vocalizations. In effect, the effective area sanpled by the detector 

 is much larger for the strong emitters than for the moderate or weak 

 emitters. Thus, direct oompariscns of relative density between 

 species based solely on bat detector results is unwise. 



Though some effort was made to determine species heard with bat 

 detectors, the observers were not experierjoed enough to feel 

 confident in the accuracy of their identification. Considering this 

 and the inherent bias discussed above, no effort was made during this 

 study to determine relative density of bats between species, or of 

 species at specific sites. 



Habitat use 



To analyze the use of various habitats, and the inportanoe of various 

 components of these habitats within the Deer lodge National Forest, 

 bat use was determined from the results of surveys conducted with 

 ultrasonic bat detectors. Bat use was defined as "bat passes per 

 hour," as heard on a bat detector. An observer cannot generally 

 differentiate between one bat passing several times, and several bats 

 passing once, so the measurement is quite relative. No attertpt was 

 made to determine species; all bat echolocation calls detected were 

 recorded and used as a measure of relative density. Bat activity was 

 arbitrarily assigned to categories of high (more than 10 passes per 

 hour ) , moderate ( 5 to 9 passes per hour ) , and low ( less than 5 passes 

 per hour). This classification is completely arbitrary, and is based 

 on results that occurred across the Deerlodge National Forest during 



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