The arrival of Brazilian free-tailed bats at the Congress Avenue Bridge began soon after the structure, which connects downtown to south Austin, was expanded in 1982. Texas Department of Transportation engineers built a four-lane bridge of concrete box beams, many separated by crevices 3/4 to 1 1/2 inches wide. Each crevice was 16 to 18 inches deep and was capped by the bridge's road surface. The department's special projects engineer, Mark Bloschock, said the crevices created, quite unintentionally, an ideal home for the bats, which seek dark, warm, narrow roosts in which to sleep during the day and to nurse their pups, born each June.
"Bats Sink Teeth Into City," read the newspaper headlines over 35 years ago. Citizens signed petitions to have the bats eradicated. "Mass Fear in the Air as Bats Invade City," the local paper proclaimed.
That's when Merlin Tuttle, founder of Merlin Tuttle's Bat Conservation, began his campaign to save the Austin bats.
"He came to talk to city officials about bats and their ecological value," said Barbara French, a biologist. "Just this colony alone is eating tens of thousands of insects in a single night, including the moths that lay eggs that eat crops and especially the corn earworm that attacks corn, cotton and tobacco."
Tuttle used "brilliant, non-confrontational environmentalism," recalled Bloschock, whose job with the Texas Department of Transportation included evaluating which state-built bridges and culverts should be used as man-made roosts for bats. "You don't get in anybody's face; you deal with the facts and you educate people and let them make their decisions."
It worked. The bat colony was left alone and now it flies in every Spring from Mexico and begins leaving with cold fronts in October or November. The bats have proven to be invaluable neighbors, providing essential pest control, attracting millions of tourists, all while decorating Austin's night skies.