotis dasycneme (Boie, 1825), Myotis daubentonii (Kohl, 1817), Myotis nattereri (Kohl, 1817), and Plecotus auritus (Linnaeus, 1758) (Masing & Busa, 1983; Masing, 1984b; Pauza & Pauziene, 1996). The study of bats in Kaunas Fortress can be divided into the following periods: (1) occasional finds of bats, with no aim of counting all or nearly all bats present (during the 20th century until 1977); (2) systematic counts of bats with the aim to get both qualitative and quantitative data on the bat population hibernating in underground rooms of the fortress (since 1978) (Masing & Busa, 1983; Masing, 1984b; Pauza & Pauziene, 1996; present work). Between 1978 and 1980 three expeditions were carried out by Estonian and Latvian student-scientists to count bats in Kaunas. …

Spatial Structure of the community of bats (Chiroptera: Vespertilionidae) hibernating in artificial caves of Samarskaya Luka

Specific features of the spatial distribution and localization of bats have been studied during their hibernation in artificial caves of Samarskaya Luka. The proportion of cave area occupied by bats varies from 70 to 93% in large caves (> 60000 m2), decreasing to 50% in medium-sized caves (10000-60000 m2) and to less than 30% in small caves (< 10000 m2). Approximately 9% of bats choose sites near cave openings, up to 25% prefer central parts, but most bats (about 66%) concentrate in the deepest parts of caves. Among wintering species, higher rates of occurrence and shelter occupancy are characteristic of Plecotus auritus. Myotis daubentonii, and M. mystacinus, whereas M. dasycneme and M. brandtii show the highest degree of aggregation. The optimal temperature range for the wintering of all bat species is 2-4 degrees C. Myotis brandtii, Eptesicus nilssonii, and M. daubentonii prefer to hibernate in open spaces of cave ceilings; M. mystacinus. E. serotinus, and Pl. auritus usually occupy the middle and upper parts of walls; while M. dasycneme and M. nattereri occur mainly in hollows on ceilings.

Small scale activity patterns of Eptesicus nilssonii – an indication of habitat preference or interspecific processes

ABSTRACT Habitat use and interspecific processes are key factors shaping regional distribution as well as local activity patterns of mammals. To assess the importance of differential habitat use and interspecific processes for the distribution of local activity in Eptesicus nilssonii, a critically endangered bat species in Germany, a bat detector transect survey was conducted in central Germany. One transect end was close to a maternity roost of E. nilssonii. We compared the bats' use of habitat types and the use of distance zones centred around this maternity roost. We arranged the 11 bat species detected into four foraging categories, E. nilssonii, Pipistrellus pipistrellus, larger open-space bats (Vespertilio murinus, Nyctalus noctula, Eptesicus serotinus) and narrow-space bats (Myotis species). General bat activity was highest in lake and lowest in agricultural habitats. We found significant differences in the use of habitats and distance zones between the foraging categories. However, these differenc...

The square-eared anomaly in New World Myotis

ABSTRACT We investigated the occurrence of abbreviated pinnae (squared ears) in little brown bats (Myotis lucifugus) and northern bats (Myotis septentrionalis) in Michigan, USA. Although the trait was not observed in 308 M. septentrionalis, squared ears occurred in 56 (0.1%) of 5,863 M. lucifugus that were examined. Squared ears were equally common in males and females. Both ears typically were affected to the same degree and most often reduced by 50% of their height, although the amount of pinna that was missing varied from 5 to 50%. Previous authors speculated that the trait was an ontogenetic malformation, but microscopic examination of squared ears from M. lucifugus in Michigan indicated that the trait consistently was associated with trauma, most likely frostbite.

