Echolocation of little brown bats has been well studied since the invention of bat detectors, electronic devices that can "hear" the ultrasonic calls bats make, which are usually beyond the range of human hearing. Little brown bats typically produce calls lasting about 4 milliseconds. Learn more about the Myotis lucifugus, more commonly known as a Little Brown Bat, in this easy-to-read species overview by the Smithsonian's National Museum of Natural History.