Located less than 20 miles from downtown San Antonio, the cave has come under increasing threat of urbanization. This June, after several years of negotiations and the assistance of many, Bat Conservation International succeeded in completing the purchase of this critical site with funds granted by the Ewing Halsell Foundation. Until a comprehensive management plan is completed, visitation to the cave is strictly limited. The bats of Bracken Cave comprise the largest known bat maternity colony in the world, producing millions of young each year. In March and April, expectant females return to Bracken after overwintering in Mexico.
Most males roost elsewhere in smaller groups.
In the latter part of June, females give birth to a single pup, nearly doubling the cave's population. As the bats give birth, cave walls become densely packed with naked pups, clustering tightly at up to 500 per square foot. Babies roost separately from their mothers. Before leaving her infant in the nursery with the other pups, each mother spends up to an hour getting acquainted with her baby's scent and vocalizations. She nurses her baby at least twice a day.