Ecology of European bats in relation to their conservation

Bat Biology and Conservation Edited by Thomas H. Kunz and Paul A. Racey SMITHSONIAN INSTITUTION PRESS Washington and London 248 E. D. PIERSON AND P. A. RACEY bat control in Middle and South America, and killing for food or because of misconceptions regarding disease risks in Africa, in Asia, and on Pacific islands. The tendency of cave-dwelling bats to form large aggregations and be highly visible, however, renders them particularly vulnerable to human-induced disturbance or mortality. Conservation efforts are frequently hampered by insufficient knowledge of the distribution and natural history of most species. Distributional maps are generally a better indication of where studies have been conducted than where the bats occur: New distribution records are still emerging, even in regions that have been intensively studied. Additionally, the specific ecological information sought by land managers is generally unavailable—information such as the number of dead roost trees per hectare that should be retained in timber operations, the microclimatic conditions that determine roost selection, the flexibility of a species in its roosting or foraging requirements, and the extent to which habitat alteration affects longevity or reproductive success. Unresolved taxonomic issues can also inhibit the formulation of species-specific conservation strategies. From both the biological and the political perspective it is necessary to define the taxonomic unit for which a policy is recommended. A taxon may be assigned different conservation priorities depending on whether it is viewed as a subspecies or a distinct species, and it can be overlooked altogether if its correct taxonomic status is not recognized. New species are still being discovered, identified, or redefined even in areas such as Europe and North America, which have been subject historically to relatively close taxonomic scrutiny. Pub^ misconceptions regarding bats have thwarted conservation efforts everywhere, but the source of misunderstanding can differ regionally. In North America it may be fear of rabies, in Middle and South America fear of vampire bats, or in Australia concern over predation in fruit orchards. The result, however, is the same: bats are often treated as vermin, subjected to eradication campaigns, and overlooked or undervalued by land managers. Most of the following chapters recognize two basic approaches to conservation: protection of individual species and preservation of habitat. Identified risk factors for individual species include small population size or rarity, evidence of population declines, limited distribution, restricted habitat requirements, and particular vulnerability to human-induced impacts. The highest priority is usually granted to endemic and monotypic species. A speciesfocused approach has been and likely will be critical for the persistence of certain taxa. For example, in areas where bats are intensively hunted or subjected to systematic eradication, habitat protection does not suffice. An additional approach is to protect habitats or habitat features critical to the survival of bat communities. Although habitat-oriented conservation efforts generally focus on areas of high biodiversity, this is not sufficient for bats. Because of the very pronounced latitudinal gradient in species diversity, if species richness were the only criterion many habitats important to bats would be overlooked. Because bat distribution is frequently more closely linked to structural rather than botanical characteristics of the landscape, conservation strategies based solely on botanical communities may not account for the habitat features most needed by many bat species (e.g., caves or rock formations). In tropical regions, low-elevation and coastal forests have been most vulnerable to conversion for human development. The loss of dry forests, which do not receive the same conservation attention as rainforests, is also of serious concern. The authors have generally recognized that conservation strategies for any species or habitat must include protection of both roosting and foraging areas. Acknowledgment of roosting requirements generally leads to the recognition that caverns (caves, old mines, and other anthropogenic structures) and mature native forests are critical to the protection of both numbers of species and overall diversity. Foraging needs are, in general, less well understood than roosting requirements, but unpolluted water sources, intact riparian zones, complex forest structure, and substantial tracts of native habitat are mentioned by a number of authors as important for the maintenance of suitable foraging areas. While the most effective conservation actions are often based on grass-roots efforts and require the dedication of many people at a local level, national and regional policies protecting bat populations are also necessary. The Australian Bat Action Plan (Richards and Hall), the establishment of federal conservation units in Brazil (Marinho-Filho and Sazima), the European Bats Agreement (Racey), the United States Endangered Species Act (Pierson), or CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) regulations (Rainey) serve as cases in point. Part Four represents a significant benchmark as the first symposium to focus on the conservation biology of bats. The inclusion of this topic in a volume of international scope signals the intention of bat biologists to provide a scientific basis for the conservation of their study animals, so as to inform policy makers and managers, in the hope that bats will continue to be major contributors to mammalian biodiversity worldwide. ELIZABETH D. PIERSON AND PAUL A. RACEY 17 Ecology of European Bats in Relation to Their Conservation PAUL A. RACEY Before bat detectors enabled field identification of foraging bats (Ahlen 1981; Baagoe 1986, in manuscript), the majority of studies of European species involved counting individuals and describing their activity and roosting habits in maternity colonies and hibernacula. Great disparities were often seen between summer and winter counts, particularly for vespertilionids, with winter populations accounting for a small proportion of those counted in summer and vice versa, depending on species. Although the most reliable estimates of population size have generally been derived from studies of maternity colonies (Gaisler 1975, 1978; Speakman et al. 