female bats captured. Female M. lucifugus thought to be gravid 

 were noted at Lower Fortine Creek and Sylvan Lake. A gravid M. 

 californicus was captured at Trout Creek, and a visibly postpartum 

 non-lactating M. californicus was captured at Big Creek. Over the 

 course of the summer, 24 percent of adult female bats were 

 classified as either lactating (n=8), gravid (n=6), or postpartum 

 (n=l) . 



Table 7.-- Lactating bats captured on the Kootenai National Forest 

 and Lolo National Forest, 1993. 



site Species Date captured 



Ross Creek Myotis volans 7/15 



Upper Beaver Creek MyoCis californicus 7/16 



Flat Creek Myotis ciliolabrum 7/28 



Canp 32 Myotis evotis (2) 7/29 



Bear Creek Myotis evotis 8/25 



Five Mile Creek Myotis californicus 8/27 



Timberlane Myotis ciliolabrum 9/1 



DISCUSSION 



Species composition and relative ai>iindance 



There are several factors that influence the data obtained from 

 monitoring echolocation calls of bats. Detection of bat calls is 

 dependent on the distance between bat and monitor, and the 

 intensity of the call. Bats using higher frequency calls (e.g., 

 Myotis lucifugus) that attenuate in the air more quickly than 

 lower frequency calls (e.g., Lasionycteris noctivigans) are less 

 detectable by echolocation monitors (Fenton and Bell 1981) . More 

 significantly, "whispering" bats (notably Plectotus toivnsendii ) , 

 emit low-intensity echolocation calls that are difficult, if not 

 impossible to detect amidst the background noise of creeks, 

 insects, etc. Generally, active bats with high-intensity 

 echolocation calls are more readily detected than other bats. 

 Since these biases may be assumed to exert their influence fairly 

 equally throughout the study area, their effects are negligible 

 for the purposes of constructing an index of bat activity to 

 determine the relative abundance of bats between areas. 



A more crucial variable affecting transect data is the weather. 

 Conditions of cold weather and rain may lessen bat activity 

 (Fenton et al . 1983). This was often observed during the study, 



13 



