Old Tunnel

  • 10619 Old San Antonio Road Fredericksburg
  • ~1 hour 40 min from Austin
  • Hours: Sunrise to 5 p.m.
  • Cost: Free

FREDERICKSBURG, Texas (KXAN) — At Old Tunnel State Park in Fredericksburg, August and September are typically the best times of the year to see bats emerge from the former railroad tunnel.

But this year, visitors should expect changes to typical bat-watching times because of the Central Texas drought.

Old Tunnel State Park typically is home to 3 million bats. State park superintendent Nyta Brown estimates 300,000 bats are emerging this summer.

“It’s not just our site. All the sites in Central Texas are noticing their populations are different due to the drought,” said Brown, who has worked at the park since 2005.

During droughts, less rain causes fewer insects to hatch, which limits bats’ food availability across Central Texas. Brown said bats are struggling to find food and water sources. So they are moving — and straying from typical summer flight routes.

Brown said this does not mean many bats are dying, but they are more active this year to seek better food and water sources.

“This nice rain we’re getting right now … it might make a difference in terms of our population,” Brown said. “We might start seeing some more bats coming in and staying with us for a while.”

At Bracken Cave Preserve in San Antonio, bats are emerging in their “batnados” around 5:30 or 6 p.m. though it doesn’t get dark until 9 p.m. This makes for great bat watching because you have a couple of hours to watch the bats in the light, said Fran Hutchins, the director of Bracken Cave Preserve.

“If it’s during a normal year and they’re coming out at 8 p.m., you only have 45 minutes or so to watch the batnado,” Hutchins said.

Bat expert Merlin Tuttle said it’s impossible to determine exact pattern changes because there are millions of bats spread through the area with over a dozen different routes.

Tuttle, who has studied bats for decades, explained droughts have a unique impact on bats that live in caves.

During droughts, carbon dioxide and ammonia gases build up in the cave and push the bats out. He said in extreme droughts, there have been few bats left in caves such as Bracken Cave in San Antonio, which is home to millions of bats.

“When that has happened, I’ve noticed that simultaneously we see far bigger emergences at bridges like Congress Avenue,” Tuttle said.

After a cold front or storm passes, bats may return to the caves. Tuttle said years when there are few bats seen at Congress Avenue, it is likely a good year for the bats.

Tuttle does expect fewer young bats, or pups, to survive in these tough conditions, though it is not possible to count how many young adults die.

Tips for seeing bats at Old Tunnel

Old Tunnel State Park visitors hoping to see bats should still expect evening bat flights, but they may be briefer and earlier than usual. Bat emergence usually lasts 45 minutes to an hour most years. Brown said this has decreased to five to 10 minutes recently.

Brown updates the state park’s social media during the week with updated bat viewing estimates. Brown recommends arriving 30-45 minutes before the earliest expected emergence time.

Bat season runs from May to October. Old Tunnell State Park is considered a “migratory stopover” for bats, which means the population fluctuates.

Texas Parks and Wildlife Department has a list of bat-watching sites in the state. Other Central Texas spots include Bamberger Ranch Preserve in Johnson City, Bracken Cave Preserve in San Antonio, Camden Street Bridge in San Antonio and the Congress Avenue Bridge.

This story is part of a KXAN series highlighting Central Texas activities — you can see our full list on our “Central Texas Things to Do” page. Do you have an idea of something we should profile? Email us at reportit@kxan.com.