1991a; Entwistle 1994), there remains considerable difficulty in establishing reliable population trends in European bat species. Conservation legislation in many European countries has protected bats but not their roosts and habitats (Stebbings 1988). More recently, however, the European Bats Agreement 1992 (part of the 1979 Bonn Convention on the Conservation of Migratory Species of Wild Animals) and the European Union (EU) Habitats and Species Directive 1992 have directed attention toward the preservation of foraging habitats. Although the miniaturization of radiotransmitters and the application of radiotracking in recent years has aided the study of bat habitat requirements, generalizations applicable on a nationwide scale have not hitherto been possible in any European country. The U.K. National Bat Habitat Survey The first national bat habitat survey was initiated in the United Kingdom in 1990, and the results have been published by Walsh et al. (1995) and Walsh and Harris (1996a, 1996b). The survey adopted a random stratified sampling system (Magurran 1988) based on a land classification that assigns every 1-km square in Britain to 1 of 32 land classes. Squares in each land class have a similar climate, physiogeography, and pattern of land use (Bunce et al. 1981a, 1981b, 1983). Within each land class a sample of 1 -km squares was selected at random, to avoid observer bias in the selection of sites and to ensure a standard sampling effort in different landscape types. Fieldwork was carried out during three consecutive summers from 1990 to 1992 and involved both professional and amateur bat biologists, the latter drawn mainly from Britain's 90 bat groups. Each volunteer was allocated one or more 1-km squares and walked a transect in each square 249 250 P. A. RACEY four times during predetermined periods in summer, avoiding nights when weather conditions were unfavorable to bats. Volunteers carried tunable bat detectors (mainly QMC Mini-2) set at 45 kHz to maximize the range of species encountered, and noted the total number of bat passes and feeding buzzes in each square and within each habitat type. The more experienced surveyors were able to identify some bats to species or species groups. Analysis of the data revealed relationships between bat activity and habitat variables within and across the 32 land classes, which for the purposes of the analysis were combined into seven major groups: three arable, two pastoral, marginal upland, and upland. Avoidance or selection of habitat types was examined by constructing Bonferroni confidence intervals around the observed use of each habitat type (Neu et al. 1974), and regression analyses were used to evaluate habitats of critical importance in determining high bat activity in each land-class group. Of the 1,030 surveyed 1-km squares, 910 provided data suitable for analysis, involving 2,700 hours of search effort with 30,000 bat passes recorded in the 9,000 km walked. Observers identified 24% of bat passes to a particular species or species group, and 71% of these were Pipistrellus pipistrellus, 17% Myotis spp., 8% Nyctalus noctula, 3% Plecotus spp., and 2% Eptesicus serotinus. Because a similar proportion of the unidentified bat passes were probably Pipistrellus pipistrellus, habitat preferences (and their implications for conservation) apply to the Vespertilionidae as a whole and to P. pipistrellus in particular. Land class was demonstrated to be a highly significant factor influencing the incidence of bat passes, with the greatest bat activity occurring in pastoral land classes. Across all land-class groups, bats tended to forage selectively in edge and linear habitats and avoided more open and intensively managed habitat types. They showed a far stronger preference for all bodies of water and woodland edges than for any other habitat type, emphasizing the importance of these habitats as key foraging sites. In the woodland category, edges were more strongly selected than openings, and seminatural broad-leaved woodland was more strongly selected than either mixed or coniferous woodland. Urban areas, which included villages, small towns, and the suburbs of some large cities, were selected in three land-class groups. Linear vegetation corridors, particularly tree-lined hedgerows and covered ditches, were also selected by bats, emphasizing the importance of landscape connectivity. Sandy, shingle, or rocky beaches and estuarine coastal marsh were also significantly selected as foraging sites. Habitats strongly and consistently avoided in all land-class groups were those that were more exposed and more intensively managed, including moorland, improved grassland, upland, and arable land. The only grassland type not consistently avoided was lowland, unimproved grassland. Bats foraged preferentially in habitats that were comparatively rare within each land-class group. For example, the percentage availability in each land-class group of the preferred habitats of woodland edge, tree lines, hedgerows, and bodies of water ranged from 14% to 31%, with a mean of 25%. In contrast, the availability of habitats that were consistendy avoided (stone walls, moorland, arable, and most grassland categories) ranged from 40% to 54%, with a mean of 47%. Optimal habitats tend to be at the perimeters of other habitat types or linear strips, and thus in comparison with contiguous blocks of pasture or arable land, for instance, their area is proportionally smaller. Bodies of water generally represent less than 1% of the available habitat, and broad-leaved woodland edge ranges from 3% to 4%. Because the selection patterns were consistent between individual land classes, the results of the analysis by Walsh and Harris (1996a, 1996b) can be summarized by habitat type rather than by land class (Table 17.1). The primary aim of the U.K. National Bat Habitat Survey was to provide a means of assessing the significance of habitat change for bat populations. By expanding the scale of previous studies of habitat preferences (reviewed in Walsh et al. 1995) and distribution surveys (Ahlen 19801981; Baagoe 1986; Rydell 1986; Jiides 1989) to a national level and using a land classification system widely accepted in the United Kingdom, Walsh et al. (1995) and Walsh and Harris (1996a, 1996b) have developed a potential method of detecting change, establishing its direction and measuring its magnitude using a protocol for simultaneously monitoring bat activity and habitat