(The Associated Press circulated the following story by Michael Graczyk on August 15, 2009.)
FREDERICKSBURG, Texas — When the sunlight begins to fade at the ends of an abandoned Texas railroad tunnel as long as a football field, up to three million inhabitants begin stirring.
It’s chow time.
Within minutes, a trickle of Mexican free-tailed bats emerge from the narrow tunnel carved almost a century ago out of what’s known as “The Big Hill” and turn into a dark swirling mass so intense it can show up on weather radar as a rain storm. The whirring wings sound like a breeze whipping through the trees.
The nightly show runs May through October as the bats depart each evening to devour tons of insects and has made the 16-acre Old Tunnel Wildlife Management Area the most popular of the more than four dozen such areas managed by the Texas Parks and Wildlife Department.
In July alone, more than 5,000 people visited the area 65 miles west of Austin in the Texas Hill Country.
“It’s an animal that not many people know too many things about,” Nyta Hensley, the wildlife biologist at Old Tunnel, said, explaining the lure of bats. “They have this air of mystery about them because they’re only out at night.”
The tunnel became home to the dark brown or gray bats some time after the San Antonio, Fredericksburg & Northern Railroad Co. abandoned its track 29 years after the first train went through the 920-foot underpass in August 1913. Workers were paid an average of 50 cents a day and took four months to burrow through the limestone from each end of the 2,300-foot Big Hill, meeting in the middle on July 15, 1913.
The train trimmed days off the trip farmers made — using oxen or horses to pull their wagons — to San Antonio to deliver their products. By the late 1930s, though, it was cheaper and quicker to make deliveries by truck, dooming the railroad and hastening abandonment of Texas’ first railroad tunnel. By 1942, rails and ties and trestles were being removed for use as far away as Alaska and Australia.
As Hensley tells the story, area ranchers in the 1950s were puzzled by what looked like smoke just before nightfall hovering over the ridge that houses the tunnel.
“They knew the railroad wasn’t running,” she said.
Turns out the shadows in the evening sky had come from bats that had taken over the tunnel and were leaving for their nightly feeding. Most of them head toward the Guadalupe River, some 13 miles to the south, flying as fast as 60 mph and as high as 10,000 feet. The bats — with a wingspan that’s about a foot-long and a body 3 1/2 to 4 1/2 inches long — can cover 30 to 40 miles each night, munching on moths, beetles and other bugs.
The state acquired the site in 1991 to manage and protect the bat colony, which swells to three million by late summer when pups are born, one per female.
Visitors get an up-close look at the bats from a pair of viewing areas, one a deck above the tunnel entrance and a second spot down a trail to the old railroad bed that gives spectators a side glimpse at the tunnel opening. Some of the young bats learning to fly get disoriented and can dart over the people seated on benches, who also can get a whiff of ammonia from the bat guano decomposing in the tunnel.
Hensley advises people to remain calm and says there’s never been a problem in the six years she’s been assigned to the site.
“The biggest misperception is that they carry rabies and diseases,” she said.
“What I’m fascinated by is the sheer number of them,” said Howard Fisher, of Houston, who came to the tunnel on a recent steamy August evening with his wife and their niece. “And everybody has thoughts of Dracula and all the horror stories of bats.”
Experts say rather than horror, bats are beneficial.
“Bats in Texas are the primary predators of night flying insects,” said Rob Mies, director of the Organization for Bat Conservation at Cranbrook Institute of Science in Bloomfield Hills, Mich. “They are important for controlling agricultural crop pests like corn ear worm moths, cucumber beetles and other detrimental insects.”
Hensley, who dons chest waders and a respirator once a month to examine the inside of the tunnel, said the bats only use about one-fourth of the entire length — favoring a section that fits their temperature and humidity desires. Other parts are too wet because of a spring that flows through the tunnel. That means as many as 200 bats are crammed into each 1-square-foot area.
The Hill Country of central Texas, which she calls “the battiest state in the country,” is home to some 100 million bats, with the Mexican free-tailed among the most common.
The privately owned Bracken Cave near San Antonio has the largest concentration, more than 20 million of them. Another famous Texas bat viewing spot is the Congress Avenue bridge in downtown Austin, home to about 1.5 million bats.
At Old Tunnel, the emergence begins some time around dusk and can last as little as 10 minutes or as long as an hour.
It’s all up to the bats.
“They don’t call us,” laughed Hensley, who’s seen the show thousands of times but never tires of it. “It’s just pretty amazing. All bats are pretty amazing.”