Day Trips

The Old Tunnel Wildlife Management Area outside of Fredericksburg hosts a bat colony twice the size of our own

The Bat Cave
The Bat Cave (Photo by Gerald E. McLeod)

The Old Tunnel Wildlife Management Area, outside of Fredericksburg, may be the smallest preserve in the state park department's inventory, but it has one of the largest concentrations of wildlife and attracts more observers than any other.

The reason? The 3 million bats that emerge from the former railroad tunnel every evening during the summer. In contrast, the bat colony under Austin's Congress Avenue bridge number about 1.5 million, says Craig Hensley, a volunteer tour guide at the Old Tunnel WMA. The largest bat colony in the world resides at the privately owned Bracken Cave near San Antonio.

This is the most easily accessible bat colony in a preserve in the state, Hensley says.

One of only two railroad tunnels in Texas open to the public (the other is in Caprock Canyons State Park), the man-made cave was on the line between San Antonio and Fredericksburg. The train carried freight and passengers from 1913 until the tracks were sold as scrap in 1944. The 920-foot tunnel removed the 2,300-foot Mount Alamo as an obstacle on the improved route between the two cities.

"It must have been a tight fit getting those cars through here," Hensley says. Sometime after the trains stopped running, the Mexican free-tailed bats took up residency. There were reports of bats at the site in the early 1950s. There were also reports of drunken parties using the bats for target practice.

In 1991, the Texas Parks and Wildlife Department acquired 16 acres around the tunnel to protect the bats. Saving farmers millions in pesticide costs and damage, the Mexican free-tailed bats serve as a moth defense shield by intercepting the corn borer moths on their annual migration from Central America.

Inside the tunnel is a nasty ecosystem of flesh-eating beetles, bat guano, and spring water. You can hear the chirping and smell the aroma. From the top of Mount Alamo, a wide view of the Hill Country unfolds. Looking into the cave from the creek bed where the steel rails once were, you can see the bats fluttering about preparing for the night's flight.

The bats begin arriving at the Old Tunnel in May and stay until the first cold front in October. In August the free-tailed bats give birth, which increases the number in the tunnel substantially. Because the hole is open-ended, the mothers find other caves and crevices to have their pups.

There are 1,100 kinds of bats in the world, and 43 reside in the U.S. with 32 species in Texas. The Mexican free-tailed bats can fly as high as 10,000 feet at speeds of 30 mph. Their territory covers a 30-mile radius of the tunnel. It is estimated that the colony is worth about $1 billion to agriculture by eating 25-37 tons of moths a night.

Shortly after 8pm, Hensley finishes his presentation on the bats. The sky is clear and turning into a inky blue. Already, bats are zipping through the trees above our heads.

The emergence starts slowly, but the whisper of thousands of bat wings grows to a soft murmur. Standing at the edge of the lower observation area looking up into the darkening sky, the colony turns into a steady stream of blurred images streaking by at phenomenal speeds. The Milky Way of black dots pours out of the tunnel, down the creek bed, and then makes a big turn into the night sky. After a few minutes, about 8:30pm, it is too dark to see anything, even though you can still hear the hushed whisper over your head.

Old Tunnel WMA is about 11 miles south of Fredericksburg off Old San Antonio Road. From U.S. 290, turn left just before you get to the city limits. Seating on the upper observation deck is free. Admission to the lower observation area and the creek bed is a great value at $5 for adults. It is best to get to the site at least an hour before the emergence. For information, call 866/978-2287.

A short walk from the Old Tunnel's parking lot, the Alamo Springs General Store and Cafe is open Wednesday through Monday, 10am-10pm, with fried foods and cold drinks. Call 830/990-8004 for information.

846th in a series. Day Trips, Vol. 2, a book of "Day Trips" 101-200, is available for $8.95, plus $3.05 for shipping, handling, and tax. Mail to: Day Trips, PO Box 33284, South Austin, TX 78704.

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