Bat lovers can once again partake in a Texas summer ritual: enjoying the natural spectacle of millions of Mexican free-tailed bats emerging from their roosts each evening.

Mexican free-tailed bats, the species most prevalent in San Antonio and the Texas Hill Country, are thriving, according to Texas Parks and Wildlife bat biologist Nathan Fuller. Fuller said that although at least 50,000 individual bats perished during Winter Storm Uri, the multiple days of sub-freezing temperatures in February 2021, the population is in good shape.

“With 35 species of bats in Texas, the Mexican free-tail is the bat everyone thinks about, and it appears to be doing pretty well. But all the others are under threat,” said Fuller.

The San Antonio area is home to the world’s largest known bat colony — the Bracken Cave Preserve — with a population so large the bats’ nightly emergence shows up on weather forecasters’ radar.

Each of the flying mammals consumes thousands of insects each evening, helping keep the ecosystem balanced. Bats help farmers save an estimated $23 billion per year by eating half their body weight in insects.

“They’re cute, interesting, awesome and can tip off humanity when the ecosystem needs attention, because they’re sensitive to that stuff,” Fuller said. “They’re these little shrewlike things that lived in the shadows of dinosaurs and became these dominant aerial insectivores of the nighttime sky.”

The Mexican free-tailed bat community in Texas eats millions of corn earworm moths and other crop pests. The Bracken Cave Preserve colony alone is estimated to consume more than 100 tons of these moths every summer night, according to Bat Conservation International (BCI), an Austin-based organization dedicated to protecting the mammalian pollinators.

Numerous bat roosts exist in our area, with Hill Country caves and urban bridges serving as bat-watching sites. Nine of the 12 bat viewing sites in the state are in the Texas Hill Country, most within a two-hour drive of San Antonio, according to Texas Parks and Wildlife.

Here are three spots for watching bats emerge during the summer months.

Camden St. Bridge

It’s not as dramatic as Austin’s Congress St. Bridge, but it’s right here in town, a short walk along the river just south of the Pearl. Parking is sometimes available around Camden and Newell streets for a quick stroll down to the bridge.

Each summer, a summer bachelor colony of about 50,000 male Mexican free-tailed bats roosts under the bridge. Each evening, the bats emerge from the concrete rafters under Interstate 35 at Camden Street and plow the skies for insects.

The San Antonio River Authority hosted an annual Bat Loco celebration for several years, but the event was discontinued during the COVID-19 pandemic. For now, no plans exist to revive the popular bat-centric event, according to SARA.

That said, anyone can mosey on over to the Camden St. Bridge around dusk and wait for the bats to start winging their way out of the concrete beams supporting the bridge. Typically, emergences occur during spring and summer 30 to 40 minutes on either side of sundown, and the bats generally emerge earlier during droughts because they have to forage more.

More information on the Camden Street site is available here. Fuller recommended calling the BCI bat hotline for the Congress Ave. Bridge in Austin to get a good idea of when the bats will emerge at Camden Street, since the urban bridge ecosystems are similar.

Bracken Cave Preserve

Mexican free-tailed bats emerge from Bracken Cave to feed as the sun sets.
Mexican free-tailed bats emerge from Bracken Cave to feed as the sun sets. Credit: Courtesy / Monika Maeckle

The best opportunity to view bats nearby occurs at Bracken Cave Preserve, about 25 miles north of San Antonio. Bat Conservation International oversees the colony, which is the largest known collection of mammals in the world.

This is a maternal colony of 6 million to 10 million bats. The population of the all-female colony doubles over the summer as the pups are born and increase the size of the colony. The spectacle becomes more dramatic as summer progresses, since the baby bats join their moms at some point to go insect hunting.

Access to the preserve where the cave is located is restricted to select weekends. Reservations are required and can be made online, with tickets/QR codes issued in advance, and presented at the preserve. More information is available here.

BCI membership (starts at $45) includes access to free member nights to which members can bring three guests. Member nights are scheduled throughout the season. For nonmembers, the cost to see the bat flight is $30 per person on public viewing nights. Both member and nonmember nights fill up quickly, so if you want to attend, book early.

The outing includes a quick overview and Q&A by BCI staff or docents. After the presentation, the group of about 50 moves to mouth of the cave, formerly a sinkhole, where benches and rocks serve as seating. Once the bats start emerging in a vortex known as a “bat-nado” the show is on and continues for hours.

Eckert James River Bat Cave

If you’re up for a more adventurous outing, consider a visit to the Eckert James River Bat Cave outside Mason, located about a two-hour drive northwest of San Antonio. The cave is operated by The Nature Conservancy of Texas and will be open for the first time in three years on most Fridays and Saturdays, June 10-Aug. 27. The Nature Conservancy encourages would-be visitors to call 325-347-5970 to confirm that the cave will be open, pending weather or other possible complications.

This maternal colony at this cave bloats from 2 million to 4 million bats over the summer as the babies get big enough to fly.

The cave is not wheelchair accessible, entails an exciting low water crossing for your vehicle and requires a short hike up a trail. There, a small outdoor seating area allows for an up-close view, as a trained docent offers a tutorial on the bats and their life cycle.

This ranks among the most intimate bat-watching experiences, as visitors perch on the rim of the cave as the bats emerge at dusk, swirling in their “bat-nado” as they climb into the skies for insect feeding.

For a complete list of bat caves open to the public, check out the Texas Parks and Wildlife Bat-Watching Sites Guide.

Threats to bats

Much of the goal of encouraging Texans to view bat colonies is to make people aware of the broader threats facing bats worldwide.

White-nose syndrome, a bat-centric disease caused by a fungus that prefers cool temperatures, continues to plague the nocturnal mammals. The disease causes a fuzzy white fungus to spread across the bat’s nose and body. The bats get dehydrated because of resulting infection, which rouses them from their hibernative state, known as torpor. This makes them wake up and burn energy, depleting the stored fats that typically get them through the winter. Many don’t make it.

Wind turbines and climate change also pose serious threats, but the Mexican free-tailed population is so robust that conservationists are relatively confident about its future at this time.

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Monika Maeckle

San Antonio Report co-founder Monika Maeckle writes about pollinators, native plants, and the ecosystems that sustain them at the Texas Butterfly Ranch website. She is also the founder and director of...