use. Analysis of habitat factors affecting high levels of bat activity resulted in equations with high predictive power and of particular value for forecasting the effects of changes in land use on bats. Although vespertilionids use a diversity of habitats, the regression models identify riparian and woodland habitats as particularly important. Once more numerous and widespread, woodland habitats are now patchily distributed and further habitat fragmentation may reduce the value of those that remain (Bright 1993). Thus, for conservation purposes the relative magnitude of such an effect may be predicted using data collected in the survey. The principal caveat in interpreting the results of the survey is that they reflect the habitat preferences of the pipistrelle, the most abundant bat in the United Kingdom (Harris et al. 1995). In future U.K. surveys, it is hoped that volunteers will be better able to identify bats to species or species groups. To achieve this goal, training courses in the use of bat detectors are being held throughout the country Conservation Ecology of European Bats 251 Table 17.1 Habitat Types Selected, Used in Proportion to Availability, and Avoided by Bats in Britain GOOD HABITATS "< Selected in all land classes Treeline Broad-leaved woodland edge Lake or reservoir -• POOR HABITATS Selected in some land classes; never avoided Hedgerow Stream Coniferous woodland edge Mixed woodland edge Broad-leaved woodland opening Mixed woodland opening Felled woodland River or canal Pond Selected in some land classes and avoided in others Open ditch Covered ditch Stone wall Coniferous woodland opening Scrub Park land Urban land Avoided in some land classes; never selected Improved grassland Semi-improved grassland Lowland unimproved grassland Avoided in all land classes Arable Moorland Upland unimproved grassland Notes: The results interpreted here are from Walsh and Harris (1996a, 1996b). "Land classes" refers to the 19 discrete land classes in their study. (Catto 1994), following a successful initiative in the Netherlands. The results of a nationwide bat distribution survey in that country, also involving volunteers (Kapteyn 1991), have been recently published (Limpens et al. 1997). A detector survey of bat distribution also has been completed in Denmark (Baagoe, in manuscript). Landscape Ecology: From the National to the Local Scale In a major study of habitat use in the province of Uppland, Sweden (59° N), de Jong (1994) found that relatively open deciduous forests and adjacent shallow eutrophic lakes were the only habitats attracting large numbers and a high diversity of bats during early summer, as a result of high chironomid productivity (de Jong and Ahlen 1991). Bats foraged in more diverse habitats later in summer, although lakes, wetlands, and deciduous forest remained important. In a landscape mosaic, patch size is important, and the number of species foraging in a patch of favorable habitat significandy decreased when the area was less than 30 ha and was mainly affected by the abundance of deciduous forest in the patch and by the extent of its isolation from other patches. Species that avoid open areas (Myotis spp., Plecotus auritus) are less likely to use such patches, but in some cases patches are only used by Nyctalus noctula. The composition of the mosaic also affects species number, and fewer species were found in patches isolated by open fields and clearcuts. Dense closed-canopy forest was avoided by all species. Observed preferences were for relatively open coniferous forest by Myotis brandti and M. nattereri, for deciduous forest by Pipistrellus pipistrellus, and for forest edge and glades by P. pipistrellus and Eptesicus nilssoni. Corridors of trees that connect feeding patches are important, particularly for M. nattereri. The corridor concept has an intuitive appeal and has been widely adopted by ecologists and land-use planners in advance of formal proof of its validity. Recent reviews (Hill et al. 1993; Spellerberg and Gaywood 1993; Dawson 1994) concluded that, with few exceptions, relevant studies lacked statistical rigor. The use of linear landscape elements by bats has been demonstrated in the Netherlands, where in the open landscape, lanes, avenues of trees, hedgerows, and canals are used as flight paths (Limpens et al. 1989; Limpens and Kapteyn 1991). In areas where linear landscape elements are abundant, bat detector surveys revealed a dense network of flight paths and foraging areas. In more open areas devoid of such elements, few flight paths and bats are recorded. Some species, such as Myotis daubentonii, make detours along hedgerows rather than cross an open area on the shortest route to a feeding habitat. In comparing bats foraging in arable land and in an adjacent nature reserve with abundant woodland, Gaisler and Kolibac (1992) noted that the density of foraging bats was lower in the farmland than in the reserve, by an order of magnitude for Nyctalus noctula and by a factor of two for the remaining species. In farmland, the bats often flew along windbreaks, which attract and provide shelter for insects, and bats frequently travel on their leeward sides (Racey and Swift 1985; Limpens and Kapteyn 1991). Windbreaks may also reduce the risk of predation (Schofield 1996) and may be used by bats for orientation by echoloca- 252 P. A. RACEY tion (Limpens and Kapteyn 1991). Pipistrellus nathusii is thus observed migrating southwest in autumn along Dutch polders (P. H. C. Lina, personal communication). In a river valley mosaic of woodland and pasture, Racey and Swift (1985) showed that P. pipistrellus used a regular nighdy route and flew directly between foraging areas. Pipistrelle bats roosting in bat boxes were studied in southernmost Sweden (57° N) for eight consecutive breeding seasons in two contrasting situations: a 150-ha pine plantation adjoining a lake and a 16-ha park dominated by deciduous trees of varying ages but surrounded by intensive farming and industry (Gerell and Lundberg 1993). The population in the latter area declined over the study period, while that in the former increased. This difference is not attributable to movement of the populations, as Lundberg and Gerell (1986) have shown high roost site fidelity in this species. Body mass indices (log,, mass/log, forearm3) were used to estimate fat reserves, and these were significantly lower in 3 of 4 years in September in the area adjacent to intensive farmland. Although