New Life for Old Mines

Mike Rauschkolb, Borax land agent, remembers the first time he held a bat in his hand. In 2001, he was in the Gerstley mine near Death Valley, trying to determine whether to close the mine entirely or install a gate to allow resident Townsend's big-eared bats to come and go.

“ They are delicate creatures,” says Rauschkolb, a trained geologist who is now a certified bat enthusiast. “I couldn’t believe how mellow they are. Here was a bat purring away in my palm, no bigger than a pack of gum, its wings folded around it. You don’t feel any weight, just the shivering.”

A big-eared bat in full flight has a ten-inch wing span, but weighs less than the change you’d get back from buying a pack of Wrigley's. Enough bats, including big-eared, pipestrelle and pallid, were found roosting in the Gerstley mine to warrant the installation of two angle-iron gates at mine openings. The vertical spaces between bars are 5 inches by 24 inches – big enough to allow bats in, but small enough to prevent entry of people scavenging for carbide lamps and other mining artifacts. (In the late 1800s, some mines were abandoned so quickly that hats, lunchboxes, and in one case, candle-wax encrusted Levis, were left behind.

Four bat-gates were installed at another abandoned mine, the Lila C, near Death Valley Junction. Here bat biologist Dr. Patricia Brown, who consulted with Borax on the project, found a hibernating colony of big-eared bats.

There are hundreds of abandoned mines in the world, and they present many dangers to interlopers looking for adventure and artifacts: cave-ins, flooding, deadly gases and discarded explosives. But abandoned mines have also become home to half of the 24 bat species in California. Before backfilling, blasting, or sealing up mines with concrete, mining companies are now working with bat biologists to make sure that roosting or hibernating bats are not entombed.

When Mike Rauschkolb returned last July to the Gerstley mine, he was pleased to see that the bat population had increased from 64 to 79. At dusk he watched two bats fluttering near the bat gate. “It looked to me like a mother bat teaching a baby how to fly through the bars.”