METHODS 



Historical records of bats from Carter County, Montana and Harding County, South 

 Dakota, obtained from the literature (see Bibliography), provide data on breeding status, 

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

 previously published, are not included here. 



Field work in 1994 was conducted in mid-June and 1 • : September. An attempt was made 

 to visit the six main units of the Sioux District (Chalk Buttes, Ekalaka Hills, Long Pines, 

 North Cave Hills. South Cave Hills, Slim Buttes). However, time and weather precluded 

 survey efforts in the Chalk Buttes. Most survey sites were chosen based on accessibility and 

 the presence of water, as bats tend to concentrate their foraging activity over water sources 

 where insects are abundant (all bats in this region are insectivorous). No potential roost sites 

 (caves, mines, cavities in trees) were visited or checked, despite the presence of several in the 

 region. 



Two methods were employed to detect bats; mist nets and ultrasound bat detectors. 

 Thomas and West (1989) provide a general discussion of sampling methods. Each method has 

 strengths and weaknesses for survey work, with neither one 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 

 not get captured in nets, however, and species present at a particular site may go undetected. 

 Detectors can determine the presence of species of bats that may be missed during mist- 

 netting, but they are not without drawbacks besides those already mentioned. Call duration, 

 time between calls, call structure, and call frequency can vary significantly with habitat and 

 between individuals (Erickson 1993), which can cause make species identifications difficult. 

 On the Sioux District, Myotis evotis was the only species of Myotis which could be accurately 

 distinguished 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. 



In the 1994 survey, mist nets were set up at dusk adjacent to feeding and/or drinking sites 

 at ponds and springs and left in place for 30- 120 min. Captured individuals were identified, 

 sexed, examined for reproductive condition, measured for morphometric data (see data forms. 

 Appendix Bl), and released. Sites were never sampled on consecutive evenings. 



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

 navigation and prey capture. Fortuitously, several studies have determined that the signals 

 emitted by many species of bats can be used as species-specific signatures (e.g., Barclay 1986, 

 Fenton and Bell 1981, Fenton et al. 1983, MacDonald et al. 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 field season. These detectors are sensitive to broadband ultrasonic 

 calls common in bat vocalizations (usually 20-180 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 cassette 

 tape recorder) were set up before dusk near bodies of water and rims where bat activity would 

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



