What you didn’t know about Austin’s bat colony

Confession time. Even though I was raised in Central Texas and went to school in Austin (Hi, City Editor London here 👋 ), I’ve never gone to see the Austin bats.

So recently, I dove headfirst into the tradition and took a little trip over to the Congress Avenue Bridge at sunset. But being the journalist that I am, I did some research first. Here’s what I learned.

Bats are really cool

Austin’s roost of Mexican Free-Tailed Bats are estimated to make up the largest urban bat colony in the world . (The world’s largest non-urban bat colony is in San Antonio’s Bracken Cave, which contains 20 million bats .)

And these bats are pretty amazing.

For one, they’re tiny — between 0.4 to 0.5 ounces — but they can live as long as 18 years . With flight speeds up to 60 mph, they’re also considered the “jets” of the bat world.

The winged creatures also provide super effective pest control, with Austin’s colony eating between 10,000-30,000 pounds of insects per night.

Chowing down food is particularly important for the bats right now, as the Congress Avenue roost is actually a nursery: almost all of the colony’s bats are pregnant females . Starting next month, there’s going to be a real bat baby boom in downtown Austin as all of the pups are born, and by fall, as many as 1.5 million bats will be taking flight from the bridge every night.

(Another fun fact: In some roosts, the density of baby bats can be as high as 500 pups per square foot.)

Austinites didn’t always embrace the bats

Bats have been in Austin since before Austin was Austin, but for years they were considered pests. Locals know bats will roost in all kinds of human structures: construction sites, attics, abandoned buildings, bridges.

When the Congress Avenue Bridge was renovated in 1980, it made the perfect haven for migrating Mexican Free-Tailed Bats.

If you stand under the bridge and look up, you’ll notice several crevices, about one inch wide and 16-18 inches deep. These crevices are an ideal place for bats, which need dark, warm, and narrow roosts — and when the Congress Bridge was completed, hundreds of thousands of bats took advantage.

At first, Austinites panicked .

News of the “bat invasion” swept through the city, and hysteria spread until bat conservation groups — including Bat Conservation International , which promptly relocated its headquarters from Milwaukee to Austin — stepped in to educate officials about the benefits of the furry little creatures.

The city decided to leave the bats in place, and their nightly flight became a cherished Austin tradition. Now, it’s estimated bat tourism brings in millions of dollars in revenue to Austin every year.

See them yourself

The bats will stay in Austin until early fall, after which they will migrate their way south to Mexico + Central America for the winter season . Until then, the best times to see their nightly flights are on hot, dry evenings .

Finding parking can be a challenge, as nearby free lots can fill up fast. (Pro tip: Park somewhere along the Ann and Roy Butler Hike-and-Bike Trail and add a leisurely stroll to your visit — the path provides great views of the skyline at night.)

Next, pick your viewpoint. There’s standing room on the Congress Avenue Bridge, of course, and a small viewing space on the trail near the north bank of the lake, but I suggest the Statesman Bat Observation Center . It’s a grassy hill perfect for busting out a picnic blanket and settling in with a drink + snack. Next time I go to see the bats, I’d also like to try renting a paddleboard or kayak for a prime viewpoint from the water.

The bats can emerge any time in a two-hour range around sunset, so get ready to spend some time downtown. Even once they start taking flight, it can take as long as 45 minutes for them all to exit.

The last pro tip? Take lots of photos — and send your favorites to us @ATXtoday .