The Volunteers of Bracken Cave

very summer, 20 million Mexican free-tailed bats (Tadarida brasiliensis) make Bracken Cave their home. The world’s largest bat maternity colony, where females give birth to their pups and raise them, is nestled in Bracken Cave Preserve, near San Antonio, Texas. In 1992, Bat Conservation International (BCI) purchased the cave and 4.7 surrounding acres, making this year the 30th anniversary of BCI’s management of the cave.

Throughout the years, BCI has worked with The Nature Conservancy and other partners to protect an area around the cave, and the preserve is now 1,458 acres.

Located just 20 miles from San Antonio—and just 10 miles from Interstate 35—the area has been subject to intense development pressure over the years. One project alone was slated to build 3,500 homes next to the cave, but BCI and partners successfully pushed back to halt the project.

The preserve is a vital home for bats, and it is also an important living laboratory, providing scientists with a place to study not just bats, but plants, birds, and invertebrates, including insects like the Texas giant walking stick.

While the cave is not open to the public, members can visit to watch the bats emerge on special member night events. With rugged terrain, Ashe juniper, and an abundance of prickly pear—along with a lack of roads—access was challenging in the early years. In the mid-1990s, BCI hosted just four member nights each year, but now several thousand visitors a year enjoy watching the bats emerge during summer evenings.

A crew of dedicated volunteers keeps it all running, from giving talks and presentations, to handling parking and the gate, greeting people, and helping with land management and restoration.

“Our volunteers are invaluable,” says Bracken Cave Preserve Director Fran Hutchins. “We have a dedicated group of people who spend their time sharing bats with the world and caring for this incredible place. They make what we do possible.”

Edith and Don Bergquist began volunteering at the cave around 2007. When they moved to San Antonio 22 years ago from St. Louis, they purchased a lot in a subdivision that backs up to the Bracken Cave Preserve property. But, like many of their neighbors, they didn’t realize the cave was there at first.

Don focuses on preparing and giving presentations, and both help with property maintenance like weed eating, mowing, moving rocks, as well as mapping the roads on the property and charting them on an app. They also both help with fire protection by removing some lower tree limbs. “We live in an Ashe juniper and oak ecosystem, and it’s very dense, so we ‘limb up’ for fire protection,” Don explains.

They also assist scientists with research, including helping one scientist find the green darner dragonfly she sought. Volunteers keep track of life on the preserve and assist with BioBlitzes, where people come out and chronicle the insects, animals, and plants they see, logging their finds on iNaturalist.

On member nights, volunteers will take their positions around the preserve, with some stationed at the gate to welcome people, some coordinating parking, and others giving presentations and talks by the guano mining shaft, sinkhole, and overlook. While waiting for the bats to emerge for the evening, these docents share their knowledge about bats, geology, topography, and other topics.

Heidi Forgione has volunteered at Bracken Cave since 2016. She completed the Texas master naturalist program, then started volunteering at the cave, which is just 10 minutes from her home. She began helping with property maintenance, as well as bat flight events. Last summer, she increased her role to also give bat talks and help with administrative tasks.

Her background is as a physical therapist, and she didn’t have any bat experience before she began volunteering, but she found she loved volunteering in the preserve and watching the bats.

“Every bat flight is a memorable moment,” Heidi says. “I don’t know how many I’ve seen, but it’s something that never gets old. It’s spellbinding and mesmerizing, and I love seeing people’s reactions to it. We have people who have seen bat flights in other places and their jaw drops when they see the one at Bracken. It seems to not be like any other that people experience in other places.”

Describing the awe and wonder of millions of bats emerging from the cave in a “batnado,” she says, “To me, it almost sounds like I’m by a body of water. The flapping of the bat wings is like being by the sea with the waves lapping by the shore. To hear it and to have no other background noise, you feel the little breeze, and it’s almost like it transports you to a different place.”

Edith adds, “It never gets old. It really is a joy to see the excitement of people when they didn’t think they would like it and suddenly fell in love with it.”