the Hendricks Mine during summer and especially 

 in winter Low netting success at the portal of the 

 Union Mine, coupled with our internal sur\c\', 

 suggests to us that this mine is unlikely to support 

 relatively large numbers of bats e\en in areas we 

 did not reach. 



Bats were present during winter at locations w ith 

 mean winter temperatures of 4.4-9. 1 °C and mean 

 relative humidity between 74-84% (Table 2). 

 Mine sites where we obserx'ed bats during the day 

 in summer (either maternity or day roosts) were 

 the warmest ( 1 0.5- 1 2.2 °C) among the data 

 logger locations (/ = 4.89. P < 0.00 1 ; adjusted for 

 unequal variances). However, occupied sites in 

 summer were not necessarily the most humid. 

 Microclimate conditions at C. townsendii roosts 

 (Tables 2 and 3, Appendix 1 ) were cold during 

 winter (averages of 4.4 and 7.5 °C), but relatively 

 warm during summer (11.3 and 1 1 .9 °C). Rela- 

 tive humidit>' at C. towiisendii roosts averaged 

 74.0 and 83 .4% in winter, 9 1 .7 and 1 00% in 



DISCUSSION AND RECOMMENDA- 

 TIONS 



Roost environments: Abandoned mines provide 

 suitable environments for a variety of roosting 

 purposes for bats (Pierson et al. 1 991 , Tuttle and 

 Taylor 1 994, Betts 1 997, Sherwin et al. 2000). 

 Abandoned mines in northwestern North America 

 are often used as hibernacula and day or night 

 roosts rather than maternity roosts because mine 

 temperatures are too cold and energy-expensive 

 for norma! rates of development of young bats 

 (Dw)er 1 97 1 ). The results of our study in south- 

 westem Montana of mine features and microcli- 

 mates favored b>- bats. particularly C townsendii, 

 conform to general patterns for western North 

 America. Our study was hampered by lack of 

 visits to each mine during the four seasons to 

 detenniiie with cenaint>- the sca.sonal use oleach 

 by bats. Nevertheless, we documented the long- 

 term climate of several abandoned mines o\ er an 



elevation gradient, and several preliminary conclu- 

 sions regarding roost use by bats in this portion of 

 Montana are possible. 



We found only one mine (McDonald Adit #2) 

 used as a maternity roost, by ('. townsendii, and 

 it was at the lowest elevation of the mines studied 

 (Table 1). Mean June-July temperature near this 

 colony was about 1 2 °C (Table 2), which is much 

 colder than at matemity sites in California (Pierson 

 etal. 1991). It is possible the McDonald Adit #2 

 matemity roost moved after our Jul>' visit to 

 wamier temperatures nearer the mine portal. 

 Similar behavior has been documented for Califor- 

 nia matemity aggregations after young are bom in 

 late July and early August (Pierson et al. 1 991 ). 

 We did not get close enough to the McDonald 

 colony to detemiine if young bats were present 

 when we retrieved our data logger on 1 3 July. 

 There are few temperature and relative humidity 

 data for other C. townsendii matemity roosts in 

 Montana. Temperature was 1 8 °C beneath a 

 matemity roost of about 75 C. townsendii in a 

 ceiling dome of Toeckes Cave ( 1 524 m elevation) 

 on 23 August 1 999 (S. Martinez personal commu- 

 nication). Temperature was likely at least a few^ 

 degrees warmer closer to the roost. 



Summer bat use of mines declined with increased 

 elevation in southwestern Montana (Hendricks et 

 al. 1999). The most plausible explanation for this 

 pattern is that mean mine temperature declined 

 significantly as elevation increased (Figure 2). 

 making higher elevation mines less attractive to 

 bats for roosting. ITiis is especially true for female 

 bats (Cryan et al. 2000) because of increased 

 energy demands related to reproduction. Bats 

 found at high ele\ations in western North America 

 tend to be males or non-reproductive females 

 (Store and Williams 1 996. Cnan et al. 2000). 

 Currently, little is known about the upper elevation 

 limit for caves and mines used by bats in Montana, 

 liule Ice Cave (2493 m elevation ) is the highest 

 known hibernation roost in the state (Madson and 

 Hanson 1992). There is also considerable activit)' 

 b\ sc\ cral species o^Myolis at the mouth of this 



