20 million bats exit Bracken Cave every night, forming swirling vortex of bats.
There is a single cave in San Antonio, Texas that is home to the largest bat colony in the world. Every night, starting in March — until they migrate south for the winter — 20 million Mexican free-tailed bats (Tadarida brasiliensis) exit from the Bracken Cave and form a “bat tornado” that preys on insects.
Kelly Sweet, a producer for National Geographic, got caught in the feeding frenzy while filming the event. In the video, you can see that Sweet was lying on the ground right in front of the cave entrance so the bats would not crash into her — and yes, as you can imagine, she was pooped on quite a bit.
“Once millions of bats are coming out, they're flooding out so there's not open space in the cave. You could not safely stand there because they will fly into you and get stuck in your hair,” Sweet said in the YouTube description.
The bats, which can live up to 18 years, leave the cave to consumer large amounts of moths and insects — up to 200 tons each night. Nursing Mexican free-tailed bats will often eat their body weight in insects every night.
As is nature’s way, there is also a whole other ecosystem that depends on these bats as a food source. Many of the baby bats won’t survive after they emerge from the cave.
Sweet said, “A lot of the young bats were leaving the cave for the first time and there's a flight pattern to what these bats need to do. These young bats have to leap off, have their first flight and then they need to continue to fly and they need to make it out without running into other bats or losing their way.”
A lot can go wrong as the bats exit the cave. “They can die from falling from flight, they can die from being stuck in cactus, they can die from being picked up by a raptor … you have things in the air and on land that are waiting to eat the bats that can't fly as well,” explained Sweet.
Even while Sweet was lying in front of the cave entrance, Western coachwhip snakes were crawling over her to try to eat fallen bats, and sometimes the snakes would fight over the bats or pick off the ones stuck in the cactus barbs.
There really is no better way to see how these animals live than to venture into their world. Bracken Cave is managed by Bat Conservation International and is now open to the public on a limited number of nights.
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