the levels of organochlorine residues and cadmium were also higher in the population living close to farmland, Gerell and Lundberg (1993) considered that the proximate cause of the decline in the pipistrelle population in the farmland and industrial area was the deterioration in feeding conditions caused by drainage and water pollution, which result in decreased aquatic insect populations. Because of the continued preference of the noctule bat Nyctalus noctula for roosting in cavities in deciduous trees rather than in houses and the loss of mature and postmature deciduous trees from managed landscapes, concerns have been expressed about the long-term survival of this species in western Europe (Hutson 1993). Nyctalus noctula does, however, make use of other anthropogenic factors, and two studies (Cranbrook and Barrett 1965; Kronwitter 1988) have shown that it forages on house crickets (Acheta domestica) over domestic refuse dump sites. Bats and Street Lamps There have been a number of studies in Europe and North America of bats foraging around street lamps (Rydell and Racey 1995). The bluish-white light of mercury-vapor street lamps, which emit ultraviolet radiation, attracts insects whose density can be determined by flash photography. In contrast, low-pressure sodium lamps, which emit monochromatic orange light, do not attract insects, and high-pressure sodium lamps that include some mercury vapor and hence emit some ultraviolet radiation are intermediate in terms of insect attraction. Rydell (1992), using a bat detector fixed to a moving car (Ahlen 1980-1981; Jiides 1989), detected northern bats (Eptesicus nilssoni) at relatively high densities (2-5/km) in southern Sweden near white street lamps, compared with 0.1-0.4 bats per kilometer of unlit road. Means of 3.2 and 3.1 pipistrelle bats (Pipistrellus pipistrellus) were recorded per kilometer of lit road in England and Scotland, respectively (Blake et al. 1994; Rydell et al., unpublished data). The gross energy intake of E. nilssoni foraging around street lamps was more than twice as high (0.5 kj/min) as that recorded in woodland (0.2 kj/min) and comparable to that over pasture where the bats foraged on dung beetles (0.6 kj/min). Street lamps may allow some bat species to increase their energy intake and may account for the frequent occurrence of these species in built-up urban areas (Rydell 1992). A radiotracking study showed that noctules (Nyctalus noctula) spent most of their foraging time (~65%) either over a lake or in a town, hunting over an asphalt surface (a car park and road junction) illuminated by strong lights (Kronwitter 1988). Adjacent woods and farmland were used only occasionally. Typically, the bats fed over the lake at dusk and later, after it was fully dark, moved on to feed over the lights in the town. During this second period, 75% of the foraging time was spent over the lights. Similar observations of noctules in England feeding over a well-lit railway yard, which subsequently became an equally well-lit prison, have been made by A. J. Mitchell-Jones (personal communication). In a contrasting study, Rachwald (1992) used bat detectors to monitor noctules in Bialowieza primeval forest in Poland where there are several villages but no street lamps. Bat activity was consistently highest over water but small forest clearings, maintained for traditional farming, were also exploited. Bats did not prefer the villages to other open areas. In a radiotracking study of serotines (Eptesicus serotinus) in England, Catto et al. (1995) showed that second to cattle pastures that provided an abundant source of Aphodius dung beetles, roads with white street lamps were the most frequendy used feeding sites. In southern Switzerland, Haffner and Stutz (1985-1986) monitored the activity of Pipistrellus kuhlii and P. pipistrellus for 3 years over about 500 km of road using a bat detector on the roof of a moving car; 94% of P. kuhlii and 45% of P. pipistrellus were observed near street lamps. The frequent use of the area around street lamps by foraging bats has obvious implications for conservation. In contrast to many other bat habitats, the illumination of streets, roads, and private properties is increasing and is likely to benefit at least some bat species. Potentially less beneficial has been a recent tendency to replace mercury vapor lamps with sodium lamps, which use less energy (and a less hazardous element) but are of less value to bats. Conservation Ecology of European Bats 253 The urban areas of large cities have depleted insect faunas (Frankie and Ehler 1978; Taylor et al. 1978), and some studies in North America have shown that few bats can survive in this kind of habitat (Geggie and Fenton 1987; Kurta and Terramino 1992). However, a major survey of bats in the London area in 1985-1986 revealed 137 active summer roosts, 75 of which were pipistrelles (Pipistrellus pipistrellus). A total of 430 summer roosts was recorded during a 36-year period; 450 possible feeding sites were surveyed and bats were recorded at 397 of these. Pipistrelles were the most abundant species, although Nyctalus noctula and N. leisleri were also widespread. In contrast, only 28 of 106 possible hibernacula surveyed were used by bats, and in 70% of these fewer than six individuals were found (Mickleburgh 1987). Gaisler (1979) showed that the number of foraging P. pipistrellus increased from the suburbs to the city center of Brno in the Czech Republic and reviewed the common occurrence of this species in several European cities, which he attributed to the presence of street fights. Different species of bats are not likely to be equally affected by the presence of street lamps. Those most likely to benefit are aerial hawking species such as Nyctalus, Vespertilio, Eptesicus, and Pipistrellus. With the exception of Nyctalus noctula, there is little clear evidence that any of the species in these genera is presently threatened (Hutson 1993). On the other hand, several European species of Myotis, Plecotus, and Rhinolophus, which do not take advantage of street lamps, have suffered population declines and are endangered, at least in some countries (Stebbings 1988). A possible negative effect of street fights is that they may attract moths that then become unavailable to bat species which are adapted to gleaning. The echolocation pulses of most Myotis and Plecotus species lack the narrowband component necessary for the long-range detection of insects