To further explore natural roost-site selection by temperate bats, we examined the use of tree roost sites by big brown bats (Eptesicus fuscus) in the West Block of Cypress Hills Provincial Park, Saskatchewan, an area where the number of human structures is limited. In this area, we found big brown bats roosted exclusively in cavities of trembling aspen trees (Populus tremuloides), despite the availability of cavities in snags of conifer trees. Most cavities had been excavated and previously used by yellow-bellied sapsuckers (Sphyrapicus varius). The use of aspens by sapsuckers relates to the relatively soft wood and susceptibility to heart rot of these trees, which provide ideal conditions for nesting: decayed heartwood with a firm sapwood shell. Orientation of cavity entrances was close to due south. The width of bats and the width of cavity entrances differed, suggesting that bats are not using roosts for protection from predators or exclusion of competitors. Bats showed fidelity to a particular group of roost trees because, despite roost switching, bats reunited in subsequent roost sites. During the day, temperatures in aspen cavities were approximately 50C cooler than in cavities of conifer snags. Microclimate differences, including temperature, may be why aspen cavities are selected over available cavities in conifer snags. All of the randomly selected cavities in aspen that we searched showed evidence of use by bats, which suggests roost sites for big brown bats in southwestern Saskatchewan may be a limiting resource. JOURNAL OF WILDLIFE MANAGEMENT 62(2):603-611Key words: bats, Eptesicus fuscus, habitat complexity, maternity colony, roost, switching, temperature, treecavity, trembling aspen.In comparison to use of nest sites by birds, relatively little is known about use of roost sites by bats, especially use of natural roosts such as tree cavities. The majority of ecological and behavioral research on temperate insectivorous bats (Chiroptera: Vespertilionidae) is from species roosting in human structures, because it is easier to find and access bats roosting in a human structure than in a natural site such as a tree cavity. As a result, factors that influence selection of roost sites by bats under natural conditions where human structures are not abundant are poorly understood (for review see Brigham and Barclay 1996).Selection of specific roost sites by breeding female bats has consequences to survival and reproductive success (Entwistle et al. 1997), and there is mounting evidence that bats choose roost sites for reasons of microclimate, protection from predators, avoidance of parasites, and 1 Present address: Ecology and Evolution Group,

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We studied the activity patterns, abundance, diversity, and diets of bats, along with the abundance of nocturnal volant insects, at 30 sites in Miombo woodland in northern Zimbabwe. The woodland at 50% of the sites had been disturbed by high elephant densities to the extent that the tree canopy was greatly reduced. The tree canopy was intact at the other sites. Intact and impacted sites differed significantly in tree ( Ͼ 3 m tall; Ͼ 15 cm basal diameter) and shrub (1-3 m tall; Ͻ 1 m tall) diversity and cover. At each site we used ultraviolet lights to sample insects and mist nets and bat detectors to sample bats. To assess their diets we collected and analyzed feces from captured bats. We caught 343 bats representing the families Pteropodidae (1 species), Vespertilionidae (11 species), and Molossidae (3 species). The molossids and vespertilionids are all aerial feeders taking airborne insects. Bat species richness, abundance, and activity were greater at intact than at impacted sites, but these differences were statistically significant only at adjacent sites ( Ͻ 5 km apart) not at more distant intact and impacted sites ( Ͼ 20 km apart). At the adjacent sites we caught a significantly greater proportion of small ( Ͻ 10 g) bats at intact than at impacted sites. These data and a significantly greater proportion of Scotophilus species ( Ͼ 10 g) caught during the early evening at intact than at impacted sites suggested that the removal of canopy trees affected roost availability for the bats. Although larger species may have commuted between intact and impacted sites, smaller species did not. In contrast, the availability of prey did not appear to have been significantly affected by the removal of the canopy trees, as indicated by the light-trap catches of insects and the bats' diets. Most bats ate mainly beetles and moths, the most abundant insects sampled at the ultraviolet lights. Our findings suggest that aerial-feeding bats such as vespertilionids and molossids do not appear to be useful indicators of disturbance in this habitat, even in the face of significant loss of tree canopy. Muriélagos y la Pérdida del Dosel de Arboles en Bosques AfricanosResumen: Estudiamos los patrones de actividad, abundancia, diversidad y dietas de murciélagos, al igual que la abundancia de insectos voladores nocturnos en 30 sitios en el bosque de Miombo al norte de Zimbabwe. El bosque ha sido impactado en un 50% de los sitios por densidades altas de elefantes, a tal grado que el dosel de los árboles ha sido reducido grandemente. El dosel estuvo intacto en los otros sitios. Sitios intactos e impactados difieren significantivamente en diversidad y cobertura de árboles ( Ͼ 3m de altura; Ͼ 15 cm de diámetro basal) y arbustos (1-3 m de altura; Ͻ 1m de altura). En cada sitio usamos luz ultravioleta para muestrear insectos y redes y detectores de murciélagos para muestrear murciélagos. Para determinar sus dietas, colectamos y analizamos heces de los murciélagos capturados. Capturamos 343 murciélagos repre- ‡ ‡ email bfenton@circus.yorku.ca ...

