Bats are a diverse groups of mammals, second only to rodents in terms of number of species. With 16 species, British Columbia has the most diverse bat fauna in Canada (Table 1). All 16 species belong to the family Vespertilionidae and feed exclusively on arthropods, most of which are flying insects. Eight of these 16 bat species appear on B.C.'s Blue-list (vulnerable or sensitive) or Red-list (endangered or threatened; Table 1), and most of them are near the northern extent of their range within B.C. This combination of vulnerability and peripheral distribution may have important implications for the biology of the province's bats, and ultimately for their conservation. Further, organisms at the limit of their range may prove to be both more susceptible to disturbance and more genetically variable.
Because of their nocturnal nature and their ability to fly, bats have been the subjects of relatively few studies and our knowledge of them lags behind that of other more conspicuous mammals. As a result, little is known about such basic aspects of bat biology as the timing and nature of reproduction, the requirements and mechanisms for overwintering, and the use and selection of critical habitats (Nagorsen and Brigham, 1993). Typically we have no idea where species spend the winter and what sort of habitat requirements they have during this time. Our knowledge of summer roosts is similarly limited, and tends to be biased toward studies of females. In addition, it is only in recent years that we have begun to learn of some species' reliance on and interaction with forest habitats (e.g., Perkins and Cross, 1988; Thomas, 1988; Rainey et al., 1992; Grindal 1996; Vonhof 1996). Given the active forest sector in British Columbia, this type of information may have important implications for maintenance of biodiversity in the province (Barclay and Brigham 1996).
Because bats often aggregate in colonies, are usually non-territorial, and are highly mobile (due to their ability to fly), their distribution tends to be very patchy in space. Many techniques and sampling protocols used to assess habitat use or abundance for other animals are therefore inappropriate for bats. The purpose of this manual is to discuss some of the techniques used to obtain presence/not detected, relative abundance, and absolute abundance data for the 16 species found in British Columbia. The problems associated with obtaining abundance estimates for bats will be addressed. This manual will provide a standardized sampling protocol for assessing community composition and relative abundance of bats.