Furthermore, the number of bats present (8) at the McDonald Mine adits on 7 December 1998 

 was nearly identical to the number (7) found in the same portion of workings surveyed on 6 

 November 1996, just prior to gate installation. This further supports the idea that the gating had 

 little impact on the attractiveness of these mine workings to bats. 



The West Adit of the McDonald Mine appears to be used mostly as a maternity site, 

 whereas the East Adit is used as a hibernaculum. The West Adit was warmest with the least 

 humidity, both of which promote more rapid development of young (Humphrey and Kunz 1976). 

 The McDonald East Adit and the two Gypsum Mine adits provide conditions suitable for use as 

 hibernacula by Townsend's Big-eared Bat: temperatures < 10°C but above freezing with high 

 relative humidity (Table 1, Figures 1-8). High relative humidity reduces water loss and 

 desiccation while bats are inactive, low temperature reduces metabolic costs and use of fat stores. 

 The temperature values are similar to those reported for big-eared bat hibernacula in northern 

 California (Pierson et al. 1991), Idaho (Genter 1986), Kansas (Twente 1955), and Oklahoma 

 (Humprey and Kunz 1976), but not as warm as in other parts of its range (summary in Webb et 

 al. 1996). 



RECOMMENDATIONS 



1) The gate design at the McDonald and Gypsum mines is bat friendly and works. Continue 

 using this design where appropriate at other adits as additional abandoned mines are 

 reclaimed. 



2) Other gate designs have been installed by the state on abandoned mine workings elsewhere in 

 Montana that are not effective in preventing unauthorized human entry. Some of these 

 designs, using brick walls that may alter airflow, could also alter mine environments and 

 affect their suitability as hibernacula or maternity roosts (Richter et al. 1993). Consider 

 replacing these with the current design, especially at sites where use by bats has been 

 documented. 



3) Continue monitoring bat use at the McDonald and Gypsum mines. Both sites are ideal for 

 long-term monitoring of a bat species of special concern, and provide both hibernacula and 

 maternity roosts. Monitoring could include multiple visits (every other month) by qualified 

 bat biologists to document timing of occupancy and location in each working throughout the 

 year; special care must be taken to minimize disturbance of bats if monitoring is done this 

 frequently. However, these data will provide a better understanding of roost requirements 

 that may help determine the suitability or lack of suitability of other abandoned mines, and 

 aid in decisions to close or gate other sites. 



LITERATURE CITED 



Dalton, D. C, and V. M. Dalton. 1995. Mine closure methods including a recommended gate 

 design. Pp. 130-135 in Riddle, B. R. (ed). Inactive mines as bat habitat: guidelines for 

 research, survey, monitoring and mine management in Nevada. Biological Resources 

 Research Center, University of Nevado, Reno. 



Genter, D. L. 1986. Wintering bats of the Upper Snake River Plain: occurrence in lava-tube 

 caves. Great Basin Naturalist 46:241-244. 