in open air (Neuweiler 1989). It may be that these bats are less efficient at exploiting insects in open situations than in cluttered environments. Alternatively, the predation risk in brightly lighted conditions in combination with open situations may be too high for slow-flying bats. Evidence from high latitudes in Scandinavia and Finland suggests that bats, particularly Myotis spp., tend to avoid open habitats such as lakes in the ambient fight conditions prevailing around midsummer, but return to such areas as the nights become darker later in the year (Nyholm 1965; Rydell 1992). Although these findings suggest that the movements of Myotis spp. may be restricted by illuminated motorways and other fit areas, Krull et al. (1991) found that radiotagged M. emarginatus made detours along a motorway to reach underpasses leading to foraging areas. National Roost Surveys The first national standardized survey of bat roosts in England—The National Bats in Churches Survey—was organized by the Bat Conservation Trust from 1992 to 1994 and involved visits to 538 churches and chapels (Sargent 1995). Visits showed that 90% of 132 churches used as roosts in the late 1960s were still occupied by bats. The most important factor influencing the likelihood of bat occupancy was age of the building, but when the relative effects of all the recorded factors were taken into account, including aspects of the building related to age, the latter decreased in its level of importance, and a specific combination of other factors described more variation in the data than age alone. The four factors having a significant effect on the presence of bats in churches and chapels were roof type, wall material, geographic location, and the level of building development around the church. Bats were more likely to occupy churches with limestone walls and lead roofing, features that probably indicate other properties which attracts bats such as temperature and roost sites. In general bats occupied churches and chapels surrounded by pre-1800 buildings and avoided those with modern neighboring buildings. Isolated rural and village churches were also favored by bats rather than those in urban areas. Autecological Studies The Greater Horseshoe Bat The greater horseshoe bat (Rhinolophus ferrumequinum) is categorized as an endangered species throughout much of Europe, with the current British population of this species estimated at about 4,000 individuals divided among about 14 major maternity colonies (Mitchell-Jones 1995). Radiotracking studies have revealed that bats usually forage within 4 km of the roost, and the conservation of foraging habitats within this radius is therefore particularly important (Jones and Morton 1992; Jones et al. 1995). During spring, bats forage in ancient seminatural woodland, but during late summer they feed mainly over pasture. The ambient temperature in woodland is generally higher than that over pasture, and this differential widens as temperature decreases. Because insect abundance increases rapidly above 6°-10°C, it is likely to be more profitable for bats to forage in woodland in spring. The shift to pastures during the summer is associated with the dominance of Aphodius dung beetles in the diet as cattle dung accumulates. The abundance of such beetles may be threatened by the use of Avermectin antihelmin- 254 P. A. RACEY thics in cattle, which because of their persistence reduce the insect fauna associated with dung (Strong 1992). Because juvenile bats forage independently of their mothers both before and after weaning, prime foraging habitat (cattlegrazed permanent pasture close to ancient woodland) adjacent to the maternity roost is likely to be important to juvenile survival. The use of Avermectin in cattle pastured in the vicinity of such roosts could be particularly detrimental to juvenile bats (Duverge and Jones 1994). A similarly detailed picture of the characteristics of the hibernacula of greater horseshoe bats has been assembled by Ransome (1968, 1971, 1990). These hibernacula contain completely dark areas with a relative humidity in excess of 95%, a range of ambient temperatures between 5° and 10°C, and regions of slow air flow resulting from two or more entrances or a sloping entrance. Close access to sheltered, often south-facing winter foraging areas is also important, as is freedom from repeated human disturbance. As a result of the protection of maternity roosts and hibernacula, the decline in numbers of greater horseshoe bats (Stebbings and Arnold 1987; Stebbings 1988) has been halted. The way in which knowledge of the autecology of horseshoe bats is being applied to their conservation in England and Wales has been detailed by Mitchell-Jones (1995) and includes designating key roosts as sites of Special Scientific Interest managed by the relevant statutory conservation agencies (English Nature and The Countryside Council for Wales). The ambient temperature of maternity roosts is increased by the use of heaters (Mitchell-Jones 1995), and gates have been installed at the entrances to hibernacula to prevent disturbance (Ransome 1990). Attention is presently being focused on the ways in which key feeding sites around maternity roosts can be protected (Mitchell-Jones 1995). The Lesser Horseshoe Bat Historically, the lesser horseshoe bat (Rhinolophus hipposideros) roosted all year around in caves (Horacek 1984), and the most marked change in its roosting behavior has been the adoption of buildings as summer roosts. In a survey of the characteristics of 156 breeding roosts in the United Kingdom (Schofield 1996), R. hipposideros selected predominantly nineteenth-century buildings (77%; n = 61) with stone walls (81%; n = 82) and slate roofs (88%; n = 77). Their roosting sites were usually located in roof spaces of attic rooms (95%; n = 76). Access to roosts was commonly through large openings (>0.5 m2), such as the open doorways or windows that often characterize derelict or semiderelict buildings. The volume of breeding roosts was frequently greater than 250 m3. Similar findings are reported from other countries in Europe (Gaisler 1963; Stutz and Haflher 1984; McAney and Fairley 1989). Comparisons of availability between 19 roost buildings and 20 randomly selected buildings in the same geographic area indicate that buildings used as roosts are located closest to stands of broadleaf and mixed woodland. Buildings containing roosts are more likely to be connected to foraging