Witnessing an emergence of bats from the maternity colony at Bracken Cave is an awesome experience that may soon be available to the public.
No two bat emergences are ever the same. Except that every time, skeins of bats will unfurl into the twilight. Overhead, the sky will become a flickering canvas of brown on blue. Whorls of bats fly overhead and the leathery flap of wings combines with a sound like crickets or cicadas as wave after wave of bats flutter past. Those clicks are bat echolocation, of which only the very lowest pitches are audible to the human ear.
Bracken Cave is open only on select nights and almost exclusively for members of Bat Conservation International (BCI), until a planned visitors’ center and other facilities are in place. However, for visitors to San Antonio who are interested in natural history, a trip to Bracken Cave is definitely worth the BCI membership price of $35.
The World’s Largest Colony of Warm-blooded Animals
The species that gathers at Bracken Cave is the Mexican free-tailed bat, a small brown bat. Each year, these tiny migratory mammals make an arduous trek from Texas down to Mexico and back, following hordes of migrating insect pests and depleting their ranks just in time for farmers to begin spring planting. Present in Texas from April through September, bat pups are usually born in mid-June and nurse for about five weeks.
A maternity colony of roughly 20 to 40 million Mexican free-tailed bats, mothers and babies, spend their summers in Bracken Cave – emerging each night, an ethereal sweep of winged bodies fanning into the sky. The hairless young hang in their own nursery area after birth: a swath of pink across the cave’s ceiling. Mother bats find their babies by returning precisely to where the young were deposited. Each mother recognizes her baby by its own peculiar scent and voice.
The Importance of Bracken Cave
A mere 30-minute drive from downtown San Antonio, Bracken Cave lies surrounded by a natural amphitheater. During an emergence, the amphitheater becomes animated by literally thousands of bats at a time pouring in cooperative confusion from the cave mouth
Bats — even those as numerous as the Mexican free-tailed — are extremely vulnerable because their nature is to gather in vast numbers in a few large colonies like the one at Bracken Cave. They become easy prey for the uninformed or can readily transmit new diseases such as the white-nose syndrome that is currently killing off alarmingly large numbers of bats in the northeast U.S.
Bat Conservation International
Founded in 1982, Bat Conservation International (BCI) is based in Austin, Texas, and is devoted to conservation, education, and research initiatives involving bats and the ecosystems they serve. An organization dedicated solely to bat conservation was needed because of alarming declines in bat numbers around the world and the importance of protecting these species.
Bats, distributed worldwide, are essential to the function of many ecosystems and provide ecosystem services important to humankind. They are prodigious consumers of insects, many of which are considered pests. For example, the roughly 40 million bats of Bracken Cave will consume approximately 200 tons of flying insects in one night!
Bats are also pollinators, and some plants such as the agave from which tequila is distilled, are entirely dependent on bats for pollination. Fruit bats also play an important role in spreading the seeds of native plants.
View a Bat Emergence
To witness an emergence at Bracken Cave, join and contact Bat Conservation International. As the emergence winds down, the fliers looping overhead will grow fewer. Night will have fallen and the bats’ silhouettes may flicker against the moon. However it ends, a bat emergence from Bracken Cave is truly one of nature’s most awe-inspiring spectacles.