Protect Mega-Populations
Bracken Cave

Saving Bracken Cave

A Historic Land Conservation Deal Protects The World's Largest Bat Colony 


Millions of Mexican free-tailed bat spiral out of Bracken Cave.
Credit: Jonathan Alonzo.

When The Nature Conservancy (TNC) acquired the 1,521-acre Galo tract adjacent to Bracken Cave in the Texas Hill Country on Halloween in the fall of 2014, it brought to a happy conclusion an at-times frantic, 21-month effort to prevent 3,500 homes from being built under the nightly flight path of Bracken’s 15 million-plus Mexican free-tailed bats (Tadarida brasiliensis). BCI Bracken Cave Preserve Manager Fran Hutchins learned in January 2013 of Galo Properties’ new plans for a proposed subdivision, known as “Crescent Hills.” Earlier attempts to meet company representatives had gone unanswered; there things stood until Galo Properties came forward with its ambitious plan.

For BCI, it was a challenge like no other in its history: prevent development of a vital tract of land, twice the size of Bracken Cave Preserve and many times more expensive—not that the land was even for sale. But its protection was critical. Each night from March until November, Bracken’s bats—the world’s largest gathering of mammals—stream out of the cave at tree-top level, taking three to four hours to empty the cave. And almost every night, their path takes them over the Galo tract.

The developer had assumed—correctly—that his proposed houses would not interfere with the Cave per se, being no closer than 1,000 yards from its mouth. He offered to create a buffer strip along his common boundary with BCI. But free-tails love bridges and buildings and will congregate around street and porch lights catching moths, notes Hutchins. “For a bat that flies more than 100 miles each night in search of food, a thousand yards means nothing,” he adds. “The houses would have been a magnet for bats seeking new roosts, learning to fly, hunting insects or wanting a drink from a swimming pool.”

Bellingen Flyout

Put simply, placing 10,000 people under 15 million bats was sure to lead to trouble. A child playing with a sick or tired young bat—a likely occurrence with 5 million-plus baby bats nearby—found in a yard or brought into a house by a cat or dog would have to get rabies shots (which though no longer an ordeal, are nonetheless expensive: $900 to $1,000 for the series). A steady stream of such children and adults would lead to increasing resentment and fear in the community and ever-stronger efforts to remove the bats.

BCI also worried that curiosity would get the better of the 3,000 kids growing up in the neighborhood.

“Imagine if you were 13 and heard you lived next to the coolest cave in the world. Wouldn’t you want to go explore it?” says BCI U.S.-Canada Director Mylea Bayless. “But ammonia and carbon monoxide levels in the cave are dangerous to people, not to mention having to walk over or wade through ten thousand years of guano. It’s an extreme environment requiring special clothing and breathing devices.”


Grassroots Advocacy Fuels Action

juvenile Mexican free-tailed bats
Juvenile Mexican free-tailed bats getting ready to fly
at Bracken Cave. Credit: Jonathan Alonzo

To make matters more challenging, it became clear that under Texas state law, local jurisdictions had little authority to deny or alter development plans that did not violate current zoning. In the quiet ranchland corner of Comal County where Bracken and the Galo tracts are located, there is no zoning.

“We went from jurisdiction to jurisdiction looking for the place in the process where we could raise environmental concerns,” says Bayless. “It turned out there was no place.”

So BCI turned to its members. In just three weeks, more than 20,000 people signed a petition urging protection of Bracken Cave as a site of global importance and packed a May 2013 San Antonio City Council public forum. BCI’s social media followers jumped from 20,000 to 60,000. Other organizations began to help, including Taking Care of Texas, a conservation group founded by former First Lady Laura Bush; the Greater Edwards Aquifer Alliance; and the Texas chapter of The Nature Conservancy, which had bought land from Galo Properties in the past. Mrs. Bush advocated publicly for protection and introduced BCI staff to other key individuals in Texas. TNC and BCI, meanwhile, began meeting quietly with representatives of Galo Properties to see what could be done.

