Bats, which are most active at night, have eyesight that ranges from very good to very poor. However, they rely primarily on echolocation to “see” in the dark. Echolocation is the transmission of sound waves to locate objects, including food, and to detect obstacles in an animal’s path. These sound waves travel out away from the bat and then bounce off objects and surfaces in the bat’s path, creating an echo. The echo returns to the bat, giving it a sense about the object’s size, shape, direction, and distance. This high-frequency ultrasound is higher than the range of human hearing and usually comes from the bat’s mouth. A few species emit sounds from their noses, freeing their mouths for eating at the same time.