areas by continuous linear landscape features such as hedgerows or stands of trees. A Bonferroni pairwise comparison (Byers et al. 1984) between the land classes established (or identified) by the Institute of Terrestrial Ecology (ITE) (Bunce and Howard 1991) in 1-km squares containing R. hipposideros roosts and those for England and Wales as a whole indicate that this species selects for those land classes associated with areas of gentle rolling and undulating countryside, often enclosed by hedgerows and tree lines. Land classes associated with flat open countryside with intensive agriculture or exposed upland areas are avoided. Details of land cover (as distinct from land class) obtained from satellite data showed that R. hipposideros selects deciduous woodland, and bats were found foraging as much as 2 km from breeding roosts in stands of broadleaf and mixed woodland, riparian trees, and hedgerows. Bats commuted to and from foraging areas and their roosts (both breeding and night roosts) along continuous linear landscape features (particularly well-grown hedgerows). In addition to providing foraging areas, the use of these features may reduce predation. The ambient light level and height at which bats flew across a 5-m gap in one of the hedgerows were recorded using an infrared video camera. At ambient fight levels greater than 1 lux, bats flew at a height of less than 1 m from the ground: at less than 1 lux, the height of flight increased to 4 m, suggesting avoidance of avian predators. Conservation strategies and recovery programs for R. hipposideros must take into account both the roosting and landscape requirements of this species. The Brown Long-Eared Bat BUILDING ROOSTS. In a study of the roosting ecology of the brown long-eared bat (Plecotus auritus) in northeastern Scotland (57° N), Entwistle et al. (1997) located 56 roosts in buildings and compared their characteristics with a randomly chosen sample of buildings from the same area. This approach revealed that this species preferentially roosted in buildings that were older, higher, and had more roof compartments (which in Scotland are fully fined with wood). Brown long-eared bats were found in such roosts between May and October, and the typical group size within the roof space was 15-20 bats. Conservation Ecology of European Bats 255 The mean temperature within roosts was 17.9°C, and roosts were significantly warmer than a random sample of buildings. When captured in their roosts, bats were generally active, and warmer roost temperatures may have reduced their dependence on torpor. The temperature inside the roost was positively correlated to the frequency of occupancy and also with the size of the bat's forearms, with larger individuals being captured in warmer roosts. The buildings used as roosts were closer to trees and water and had a larger area of woodland within 0.5 km than a random sample of buildings. Brown long-eared bats are foliage gleaners (Anderson and Racey 1991, 1993), and radiotracking revealed that bats foraged mainly in deciduous woodland in the vicinity of the roost, using a series of feeding sites to which they frequently returned and that were occasionally shared with other bats from the same roosts. Females spent most of their foraging time within 0.5 km of the roost, whereas males traveled further. Bats returned to the main roost on 77% of mornings, but also used alternative sites, which had cooler internal temperatures, following colder nights (Entwistle et al. 1996). The characteristics of the roost and its location were related to the ecology and behavior of its occupants. Across the different roost sites examined, the area of deciduous woodland within 0.5 km of the roost was correlated with foraging patterns, colony size, and the progress of the male reproductive cycle (Entwistle 1994). Although large-scale distribution patterns for this species are probably linked to areas of woodland, local abundance of bats may be affected by the availability of suitable roost sites. The implications of the work for conservation and management are clear. Building roosts are important and need protection, but so also do the adjacent woodlands, which should be maintained and their quality improved where appropriate. But if building roosts of brown long-eared bats have a suite of characteristics that distinguish them from other roof spaces, why are bat boxes attractive to this species? BAT BOXES. Bat boxes have been widely used for many years throughout Europe (Mayle 1990), and their occupancy rate is highest when they are used in large numbers in coniferous plantations devoid of natural roost sites, although bird boxes are also used by bats in deciduous forests (Schlapp 1990). In the 1970s, a scheme involving 3,000 bat boxes was initiated at six sites across a north-south transect in the United Kingdom by R. E. Stebbings. From data collected at one of these sites, Thetford Forest, Norfolk (53° N), one of the few comprehensive studies of the contribution of such boxes to the population ecology of bats was conducted. Boyd and Stebbings (1989) analyzed the brown long-eared bat occupancy of 480 wooden boxes attached to 100 trees around the perimeter of a 7-ha rectangle in the center of a plantation of mature Corsican (Pinus nigra Arnold) and Scots pine (Pinus sylvestris Linn). The boxes were checked two to four times a year for 10 years, and a total of 219 females and 182 males were captured and individually marked. Following the establishment of a population of bats in the boxes, immigration probably accounted for a small proportion of the total recruitment, the remainder coming from reproduction within the population. The mean number of young born per female per year was 0.55, and the total population increased during the study from 74 to 140 bats, giving a doubling time of 10 years. The annual survival rate was 0.78-0.86 for females, depending on the method of estimation used, and 0.60 for males, similar to rates found in populations of brown long-eared bats roosting in houses in northeast Scotland (Entwistle 1994) and on the south coast of England (Stebbings 1970a). Benzal (1991) studied brown long-eared bats occupying 520 bird boxes in a 130-ha Pinus sylvestris forest at the comparatively high altitude of 1,400 m in central Spain. The boxes were widely used in the first summer after installation; a total of 197 individuals was found in 3% of box inspections and droppings were found in an additional 