Science, Life Science
Grade 1- 3
Students will learn about echolocation.
Echolocation is the method that some bats use to catch insects and other moving creatures. They are able to use sound waves to determine where the insect is. When a bat is hunting it makes a series of high-pitched sounds. The sound waves travel through the air and bounce off of objects. When the sound waves return to the bat it can tell the bat where the object is. A bat can use sound waves to tell the difference between objects that are stationary or moving. For example, a bat uses sound waves to avoid hitting a tree and immediately afterwards uses sound waves to catch a mosquito. Bats probably have the best techniques for echolocation of any animal on earth. The sounds they make are often much higher than the human ear can hear.
How do sound waves travel back to a bat? It is similar to how a mirror reflects light. If you hold a small mirror in your hand and maneuver it in the sunlight you can see the light reflecting off of the mirror and onto other objects. This is similar to how sound waves are reflected. The bat emits a high-frequency sound. The sound waves hit an object and are then reflected back to the bat. This high-tech system allows bats to fly in total darkness. They not only see where they are going, but can also catch their prey. When you look at pictures of bats you can see that many have large ears and interesting nose shapes. Some bats use their ears to catch sound waves and other bats use their odd-shaped noses to direct sound waves.
- Provide your children with hand mirrors and take them outside on a sunny day. Ask each child to reflect the sunlight off of the mirror and onto the sidewalk, side of a wall, or the school building. Ask the child to think about how the mirror is reflecting the light. Explain that bats reflect sound waves off of objects in much the same way. (Note: Warn the children to not reflect the light directly back towards anyone's eyes or face.)
- Gather the children around you and ask them to look at the size of their classmates' ears in comparison to their bodies. Show pictures of bats with large ears and ask the children to compare the size of the ears to the bats' bodies. Remind the children that megabats have small ears and microbats have large ears. Scientists divide bats into two groups-megabats and microbats. There are about 200 kinds of megabats and about 800 kinds of microbats. Megabats have large eyes and excellent eyesight. Most megabats have short, round ears. Most megabats eat fruit and have a good sense of smell so that they can find ripened fruit. They can have wingspans up to six feet (1.90 meters). They roost together in trees and wrap their wings around themselves to keep warm. Microbats are generally smaller than megabats with wingspans up to five inches (13cm). They have large ears and small eyes. Most microbats eat insects and use echolocation to hunt. Their ears and noses come in a variety of shapes and sizes.
- Are humans more like megabats or microbats? Have the children cup their hands around their ears. Continue talking to the children and ask if they notice a difference in the loudness of your voice. Ask them to tell why they think the sound is louder. Provide each child with a large paper circle (with approximately a 12 inches [30 cm] diameter) that has been cut in half. Ask the children to cup one half-circle paper around each ear to form a pair of larger ears. Talk to the children for a few minutes with their larger ears in place. Be certain to not talk louder than when the children initially listened to your voice. Ask them to share how you sounded to them this time. Did your voice sound louder? Explain to children that their enlarged ears were able to collect more sound waves which improves their hearing.
- Complete the activity sheet about the bats' noses as a class. Work together to match the names with the bat noses. If necessary, you can use reference books or the Internet to find the answers.
- copies of the activity page entitled, What a Nose!
- small mirrors
- paper circles 12 inches (30 cm) in diamter, cut in half