The media also took a strong interest. The New York Times and National Public Radio ran stories. Regional and local coverage were extensive, with San Antonio’s major daily, The Express-News, running a series of influential articles and editorials throughout the nearly two-year effort.

City Councilman Ron Nirenberg
City Councilman Ron Nirenberg Credit: Jon Alonzo

The next ingredient, influential political leadership, was provided by both sides of the political aisle. State Rep. Lyle Larson; Texas Speaker of the House Joe Straus; Bexar County’s Kevin Wolf and his father, Nelson Wolf; and others were all instrumental in bringing public and government attention to the issue. U.S. Congressman Lamar Smith was equally supportive—and a lover of Texas’ bats.

But it was then-San Antonio Mayor Julian Castro and the San Antonio City Council, including a recently elected first-time politician, Council Member Ron Nirenberg, who provided the final piece of the preservation puzzle. Nirenberg and the City recognized something else about the Galo tract: It was enormously important for recharging the Edwards Aquifer on which San Antonio, Austin and other Hill Country communities depend for drinking water and irrigation. With Texas in a multi-year drought, which climate change models suggest is only a foretaste, saving the Galo tract took on new significance.



Mutual Interests Find Resolution

Lets Celebrate!
Lets Celebrate! Credit: Marvin Gohlke Jr.

TNC, the City and BCI redoubled efforts to acquire the 1,521-acre property and over the summer of 2014 struck a $20.5 million deal. BCI pledged to raise at least $5 million in charitable gifts if the City of San Antonio would provide $5 million from its aquifer-protection fund. Forestar Real Estate Group, wanting to build a retirement center on a nearby golf course-residential complex, purchased what’s known as “impervious cover credits” from the Galo Tract for another $5 million. The Department of Defense, Bexar County, the Edwards Aquifer Authority and Green Spaces Alliance also contributed funds.

By closing, $16 million had been raised, enough for TNC’s international headquarters to approve a bridge loan allowing the Texas chapter to buy the property on Halloween. BCI and TNC are now working together to raise the final $5.5 million to repay the bridge loan. The two organizations will co-own and manage the land.

“Without Ron Nirenberg in particular, the project would probably not have happened,” says BCI Executive Director Andrew Walker. “He showed extraordinary leadership and patience throughout, bringing all parties ever closer together. It would have been a remarkable accomplishment for any politician, but for a newly elected leader it was almost unthinkable.”

But for San Antonio’s District 8 councilman it was a natural choice. “I think the entire public understood what the right thing to do was,” Nirenberg says. “The challenge for policymakers was there was no blueprint or game plan about how to make it happen.”

Bellingen Flyout
Left to right: Garry McCracken, Bettina Jary-Mathis, Joy Gaddy, Andrew
Walker and Mylea Bayless. Credit: Micaela Jemison
Often overlooked in these situations, however, is the role the landowner plays. Brad Galo saw that San Antonio was growing rapidly in the direction of Bracken Cave and sought to capitalize on that trend when he purchased this property more than 10 years ago. “It’s understandable that the complex issues regarding bats would not have been immediately apparent to him,” says Walker. “We owe him a debt of gratitude for selling the property at a fair and achievable price.”

“After years of work, this highly complex conservation deal came together with decisive action and investment from a broad spectrum of trusted partners,” says Laura Huffman, Texas state director of The Nature Conservancy. “Our collective efforts have resulted in a trifecta of conservation success for the entire region: safeguarding Bracken Bat Cave, preserving important habitat for warblers and safeguarding Texas’ most valuable resource: clean, fresh water.”

BCI and TNC, in addition to collaborating on fundraising, are beginning ecological management of the tract, removing junipers and other brush in advance of future controlled burns, which will benefit the federally endangered golden-cheeked warbler (Setophaga chrysoparia) and enhance the insect population on which Bracken’s juvenile bats depend as they learn to forage and fly. Planning for passive recreational use by the public is also underway. BCI will eventually build an interpretive visitor pavilion near the cave to accommodate the thousands of BCI Members, school and church groups, families and individuals who come to watch birds and, of course, bats.

