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Tuning in: scientist Bruce Miller listens to bats as they use shrieks and chirps to find food.

Each night, hoards of bats swoop through the jungles of Belize, many letting out shrieks and chirps as they fly. Although other bats can hear these sounds, most of the calls are too high-pitched for humans to hear. But zoologist (zoo-OL-uh-jist) Bruce Miller has found a way around that.

He uses an AnaBat--a machine that can pick up bat sounds and turn them into beeps and clicks that humans can hear. Miller can also record these sounds with the AnaBat. He often studies the recorded voices and tries to decode the meaning behind them.

Sound Science

But before scientists like Miller can understand bat language, they must first understand sound. Sound is a form of energy that is produced when an object--like your voice box--moves rapidly back and forth, or vibrates (VYE-brates).

As the object vibrates, it causes the molecules (MOL-uh-kyools) in the air to vibrate too. The molecules cram together, then move away from each other. That creates sound waves. These traveling waves carry sound from the vibrating object to our ears. The stronger the vibration, the louder the sound.

Bats Speak Up

Some sounds, however, are ultrasonic (UHL-truh-SON-ik). They cannot be heard by human ears. These ultrasonic sounds are often made by bats.

Most bats produce ultrasonic sounds in their larynx (LAH-rinks), or voice box, and release them through their mouth or nose. Some bats can also make such sounds by clicking their tongues.

According to Miller, most bats make these sounds while using echolocation (EK-oh-loh-KAY-shun). In echolocation, bats produce a sound that travels until it hits an object. The sound then bounces off the object and echoes back to the bats. Bats often use this process to find their food.

Echolocation also helps a bat determine the distance of the object. The longer it takes a sound to come back to the bat, the farther away the object is. If a sound bounces back quickly, an object is really close.

The AnaBat tells Miller how a bat uses echolocation, For example, when Miller hears a similar pattern of beeps and clicks, he knows that a bat is just flying around searching for food. But when the beeps become loud and too fast to count--BEEP! BEEP! BEEP! BEEP!--he knows the bat has found a snack and is homing in on it.

Guided by Voices

Miller also uses the AnaBat to study bat voices. Each bat family has a unique voice. For example, common brown bats make very loud sounds, while leaf-nosed bats are soft-spoken.

Miller will often trap a bat and look at it to identify what family it is from. He then records its voice with the AnaBat before releasing it to the wild. Later, as other bats fly by, he can compare the sounds they make with the recording on the AnaBat. If the sounds are the same, Miller knows they belong to the same family. "By studying bat sounds, we can tell which bats are where," he says. Miller uses this information to learn if certain bat families are in danger.

Bats Attacked

In the jungles of Belize, people often cut down trees for wood or to clear the land for farming. This is a problem for bats that use these trees for shelter. When a tree is cut down, an entire bat population can be destroyed.

When Miller hears fewer sounds being made by a bat family that has been noisy over the years, he suspects they may be in danger of dying out. He gives the information to conservation groups, who then take action to protect the bats.

Sometimes Miller's findings offer happy surprises. The shaggy bat was considered one of the rarest bats in Belize. Because people hadn't seen the bat for a long time, they thought it was dying out. "But now we know (because of sound) that they're everywhere," says Miller.


1. The world's smallest bat is the bumblebee bat. It weighs less than a penny!

2. Vampire bats really do drink blood! These bats feed mainly on the blood of cattle and horses.

3. Bats are not blind! "Blind as a bat" may be a popular saying, but it's not true. All bats can see. In fact, some bats use their sight--not sound--to find food.

4. The world's largest at is the flying fox. It's about 45 centimeters (18 inches) long and its wings can stretch out to about 2 meters (6 feet)!

quick quiz

1. What does Bruce Miller use the Anabat for?

A. to capture bats

B. to listen to bat sounds

C. to study the food bats eat

D. A and B

2. Why do bats use echolocation?

A. to find food

B. to speak to Bruce Miller

C. to determine the distance of objects

D. A and C

3. What type of scientist is Bruce Miller?

A. an ecologist

B. a zoologist

C. a glaciologist

D. a batologist

Think about it: Sound can warn us when there's a fire, tell us that class is about to begin, and give us directions when we are lost. What are some sounds you hear each day? Do they help you? If so, how?

Words to Know

Zoologist--a scientist who studies animal life

Sound--a form of energy produced when an object vibrates

Vibrate--to move rapidly back and forth

Molecule--a particle of two or more atoms (the basic building blocks of matter) joined together

Ultrasonic--beyond the range of human hearing

Larynx--the voice box

Echolocation--a system used by some animals to locate objects using sound waves

Family--a group of animals or plants that are related


For Grades K-4

* Light, heat, sound, electricity, magnetism

* Characteristics of organisms

For Grades 5-8

* Transfer of energy

* Structure and function in living organisms


Language Arts--Reading comprehension


Set a Purpose

To learn how bats use sound to find food.


* Echolocation was discovered in 1938 using a sonic detector.

* Some bats have flaps of skin around their noses (called nose leaves) to help direct the sounds emitted in echolocation.

* There are 200 species of fruit bats that do not use echolocation to find food. These bats use their sight!

Discussion Questions

* Most bats search for food at night. How might this be challenging? (Possible answers: It's hard to see; if they eat animals, there aren't many animals out.)

* Pretend that you're in a dark room. How might you be able to find food? (Possible answers: You can feel your way around until you find it; you can smell it.)

* How do you think animals find food in the dark? (Possible answers: They have special eyes that allow them to see food in the dark; if they eat other animals, they can hear those animals move; they can smell food.)


Discussion Questions

* What are some qualities that Bruce Miller must have to do his job? (Possible answers: He has to like bats; he likes to study sound; he likes to work at night.)


Outside and Inside Bats by Sandra Markle (Atheneum, 1997) has terrific photographs and interesting facts about bats. There is a glossary as well as a list of questions at the end of the book. There's even an address to write to for directions on building a bat house. is the web site for Bat Conservation International. There is a bat camera showing flying foxes (large bats which do not use echolocation to hunt), recordings of bat sounds, and links to other sites.


* QUICK QUIZ (Student Edition, p. 9)

1. B 2. D 3. B
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Title Annotation:physical science
Author:Prokos, Anna
Date:Oct 1, 2004
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