O ver the last decade, an increasing concern about liability by private and public land owners, as well as federal and state agencies, has prompted an exponential increase in the efforts to safeguard abandoned mines. Abandoned mines have long been recognized as habitat for a large number of bat species as well as other kinds of wildlife. Since safeguarding typically involves destruction by blasting or backfilling, this has stimulated growing interest in their potential for wildlife habitat. Although a systematic program of evaluation of abandoned mines prior to closure has been slow to implement, enough mines have been surveyed to illustrate that they are a significant habitat resource for bats of several species. Use by maternity colonies of any kind, use for large hibernating colonies, use as a migratory stopover, and use for colonial reproductive behavior are relatively clear examples.
Prudence dictates that any kind of use that is previously undocumented qualifies as well.
Significance of use varies regionally and is generally best determined by the best judgment of bat biologists familiar with the region. Large numbers of underground mines were not a common feature of the environment in the western United States until a few decades before the dawn of the 20th century. By the same reasoning, we should not need wildlife preserves or national parks. Many bat species are in decline as a direct or indirect result of human activity. A significant part of this decline can be attributed to destruction of natural roost sites or human disturbance at roost sites.