Guide to Bat Season in Austin

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 met with Katy Dougharty of Lone Star Riverboat Cruises to celebrate the beginning of bat season and learn more about this huge colony of Mexican free-tailed bats.

Lone Star Riverboat Bat Cruise

COVID-19 disclaimer: Lone Star Riverboats are temporarily closed due to the pandemic, and are set to reopen August 1, 2020. Please check their website for the most up-to-date information.

In 1987, Lone Star Riverboats was launched by owner Mike Pearce, who ran every cruise himself with one double-decker boat. The family-run business grew, and Katy began conducting cruises in the late 90’s while attending UT. Now she does marketing and site management for the company as well.

The one-hour Bat Watching Cruise leaves from the southeast side of the First Street Bridge about 30 minutes before sunset. This tour is a great way to see the city, as it includes some sightseeing of the Stevie Ray Vaughn statue and new buildings popping up downtown.

The Bat Watching Cruise runs nightly, starting in early March and ending in early November each year. Even if it is raining, there are always a few Austinites and visitors from around the world hoping to catch sight of the cloud of bats. The two large pontoon boats, Northern Star and Southern Star, seat up to 60 people. The smaller boat, Little Star, carries 30.

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.

The babies usually only stay around for the first season of their lives, but the mothers will always attempt to return to the location where they gave birth the prior year. Male Mexican free-tailed bats are plentiful in Austin as well, but they usually cluster in smaller groups of a couple dozen up to 100. Often they will roost in the tops of stadiums or on the side of buildings.

Mexican free-tailed bats live for 8-9 years and only grow to weigh roughly 12 grams. Their wingspan is about 11”, but with their wings retracted, they can fit in the palm of a hand.

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.

When Will the Bats Come Out?

The cloud of bats everyone hopes to catch sight of is the “first shift” of bats exiting the gaps of the bridge to hunt for flying insects such as mosquitos and moths. This initial wave flies out right before sunset, and it can take 2-3 hours for all of the bats to come out.

During the gestational period in April–May, the mother bats are very hungry so there are a lot of good nights to catch the 750,000 bats exiting. They all give birth in the same 2-week window in early June, which causes them to leave later in the night and lowers our chance to see them. In late July/early August the nursing period is ending and the babies start flying on their own. This is considered “peak season,” since the entire population of 1.5 million flies out to hunt.

The bats do continue to fly out every single night, but some nights they are very difficult to see. By the first week of November, the bats have begun to migrate, for it is starting to get cold and there is low visibility.

Every morning, the bats return to the bridge about 30 minutes before sunrise. They are out for around 7-8 hours. They hunt by themselves, and it is not as big of a spectacle when they come back since they do not return in waves.

The Bats Want You to Know…

In the early 1980s when only about 350,000 people lived in Austin, some were fearful of a “rabies apocalypse” since the bats outnumbered the human population. Petitions were created to have the colony exterminated. Thankfully, people like Bat Conservation International founder Merlin Tuttle were able to save Austin’s bat colony through education that quelled fears.

If a bat does become infected with rabies, it dies within 2-3 days and one of the earliest symptoms is paralysis. If you see a bat on the ground, leave it alone. If a bat does touch you, some people recommend you catch the bat to have it tested for rabies.

Though this species of bat is known to be extremely strong and fast in flight, when the young bats begin to fly in late July, they tend to swoop lower. They can also fail at launch and land in the water, but they will backstroke and climb up the pylons to save themselves. Please leave the bats alone if you spot one in the water.

Each season has a distinct personality and Lone Star Riverboats will stay out until 8:15 p.m. or so with spotlights, to make sure people can see the bats on the nights when visibility is low. They use red, filtered lights because this does not startle the bats. Please do not use an unfiltered, white light at the park or on a boat because this can impede the bats’ flight.

Onboard the Bat Boat

COVID-19 disclaimer: Lone Star Riverboats are temporarily closed due to the pandemic, and are set to reopen August 1, 2020. Please check their website for the most up-to-date information.

Lone Star Riverboats has partnered with Bat Conservation International, which headquarters in Austin. Together, they keep track of the bats’ departure times nightly. When tours are running, check Lone Star Riverboat’s Facebook to follow their posts on bat departures. Reservations are recommended for the nightly bat tours. Please see their website for pricing and the other boat tours they offer.

I’d like to give a special thanks to Captain Katy Dougharty for providing all of these wonderful facts and tips regarding Austin’s bats, while showing me an amazing view of our city.

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@theAustinot wants to know:

Have you seen Austin’s bat colony take flight?

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The original version of this article was published March 10, 2015.