Experience a Bat Tornado in This Video From National Geographic
According to Bats Without Borders, bats help maintain the proper balance of the ecosystem by feeding on night-flying insects. In this video from National Geographic, the world's largest colony of Mexican free-tailed bats emerges from Bracken Cave near San Antonio, Texas to feed on approximately 200 tons of insects. In order to protect this bat colony, the City of San Antonio, The Nature Conservancy and Bat Conservation International have protected over 1,500 acres adjacent to the cave.
https://youtu.be/g9M6ZbyJXjo