The colony consists of Mexican free-tailed bats and Cave myotis bats.
The abandoned tunnel served as a railway bypass for the Fredericksburg and Northern Railway.
During peak season, the bat emergence can take up to an hour to complete.
The bats in the tunnel are migratory and typically leave the area for Mexico in the fall.
The park was once a significant commercial rail route before the advent of truck transport rendered it obsolete.
The bats exit the tunnel at high speeds to hunt insects, consuming tons of pests every night.
Old Tunnel State Park is home to a former railroad tunnel that serves as a seasonal roost for up to 3 million Mexican free-tailed bats. The park features a nature trail that winds through the Hill Country landscape, ending at a viewing area near the tunnel entrance. The tunnel was originally constructed in 1913 for the Fredericksburg and Northern Railway. It ceased railway operations in 1942, allowing the bat colony to establish itself permanently. The park is managed by the Texas Parks and Wildlife Department and strictly monitors wildlife behavior. Visitors are prohibited from entering the tunnel to protect the fragile bat habitat. Educational presentations are frequently hosted by park staff regarding local ecology and bat biology.
The viewing area terrace which provides a clear line of sight to the tunnel portal.
Bring a portable chair for comfortable viewing, as seating is limited in the designated areas.
Arrive early during peak summer months to secure a spot, as the parking area has a strict capacity limit.
Check the weather before arriving, as bats may not emerge during heavy rain or cold fronts.
Do not attempt to enter or approach the tunnel entrance; do not bring pets to the viewing area.
Bat viewing season is seasonal; the park experience is significantly reduced during winter months when bats are not present.
Maintain silence during bat emergence; no flash photography or bright lights allowed.
