SAN ANTONIO – One by one, they emerge, and as the sun sets, they’re on a mission. The Bracken Cave Preserve north of San Antonio is home to an estimated 20 million Mexican Free-tailed bats that are vital to our ecosystem.
A KSAT crew visited the cave recently to get an up-close look at this Texas Hill Country phenomenon.
“They’re coming out for dinner. They’re going to come out and forage all night long, flying at least 60 miles away,” said Fran Hutchins, bat conservation international director at Bracken Cave Preserve.
The Mexican Free-tailed bats have become a sight to see. They migrate from Mexico to the Hill Country in mid-February.
“They’re here all summer long to have their babies, and they’ll be leaving somewhere around Thanksgiving, early November. When we get our first big cold snap, they’ll be heading back south to Mexico,” said Hutchins.
As millions of bats fly out of the cave, they create what’s called a “batnado” to help get thousands of their colonies in the air.
“The bats are coming out of the bottom of an 80-foot deep sinkhole, so spiraling out in a counterclockwise vortex. We call it a ‘batnado,’” said Hutchins. “When they drop off the ceiling, the vortex is spiraling. The vortex allows those smaller groups to get together, so they’re out foraging together.”
Hutchins said the bats will consume over 150 tons of bugs and insects on any given night.
“Most of those bugs are going to be agricultural pests, so they’re real important to our local farmers for all the agricultural pests that they eat,” said Hutchins. “That saves farmers money, saves us money. We don’t have pesticides being sprayed on the crops and contaminating our water. It’s a win-win for our farmers and the bats.”
While the Mexican Free-tailed bats are the main tenants, they aren’t the only bat species in our area.
Wildlife biologist Jeremiah McKinney is conducting an acoustic survey at Natural Bridge Caverns to identify how many species call the San Antonio area home.
“We’ve documented, with the software indicating possibly 16 species at the ranch, which is a very wide array of species,” said McKinney.
Unlike the Mexican Free-tailed bats, many of these species are tree bats, and in the past 15 years, these experts say urbanization and drought are their biggest threats.
“You’re obviously losing diversity because they’re having to search far and wide to get to water,” said McKinney.
“We have 32 different species of bats that call Texas home,” said Hutchins. “When we’re losing that green space, we’re losing that habitat for those bats.”
On the evening we visited, the bats came out of the cave earlier than usual, a sign they may have to stay out longer to forage for food.
“The amount of rainfall we have in the area affects the amount of food for the bats. It’s been over 100 degrees for the last couple of months every day,” said Hutchins. “We see all the crops that are crispy brown out in the fields. They have to come out earlier in the evening to be out long enough to get enough to eat. More rainfall means our crops are doing really well, means more food, so the bats don’t have to work as hard.”
The winds on this night are directing the Free-tailed bats to the southeast, taking them as far away as Pleasanton before they return home to rest and do it again the next evening.
“You can’t beat being here because you can hear the bats, you can smell the bats and you can see the bats,” said Hutchins. “This emergence that we’re seeing right now is going to last for at least three and a half hours.”