Mexican free-tailed bats (Tadarida brasiliensis) are fast little creatures, traveling at speeds of up to 65 mph. The smallest of the free-tailed bat species, they can be found across Arizona, although they typically migrate south to Mexico and Central America during the fall, according to the Arizona-Sonora Desert Museum. These mammals are rangy in terms of where they like to roost, too: While they prefer caves, they’re also happy to find shelter in abandoned buildings or under bridges, especially near water. That might explain why the bats pictured here were drawn to the ghost town of Ruby. There are numerous abandoned buildings there, along with old mine shafts, a human-made lake and plenty of moths and other insects to eat.