“Working with BCI on the Crescent Hills/Galo acquisition has been a highlight of my career,” says TNC’s Jeff Francell. “I’ve never been involved in a local land acquisition project with such a range of support—from grassroots to local government to private philanthropy. The best part of the entire transaction has been the outcome, removing a serious threat and ensuring that Bracken Cave will never be surrounded by incompatible development.”

Bracken Cave Map

Visitation FAQs

Why isn’t Bracken open to the public to just stop by and go in?

  • The cave is located on private property that is owned, managed and protected by Bat Conservation International. To best protect this sensitive area, we must restrict access to small, reserved groups.


How do I visit Bracken Cave Preserve?

  • If you are interested in booking a private event or a group visit for your organization, please email This email address is being protected from spambots. You need JavaScript enabled to view it.
  • Individuals interested in visiting may do so by registering for a Member Bat Flight. You must be a member of BCI to register. Member Bat Flights are available each year on select dates from mid-May to mid-September. You can find the full Member Bat Flight schedule and information on how to register or how to become a member at


What are Member Bat Flights?


I am a member.  How many guests can I bring to a Member Bat Flight?

  • Members supporting BCI with a $45 annual membership and those who have added an annual membership to an adopt-a-bat: up to 3 guests for a total party of 4 including the member.
  • Members supporting BCI monthly or with a $60 annual membership: up to 5 guests for a total party of 6 including the member.  These members will also have earlier access to register for a Bat Flight.


I am a member. How often can I come?

  • Members can attend one Member Bat Flight at Bracken each season (1 Membership = 1 Member Bat Flight per year).


Why are Member Bat Flights only offered from mid-May through mid-September?

  • The Bats at Bracken Cave migrate south during the winter months.


What are the best months to view the bats?

  • July and August, because baby bats are born in June and begin flying in July; and days are longer which means more bat viewing time.


How long does the tour last?

  • Plan to stay 2-3 hours depending on sunset.
  • Please be on time.
  • We cannot predict exact times when the bats will emerge, so we meet early enough so visitors have time before the emergence to learn about this important maternity colony.


Can I leave early if I have something important to do?

  • Please be prepared to stay the entire 3 hours if you make a reservation with us. Arrangements can be made to leave early, please check with your guide upon arrival.


Where is the cave?

  • View Map. Turn left at “BCI Event” sign.


If I am disabled will I be able to make it to the cave?

  • If you have special accessibility needs, please let your guide know at check-in.


How far do I have to walk?

  • Approximately ½ mile on gravel trails.
    Please consider physical limitations and the Texas summer heat when planning your trip.


Can we bring alcohol?

  • No.


Can I bring my dog (pet)?

  • No, only trained service animals as defined by the ADA are permitted to enter the Preserve. Additionally, if a particular service animal is out of control and the handler does not take effective action to control it, or of the animal is not housebroken, the handler will be required to remove the animal from the premises. Additionally, it is too hot to leave any animal in your car.


Can I bring my baby?

  • Please use discretion if you are considering bringing young children. Because Bracken Cave is located in a natural, unimproved area, children need to be supervised at all times and cannot “run-free”– so keep this in mind when making your reservation.  Childcare services are NOT provided. Tours can last up to 4 hours and Texas summers are notoriously hot. We do not recommend bringing children under the age of 6 to Bracken for these reasons.


Can I smoke on the property?

  • No. Electronic cigarettes are also prohibited.


Can I bring a chair?

  • Not needed as we have benches.


Can I bring a snack?

  • Small snack foods are fine, but please, no coolers. Food attracts unwanted visitors, like fire ants and skunks.


What do I wear?

  • Comfortable clothes and closed-toed shoes.


What should I bring?

  • Cameras (please no flash photography), binoculars, sunscreen, bug repellant, and bottled water (again, no coolers please).


Are there bathrooms?

  • There is a unisex Port-a-John with hand sanitizer.


It’s Saturday but no one is answering my emails or phone calls. Why?

