Observations on Seasonal Cycle, Population Patterns and Roost Selection in Summer Colonies of Plecotus townsendii virginianus in Kentucky

Abstract

-Limited information is available on the use of summer roosts by Virginia big-eared bats (Plecotus townsendii virginianus) or on the timing of the summer reproductive cycle for this subspecies. We measured internal temperatures and structural characteristics of roosts, and used emergence counts with night vision equipment and mist netting to monitor P. t. virginianus at three maternity roosts and one bachelor roost in Kentucky, during 1990, 1991 and 1992. Structural characteristics of roosts varied. All colonies selected limestone caves except one that used a sandstone rock shelter. There were no differences in internal temperatures between the rock shelter roost and a cave roost in summer 1991. Timing of establishment of maternity colonies varied among roosts. Roost abandonment (switching) occurred with maternity colonies in caves. Females at the rock shelter roost were pregnant on 10 May and lactating on 17 June 1991; young were volant on 5 August. Bimodal activity patterns were observed at maternity roosts, except during lactation when activity of bats at roost openings persisted throughout the night. Population patterns at the bachelor roost were consistent across years. Low numbers in the bachelor roost in mid-August coincided with the descent of testes and the onset of mating activity. INTRODUCTION The Virginia big-eared bat (Plecotus townsendii virginianus) is one of two eastern subspecies of Townsend's big-eared bat (P. townsendii) listed as endangered by the U.S. Fish and Wildlife Service, because of its restricted distribution and the paucity of data on location and use of summer roosts (Bagley, 1984). The only studies of a P. t. virginianus maternity colony have reported data on activity patterns and food habits in Virginia (Dalton, 1983; Dalton et al., 1986). For the Kentucky population of P. t. virginianus, only sporadic population estimates exist for summer colonies (J. MacGregor, pers. comm.). Plecotus townsendii virginianus are vulnerable to human disturbance at summer maternity roosts (Barbour and Davis, 1969; Harvey, 1975; Bagley, 1984). This has hindered attempts to collect data on summer colonies of this subspecies; consequently, no information exists on its reproductive cycle. In this paper we report data on roost characteristics, population patterns and seasonal cycle of P. t. virginianus maternity and bachelor colonies in Kentucky. STUDY AREA AND METHODS This study was conducted in Lee County, Kentucky, within the Stanton Ranger District of Daniel Boone National Forest. Lee County is approximately 80% forested (Newton et al., 1974) and has a climate characterized by warm and humid summers and moderately cold winters. Average maximum and minimum temperatures are 34 C in August and -18 C in January (Newton et al., 1974). Average monthly precipitation is 9 cm (Newton et al., 1974). July and October are the wettest and driest months, respectively. The only known population of Plecotus townsendii virginianus in Kentucky hibernates in Present address: Cape Canaveral National Seashore, 308 Julia St., Titusville, Florida 32796