Old Tunnel

INTERPRETIVE GUIDE OLD TUNNEL STATE PARK While you marvel at the bats or admire the old railroad tunnel, please remember that everything you see is protected. Artifacts, rocks, animals, and plants are all part of the region’s rich natural and cultural heritage. Help us keep Old Tunnel State Park a special place for everyone. DISCOVER HOW AN ENGINEERING MARVEL TURNED INTO A COZY HOME AT OLD TUNNEL STATE PARK. AT JUST 16 ACRES, OLD TUNNEL IS THE SMALLEST STATE PARK IN SIZE, BUT HAS THE LARGEST SEASONAL POPULATION OF WILDLIFE. COME FOR THE BATS BUT STAY FOR THE HISTORY AND HIKING TRAIL THAT MAKE THIS LITTLE • Hike only on designated trails and stay out of closed areas, including the tunnel. • Leave no trace. Keep your park clean by picking up your trash. • Safeguard the park for future generations and leave plants, animals, and fossils where you find them. • Never touch or handle a bat. • Volunteer opportunities are available, especially during the evenings when the bats are in residence! Email the park for more details: old.tunnel@tpwd.texas.gov Old Tunnel State Park 10619 Old San Antonio Road Fredericksburg, TX 78624 (866) 978-2287 www.tpwd.texas.gov/oldtunnel PARK A BIG DESTINATION FOR NATURE LOVERS. © 2022 TPWD. PWD BR P4503-0259D (7/22) TPWD receives funds from the USFWS. TPWD prohibits discrimination on the basis of race, color, religion, national origin, disability, age, and gender, pursuant to state and federal law. To request an accommodation or obtain information in an alternative format, please contact TPWD on a Text Telephone (TTY) at (512) 389-8915 or by Relay Texas at 7-1-1 or (800) 735-2989 or by email at accessibility@tpwd.texas.gov. If you believe you have been discriminated against by TPWD, please contact TPWD, 4200 Smith School Road, Austin, TX 78744, or the U.S. Fish and Wildlife Service, Office for Diversity and Workforce Management, 5275 Leesburg Pike, Falls Church, VA 22041. This publication can be found at tpwd.texas.gov/park-pubs O L D T U N N E L S T A T E P A R K A RAILROAD LEGACY Old Tunnel State Park’s namesake—the railroad tunnel— symbolizes persistence and resourcefulness. When European settlers moved into this area in the mid-1800s, they needed a reliable way to connect nearby Fredericksburg to San Antonio. They were thwarted by the cost of breaching the Big Hill, the site of what is now Old Tunnel State Park. Since trains weren’t quite powerful enough to climb this ridge, the rail line needed a tunnel. By 1913, local residents had raised enough money to build the tunnel. Workers bored 920 feet through solid limestone—that’s the length of two and a half football fields! Around 100 workers, probably local laborers of German descent, dug out most of the tunnel by hand. During its construction, the tunnel became a popular tourist attraction, much like it still is today. The San Antonio, Fredericksburg, and Northern Railway used the tunnel until 1941. Despite its popularity with local residents, the rail line was never profitable. It was deemed unessential to the World War II effort and was dismantled so the ties and rails could be used for other things. Some of these pieces were used on the Alaska-Canadian Highway, and others went to railroads as far away as Australia. Once the tunnel was abandoned by people, new residents moved in—bats. A GREAT PLACE TO HANG OUT During the summer, millions of Mexican free-tailed bats spend their days in the tunnel and their nights on the wing. The Old Tunnel provides them a secure roosting place, protected from predators while they rest. This is a pseudo-maternal colony. In the spring, female Mexican free-tailed bats migrate and land here, but they move out to have their babies elsewhere. Male bats then move in. In August, the females return with their babies and the population of the tunnel balloons to approximately three million bats. It’s this time of year that the evening bat flight is the most astounding. Millions of bats spiral out of the tunnel near sunset, gaining speed and altitude to spend the night hunting insects. Everyone leaves for warmer climates when the weather cools down, and the tunnel is mostly empty again until spring. Old Tunnel is vital to the survival of millions of bats, but it’s also an important place for scientists. Bat researchers at universities and government agencies like Texas Parks and Wildlife have gathered data here to learn more about these flying mammals. Some of the studies have changed our understanding of bat migration, winter food sources for bats, and their importance to the environment. MEXICAN FREE-TAILED VERSUS CAVE MYOTIS BATS Two kinds of bats live in the tunnel, though it is hard to tell who’s who when they are zooming through the air. One thing that Mexican free-tailed bats and cave myotis bats have in common is that they like to roost in similar places. However, since they’re separate species, they have a lot of differences, too! Mexican Free-tail Bat Cave Myotis Bat 3 million 3,000 Size 3.5–4.3"/90–110 mm 3.5–4.5"/90–115 mm Range Argentina to Iowa Honduras to Kansas Population Here HOUSEKEEPERS FOR BATS Biggest Colony 15-30 million 15,000 Favorite Food Moths and flying ants Moths and beetles E ver sniffed the distinctive odor of a bat roost? Bats get a bad rap for being smelly, but the beetles that live with the bats are partially responsible. Dermestid beetles are like housekeepers for bat roosts. They eat the bats’ poop, called guano. These flesh-eating beetles also take care of any bat— or other creature—that is unlucky enough to fall to the ground. Without dermestid beetles, bat roosts would be overwhelmed with guano and bats would eventually run out of places to stay. When biologists capture a bat like this cave myotis, they’re collecting data like age, sex, and weight, and taking body measurements. Only trained and rabies-vaccinated biologists should handle bats. Never pick up a bat!