METHODS 



Historical records of bats from northwestern Montana and adjacent areas of Idaho and Canada 

 were obtained from the literature (see Bibliography). These records provide data on breeding 

 status, habitat use, seasonality of occurrence, and distribution. Museum records, other than those 

 previously published or from northwestern Montana, are not included in this report. Collecting 

 in Montana has been sporadic, and the number of bat specimens from the Kootenai National 

 Forest area is minimal. 



Field work in 1994 and 1995 on the Kootenai National Forest was conducted from mid- July 

 to mid-September. Ultrasound detectors were used in both years and represent the primary 

 survey technique. Mist-netting was also employed in 1995, and used by Roemer (1994) in 1993. 

 Thomas and West (1989) provide a general discussion of sampling methods for bats. Each 

 method has strengths and weaknesses for survey work, with no single method being definitive. 

 Mist-netting has the advantage of allowing in-hand identification of individuals and collection of 

 data on sex and reproductive condition, neither of which are obtainable with bat detectors. Some 

 bats may escape capture in nets, however, and some species present at a particular site may go 

 undetected. Detectors can determine the presence of species that may be missed during 

 mist-netting, but they are not without drawbacks. Call duration, time between calls, call 

 structure, and call frequency can vary significantly with habitat and between individuals 

 (Erickson 1993), often making species identification difficult. On the Kootenai National Forest, 

 Myotis evotis was the only species of Myotis which could be distinguished from other members 

 of the genus with accuracy using a bat detector. Ideally, a combination of mist-nets and bat 

 detectors would be employed at a given site in order to obtain the most accurate picture of 

 distribution. Mist-netting is time-consuming, however, and therefore permits fewer sites to be 

 surveyed within the allotted time period. 



Microchiropteran bats use a variety of ultrasonic vocalizations as echolocation aids for 

 navigation and prey capture. Fortuitously, a number of studies have determined that the signals 

 emitted by many species of bats can be used to distinguish among species (e.g., Barclay 1986, 

 Fentonand Bell 1981, Fentone/a/. 1983, MacDonald er a/. 1994). This characteristic permits 

 the assessment of species-presence during inventory work through use of portable ultrasound bat 

 detectors. 



ANABAT II bat detectors (Titley Electronics, Ballina, Australia) were used during the 1994 

 and 1995 field seasons. These detectors are sensitive to broadband ultrasonic calls common in 

 bat vocalizations (usually 20-1 80 kHz) . Ultrasonic signals in the range of bat vocalizations are 

 captured, converted to an audible frequency (up to 10 kHz), and recorded on magnetic tape. 

 Detector units (consisting of the detector, timer/tape-driver, and a voice-activated cassette tape 

 recorder) were set up before dusk near bodies of water and forest openings (where bat activity 

 would be expected) and left in place overnight; usually one cassette tape was sufficient to record 

 activity at a single site. Detectors were sensitive to bats within a minimum range of 20 m. 

 Recorded tapes were returned to the laboratory and analyzed on an IBM compatible PC using an 

 ANABAT II ZCA Interface Module and software. Assignment of vocalizations to a particular 

 species of bat was achieved by matching field recordings with a reference set of calls obtained 



