SAN ANTONIO – The world’s largest bat colony can be found at Bracken Cave, just 20 minutes outside the city of San Antonio.
Every June, the Mexican free-tailed bats at Bracken Cave give birth to one pup each, bringing the total population up to about 20 million bats.
The pups start flying in July which makes visiting the cave in July and August the best for bat viewing, according to Bat Conservation International.
“This vortex, a swirling ‘batnado,’ will start rising out of the sinkhole, and once they get up to the tree-top levels, they’ll start streaming away from the cave. They stay tight, like a river of bats, because of predators in the area,” said Bracken Cave director Fran Hutchins.
The cave isn’t open to the public but members of BCI are typically able to view the bat emergence on certain designated nights each year.
Bats are incredibly important to Texas for many reasons.
For one, bats help the environment by eating their body weight in bugs every night.
"This colony tonight, when they go out to feed, is going to eat somewhere in the neighborhood of 140-147 tons of insects. Most of those insects are what we call ‘crop pests,’ and that’s going to save farmers in the Texas Hill Country hundreds of thousands of dollars every season,” Hutchins said.
This cuts down on the amount of pesticide farmers have to use for their crops, and in turn, helps keep chemicals out of the air and out of the food, which helps the people who live in South Texas.
Bats are also considered a keystone species that is vital to certain ecosystems.
Without bats’ pollination and seed-dispersing services, local ecosystems could gradually collapse as plants fail to provide food and cover for wildlife species near the base of the food chain, according to Batcon.org.
Love margaritas? The agave plant, which produces an essential ingredient in tequila, depends on bats for pollination.
Other products that depend on bats for pollination are bananas, peaches, cloves and balsa wood. This doesn’t include the hundreds of plants and flowers that count on bats to survive.
Regenerating forests after clear-cutting is a multifaceted process that requires animals to scatter seeds. Birds are cautious about crossing large open areas because of predators -- cue the bats.
Fruit bats forage at night and cover great exposed distances. They disseminate huge amounts of seeds necessary for reforestation.
Threats to survival
“They’re losing habitat like these caves that we have all over Central Texas. Wind farms are killing hundreds of thousands of bats every year, and now in Texas we have the fungus that causes the white-nose syndrome disease,” Hutchins said.
White-nose syndrome is a deadly fungus that has killed millions of bats in North America and Canada, with some states seeing a 90 percent decrease in their bat populations.
The fungus has already been detected on species of hibernating bats in North Texas counties and has also been detected at Bracken Cave.
Importance to the ecosystem
The Bracken Cave bat colony is listed as a species of greatest concern and their loss could be devastating for the environment and the South Texas ecosystem, said cave director Fran Hutchins, with Bat Conservation International.
Raising awareness and educating the public about the importance of bats is key to their sustainability and survival.
“We should really be paying attention to how logging, oil and even wind industries are affecting wildlife populations, including bats,” said Jennifer Tucker, president of Sticks and Stones Bat Rescue.
Bat Conservation International has purchased the land where the cave is located and approximately 1,500 acres around the cave, also known as the Galo Tract, “to conserve not only the bats, but also the many other native and endangered species found on the Bracken Cave Preserve,” according to Batcon.org.
This land purchase was a win for the bats after a 21-month long effort to deter a builder from putting a 3,500 home neighborhood in the flight path of the free-tails.
“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,” Hutchins said.
Bats aren’t dangerous, but the housing development could have potentially negative repercussions. Kids are curious and might go try and search for the cave. Dogs might find an injured bat and get bitten. Rabies shots can be expensive and it could potentially lead to resentment of the free-tails, experts said.
A 2013 grassroots campaign to stop the development was a success.
Then-councilman Ron Nirenberg recognized the land as vital for recharging Edwards Aquifer, which led to BCI’s acquisition of the Galo Tract, according to Hutchins.
There are now 3,500 acres of protected land surrounding the cave, including the 2,000 acres that belong to the Texas Nature Conservancy.
“Thirty-five hundred acres that’s now a preserve to protect the Edwards Aquifer recharge zone, which protects the aquifer, habitat for the Golden Cheek Warblers, which is an endangered migratory songbird, and we’re protecting this cave of Mexican free-tailed bats forever. So that’s a great thing,” Hutchins said.