monitoring, and evaluating the potential for human entry into the mines for internal 

 survey. All mine openings that were approachable were examined for bat guano or other 

 bat sign. External ultrasonic monitoring (Anabat units) and mist netting were conducted 

 at, or near, selected mine openings that appeared to have potential for bat use. 



Mines were evaluated for their current potential to serve as habitat for bats. This 

 preliminary evaluation was based upon characteristics such as size of the opening, 

 presence of obstructions (e.g., grates), detectable air flow, observable depth, presence of 

 multiple openings that may be connected, and evidence of bat use (e.g., guano, insect 

 parts). Categories ofpotential bat use were: none, low, moderate and high. The 

 locations of mine openings were recorded on 7.5-minute topographic maps and/or 

 recorded with GPS. 



A geographic information system (GIS) is being used to manage locality data and to 

 merge locality information with base-map layers of land ownership, elevation, roads, and 

 hydrology. Survey data tables will be linked to the GIS. 



RESULTS AND DISCUSSION 

 Mine Survey 



Mines and mine openings 



Eighty-six abandoned and inactive mines were visited during August 18 to October 17, 

 1 997 (Table 1 ). Forty-nine of these mines were on the initial list provided by the Dillon 

 Resource Area and 37 were additional mines (named and unnamed) in close proximity to 

 the those mines on the BLM list. Mine openings (total = 166) that might be suitable for 

 bats were found at 68 mines. Openings consisted mostly of adits, shafts and inclines. At 

 least 32 of the visited mines had multiple openings. 



Mines with no openings (total = 18) currently have no potential for bat use (Table 1). It 

 is possible that mines with collapsed openings could re-open in the future, subsequent to 

 continued movement of debris. Eleven mines were rated as having high potential to 

 provide bat habitat. These mines usually had multiple openings and should be a priority 

 for future external and internal surveys. Twenty-nine mines were rated as low-to- 

 moderate or moderate for bat potential. Mines in this category often had only one or a 

 few openings, most of which were partially or mostly collapsed, and/ or we were unable 

 to determine the extent of the internal workings. Many mine openings were covered 

 with grating ( r'x3" openings) or metal cable netting (4" to 6" openings). These sites 

 were usually ranked as low bat potential. However, at some sites there appeared to be 

 adequate space around the edge of the grating to allow bat entry. In other instances 

 wooden planking completely covered mine shafts, possibly precluding bat use. 



