It’s peak bat season at the world’s largest bat colony, right in the Texas Hill Country

The Bracken Cave Preserve, outside of San Antonio, is home to as many as 20 million bats.

By Mose Buchele & Patricia Lim, KUTSeptember 27, 2023 10:45 amEnergy & Environment, KUT, Texas Newsroom

Patricia Lim / KUT

Millions of Mexican free-tailed bats fly out of Bracken Cave Preserve at sunset. Late summer is the peak season for viewing the bats because of their migration and reproduction cycles.

From KUT:

Bats in North America face a daunting list of challenges. Pesticides kill off the bugs they need for food, climate change disrupts their ecosystems and white nose syndrome — a deadly disease caused by an invasive fungus — threatens some species with near-extinction.

Despite all those challenges, you can still find active colonies all around Texas. And, for migrating species like the Mexican free-tailed bats, late summer and early fall is peak season for viewing.

By late August, bats born earlier in the year are big enough to fly. Their numbers swell the ranks of the colonies that pour out nightly from roosts all around the state.

Patricia Lim / KUT

"Squeak!" says a Mexican free-tailed bat in the hands of a scientist at Bracken Cave.

Soon, the majority of these bats will depart to happier hunting grounds south of the border, returning next year in reduced numbers. But, for the time being, this new generation living and hunting along with their parents means the colonies are bigger than at any other time of year.

The world’s biggest colony can be found right outside of San Antonio.

Bracken Cave Preserve is home to between 15 to 20 million bats. It’s recognized by Guinness World Records as the largest bat colony in the world.

The creatures emerge nightly from the cave in a tornado of leathery wings that spins upwards and unwinds into a massive ribbon of bats streaming to the horizon in search of insects. The colony eats about 400,000 pounds of bugs a night.

Patricia Lim / KUT

The Bracken Cave bat colony eats about 400,000 pounds of bugs a night.

While the bats come out to feast, others feast on them. On a recent night, hawks crashed into the swarm leaving the cave, flapping away with squeaky snacks. Barred owls swooped silently among the trees along the bats’ flightpath, while snakes slithered toward the bat cave entrance in search of unfortunate fallen flyers.

There are so many millions of bats that it takes hours for the cave to empty.

Bracken Cave, managed by the group Bat Conservation International, isn’t a place visitors can stop by unannounced. But BCI does offer reservationsevery year. They’re mostly for people who have paid a $45 membership fee, but the group saves some spots for the general public.

Patricia Lim / KUT

You can also find Mexican free-tailed bats all over Texas in caves, highway overpasses and bridges.

If you can’t make it to Bracken Cave, keep your eyes peeled. Mexican free-tailed bats roost all over Texas in caves, highway overpasses and bridges, like Austin’s Congress Avenue bridge, where the city’s famous urban bat colony lives.

They may be closer than you think!

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