baseline data will enhance the accuracy of future determinations of abandoned mine suitability 

 for bats in Montana, especially for sites where no bats were directly observed. 



Identifying mines used by bats can be relatively simple. For mines where entry is 

 possible, presence of bat droppings indicates a mine has been used relatively recently. For mines 

 considered too hazardous to enter, or where entry is prohibited or limited due to obstructions, use 

 of electronic bat detectors or some form of capture technique can provide evidence of current 

 use. Yet determining why bats are using different mines may be more involved. Reason for use 

 (of interest to bat biologists and animal ecologists) may be immaterial to a management agency, 

 so long as used sites are identified and protected. However, limited monetary resources could 

 restrict the number of used mines that can be protected and maintained for bats. In such cases, 

 highest priority mines are those used as maternity and/or hibernation roosts (Turtle and Taylor 

 1994), and it is very desirable to identify these from night roosts, places where bats rest in safety 

 to digest an evening meal. 



In the Beaverhead/Madison counties survey area, most mines where bats were recorded 

 appeared to be summer night/day roosts, with only a subset of these known or likely to be 

 hibernacula. Temperatures recorded during internal inspections in June and September (8.5- 

 16.5°C) were near or below lower threshholds recorded at maternity colonies in other areas (e.g., 

 Twente 1955, Turtle and Stevenson 1978, Pierson et al. 1991, Berts 1997, Williams and 

 Brittingham 1997, Hurst and Lacki 1999). However, our temperature and relative humidity data 

 are of limited use because they were taken usually during a single visit, and do not provide an 

 adequate picture of temporal or spatial climate variation within many of these mines. 



The microclimate of a mine, especially temperature and relative humidity, determines 

 whether bats can use it at all and if so, in which season and for what purpose. In Montana, long- 

 term climate data are not available for mines used by bats. Currently, climate measurements 

 taken during internal mine surveys to determine potential suitability for bats throughout their 

 annual cycle are compared with roost data from other regions. However, there is no reason to 

 assume a priori that ranges in climate variables at roosts are invariant across species ranges, and 

 we anticipate that climate in mines used for roosts in Montana may be somewhat cooler than in 

 more southern regions of western North America. Using climate data from elsewhere as the 

 basis for determining the range of suitable sites in Montana might result in exclusion of some 

 usable mines. 



Once more is learned from the data logger samples of climate regimes in the abandoned 

 mine workings where they were placed (each of which was used by bats), it may be suitable for 

 the BLM to a) consider sponsoring additional internal hibernacula surveys according to 

 temperature, b) put an emphasis on future searches for maternity colonies in unsurveyed mines at 

 lower elevations, and/or c) assign priorities for protection in a way that also considers likely 

 thermal regimes best suited for bat hibernacula or maternity use. 



Importance of abatidoned mines in the inventory area 



The determination of importance or significance of a mine working for bats is difficult. 

 Almost any mine working in the inventory area still accessible to bats should be considered 

 potentially important for them, especially those at which monitoring was conducted (Table 1), 

 and particularly for workings where significant activity was recorded (e.g., bats captured, more 

 than 10 passes recorded; see Tables 2 and 3). These comments are based on a combination of 

 factors, including inadequate surveying of the entire area (partly due to complex ownership 

 patterns), incomplete monitoring at mines visited (e.g., multi-season visits [see Altenbach 1995] 



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