THEY SEE WITH THEIR EARS

•  Bats have an interesting way of looking at their world. They are mostly nocturnal, which means they are most active at night. They don’t find their way around obstacles with their eyes, but rather with their ears. Bats are among a very select group of animals (which also includes whales, porpoises, and dolphins) who use an high-frequency pulse of sound, or ultrasound, to do many things for which other animals use their eyes. This skill is known as echolocation. Echolocation allows bats to hunt for food, avoid obstacles in their path as they fly in the dark, and even communicate with other bats.

• So how does echolocation work? If you have ever experimented with echoes in a large, empty room or at the edge of a canyon, then you have the beginnings of an idea about how echolocation works. Bats move air across their vocal chords just like people do when they speak or yell. Some bats make the sound come out of their mouths, and others make the sound come out of their noses! The sound they make has a very high pitch, which means the sound waves it creates move very quickly. The energy from their sound waves goes out in front of them and bounces off any objects and creates an echo that returns back to the bat. You may have noticed that a bat’s ears often appear quite large compared to the size of its head. Depending on where the sound hits on the folds of the bat’s ear, the bat can tell very precisely, where an object is. The strength of the echo can even tell the bat how large the object is. A moving object, like an insect the bat would like to eat, will have a softer or louder echo than the original noise made by the bat, depending on whether the insect is moving closer or farther away.

• Believe it or not, the entire complicated process of echolocation is automatic for the bat. The bat does not have to think about listening, or what to do next. It works so well that the bat doesn’t care that he is “as blind as a bat.” He can see with his ears!

 Name:__________________________________

Answer the following questions based on the reading passage. Don’t forget to go back to the passage whenever necessary to find or confirm your answers.

1)  What are the advantages of using echolocation to see?

2)  What are the disadvantages of using echolocation to see?

3)  What would you miss if you suddenly switched from seeing with your eyes to echolocation? Why?

4)  What is the purpose of this reading passage?

  

5)  What might cause echolocation to work differently for whales than it does for bats?