Witnessing over 1.5 million Mexican Free Tail Bats, traveling at speeds of up to 60 mph will change your life. These bats live in a bridge filled with only bat mothers and their children. The bats are helpful because they eat insects that can damage crops. They have been seen at over 10,000 feet in the air and they migrate about 1000 miles in the winter to Mexico. Every night they leave their roost. Scientists think they go hunt at the Colorado River, but no one is sure exactly where they go.