The California Leaf-nosed Bat (Macrotus californicus), found in the Caribbean islands, Guatemala and Mexico, is also a year-round resident of arid desert scrub habitats of the southwestern United States. Its northern range is apparently possible only because geothermally heated mine tunnels provide unusually warm roost sites.
The dangers of open mines are clear, and the Bureau of Land Management (BLM) requires that steps be taken to remove hazardous conditions-either by capping or blocking entrances or erecting fences. BCI member, Dr. Pat Brown of the Maturango Museum in Ridgecrest, California, brought to our attention the fact that mine closures could severely endanger the California Leaf-nosed Bat in the southern California desert, possibly resulting in its extirpation from the state. Another BCI member, Robert Currie, a biologist with the U.S. Fish and Wildlife Service and an expert on cave gate design, provided recommendations to the BLM.
The BLM now has directed that appropriate alternative methods for mine shaft closures be implemented where bats are found. Without the unified action of concerned BCI members, such protection may never have occurred.
The California Leaf-nosed Bat feeds on grasshoppers, cicadas, noctuid moths, caterpillars and various beetles. Studies indicate that it has a small foraging range, some colonies seeming to feed within only a few hundred yards of their daytime roosts. For these bats, the loss of old mines could be devastating.
Leaf-nosed bats also occur in abandoned mines in parts of Arizona and Nevada. It is hoped that similar protective measures will be undertaken by the BLM in these states as well.