About Austin's Bats

When people talk about Austin’s bats, they're usually referring to the world-famous colony that lives under the Ann W. Richards Congress Avenue Bridge. The species is officially known as the Brazilian free-tailed bat, although many still refer to them as Mexican free-tails. Whatever you call them, just remember — they appreciate it if you don't shine bright white lights on them while they’re emerging each evening

How many bats live under the bat bridge in Austin?

Each summer, the Congress Avenue Bridge in Austin becomes home to an impressive colony of up to 1.5 million Brazilian free-tailed bats. This makes it one of the largest urban bat colonies in the world — a breathtaking sight when they emerge at dusk.
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Why do bats like living under a bridge in downtown Austin?

When the Congress Avenue bridge was expanded in 1982, TXDOT added concrete support beams with narrow crevices about 16 to 18 inches deep. These spaces turned out to be the perfect home for bats — they love dark, cozy roosts where they can rest during the day and raise their pups safely.
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Do the bats live under the bridge all year?

Although many bats migrate south each fall, a portion of the colony — as many as 100,000 individuals — stays under the bridge all year. Even in mid-winter, you might catch tight, column-shaped emergences as they head out to feed. The true highlight of bat season, though, is late July through August, when up to 1.5 million bats take to the skies as the pups join their mothers on nightly flights.
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Most of the source data for these FAQs can be found on the website maintained by Merlin Tuttle’s Bat Conservation: https://www.austinbats.org/

Much more to come! Last updated 10/4/25