Most people have heard of bats' ability of echolocation. It's a natural type of sonar. Bats use it to navigate, hunt and find spots to roost. To perform echolocation, a bat makes a loud sound, and then measures the time it takes for the sound to bounce back to determine how far away things are. They can also tell what they're near to by the sound quality of the echo they hear.
Because they use echolocation to get around and can't use their eyesight much while hunting, you'd think bats would need to have very good hearing. And they certainly do. They can hear between 20 to 120,000 Hz. They are very sensitive to high-frequency sounds, way beyond what humans can hear. Even the shape of bats' ears contribute to being able to hear better.
Animal echolocation on Wikipedia
The Secret Life of Bats
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