used workings (3.44 ± 4.18 m 2 , n = 17), but the difference was not statistically significant (t = 

 0.43, df = 48, P = 0.670). Some used workings were covered with wire netting or gates, and the 

 "mesh size" was used in the above calculation. Using only the portal area itself behind the gate 

 or mesh made the actual mean area of openings at used workings (3.26 ± 5.19 m ) nearly 

 identical with that of non-used workings. The large standard deviations indicate the wide range 

 in portal sizes at used and unused workings. 



Each major type of mine working was used by bats, but there was a difference in the 

 frequency of their use (Fig. 3). Adits were used in much greater frequency than shafts (including 

 pits) in 1998 (G = 8.720, df = \,P< 0.005). This result is not biased by elevation distribution of 

 the different types of sampled workings, as distributions were very similar (Fig. 1). Only 1998 

 data were used in this analysis, however, as there was slight overlap in the range of survey dates 

 during the two years. External surveys were conducted from 4 August- 16 October in 1997 and 9 

 June- 19 August in 1998. Nevertheless, the pattern was similar, albeit weaker, in 1997, when 

 65.6% of monitored adits were used by bats versus 50% of shafts (G = 1.242, P > 0.1). Different 

 dates of sampling (as well as different sampling conditions) may account for some of the annual 

 disparity. 



Obstructed openings also affected use of mine workings by bats. Bats were detected at 

 41.7% of unobstructed shafts (n = 24) and 65.2% of unobstructed adits (n = 23) that were 

 monitored in 1998. Respective values for obstructed workings were 1 1 . 1% (n = 9) and 63.6% (n 

 = 11). For years combined (including mine workings sampled in both years), 60% of 

 unobstructed workings were used versus 42.9% for obstructed workings. Bats were more likely 

 to use unobstructed adits in 1998 than unobstructed shafts (G = 2.644, P = 0. 12). Likewise, bats 

 were more likely to use obstructed adits in 1998 than obstructed shafts (G = 6.222, P < 0.025). 

 Even though some workings were grated, screened or gated, all sampled workings were 

 considered as possible bat habitat because each provided potential avenues of access to 

 underground workings around the obstruction. 



Internal Surveys 



Twelve mine workings were inspected internally in 1998 for the presence of bats (Tables 

 1 and 4). Two of these were steep inclines ("shafts"), the remainder were simple or complex 

 adits. Elevation of these mines ranged from 5640-7380'. Eight were < 200' in length, relatively 

 simple, and completely explored. Mine air temperature in September in this group ranged from 

 47.5-52.0°F near the drift faces. Another two (Unnamed Gold Deposit #2 and #3) were > 200' 

 but not fully explored (mine air temperature = 48.0°F), and the last two mines (Union #4 and 

 Hendricks) were > 400' and >1000' in length, respectively, with multiple levels, but not fully 

 explored. Air temperature 323' from the portal of the Union #4 was 55°F. Air temperature in the 

 Hendricks ranged from 41.5°F (400' from the portal) to 54°F (700' from the portal). Most mines 

 were damp or contained standing water, but at least two were completely dry at the time of 

 inspection. Data loggers were placed in six of the mine workings in September and will be 

 retrieved in late August 1999. Each data logger is set to record mine air temperature and relative 

 humidity every 6 hours. 



Only the Hendricks Mine had significant quantities of guano scattered throughout the 

 mine workings. Scattered guano in small quantities was present in the other mines. Bats were 

 observed during internal surveys of three mines. One Western Small-footed Myotis (Myotis 

 ciliolabrum) was observed in the Hendricks Mine on 13 June. Also in the Hendricks, one Small- 

 footed Myotis and one Big Brown Bat (Eptesicus fuscus) were observed hibernating about 320' 



