But, while some abandoned mines offer refuge for bats, they can be very hazardous for humans, who might fall into hidden mines or enter unstable tunnels. Approximately 400 mines are scheduled for closure annually as safety hazards by the Division of Minerals and Geology of the Colorado Department of Natural Resources. Typical closure methods involve sealing the opening with concrete or rock and/or backfilling and blasting the mine.

This process renders mines safe for humans but is disastrous for bats, either burying them alive or sealing them out of essential habitat.

The solution lies in the Bats/Inactive Mines Project. Each spring and summer, teams of wildlife volunteers hike to the sites of mines scheduled for closure. Without entering the potentially dangerous mines (safety training is required before participating in any surveys), the volunteers survey for bat activity by using bat detectors—instruments that translate a bat's ultrasonic cries into frequencies audible to people. Waiting at the mine entrance in the evening, the surveyors detect bats leaving the mine for their evening hunt. Mines found to have active bat populations are sealed with "bat gates" (a grid of steel bars or angle iron) instead of solid closures. The gates allow bats to enter and leave the mines without permitting human access.

To date (1996–Editor), of nearly 700 mines surveyed, 70 have been recommended for fitting with bat gates, thus protecting valuable habitat for bats. If you would like to volunteer for the program, contact the Bats/lnactive Mines Project Coordinator, 6060 Broadway, Denver, CO 80216.

End of this issue.

(The information contained in this issue of Colorado's Wildlife Company was accurate at the time of original publication. Situations and circumstances described, staff positions, contact information, and dates of some events may have changed in the interim. Present knowledge and understanding of biological and behavioral facts and information may also be different, now, than presented here.)