Though we see bat imagery all over Austin, many Austinites have yet to experience one of the most incredible sights that takes place along one of our busiest streets every year from March to November.
Underneath the Ann W. Richards Congress Avenue Bridge lives the largest urban bat colony in North America. When they emerge in the evening during “bat season,” it’s like a cloud flying toward the east.
There are several locations where you can see the group of bats. The Austin-American Statesman park on the southeast side of the South Congress Bridge is free and open to the public. There is also standing room along the sidewalk of the bridge itself. Another way to see the bats and the city is to take a boat ride on Lady Bird Lake.
I recently met with Katy Dougharty of Lone Star Riverboat Cruises to celebrate the beginning of bat season 2015 and learn more about this huge colony of Mexican free-tailed bats.
About Austin’s Bats
As Katy and I floated underneath South Congress, we could hear the chirping sound of the bats known as “colony chatter,” which they do all day, every day. This high-pitched, but rather pleasant noise is the first indication they have returned from their migration to Mexico. Their annual trip takes them as far as the Yucatan and further inland to Mexico City.
When our bats migrate back to Austin, the original population will total about 750,000 bats. They are all pregnant females, making this a maternity colony. During their stay under the South Congress Bridge, they each give birth to one pup that is 1/3 their size, with a 50/50 split of gender ratio. With that, the population doubles to 1.5 million Mexican free-tailed bats.
Where Are the Bats Exactly?
The support structure of the South Congress Bridge, such as the buttresses, pylons, arches and posts, are original to the 1910 construction. When the road was rebuilt in 1980, engineers included small gaps running along the length of the bridge’s bottom.
Completely by accident, this attracted the bats that already inhabited the drains underneath the north side of the bridge. They remade their homes in the cracks, where they are able to stack on top of each other. Their population increased and reached maximum capacity in just three years.
Now the north end of the bridge is considered the “nursery,” since this is where the mothers stash their babies. After they go on their nightly hunt for food, they return to the north end of the bridge and look for their pups by sound and scent, which can take 2-20 minutes. Once they nurse their babies, the mothers take shelter a bit further along the bridge.
For more see the full guide here