Bats: Masters of the Night Skies
Bats are in serious decline nearly everywhere. Worldwide, there are almost a thousand different kinds of bats which comprise nearly 1/4 of all mammal species. Of the 43 species living in the U.S. and Canada, nearly 40 percent are endangered or are candidates for such status. The biology and ecology of bats is not well understood. Their nocturnal behavior, inaccessible breeding and roosting sites, and migratory behavior have made them difficult to study. As a result, we know little of bat ecology or management needs on public lands. Despite a lack of knowledge, we do know that bats often use trees, cliffs, caves, human dwellings, natural waters and water developments, bridges and mine shafts in a variety of habitats. There are clearly opportunities to begin specific management actions to protect or enhance this diverse and threatened group of mammals. One method that the Forest Service is using to protect critical bat habitats is the installation of iron grates over abandoned mine entrances. These "bat-gates" serve two primary purposes: they protect the public from stumbling into a mine that might be dangerous, as well as protecting habitat allowing passage for bats. In the past, many abandoned mines have been filled in with earth, often a costly proposition that is deadly for bats. Maintaining the mine for bats provides a win-win situation that is both simple and cost-effective. With approximately 25,000 abandoned mines on Forest Service lands and an estimated 200,000 across the U.S., there is great potential to make a significant positive impact on bat populations through this method of protection. Bat Barracks: Abandoned MinesAbandoned mines have become key year-round resources for bats. Mines seem to be most important for rearing young in summer, for hibernating in winter, and for use as temporary rest stops during migration. Throughout the United States, human disturbance of caves, cave commercialization, deforestation, and urban and agricultural development have forced many bats from their traditional roosts in search of new homes. Old mines are often the only suitable temperature-controlled shelters left midway between a bat's summer and winter roosts; without these protected resting places, many species' migratory mortality could greatly increase. Over the past 100 years or more, displaced bats have gradually moved into many mines. In more than 6,000 mines surveyed by researchers in Arizona, California, Colorado, and New Mexico, 30 percent to 70 percent in each state showed signs of use by bats. An average of 10 percent contained important colonies. From the Great Lakes Region eastward in the U.S., up to 70 percent of subsurface mines may be used by large bat populations. Bats, due to their colonial nature, are especially vulnerable during hibernation both to vandals, and to rapid mine closures. The largest recorded hibernating population of western big-eared bats was recently destroyed in a New Mexico mine shaft where vandals had set old timber on fire. In New Jersey, the state's largest population of hibernating bats was inadvertently trapped in the Hibernia Mine when it was capped. Had state biologists not convinced state authorities to reopen the entrance immediately, these bats would have perished. Likewise, the Canoe Creek State Park limestone mine in Pennsylvania was reopened in the nick of time to save its bats and now shelters the largest bat hibernating population in the state. Clearly, the difference that protecting and stabilizing just one mine shaft can make is tremendous. Bat BiologyEcholocation
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