The Mexican Free-Tail Bats of Austin, Texas
Largest Urban Colony of Bats in the U.S. puts on Nightly Summer Show
May 14, 2009
Austin, the state capital and home to the University of Texas, is known as the "Live Music Capital of the World." It also takes pride in being the "Bat Capital of the World.", being the spring and summer home for a million and a half Mexican free-tail bats.
The Mexican Free-Tail Bat
The Mexican free-tail bat (Tadarida brasiliensis) is relatively small, less than four inches in length with a wingspan of about 13 inches and weighing less than a half ounce. The name comes from the fact that the lower half of their tail, unlike other bats, is free of the membrane. They are one of the most numerous mammals in North America, and crucial to the control of agricultural insect pests, eating millions of Cotton bollworm and other small moths each night. They are known as the "jet fighter" of all bats, flying up to 60 miles per hour and reaching altitudes as high as 10,000 feet.
The Bat Colony at Austin's Congress Avenue Bridge
As urbanization and other habitat encroachment has forced bats from natural roosting areas such as caves, the bats have adapted well to non-natural structures such as bridges and culverts. Expansion joints run under the Congress Avenue Bridge, and the Mexican free-tail bats have found these narrow crevices ideal roosts. Although only an inch wide, these joints can house as many as 200 bats in a single square foot of space.
The Texas Mexican free-tail bats winter in Mexico and migrate to Texas in March. About 750,000 pregnant females return to the nursing colony in Austin each year, making their home in the expansion joints under the Congress Avenue bridge. In June and July, each female bat gives birth to a single pup, and the young learn to fly five weeks later, joining the mothers in a nightly hunt for insects. Beginning in August, up to one and a half million bats emerge each evening. The bats emerge from under the bridge at sunset, putting on a show that lasts up to an hour and that draws tens of thousands of tourists from March through October, when the bats return to Mexico.
When and Where to See the Austin Bats
The Congress Avenue bridge crosses Lady Bird Lake (formerly Town Lake) just a few blocks south of the state capital. The primary city newspaper, The Austin American-Statesman, is headquartered at the south-east end of the bridge, and opens its parking lot to bat-viewers each evening at 6:00 p.m. The paper maintains a park-like Bat Observation Center between the parking area and the lake. This grassy area contains interpretive signs, and is an ideal place to watch the bats emerge from the nearby bridge.
The bats begin emerging as the sun sets, flying out from under the bridge and heading east above the lake. What begins as a trickle of bats, quickly turns into a river of darting objects, hurtling out from under the bridge at 35 miles per hour and accelerating across the sky. This torrent of bats lasts perhaps an hour, well beyond the daylight needed to see them.
For current flight times, call the Austin American-Statesman information line, 512-416-5700, category 3636. Additional information can be obtained from Bat Conservation International (BCI). BCI is an Austin-based non-profit organization founded to protect and preserve bats and their habitat.
Austin marks the eastern edge of the bird-rich Texas Hill Country, and lies within the Texas Bluebonnet belt. A great tourist destination for many reasons, Austin is also worth visiting just to experience the nightly Mexican free-tailed bat show.
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