Man-made Cave to Offer Bats Haven from Disease

Sep 14, 2012

New tenants wanted: must be quiet during the day, must enjoy bugs. It might not sound like your kind of real estate, but then, you’re not a bat.

A new man-made cave near Clarksville is being built to give thousands of bats a safe haven from a devastating infection called white-nose syndrome; the experimental project may house bats’ best hope against the disease.

The construction is a concrete box about as long as a basketball court, but only half as wide. For insulation, earthmovers have been dumping four feet of dirt on top.

“I was wondering what it is, what this place is for,” says worker Elko Husinovic, “but my boss told me it’s for bats, whatever, I was like ‘cool.’”

The unique features inside include surveillance cameras that detect heat without getting warm – or making any noise. That’s because even ultrasonic sound could be a deal-breaker for house-hunting bats.

What’s meant to set the man-made cave apart from a natural one is it can be disinfected. A mysterious fungus that kills bats wholesale is spreading; it grows like white fuzz on their faces and wings as they hibernate. The idea is to build bats a cleanable winter home where white-nose syndrome can’t run wild.

“If we get the conditions right,” says Cory Holliday, biologist for The Nature Conservancy, “there could be over 200 thousand bats here, is what we’ve estimated.”

Holliday hopes a few hundred trend-setters will move in this winter, and tell their friends: “And we will be broadcasting sort-of ultrasonic bat calls from around the entrance area, just hoping to draw them in.”

Just a few winters

There’s serious pressure to get lots of bats hibernating in the cave, and soon. Early stages of white-nose have already been found in a big cave next door, perhaps unwittingly brought home from other bats. And it often takes just a few winters to ravage a sleeping population.

Ann Froschauer works for the U.S. Fish and Wildlife Service in Massachusetts. Since it was first found in New England six years ago, the disease has spread from Canada to Alabama, leaving millions of dead bats in its wake. Froschauer witnessed firsthand one of the worst die-offs.

She says the cave floor was strewn with long, skinny bones. In her mind they were like pine needles.

“I knew that that’s not what it was,” Froschauer says, “but it was just really impossible for me to understand there’s an inch and a half, two-inch thick carpet of just bones on the floor here, and skulls, and if you crouch down and look, you can see there’s little clumps of fur and decaying tissue.”

Froschauer cried when she got home. Bats often live decades, and she’d just seen whole generations undone.

Not easy to replace

Biologists fear regional extinction – and they say it could be expensive. Bats provide a kind of insect control service, eating crop pests. Some have pegged the agricultural value of eating so many bugs in the billions, if not tens of billions. When bats die, Froschauer says they’re not easy to replace.

“They’re very slow reproducers – one pup a year. They’re very labor-intensive babies, just like human babies. They’re breast-fed milk by their mothers and take a lot of work. So even if this disease were to stop in its tracks today, and we were to stop seeing the mortality that we’ve been seeing with the disease, it would take hundreds and hundreds of years to repopulate.”

That’s part of what’s driving the artificial cave project. Aside from efforts to fence caves off so humans don’t spread white-nose, Cory Holliday says there hasn’t been much people could really do to stem the disease. Some have pondered treating or vaccinating bats, but Holliday thinks the man-made cave could save more bats, faster.

“We would’ve liked to have had more time,” he says, “but with white-nose syndrome moving as rapidly as it is, we just didn’t feel like we had that time.”

That’s why The Nature Conservancy fronted a big part of the $300 thousand to build the man-made cave. If it succeeds, Holliday hopes similar artificial caves will follow, and leave enough bats, with enough time to move in.