Bracken Cave Preserve
Jonathan Alonzo

Preserving Bracken Cave and the largest bat colony in the world

Located less than 20 miles from downtown San Antonio, Texas, Bracken Cave is a legendary bat roosting site, home to approximately 20 million Mexican free-tailed bats. Bat Conservation International (BCI) has spearheaded the protection of Bracken Cave for decades in order to preserve the majesty of this location for years to come. This effort was the culmination of outreach to raise public awareness and support, and close work with San Antonio politicians who were instrumental in the success of the purchase. Our Bracken Cave story is now a case study for conservation groups that are striving towards similarly ambitious goals.


Ensure Mexican free- tailed bat population at Bracken Cave is protected and healthy

Project Details

In 1992, we purchased Bracken Cave and the surrounding 4.7 acres of land to protect the largest single species colony of bats in North America. Nearly 25 years later, through a series of additional land purchases, that small initial acreage has grown by more than 300% into our 1,458-acre Bracken Cave Preserve.

Together, we co-manage 3,462 contiguous acres of rugged Texas Hill Country with The Nature Conservancy (TNC). This protected wild space is 20 miles east of San Antonio and less than ten miles from Interstate 35, amid one of the most rapidly urbanizing highway corridors in the United States. We have secured a meaningful buffer between the bats and the nearby growing human population, and developed a preserve that will serve as a home to the plants and animals that are native to the Texas Hill Country.

Bracken Cave Preserve
Jonathan Alonzo

Habitat Protection

We purchased more than 1,400 acres to create the Bracken Cave Preserve. The Nature Conservancy also dramatically aided the bats through a 1,521-acre purchase of neighboring land. For over a decade BCI has been monitoring Bracken Cave annually for the fungus that causes WNS disease and as a result of this monitoring BCI detected Pd, the fungus that causes WNS disease in February 2019. By 2025, with partner organization support, we aim to encourage a natural fire regime for Bracken Cave Preserve resulting in reduced need for prescribed burns.

Members at Bracken Cave
Jonathan Alonzo

Visit Bracken Cave

Bracken Cave contains the largest single-species bat colony in the world, with an estimated 20 million Tadarida brasiliensis, or Mexican free-tailed bats. The nearly 1,500 acre preserve ensures human encroachment and artificial lighting remain away from the bats’ roosting site. The preserve also protects important recharge zone for the Edwards Aquifer which supplies 90 percent of San Antonio’s water supply and critical nesting habitat for the endangered migratory Golden-cheeked warbler. We conduct evening guided tours to watch the hours-long dramatic departure of millions of bats.


We protect the 1,458 acres that are Bracken Cave Preserve, home to millions of Mexican free-tailed bats.