Species structure and dynamics of bat communities (Chiroptera: Vespertilionidae) hibernating in artificial caves of Samara Luka

Long-term data on the composition and absolute and relative abundance of eight bat species hibernating in artificial caves of Samara Luka are considered. About 13,000 hibernating individuals are annually accounted there. The relative abundance of the species decreased in the following order: Myotis brandtii (35%), Plecotus auritus (20%), M. daubentonii (13%), M. mystacinus (13%), Eptesicus nilssonii (8%), M. dasycneme (8%), and M. nattereri (2%). Singular E. serotinus were recorded not every year. The number of hibernating animals in pits was proportional to their size and the number of shelters. Bats used previously chosen shelters and were never found in adjacent caves. The maximum species diversity (H') and evenness (E) were observed in bat communities in medium-sized caves. One of the main factors of increasing abundance of hibernating bats in abandoned pits is their gradual colonization by the animals.

HIBERNATION TEMPERATURES IN SEVEN SPECIES OF SEDENTARY BATS (CHIROPTERA) IN NORTHEASTERN EUROPE

During 30 years of observations carried out in over 1,000 underground and semi-underground bat hibernation sites in Estonia, air temperature was measured near sleeping bats. In 1978, the ‘lower critical temperature of hibernation’ (LCT) was determined for two boreal bat species, Plecotus auritus and Eptesicus nilssonii. The LCT was defined as the mean value calculated on the basis of temperatures at which animals of a certain bat species awoke as a result of temperature decrease at their sleeping sites. For the first species, the LCT was -2.24°C, while for the second it was -3.13°C. During the past 20 years, we have registered new records of minimum hibernation temperatures for the following four sedentary bat species: Eptesicus nilssonii (-5.3°C), Myotis dasycneme (-2.5°C), Myotis brandtii (-2.5°C) and Myotis nattereri (-1.0°C). The highest temperatures (up to +10.5°C) were recorded near bats sleeping in cellar-type shelters in October and November. As a result of research, we concluded that the upper li...

Bats (Chiroptera) of the Silesian Beskid Mountains

During a study conducted in 2000-2007 the following 15 species of bats were recorded in the Silesian Beskid Mts. (Western Carpathians, S Poland): Rhinolophus hipposideros, Myotis myotis, M. bechsteinii, M. nattereri, M. emarginatus, M. mystacinus, M. brandtii, M. daubentonii, Vespertilio murinus, Eptesicus nilssonii, E. serotinus, Nyctalus leisleri, N. noctula, Plecotus auritus, and Barbastella barbastellus. The survey of the bat population was carried out by catching bats in nets, with the dominant species captured being M. daubentonii (37.0%), P. auritus (16.0%), M. mystacinus (11.4%), and M. nattereri (10.4%). Bats from the genera Eptesicus and Nyctalus were only caught on very rare occasions. The bat community found in caves consisted of seven species, mainly R. hipposideros (59.7%) and M. myotis (26.7%).

FLEXIBILITY OF HABITAT USE IN EPTESICUS NILSSONII: DOES THE SPECIES PROFIT FROM ANTHROPOGENICALLY ALTERED HABITATS?

In an environment subjected to rapid anthropogenic alterations, the distribution and abundance of mammalian species often reflect their flexibility in habitat use. The northern bat (Eptesicus nilssonii) is patchily distributed in Germany, where it is classified as a critically endangered species, but is abundant in Scandinavia. To assess its flexibility in habitat use, we radiotracked 10 females and 3 males captured at a maternity roost in Lower Saxony, Germany, during the summers 2002‐2003. These bats had access to a variety of habitats including pristine areas (unimproved grassland and forest) and anthropogenically altered habitats (pastures, euthrophic lakes, urban area). The widely overlapping home ranges had a median area of 524 ha. They extended asymmetrically around the maternity roost and reflected a preference for elevations around and below roost level, that is, 365 m elevation. Males traveled up to 70 km per night during exploring flights. E. nilssonii used forest habitats opportunistically before birth of the young and avoided them thereafter, whereas most bats preferred urban habitats and especially streetlamps after births. Intraspecific encounters were more frequent after births, particularly around streetlamps, suggesting an increased intraspecific competition at these sites. Interestingly, females spent 27% but males only 3% of their foraging time hunting with conspecifics. Thus, the species is a habitat generalist for which urban areas provide a supplementary seasonal habitat. However, because such habitats may not always remain profitable, natural habitats of forest and grassland will remain essential to the survival of this bat species in Germany.