8%. Although the bats arrived in the study area in the first half of May and stayed until the beginning of November, they left the boxes at the end of May to form maternity colonies in small caves and attics and returned to them in mid-July with flying young. These studies provide ecological data that support the promotion of bat boxes as alternative roosts for bats, particularly in areas devoid of such roosts, although the Spanish study suggests that boxes may not always be appropriate for breeding. Long-term studies are now needed to compare the population dynamics of bats occupying different types of boxes, particularly those made from sawdust and cement, which are often preferred to those made only of wood (Taake and Hildenhagen 1989; Mayle 1990). Despite the positive conservation values of bat boxes, they should not be considered as a substitute for hollow trees, the loss of which is a major threat to less synanthropic species such as Nyctalus noctula. The Serotine Bat The serotine bat (Eptesicus serotinus) is widely distributed in mainland Europe even at more northerly latitudes (Schober and Grimmberger 1993) where it is associated with highly exploited landscapes and appears to be increasing its range (Baagoe 1986). By contrast, in Britain this species is largely restricted to southern England (Hutson 1991). Radiotracking studies have revealed that serotines in Britain generally 256 P. A. RACEY forage within 3 km of their roosts, using as many as five foraging sites a night in a wide range of habitats that include chalk grassland, scrub, pasture, and areas around white street lamps. Serotines located and exploited temporary feeding sites such as recently mown grass from which summer chafers (Amphimallon solstitialis) emerged (Catto et al. 1995). The increasing incidence of Aphodius beetles in the diet of serotines as summer progressed, reaching a peak of 85% of identifiable fragments in the feces in August, confirmed the importance of cattle pasture as feeding habitat for this species (Catto et al. 1994). Catto et al. (1995) concluded that serotines are well adapted to an anthropogenic environment. They are strongly philopatric to their roosts in houses that are located close to a range of feeding sites where they can take advantage of current farming practice and street lamps. DaubentoiTs Bat Daubenton's bat (Myotis daubentonii) forages almost exclusively over water and around riparian vegetation (Jones and Rayner 1988; Kalko and Schnitzler 1989), feeding opportunistically on insects that swarm in such situations, principally chironomids (Swift and Racey 1983; Kokurewicz 1995). Increased numbers of this species of bat, sometimes of several hundred percent, have been reported from counts of hibernating individuals in the Netherlands (Daan 1980; Voute et al. 1980; Weinrich and Oude Voshaar 1992), Czech and Slovak republics (Barta et al. 1981; Cerveny and Burger 1990), and southwest Germany (von Helversen et al. 1987). Kokurewicz (1995) postulated that the increase in Daubenton's bat is attributable to eutrophication and canalization of waterways throughout Europe, factors which increase the numbers of chironomids. This hypothesis was recently tested in northeast Scotland by comparing the activity of pipistrelles and Daubenton's bats in two rivers with sharply contrasting nitrate levels, one of which may be designated as a nitrate-sensitive area by the European Union (Racey 1998). This study provides some support for Kokurewicz's hypothesis and is one of the few examples of a beneficial effect of aquatic pollution on bat populations. Hidden Biodiversity Many of the recent additions to European national faunas have been bats. Plecotus austriacus was first described in the United Kingdom by Stebbings in 1967. Although Topal (1958) first questioned the status of subspecies of Myotis mystacinus, it was not until more than a decade later that Hanak (1971) eventually distinguished Myotis brandti as a separate sympatric species. These two sibling species are now widely recognized throughout Europe (Baagoe 1973; Corbet and Harris 1991), and recent molecular work by Nemeth and von Helversen (1993) has pointed to the existence of a third European species in the M. mystacinus group. Jones and van Parijs (1993) described two phonic types of Pipistrellus pipistrellus, and evidence is amassing that these are separate species (Barratt et al. 1995). It also raises the question of whether additional cryptic bat species remain to be recognized. Pipistrellus nathusii is a migratory species (Strelkov 1969) and moves southwest from the Baltic states into the low countries in autumn. The first breeding colony of P. nathusii was recently recorded in the Netherlands (Kapteyn and Lina 1994), and since its first appearance in Britain in 1969 (Stebbings 1970b) it has been recorded there with increasing frequency in autumn (Speakman et al. 1991b) and summer (Rydell and Swift 1995; Barlow and Jones 1996). Conclusions The first national bat habitat survey of a European country concluded that the main foraging habitats of vespertilionids are associated with broad-leaved woodland and water. Many autecological studies indicate that these conclusions are widely applicable throughout Europe, and one of the benefits of the European Union is that initiatives to restore woodland and to maintain the quality of rivers apply in all member states. For example, the long decline in total woodland cover in the United Kingdom continued until 1920 when woodland occupied only 5% of the U.K. land surface. Since then, a large reforestation program has increased total woodland cover to 10%. Although conifers account for most of this increase, the proportion of broadleaf trees planted each year has increased 10-fold since 1985 and now exceeds conifer planting, so that a third of the 2.4 X 106 ha of woodland in the United Kingdom includes broadleaf trees. This change has been largely driven by the provision of generous financial incentives for broadleaf planting, not only because of its aesthetic value but because of a wide appreciation of the value of such trees to many faunal groups (Osborne and Krebs 1981; Kennedy and Southwood 1984). Similar grant aid has been available for the restoration of ponds, 75% of which have been lost in Britain since 1880 (Alstrop and Biggs 1993). Such schemes have the added value of providing good foraging habitat for bats and countering the trend toward habitat fragmentation. Unfortunately, the