Some effort was made to determine species heard with bat 

 detectors. Because of the biases discussed above, a quantitative 

 comparison of relative densities of species will not be made. 

 However, Myotis species were by far the most commonly heard bats 

 at all sites except one (the Eva May Mine 5 miles northeast of 

 Basin had only Big brown bats). 



Habitat use 



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

 various components of these habitats within the Deerlodge 

 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. For the habitat analysis, no attempt was made 

 to differentiate 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 1991 and 1992. Of 31 

 hours of transects run during 1992, only 13% recorded more than 

 21 bats per hour, and about 65% had less than 10 bats per hour. 

 In other localities 10 or even 60 bat passes per hour may be 



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