78 M. D. Adam, M. J. Lacki, and L. G. Shoemaker 



Wiebers 1980) and free-ranging conditions (Kurta et al. 1989, Kurta 

 et al. 1990). This would suggest that selection for adaptations to 

 minimize water loss should evolve in bats, particularly in association 

 with flight because of the high surface area to volume ratio of bat 

 wings. 



Bats inhabiting arid environments show a direct relationship 

 between urine concentrating ability and evapotranspiration to pre- 

 cipitation ratio (Bassett 1986). In wetter regions, bats should encounter 

 fewer problems of water balance. Flexibility in foraging strategy, such 

 as reduced activity on less humid nights (i.e., increased vapor 

 pressure deficits), should help to maintain water balance. 



Using radio telemetry we monitored flight activity of a temperate 

 zone insectivorous bat, Plecotus townsendii virginianus, and related 

 observed activity patterns with data for local environmental conditions. 

 We tested the hypothesis that flight activity of P. t. virginianus is 

 reduced as relative humidity declines, which would be expected if 

 water balance is a critical selective pressure for temperate zone bats. 



METHODS 



The study area was located in the Cumberland Plateau, 

 Lee County, Kentucky. Lee County is 80% forested and sparsely 

 populated by humans (Newton et al. 1974). Mixed mesophytic forest is 

 the dominant habitat (Braun 1950) with most stands being second 

 growth timber because of past logging practices. The climate of the 

 region is temperate, characterized by warm and humid summers and 

 moderately cold winters. Average maximum and minimum tempera- 

 tures are 34C in August and -18C 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. Additional 

 site details are provided by Adam et al. (1994). 



Sixty bats were fitted with transmitters during 1990 and 1991, 30 

 each summer. Because this subspecies is very sensitive to disturbance 

 (Bagley 1984), we studied males in 1990 and females in 1991 and 

 addressed any problems that occurred with males in 1990 before 

 handling females in 1991. Bats were mist-netted as they emerged from 

 bachelor and maternity roosts, along cliffs, and on an abandoned 

 logging road. Bats were weighed, sexed, aged, and then fixed with a 

 0.8-g transmitter (Type BD-2A, 172-173 MHz; Holohil Systems, Ltd., 

 Ontario, Canada, and Wildlife Materials, Inc., Carbondale, Illinois) 

 on the dorsum between the scapulae. The surface was prepared by 

 trimming the fur with scissors and applying surgical cement 

 designed to hold the transmitter for about 10 days. 



