Echolocation is the combined use of morphology (physical features) and sonar (SOund NAvigation and Ranging) that allows bats to “see” using sound. A bat uses its larynx to produce ultrasonic waves that are emitted through its mouth or nose. Some bats also produce clicks using their tongues. The bat hears the echoes that are returned and compares the time between when the signal was sent and returned and the shift in the frequency of the sound to form a map of its surroundings. While no bat is completely blind, the animal can use sound to “see” in absolute darkness. The sensitive nature of a bat’s ears enables it to find prey by passive listening, too. Bat ear ridges act as an acoustic Fresnel lens, allowing a bat to hear the movement of ground-dwelling insects and the flutter of insect wings. Some of a bat’s physical adaptations are visible. A wrinkled fleshy nose acts as a megaphone to project sound. The complex shape, folds, and wrinkles of a bat’s outer ear help it receive and funnel incoming sounds. Some key adaptations are internal. The ears contain numerous receptors that allow bats to detect tiny frequency changes. A bat’s brain maps the signals and even accounts for the Doppler effect flying has on echolocation. Just before a bat emits a sound, the tiny bones of the inner ear separate to reduce the animal’s hearing sensitivity so it doesn’t deafen itself. Once the larynx muscles contract, the middle ear relaxes and the ears can receive the echo.