Last week, Mary and I made a trip to the Old Tunnel Wildlife Management Area which is located just south of Fredericksburg. The trip was organized by our Hays County Chapter of the Texas Master Naturalists and we were quite excited to go.We had seen the bat emergence at the Congress Avenue bridge in Austin, but this one promised a closer look.

Old Tunnel is the smallest WMA operated by Texas Parks and Wildlife Department containing only 16 acres of land. There is a small hiking trail and of course the Old Tunnel. The area is open to the public year-round. There are two main viewing areas: one at the top of the hill which the tunnel goes through and another lower and quite near the tunnel entrance.

The tunnel is an abandoned railroad tunnel of a small private railroad built in the early 1900s to make it easier for the Germain settlers in the Fredericksburg area to make the trip south to San Antonio. The railroad operated for about 29 years. The tunnel is 920 feet long, bored right through the limestone hill. Here’s a photo of the south entrance to the tunnel and you can see the north entrance at the far end. Shortly after the railroad was abandoned, the bats moved in.

The main colony consists of between 1 and 3 million Mexican Free-tailed bats. Their bodies are about 3.5 inches in length and weigh about 1/2 ounce.

Nyta Brown, a TPWD bat education specialist, gave us an introduction to the area and discussed the bats and their habits as we waited for dusk. The bats feed mainly on insects as they head out on their nightly run. They play an important role in our ecosystem as well as to our agricultural industry by keeping the insect population in check.

We were seated in a lower viewing area which was just a little higher and to the west of the south tunnel entrance. I think we were within 100 feet of the entrance. While it was still daylight, we occasionally saw a few bats flitting about and we could see more, with binoculars, flying within the tunnel from the vantage point of the first photo above. As dusk fell, we began to see more, but still single, bats about. The start of the full emergence was at 8:47 pm. For at least the next half-hour there was a continuous stream of bats.

They emerged from the tunnel and flying quite low, made a counter-clockwise corkscrew turn to gain altitude and eventually flew over the trees and away. Flash photography is not allowed, so all I have are my impressions to report. A few times and briefly, Ms. Brown swept a red-colored flashlight beam on the stream to let us have a better look. This provides minimal disruption to the bats. It was getting dark but you could see hundreds of bats flying by every minute. Occasionally one would veer over our heads before turning and heading back into the main stream.

Everyone was also asked to be quiet, again, to not disrupt the bats, and while we could not hear the ultrasonic echolocaton calls, we could hear the light fluttering of the bat wings, even above the katydid and cicada calls.

We stayed for about 1/2 hour and while the emergence was not over, it was too dark to see it anymore.

If you get a chance,  you should drive out to the Old Tunnel WMA and experience this wonderful event. I’m glad we did.