SAN ANTONIO — As the sun sets every summer night at Bracken Cave in the Hill Country, a vortex of Mexican free-tailed bats rushes forth. For as long as four hours in the evening, a continuous stream of bats leaves the cave to dart south, over the tree line, for their nightly hunts. The scene at the cave is repeated in reverse at dawn when the bats return.
Making up the largest colony of flying mammals in the world, the bats can number as many as 20 million. But a plan to build a subdivision near the cave has conservationists worried about the colony’s fate — and the conflict over that plan is raising broader questions about San Antonio’s rapid growth.
“There’s nothing else like this in the world,” Fran Hutchins, Bat Conservation International's coordinator for the cave, said of the colony. “And we don’t really know what will happen if they build here.”
The cave’s size draws the bats to migrate from smaller caves to congregate and give birth. From March to October, every bat eats its weight in insects each night — from pesky mosquitos to harmful agricultural pests like the Cotton Boll moth.
Much of the land around the cave is protected. But Galo Properties of San Antonio, which owns a 1,500-acre property south of the cave, plans to develop the land into a 3,800-home subdivision, which the developer calls Crescent Hills.
“It’s uncanny how perfectly this development aligns with the bat’s flight path,” said Mylea Bayless, the director of conservation programs for Bat Conservation International. “If we come in and put high-density development right under the flight path, we’re creating a situation where bats and humans are going to be coming into regular contact.”
Bayless said the bats would likely hunt insects that congregate near the development’s outdoor lighting, near streetlights and porches. The animals, which drink while flying, might also find the development's swimming pools an excellent source of water. It would be only a matter of time, she added, before homeowners would talk about “the bat problem.”
The conservation group has a host of other concerns. They fear an increased potential for human exposure to sick bats. There’s also the possibility of trespassers in and around the cave, where dense guano deposits — more than 60 feet deep in parts of the cave — pose a high risk of toxicity and fire.
But Bayless said there aren’t many ways to contest development plans. The group has turned to the public, hoping outside pressure will encourage the city of San Antonio to take action. That’s led them to target the infrastructure that will allow the development to be built.
The land in question is in Comal County, outside of San Antonio city limits. But the San Antonio Water System has agreed to expand capacity for water mains and sewer lines to the proposed subdivision — the first such agreement SAWS has made with a subdivision entirely within Comal County. The oversized water mains the agency would build also allow easy expansion to future subdivisions in the area.
That has triggered other conservation groups to join in opposition to Crescent Hills, including the Greater Edwards Aquifer Alliance, a San Antonio-based organization that aims to slow development over the Edwards Aquifer recharge zone.
The conservation groups involved, and some residents of the area, are urging the city council to revoke SAWS’ plans to expand capacity to Comal County, which would force Galo Properties to reduce the density of the development.
San Antonio gets most of its water from the Edwards Aquifer, a large artesian aquifer that underlies most of the Texas Hill Country. The Edwards’ recharge zone includes the land where Crescent Hills would be located.
The recharge zone has seen significant development in recent years, decreasing the amount of land available to replenish the aquifer's stores.
Annalisa Peace, the Alliance’s executive director, said preventing the municipal water system from expanding its infrastructure to Comal County is critical to the aquifer's future.
“SAWS is trying to build infrastructure which will help expand growth in that area,” she said. “We’re trying to stop this because of the potential for other developments to tie onto that. It’s not just about this one developer.”
Galo Properties did not respond to requests for comment from the Tribune.
But Greg Flores, vice president of communications with SAWS, said that the agency is required by the state to expand capacity to the development. If SAWS refused, he said, the state could force the agency to do so or restrict its right to operate in a wider area.
“If there are areas where the city has the potential to grow in the future,” he said. “Then we are going to be there to support the city and provide the services for that growth.”
The aquifer debate has flared many times in recent years as San Antonio — now the seventh-largest city in the country — looks for room to expand.
But there are other environmental concerns — the land around Bracken Cave is also home to the Golden-cheeked Warbler, an endangered finch which breeds only in Central Texas, and a number of other at-risk species.
While there are concerns about other animals that currently make the future development their home, including the Golden-cheeked Warbler, Bracken Cave’s bat colony has catalyzed the most public opposition to Crescent Hills. More than 30 San Antonio residents attended a March 29 city council meeting, where they asked the city to take action against the subdivision. None of them spoke in favor of the development.
While talks with the project’s engineers have been cordial, the conservation group and residents say, the developer has expressed its intent to move forward with the project.
BCI and others have floated proposals to pay the developer to reduce density or to buy the land — though where the money would come from is unclear.
There’s also House Bill 36, filed during the special session by state Rep. Lyle Larson, R-San Antonio, that would put a moratorium on development near the cave until a study is conducted on its potential impact.
The project’s engineer, Gene Dawson, told the San Antonio Express-News last week that the company’s owner, Brad Galo, had the right to build on his own property.
“Galo is a developer. He builds subdivisions for a living,” he said. “BCI is welcome to buy this property and do whatever they want with it.”
For Hutchins of BCI, who gives public tours of Bracken Cave, the debate shows the human inclination for short-term thinking over long-term considerations.
“They’ve been here for 10,000 years,” Hutchins said of the bats. “But it wouldn’t take very long at all for them to disappear.”
Editor's note: This story has been updated to include comment from the San Antonio Water System.