As many as twenty million Mexican free-tailed bats spend their summer months in Bracken Cave, Texas making it home to the largest congregation of warm-blooded animals in the world. Join journalist Millie Kerr as she captures the unforgettable sight of these bats emerging at dusk to feed, and spends some time with leading bat expert and photographer, Merlin Tuttle to discuss the threats facing these often misunderstood mammals. Video thumbnail: Merlin Tuttle