The Bats of Selah

The Chiroptorium –

Bamberger’s Folly

Entrance to the Chiroptorium, Bamberger’s man-made bat cave

If you’ve lived in the Hill Country long enough, you notice the changes that have been occurring as human population and urban growth have been chipping away at open space throughout the area. Worried that we are inflicting irreparable damage to Mother Nature, J. David wanted to build something that might mitigate the damage we are doing to the natural world. As more high lines and highways and rooftops continue to encroach on the natural world, could we build something that was strictly for Mother Nature?

Always a conservationist, J. David Bamberger was inspired to build his own bat cave on the Bamberger Ranch after years of volunteering with Bat Conservation International’ Bracken Cave project. The awesome sight of 20 million bats emerging nightly during the summer months from Bracken Cave outside of San Antonio would inspire even the weakest soul! J. David first looked for a limestone cave on his ranch to see if it could be properly excavated for bats. Finding nothing suitable, a site was chosen on the ranch that met several criteria: it be accessible for educational tours, and it would be designed in a way that the guano could easily be extracted, once bats inhabited the site. (See the How to Build a Bat Cave article from BCI web site chronicles the construction of the Chiroptorium. for more details). Plans are that once there is enough guano in the cave, we will use that as natural fertilizer on about 15 acres of improved pasture land. Currently we use chemical fertilizers on our Coastal Bermuda fields; pastures that we are able to heavily graze with cattle in times of drought and stress, thereby resting our native grass pastures. Once we begin using guano as opposed to chemicals, we will be able to certify our cattle as “organic”, which translates into real economic dollars.

Completed in 1998, the Chiroptorium is designed to house 1 million Mexican Free-tailed Bats. For the first few years, bats came and went. Most seemed to be travelers; they would stay for a few days or sometimes for a few months. There was much early publicity, as everyone was anxious to report about this eccentric project and predict what the results might be. Each summer, journalists and reporters would call for an update, and J. David and the staff kept a good sense of humor about the small numbers. Sometimes J. David would say that if it didn’t draw bats, we would turn it into a dinosaur exhibit for Margaret’s educational programs. Sometimes he would say it would be the world’s largest wine cellar. All the while, as the summers came and went and the bats did not arrive in big numbers, we worried about people calling this project “Bamberger’s Folly.” Scientists were always confident that they would come, but the media was never very patient.

Plagued with droughts, even the rural area caves reported smaller colonies. It seemed that nothing was working in our favor. Then in the summer of 2002, we noticed that several hundred bats came to the cave. There are three plate glass observation windows that would allow visitors to see bats at roosting height and each of those windows had smudge marks on them. We quickly figured out that as the bats circled to warm up before emerging from the cave, they were hitting the windows. We believed at that time that we had discovered the reason of why we could not keep a population: the bats left an area that hurt them. We developed two hypothesis: either they weren’t echolocating the smooth surface of the glass, or they were heading towards a minimal amount of light that was reflecting through the windows. So the staff did several things to the windows: we put black fabric on the exterior surface of some of the windows and we spray painted the interior of others. We wanted to see if it was the light or the smooth surface that was causing the bats to bang into the glass.

We fine-tuned our efforts with the glass in the winter of 2003 by putting up plywood on the windows and replacing the fabric that had torn from the previous attempt. Bats came that spring. Estimating several thousand in the early summer months of 2003, we believed that we had found the solution and we were happy. Then on August 5, 2003, J. David went up to the cave before sun-down to view his “several thousand” and what he saw changed the whole picture: several hundred thousand were emerging from the cave, coming out in a column over the road and flying off into the night sky. Strong emergences regularly lasted 30 minutes each night. Scientists estimated at that time that we had at least 200,000 bats and we were ecstatic! They stayed until the migration period back to Mexico in October. And we held our breath.

Bats returned this spring. We have estimated about 10,000 Mexican Free-tailed bats emerge every night, which takes about 5 minutes. But the best news came on June 22, 2004. Dr. Gary McCracken, a leading bat biologist who is studying the eating habits of Mexican Free-tailed Bats, came to the ranch before heading to his Uvalde research site. After viewing the five minute emergence, Dr. McCracken and several staff members went into the cave to see how much guano was on the ground. What they found was several meter squares of pups on the walls. Dr. McCracken estimated that about 5,000 pups roost in one-meter-square and we had several meters on the wall. Adult bats can roost 200 per square foot, and pups can roost up to 500 per square foot. This was incredibly exciting news, that we are a maternal colony!

All along, we have felt that once we were a maternal colony, we would be considered a success. This is no longer “Bamberger’s Folly” but rather “Bamberger’s Success”!