We surveyed each mine internally at least twice to 

 the fullest extent possible where deemed safe. No 

 vertical workings (shafts) were entered during this 

 study. At least two people entered each mine 

 during surveys. We recorded presence, number, 

 location, and identity of bat species when possible. 

 During surveys, we recorded the following "struc- 

 tural" habitat variables: vegetation cover at the 

 mine, portal elevation, number and size of portals, 

 length of underground workings, presence of 

 standing water, cross-section dimensions of main 

 tunnels, and number of levels. We ranked mine 

 complexity as simple (mam passage with non- 

 branching side timnels), moderate (main passage 

 with branching side tunnels or < 3 levels), or 

 complex (mam passage with multiple branching 

 side tunnels or > 2 levels). 



We gathered tune-series temperature and relative 

 humidity data by installing at least one data logger 

 (HOBO H8, Onset Computer Corporation, 

 Pocasset, Massachusetts) in each mine, usually 

 near microsites where bats or bat sign were 

 observed, hi two shallow mines data loggers 

 were placed where we considered the mine 

 environment likely to be the most stable. Fifteen 

 data loggers were placed in the mines; only two 

 mines contained more than one data logger. Data 

 loggers were attached to an extendable aluminum 

 rod and positioned < 30 cm below the tunnel 

 ceiling. Data loggers were set to record tempera- 

 ture and relative humidity every six hours. We 

 calculated daily means fi-om these data and used 

 daily mean values in the analyses we present in this 

 report. 



Because of the small sample of mines studied our 

 analyses are largely inferential. Where statistical 

 analyses were performed we followed standard 

 procedures (Sokal and Rohlf 1981) using Statistix 

 version 2.0 (Analytical Software, Tallahassee, 

 Florida). 



RESULTS 



Mine habitat features. Use by bats of aban- 

 doned mines in our sample did not appear related 



in any obvious way to vegetation cover, mine size 

 or complexity (Table 1 ), size or number of portals, 

 or availability of standing water. All mines were in 

 sagebrush or sagebrush intermixed with scattered 

 conifers, and all mines had either one or two 

 fianctional portals with dimensions that ranged from 

 1.2-2.1 m high by 1.2-2.0 m wide. Five of the 

 mines contained standing water. Six mines 

 (McDonald Adits #1 and #2, Gypsum Adits #1 

 and #2, Union, Hendricks) had some form of gate 

 at their portals. 



Mine temperature and relative humidity. We 



placed data loggers in six mines in September and 

 retrieved them the following August (Table 1 ). At 

 four mines we placed data loggers in December or 

 January and retrieved them the following July. 

 Data loggers failed to record for the duration of 

 installation at two mines; m the Gypsum Adit #1 

 the logger failed to record any data, and in the 

 Unnamed Adit #3 the logger became wet and 

 ceased operation by March, 1 74 days after 

 installation. Continuous temperature and relative 

 humidity profiles are shown in Appendix 1 for all 

 loggers that recorded any data. 



Maximum daily temperature recorded among the 

 mines (Table 1 ) was 14.6 °C in late July at the 

 Unnamed Adit #2. However, portions of some 

 mines never achieved temperatures > 6 °C, even 

 in summer (Appendix 1). The lowest mine tem- 

 perature, -1 5.9 °C, was recorded in late Decem- 

 ber; in general mine temperatures dropped below 

 freezing only in mines or portions of mines where 

 there was significant movement of air. In several 

 mines, relative humidity reached lowest values 

 near or below 30% during December or January 

 while maximum values (85-1 00%) were recorded 

 in July or September (Appendix 1 ). 



Table 2 shows mean temperature and relative 

 humidity data from each mine for the same winter 

 and summer time periods, thereby making com- 

 parisons among mines the most meaningful. Mean 

 temperatures for January through April varied from 

 -1 .4 °C to 1 1 .8 °C, depending on the mine and 

 location within the mine. Interestingly, the ex- 

 tremes were found in the same mine, the 



