Executive Summary 



Roost environments often abandoned mine 

 workings known to he used by bats were studied 

 in detail during 1 ^)98- 1 999 to expand on scant 

 knowledge of underground roost requirements for 

 bats in Montana. Objectives were to: 1) docu- 

 ment dail\' mine ambient temperature and relative 

 humidit) during \\ inter and summer using elec- 

 tronic dataloggers, esj^ecially at underground 

 microsites where evidence of bat use was found, 

 2) document the seasons when mines were used 

 for roosting, and identify the bat species using the 

 mines, and 3 ) detemiine mine characteristics 

 obtained from external sur\eys that might be useful 

 for identi tying luiderground en\'ironments suitable 

 for bat roosts in abandoned mines. Special 

 attention was paid to Townsend's Big-eared Bat 

 ( C 'orynorhiuus lownseiulii). a Montana animal 

 species of special concern, a Montana BLM 

 Special Status species, and a species of high 

 conservation concern throughout its range. 



Foui^ bat species were identified using these mines. 

 TowTisend's Big-eared Bat (Corynorhimis 

 towmendii) was present at six mines. Western 

 Small-footed Myotis {Myotis ciliolabrum) at five 

 mines. Western Long-eared Myotis (A/, evolis) at 

 one mine, and Big Brown Bat (Eplesicusfuscus) 

 at one mine. 



Summer ambient mine temp)erature was generally 

 too cold (usually < 1 °C) to be suitable for 

 matemit) roosts. However, suitable sites were 

 present in some underground workings, and one 

 C. lowmendii matemit\ roost a\eraged 1 1 .9 °C 

 during June and July. Maximiun mean daily 

 temperature recorded in any mine was 14.6 °C. 



Ambient mme temperature decreased signillcanth 

 as elevation increased, and summer iind winter 

 mine temf)eratures were highly correlated and 

 relati\ el> predictable using time-series data. 



Howe\ er. complex mines at higher elevations may 

 contain internal microsites, not detectable from 

 external sur\'eys, with temperature and relative 

 humidity regimes suitable at all seasons for roost- 

 ing bats. 



Relative humidity fluctuated dramatically in man\ 

 mines, and tended to be lowest and least stable in 

 winter, when means in some mines were < 50%. 

 At two known Townsend's Big-eared Bat hiber- 

 nation roosts, winter mean relative humidity was 

 74.0% and 83.4%. while respective ambient mine 

 temperatures averaged 7.5 °C and 4.4 °C. 



Mine suitability for roosting bats was not apparent 

 from external variables, such as portal size, 

 number of portals, detectable airflow, or even 

 elevation. Tlie most useful infomiation obtained 

 during extemal visual inspections was the presence 

 or absence of obstructions at portals and the 

 extent of underground workings, if \isible from the 

 portal. 



All mines should first be ex'aluated for use by bats 

 before reclamation takes place. Usefiil informa- 

 tion about the potential for roost use can be 

 gathered from external inspections and monitoring 

 (visual, auditory, trapping) at mine portals. How- 

 ever, where possible and safe, the best method for 

 assessing mine structure and use by bats is under- 

 ground sur\'e\-. Identifying mines suitable for 

 hibemating bats requires underground inspection. 

 1 rapping at mine portals for pregnant and lactating 

 females ma\ be etTecti\ e in identitving mines u.sed 

 as maternity roosts, but even here internal in\en- 

 tory is the best survey method. Mines that are 

 used for night and day roosts can be effectively 

 monitored on multiple \isits v\itliout mine entn. 

 preferabh during dilTerent seasons, but e\ en a 

 single underground \isit can reveal if there is any 

 e\ idence of more extensive use bv bats. 