  • Please keep in mind that BCI is not open on the weekend thus reservation requests and questions are not processed until the following week.


Will my car make it in on the roads to the cave?

  • Roads leading to the cave are rough and dusty. You may need to wash your car after your trip to Bracken but other than that, you should be fine.
  • Motorcycles are not allowed on the preserve. Roads are rough and dusty and their noise disturbs the animals.
  • Motor homes and RV's are not allowed on the preserve, as the roads are rough and parking is limited.


Can we camp overnight?

  • Overnight camping is generally reserved for scouting and educational groups (fee applies). Please contact Fran Hutchins at This email address is being protected from spambots. You need JavaScript enabled to view it.  


Protecting a Jewel in Texas

BCI members watching the emergence from Bracken Cave

Bracken Cave is the summer home of more than 15 million Mexican free-tailed bats (Tadarida brasiliensis), making it the world's largest bat colony and one of the largest concentration of mammals on earth. The emergence of these millions of bats, as they spiral out of the cave at dusk for their nightly insect hunt, is an unforgettable sight.

Located less than 20 miles from downtown San Antonio, the cave has come under increasing threat of urbanization. If not for the generous donations of BCI's members and friends, the cave and its remarkable bats likely would have been engulfed by subdivisions. Bat Conservation International (BCI) first purchased the land on which the cave is located in 1992. Since then BCI and our conservation partners have continued to purchase land around the cave to conserve not only the bats, but also the many other native and endangered species found on the Bracken Cave Preserve. BCI stewards the entire property, protecting endangered birds and rehabilitating the land by removing invasive vegetation and reviving native plants.

The largest known bat maternity colony in the world

The bats of Bracken Cave comprise the largest known bat maternity colony in the world, producing millions of young each year. In March and April, expectant females return to Bracken after overwintering in Mexico. Most males roost elsewhere in smaller groups. In the latter part of June, females give birth to a single pup, nearly doubling the cave's population.

As the bats give birth, cave walls become densely packed with naked pups, clustering tightly at up to 500 per square foot. Babies roost separately from their mothers. Before leaving her infant in the nursery with the other pups, each mother spends up to an hour getting acquainted with her baby's scent and vocalizations. When she returns, she accomplishes a remarkable feat: she finds her own young among the millions of others vocalizing and straining for attention. She nurses her baby at least twice a day.

Juvenile Mexican free-tailed bats and their mother
Juvenile Mexican free-tailed bats and their mother

After four to five weeks, youngsters begin learning to fly under the most difficult of conditions. If all goes well on its first flight, a young bat drops into complete darkness, flies at a speed of at least 20 feet per second, and turns an almost complete somersault with millimeter precision to land on the cave wall just seconds after taking off. It must also avoid several collisions a second with thousands of other young fliers testing their skills, while at the same time relying on a echolocation system that is itself being tested for the first time.

Collisions with other bats or cave walls can be fatal. An emergency landing is certain death; the floor is teeming with millions of carnivorous dermestid beetles that can reduce a young bat to a cleaned skeletown within a few minutes. Fatalities are high, and at least half won't survive their first year.

By late July, young bats are ready to test their flight skills outside the cave, joining their mothers to feed on insects. Although they are weaned soon after, their initial energy demands are high, forcing nursing mothers to consume more than their body weight in insects each night. To find sufficient food, the bats often emerge up to three hours before sundown, creating one of the most spectacular sights in all nature, an event spanning several hours.

Bracken Video Carousel

Residents of Bracken Cave: Hawks

Weather & Emergence Times

Current emergence times at Bracken Cave are approximately 7:30 PM.

Current Bracken Weather


Bats and Doppler Weather Radar

Did you know that weather radar systems track bats through the night over Central Texas? When millions of Mexican free-tailed bats leave Bracken Cave and other roosts each summer evening to hunt down insect pests, they appear on radar images as great mobile clouds. The looped map below is in relative real time (2-10 minute lag).

Don't forget to come back and see this activity during emergence times!


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