Mattson, Todd A. and Bogan, Michael A. 1993. Survey of Bats and Bat Roosts in the southern Black Hills in 1993. 15 p.
Abstract
Turner (1974) reported ten species of bats from the Black Hills of South Dakota and Wyoming. At least six species are resident throughout the year, forming wintering colonies in caves and mines. Perhaps the most significant bat hibernation site in the Black Hills is Jewel Cave, where over 1300 bats spend the winter months (Martin and Hawks 1972, Worthington 1993). The most abundant species in Jewel Cave during the winter is Townsend's big-eared bat, Plecotus townsendii pallescens. In 1992 there were about 1200 P. townsendii in the cave; this is the largest known hibernating colony of this species in the western United States (Worthington & Bogan 1993).
Most bats that use Jewel Cave during the winter roost elsewhere in summer. This use of alternate summer roosts may a historic pattern or it may reflect changes in resources that are important to bats. In any case, it is unkown where these bats go during the summer. No long distance migrations have been reported for P. townsendii (Kunz & Martin 1982). This species moves an average distance of 11.6 km between winter and summer roosts in the southern Great Plains (Humphrey & Kunz 1976); P. townsendii that winter in Jewel Cave likey remain in the Black Hills during the summer.
In recent years, many bat populations have declined drastically, largely because of vandalism and the loss of roost sites (Mohr 1972, Tuttle 1979). Bat populations are susceptible to delines because they have low reproductive rates (generally one young per year) and many species aggregate in large colonies, making significant portions of populations vulnerable to either natural or anthorpogenic disturbances. P. townsendii is particularly susceptible to human disturbances because they often roost on exposed surfaces near the entrance of caves or mines.
Human access to Jewel Cave is restricted during the winter, affording the hibernatng bats significant protection. However, nothing is known about location and security of summer roosts of P. townsendii in the southern Black Hills. Our objective was to locate summer roosts of P. townsendii and assess their vulnerability to disturbance. Report prepared for Jewel Cave National Monument, National Park Service, Custer, SD.
