The Congress Avenue Bridge spans Town Lake in downtown Austin, TX and is home to the largest urban bat colony in North America. The colony is estimated at 1.5 million Mexican free-tail bats that migrate each spring from central Mexico. Each night from mid-March to November, the bats emerge from under the bridge at dusk to blanket the sky as they head out to forage for food. During the best flights, up to five columns of emerging bats can be seen for miles as much as 45 minutes before sunset.
In 1980, while reconstructing the Congress Avenue Bridge in downtown Austin, bridge engineers had no idea that new crevices created beneath the bridge would make an ideal place for a bat roost. Even though they had lived there for years, it was headline news when bats suddenly began moving in under the Austin bridge by the thousands. After the novelty of this unusual occurrence had worn off, the public began to react in fear. Many activists within the Austin community began petitioning to have the colony eradicated.
About that time, a group now know as Bat Conservation International, stepped in and began an educational process about the bats. They educated Austinites to the fact that they are gentle and incredibly sophisticated animals, and that they eat from 10,000 to 30,000 pounds of insects, including mosquitoes, each night.
The campaign proved to be successful as Austin came to appreciate its bats and even erected a bat sculpture in honor of this unique and spectacular mammal. They emerge at different times every night, but the hotter and drier the weather gets, the earlier they will get hungry and set out for food. August is the best viewing month, not only because they come out before sundown, but because the newborn bats (called pups) are just beginning to forage with their mothers.
Most of the colony is female, and in early June each one gives birth to a single pup. The pink, hairless babies grow to be about three to four inches long, with a wingspan of up to a foot. In just five weeks, they'll learn to fly and hunt insects on their own.
The bat flights have become one of the most spectacular and unusual tourist attractions in Texas. There are several points from which to view the event, and an information kiosk is located on the north bank of the river, just east of the bridge. A study made in 1999 by Dr Gail R. Ryser and Roxana Popovici concludes that the economic impact of the bats to Austin city is $7.9 million each year. Today, businesses are using the bats as a symbol for Austin.
Interesting Bat Facts
Bats Season is Mid-March to Early November
Bats can live to be 30 years old.
Mother bats give birth to a single pup each year. The pups birth weight is nearly 1/3 that of its mother.
Bats are mammals and nurse the pups from mammary glands. Each female recognizes her pups voice and smell and will nurse only her pup.
During migrations to Mexico and back, bats may reach an altitude of 10,000 feet and velocities of 60 miles per hour.