captured males were classified as scrotal one E.fuscus at the Kent/Bluewing E on 24 July 1998, 

 one M. ciliolabrum at the Kent/Bluewing F also on 24 July 1998, and oneM evotis at the 

 Huron/Cottontail C on 20 August 1997 



Ultrasonic Monitoring 



Ultrasonic bat detectors were placed at 78 different workings (Table 1) Bat activity was 

 detected on at least one night at 51 (65.4%) of the workings (Table 3). Most detections (at 47 of 

 50 workings) were classified as unknown bat or Myotis species, for 992 recorded passes during 

 the survey, 793 (79.9%) were classified in these two groupings Western Long-eared Myotis 

 {Myotis evotis) was tentatively determined at 10 workings. Big Brown Bat (Eptesicus fuscus) at 

 12 workings, Townsend's Big-eared Bat (Corvnorhinus townsendn) at 6 workings, and Silver- 

 haired Bat (Ixtsionycteris noctivagans)/Hoary Bat (Lasiurus cmereus) at 4 workings, 3 of which 

 were shafts Shafts probably are the kind of mine working where these non-mine inhabiting 

 species are most likely to be detected, as they forage over the mine area. 



Activity at most sites was relatively low, based on the number of passes detected For 54 

 nights of monitoring at 50 workings (number of passes were not recorded at one site), the mean 

 number of passes (± SD) was 18 4±38 2 The large standard deviation indicated the wide range 

 of activity at individual sites where bats were detected (from 1 to 187 passes/detector night) 

 Only 16 (31.4%) of the samples included > 10 passes/detector night, and eight of these were < 30 

 passes For workings with <30 passes/detector night (n = 47), the mean number of passes was 

 6.3±5.2. Sites with more than 100 passes/detector night included the Ermont #19 pit + shaft (145 

 passes on 18 August 1997), Hendricks gated adit (154 passes on 21 August 1997), and the 

 unnamed shaft T3SR7WS33NESW (187 passes on 29 June 1998) Of course, there was no way 

 of determining how many individual bats were active at any of the workings based only on the 

 recorded vocalizations. Also, weather and battery failure interfered with some all-night 

 recordings, limiting their reliability as a measure of relative activity. 



Patterns of Mine Use 



Bats used all three categories of mine workings (adits, "shafts", pits) across a wide range 

 of elevations and habitat types, from 9 June to 15 October (nearly the extreme dates for external 

 surveys) However, some patterns of mine use were evident upon closer examination of the data 

 The analyses that follow are necessarily crude, because several variables that were not sampled 

 adequately may also influence patterns These will be addressed at greater length in the 

 Discussion 



Mine sites with evidence of bat use tended to be at lower elevations (Fig 2. G = 6 680, df 

 — 2, P< 0.05). Over 86% of monitored sites <6000' showed evidence of bat use, while the 

 respective values for 6000-6999' and >7000' were 57.6% and 62 5% 



The proportion of mine sites with solitary workings that were used by bats (78 8% of 33 

 sites) was similar (G = 256, P > 5) to use of mine sites with more than one working (84% of 

 25 sites) Obviously, the criterion used to define a solitary or isolated working was very arbitrary 

 (whether or not the named or apparent mine site had one or multiple significant and open 

 workings) Using a larger number of categories to define the number of portals per mine site 

 may result in a different conclusion Such was not possible in this inventory because of 

 relatively small samples of monitored mine sites with different numbers of workings 



A rough measure of portal size could be calculated for 50 of the monitored workings. 

 Mean area (± SD) of used workings (2 80 ± 5.35 m 2 , n = 33) was slightly smaller that for non- 



