Discover Austin: The Bats - Episode 41

This episode of Discover Austin features the largest colony of Mexican free-tailed bats.  They live in the heart of Austin for much of the year, under the Congress Avenue bridge.  If you'd prefer to to read about the bats, the script can be found below the video.

Other Discover Austin topics mentioned or seen in this episode: Lady Bird Lake

During the peak season of late July and early August, there are 1.5 million Mexican free-tailed bats that live under the bridge.  Each night starting around sunset, they fly out in search of insects to eat.  The bats are gone for much of the night, generally returning less than an hour before sunrise.

Though the Congress Avenue Bridge originally opened in 1910, the bats didn’t appear until 1980 after a reconstruction project changed the underside of the bridge into a bat-friendly haven.  As we say in real estate, Location, Location, Location.  The bats loved the changes made to the bridge and brought their friends.

The bats migrate from Mexico in late February.  The colony is entirely female and they arrive in Austin already pregnant.  At this point, the colony numbers around 750,000 and is predominantly bats who have previously lived under the bridge as they usually return to the same location each year.  By early June, the bats give birth to one pup each, doubling the size of the colony to 1.5 million bats.  For about 5 weeks, the pups remain at the bridge while the mothers fly out each night for food them come back to nurse.  The mother and baby bats use sound and smell to identify each other reuniting among the massive colony.  By late July, the pups are ready to fly and all 1.5 million bats head out for food which is why this time of year is the best for viewing as there are so many bats leaving the bridge each night.  As the pups get larger, the bridge gets more crowded and some bats leave in search of a new home so the populations drops a bit starting around mid August.   Sometime in late October or early November, the bats begin to migrate back to Mexico, though generally a few thousand stick around all winter.

There are several ways to view the bats.  You can line up along the top of the east side bridge and watch them fly out from underneath you, but it gets harder to see the bats as it gets darker.  A popular spot is  the Austin-American Statesman’s Bat Observation Center, which is the land under the southeast corner of the bridge.  When you watch from here, you see the bats fly out silhouetted against the sky and streetlights.  If you’d like to watch from the water, there are also a number of boat cruises available.

Watching the bats leave the bridge really is a sight to behold.

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