Bat-watching along the banks of Austin's Town Lake and Congress Avenue Bridge is a time-honored tradition, and the source of an estimated $10 million in ecotourism revenue annually. Now Houston is capitalizing on bat bridges, too.
Standing atop the Waugh Drive bridge at Allen Parkway, a group gathers to hear TPWD urban biologist Diana Foss talk about Houston's bats, and to witness their nightly emergence. The Waugh Drive bridge has been an underground bat-watching mecca of sorts for the handful who knew about it. But bat-watching is about to take off. The event is the first of many bat-focused programs that will be led by the newly formed Houston Bat Project Team - a coalition of nonprofits, TPWD and the City of Houston.
Foss passes around photos and hands out bat detectors (devices that click when they detect the bats' echolocating signal) to the kids. Although the bridge has the same species, Mexican free-tailed bats (Tadarida brasiliensis), and the same type of crevice, the Waugh bridge colony differs from all others in Texas. "There are bats occupying the bridge crevices every month of the year," says Foss. "The other colonies in Texas migrate to Mexico, usually around September. "We can't say that they are ‘non-migratory' because we don't know if some Waugh bats leave and migrate to Mexico, and then others from other places migrate to Houston and fill in the crevices again."
To answer these and other questions, the Bat Patrol Team conducts emergence and roosting census counts. So far, there are as many questions as answers. How many? Where do they go at night? How many insects, including agricultural pests, do they consume?
As Foss talks, someone points to the sky. The bat emergence has begun. Bats pour out of the underside of the bridge in a seemingly endless stream, and bat detectors start clicking away. "It seems that the bats emerge from the crevices and create a tornado-like vortex beneath the bridge first," explains Foss. "They currently emerge on the east side of Waugh Drive bridge, usually a few minutes after sunset." As in Austin, the bats fly out over the water, along Buffalo Bayou.
The Waugh bridge is smaller than Austin's bridge, so the colony will always remain smaller, around 300,000 compared to Austin's 1.5 million, but it offers a much closer view. From atop the bridge, it's only a few feet to the bridge's underside. From beneath the bridge, it's easy to see the bats tucked in their cozy crevices, wings folded at their sides.
Bat Conservation International and the Texas Department of Transportation started a Bats and Bridges program in which the state now designs bat-friendly bridges. Besides Houston and Austin, bridges with confirmed colonies exist near Uvalde and Round Rock, and TPWD is seeking information on unknown bat bridges. Report new sightings to Meg Goodman at (512) 912-7042.
In Houston, local nonprofits plan to offer dusk bat-viewing boat tours of the bayou, and the Bat Project Team will continue to research the private lives of bats. On the third Friday of every month, TPWD has a team of volunteers available at the bridge to give a brief presentation and answer questions about the bats, prior to their emergence at sunset. The number for information is (281) 456-7029 (TPWD Urban Office) or (713) 845-1329 (Houston Parks Dept.) or visit www.houstonparks.org.
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