on the way to or from foraging or watering areas (Thomas and West 

 1989 ) . There is therefore an inherent site bias that cannot 

 provide unequivocal information on the distribution of bats among 

 sites or habitats using mist-nets as a survey method (Thomas and 

 West 1989). Mist nets were used in this study to document 

 species occurrence, while realizing that there are inherent 

 biases in the method that select against the documentation of 

 some species. 



A potential problem with capture methods such as mist-netting is 

 mis-identification of bat species. Most species in Montana can 

 be identified easily using one of several available dichotomous 

 keys, such as van Zyll de Jong (1985). When there was any 

 question of identification during this study, the bat in question 

 was collected and taken to an expert for positive identification. 

 Bats most easily confused on the Deerlodge National Forest are 

 the Fringed myotis (Myotls thysanodes) with the Northern long- 

 eared bat (Myotis evotls), and the Little brown bat complex: Yuma 

 bat (Myotis yumanensis ) , California myotis (Myotis californlcus) , 

 and Little brown bat (Myotis lucifugus) . 



Relative density 



Relative density between sites and between habitats by different 

 bat species can be determined using ultra-sonic bat detectors. 

 Discussions of the various types of ultrasonic detectors, along 

 with their inherent strengths and weaknesses, can be found 



27 



