Devil's Sinkhole State Natural Area

Texas hill country Region

The main attraction at Devil’s Sinkhole SNA is the Devil’s Sinkhole itself. The main cavern is circular, up to 60 feet wide at the opening, and 350 feet deep, making it the largest single-chambered cavern and the third deepest in the state. The Statue of Liberty could easily fit inside. About 3 million Mexican free-tailed bats inhabit the sinkhole seasonally, from May through October. These small, flying mammals put on quite a show in the evenings, forming a “tornado of bats” as they leave the cave to forage. About 3,000 to 4,000 cave swallows inhabit the cave at night while the bats are gone, and it is quite a sight to watch the cave swallows returning to the cave for the night while the bats are just beginning to emerge! Since the bottom of the cave is below the water table, there are freshwater lakes around its perimeter. These lakes support two unique organisms: one, an endemic amphipod, a shrimp-like organism found nowhere else in the world, and the other, a rare aquatic isopod, which looks like a colorless pill bug. Also, the walls of the vertical shaft of the cave support a Mexican fern species found in few locations in the United States.

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Bat Fact

Mexican free-tailed bats are very important for keeping crop pests in check as they can eat up to two-thirds of their body weight in insects each night, especially while lactating and feeding young. With the large numbers of agricultural pests they eat, research has demonstrated that these bats can save farmers up to two applications of pesticides per year.