We studied the activity patterns, abundance, diversity, and diets of bats, along with the abundance of nocturnal volant insects, at 30 sites in Miombo woodland in northern Zimbabwe. The woodland at 50% of the sites had been disturbed by high elephant densities to the extent that the tree canopy was greatly reduced. The tree canopy was intact at the other sites. Intact and impacted sites differed significantly in tree ( Ͼ 3 m tall; Ͼ 15 cm basal diameter) and shrub (1-3 m tall; Ͻ 1 m tall) diversity and cover. At each site we used ultraviolet lights to sample insects and mist nets and bat detectors to sample bats. To assess their diets we collected and analyzed feces from captured bats. We caught 343 bats representing the families Pteropodidae (1 species), Vespertilionidae (11 species), and Molossidae (3 species). The molossids and vespertilionids are all aerial feeders taking airborne insects. Bat species richness, abundance, and activity were greater at intact than at impacted sites, but these differences were statistically significant only at adjacent sites ( Ͻ 5 km apart) not at more distant intact and impacted sites ( Ͼ 20 km apart). At the adjacent sites we caught a significantly greater proportion of small ( Ͻ 10 g) bats at intact than at impacted sites. These data and a significantly greater proportion of Scotophilus species ( Ͼ 10 g) caught during the early evening at intact than at impacted sites suggested that the removal of canopy trees affected roost availability for the bats. Although larger species may have commuted between intact and impacted sites, smaller species did not. In contrast, the availability of prey did not appear to have been significantly affected by the removal of the canopy trees, as indicated by the light-trap catches of insects and the bats' diets. Most bats ate mainly beetles and moths, the most abundant insects sampled at the ultraviolet lights. Our findings suggest that aerial-feeding bats such as vespertilionids and molossids do not appear to be useful indicators of disturbance in this habitat, even in the face of significant loss of tree canopy. Muriélagos y la Pérdida del Dosel de Arboles en Bosques AfricanosResumen: Estudiamos los patrones de actividad, abundancia, diversidad y dietas de murciélagos, al igual que la abundancia de insectos voladores nocturnos en 30 sitios en el bosque de Miombo al norte de Zimbabwe. El bosque ha sido impactado en un 50% de los sitios por densidades altas de elefantes, a tal grado que el dosel de los árboles ha sido reducido grandemente. El dosel estuvo intacto en los otros sitios. Sitios intactos e impactados difieren significantivamente en diversidad y cobertura de árboles ( Ͼ 3m de altura; Ͼ 15 cm de diámetro basal) y arbustos (1-3 m de altura; Ͻ 1m de altura). En cada sitio usamos luz ultravioleta para muestrear insectos y redes y detectores de murciélagos para muestrear murciélagos. Para determinar sus dietas, colectamos y analizamos heces de los murciélagos capturados. Capturamos 343 murciélagos repre- ‡ ‡ email