Explain how bats use ultrasound to catch their prey. 

Bats have weak eyes, so they cannot see their prey. They search out prey and fly in the night by emitting and detecting reflections of ultrasonic waves. The high-pitched ultrasonic squeaks of the bat are reflected from the obstacles or target and return to the bat's ear. The nature of reflections tells the bat where the obstacle or prey is and what it is like. Bats catch insects with the help of a progressive navigation technique known as echolocation. They are known to emit high-frequency ultrasonic waves which are too high for the biological hearing of humans. These sounds get reflected when they hit various objects and revert to the bats as echoes.