. >>> forget sharknado get ready to behold a nonfiction batnado where creepy creatures in a dank cavend of 40 million wings. from vampires to bloodsuckers, the little guys have definitely got an image problem. as it turns out they're doing us a big favor every time they feed. there is so much more than the stuff of halloween nightmares. abc's ryan owens traveled to texas to witness the feeding frenzy. >> reporter: welcome to the batnado. that's right, a real tornado of creepy creatures, a funnel of freaky fliers that emerges every night from this cave in texas. look at that. and you feel the wind. wow, look at them. >> we are in the middle of it right now. >> reporter: you are watching 20 million, yes, 20 million mexican free-tail bats whirl their way out of the single cave to hunt for food. >> the way that they're climbing up out of the hole. gaining altitude. like an airplane. gaining altitude. get up. you can see they keep their form. go off into a river off, 30 miles away. out to eat. 100 tons of bugs every night. >> reporter: our guide for this tour of the bracken bat wave north