rate of loss of hedgerows, which are important landscape elements for bats, still exceeds the rate of their replacement (Barr et al. 1994). The widespread use of agricultural pesticides and remeConservation Ecology of European Bats 257 dial timber treatments with organochlorides may have had major deleterious effects on bat populations in the 1950s and 1960s. Restrictions on the most persistent and toxic chemicals may have resulted in the reported increase in numbers of some bat species, similar to the recovery that has occurred in raptors. Pollution is also being reduced in many rivers, although eutrophication may have a beneficial effect for those species that feed over water. The principal way in which the value of conifer plantations is being enhanced for bats is by the provision of roosting boxes, and viable and self-sustaining populations of bats become established in such boxes when large numbers are provided in relatively small areas. Further research is needed on the population dynamics of bats inhabiting boxes made of sawdust and cement, which are more attractive to them than wooden ones. Recent studies have detailed with some statistical rigor those physical features associated with buildings used by bats as roosts. Several vespertilionid and rhinolophid species forage within a relatively short distance of such roosts so that the conservation and management of adjacent woodland is particularly important. One of the most valuable farmland habitats for bats is unimproved pasture, where bats forage on insects with subterranean larval stages, such as chafers, or on dung beetles. Farming practices such as the use of antihelminthics that reduce the insect fauna associated with dung or which reduce the availability of dung such as zerograzing (transporting cut grass to cattle) may adversely effect several bat species. Bats generally forage on a variety of insect groups, and we need to know whether the loss of certain taxa can be accommodated by a shift toward others. In some cases, however, particularly for highly endangered species such as horseshoe bats, financial incentives are needed to stimulate management of farmlands near roosts. Bats are among the most synanthropic mammals, relying on human-made structures for roosting in both rural and urban areas. They feed opportunistically on concentrations of insects, such as those around white street lights and domestic refuse dumps. The use of white street lights may have some conservation value because the energy intake of such bats is enhanced. Unfortunately, those species exploiting this feeding opportunity are less threatened than those that do not. In many European countries, bats are the most important contributors to mammalian biodiversity, and the use of bat detectors and application of the powerful techniques of molecular genetics continues to add bat species to national faunal lists. This is potentially important because at the 1992 Rio Convention on Biological Diversity many participating politicians pledged to halt the worldwide loss of animal and plant species and genetic resources. The first conference of the parties to the European Bats Agreement held in the United Kingdom in 1995 agreed to a wide-ranging conservation and management plan, which involves survey and monitoring of populations, the identification and protection of important roosts and foraging habitats, and the promotion of public awareness about bats. The majority of these goals will be achieved by a strong voluntary sector willing and able to undertake surveys and monitoring, underpinned by the work of ecologists in identifying and characterizing important roosts and foraging habitats. Acknowledgments I am grateful to the following colleagues who commented on various drafts of this chapter: H. Baagoe, J. Burton, C. M. C. Catto, M. B. Fenton, J. Gaisler, A. M. Hutson, G. Jones, S. 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Symposia of the Zoological Society of London 67:325-344. Weinrich, J. A., and J. H. Oude Voshaar. 1992. Population trends of bats hibernating in Marl Caves in the Netherlands (1943-1987). Myotis 30:75-84. 18 Impacts of Ignorance and Human and Elephant Populations on the Conservation of Bats in African Woodlands M. BROCK FENTON AND I. L. RAUTENBACH The Ethiopian zoogeographic region (sub-Saharan Africa) covers an area of 23,426,000 km2, of which less than 10% historically was rainforest (Keast 1972). Although the region is best known for its large mammals, the Chiroptera include more species than any other order of mammals. Approximately 174 species of bats live mainly in the Ethiopian region, showing a high level of endemism (24 of 41 genera) with the ranges of only about 6 species (3%) extending beyond this area (Hayman and Hill 1971; Nowak 1994). Approximately 24 other species whose ranges extend into Africa occur mainly outside the Ethiopian region, making a total of about 198 species of bats known from Africa (Hayman and Hill 1971). The purpose of this chapter is to consider the conservation challenges posed by bats in African woodlands. We selected these habitats for two reasons: First, our collective experience is focused there, and second, the woodlands dominate the zoogeographic region (Figure 18.1) and often overlap with areas of high human population density. In this chapter, we use the nomenclature for bats presented in Nowak (1994). The General Situation The human population in sub-Saharan Africa is projected to increase five-fold in a little more than a hundred years, from 0.6 billion in 1990 to 2.8 billion by 2100 (Bongaarts 1994). In 1989, the human population density in Africa ranged from 2 to 265 (mean ± SD, 41.8 ±51.5) persons per square kilometer (Stuart et al. 1990). The potential impact of the expanding human population for the conservation of African biota cannot be overstated. For example, since 1900, the human population in Zimbabwe has increased from 0.5 to more than 10 million (Cumming 1991), and in the past 40 years the rate of land clearance in the Sebungwe District of Zimbabwe has been about 4% per annum (D. H. M. Cumming, personal communication). Changes of this magnitude are expected to have profound effects on habitats and thus pose a major threat to the survival of the African fauna (Martin and de Meulenaer 1988). The direct and indirect effects of an expanding human population are expected to be the principal factor causing the extinction of many organisms, including bats. 261