Robinia pseudoacacia (Black Locust) as Day-roosts of Male Myotis septentrionalis (Northern Bats) on the Fernow Experimental Forest, West Virginia

During the summer of 2003, we captured and radiotagged ten male Myotis septentrionalis (northern bats) on the Fernow Experimental Forest (FEF) in the Allegheny Mountains of West Virginia to investigate day-roost selection. Of 16 roosts that were located, 13 were in Robinia pseudoacacia (black locusts), five in snags and eight in live trees. The other three roosts occurred in a Sassafras albidum (sassafras) snag and two live Acer saccharum (sugar maples). All live trees used as roosts were medium to large, canopy-dominant trees with considerable amounts of exfoliating bark and numerous broken limbs and cavities. Snags used as roosts were smaller than trees and other snags in surrounding stands, whereas live trees used as roosts were larger than other trees and snags in surrounding stands. Similar to previous research on female northern bats in the Allegheny Mountains, we observed a strong preference for both live and snag black locust as roosts over other available species. The high abundance of black locust as an important component on the FEF has been a relatively recent development dating to the early 1900s. Use of live canopy-dominant black locust with characteristics of mature forest trees lends support that older forests with decadent conditions provide important day-roost habitat, whereas use of both canopy dominant live trees and long-lasting black locust snags may support the ecological concept of roosting “areas” for northern bats.

New Data on Bats Hibernating in Underground Sites in Vilnius, Lithuania

Investigations into bat diversity and abundance were carried out in Vilnius in 2005. Ten bat hibernation sites were investigated in the city where six bat species were found: Daubenton's bat (Myotis daubentonii), pond bat (Myotis dasycneme), Brandt.s/whiskered bat (Myotis brandtii/mystacinus), brown long-eared bat (Plecotus auritus), barbastelle bat (Barbastella barbastellus) and northern bat (Eptesicus nilssonii). More than 820 bats roosted in Vilnius: Daubenton.s bats constituted 62.5 %, barbastelle bats – 11.1% and pond bats – 10.7%. Pond bats, Daubenton's bats and barbastelle bats made up the largest known hibernating populations in south-eastern Lithuania. Brandt’s/whiskered bats have been recorded in Vilnius hibernation sites for the first time.

Vilnius City Theriofauna

Mammal diversity investigations in Vilnius were carried out in 1992, 1998–2004. The following 51 mammal species were registered in the city: five species of insectivores (Insectivora), 11 of bats (Chiroptera), 18 of rodents (Rodentia), two of hares (Lagomorpha), 11 of carnivores (Carnivora) and four of ungulates (Artiodactyla). Fourteen mammal species are included into the Red Data Book of Lithuania, namely pond bat, Brandt's bat, barbastelle, brown long-eared bat, noctule, Leisler's bat, serotine bat, northern bat, particoloured bat, northern birch mouse, mountain hare, stoat, brown bear and otter. All insectivorous mammals in the city are common. During the warm span of the year we registered nine, and in hibernacula seven species of bats. The most widely spread and the most abundant small rodents of Vilnius were bank and common voles and yellow-necked mice, whereas muskrats and water voles were less frequent. The most numerous city carnivores were pine martens, with otters and badgers, and in particula...

The importance of small cellars to bat hibernation in Poland

Inspections of 521 small cellars inhabited by bats in Poland revealed the occurrence of 10 species: Myotis myotis, M. nattereri, M, brandtii, M. dasycneme, M. daubentonii, Eptesicus nilssonii, E. serotinus, Plecotus auritus, P. austriacus, and Barbastella barbastellus. P. auritus was the most frequent and abundant (410 sites, 54.5% records). M. daubentonii dominated in cellars of the NW and NE regions of the country, while P. austriacus was the most abundant in the SW region. Communities of bats hibernating in small cellars and large underground hibernacula differed significantly. Plecotus spp. clearly preferred small hibernation sites, while M. myotis large ones. Species richness and diversity were highest in NW and NE region where this type of roost had greatest importance to bat hibernation. Despite the fact that only single individuals occurred in 44.7% of cellars, these roosts, common and numerous in Poland, could be in total inhabited by tens of thousands of bats yearly.