As the city came to appreciate its bats, the population under the Congress Avenue Bridge grew to be the largest urban bat colony in North America. With up to 1.5 million bats spiraling into the summer sunset, Austin now has one of the most unusual and fascinating tourist attractions anywhere!
Congress Avenue Bridge's bats are mostly Mexican free-tails (Tadarida brasiliensis). These bats migrate each spring from central Mexico. Most of the colony is female, and early June each one gives birth to a single baby bat. At birth the babies weigh one-third as much as their mothers (the equivalent of a human giving birth to a 40-pound child!). The pink, hairless babies will grow to be about three to four inches long, with a wingspan of up to a foot. In just five weeks, they will learn to fly and hunt insects on their own. Until that time, each Mother bat locates her pup (baby bat) among the thousands by its distinctive voice and scent.
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