Bat Echoes

Objectives

Student will learn to:

Method

Students will simulate a natural predator/prey relationship in a game of tag.

Background

Almost all bats in North America are insectivores (insect eaters). A single Little Brown Bat can eat as many as 3,000 mosquito-sized insects in a single night. Bats are often seen at dusk swooping around street lights and outdoor lamps. The light attracts night-flying insects, the bats' food source.

Despite the saying "blind as a bat", bats can see quite well. However, sight is not what makes them such skillful predators. Bats use their sense of hearing to navigate and find food in the dark. Using their voices and their ears, bats locate objects by a method called echolocation.

The ears of bats are specially adapted to gather sound waves. Their ears are large with a broad, scoop-like form and project well above their heads to allow better hearing. While flying, bats continuously emit high-pitched, ultrasonic squeaks through their mouths or noses. These sounds are inaudible to humans. The emitted sounds radiate out until they hit an object and bounce back to the bats as an echo. Hearing the echo, bats can judge the distance, location, and size of objects in their paths. If an object appears large, bats steer away; if the object is small and in motion, the bat dives quickly to catch the insect prey.

Materials

Procedure

  1. Explain to students that bats are not blind, but that eyesight may not be the most important sense they use to find food. Ask if anyone knows how an insect-eating bat finds its food. After discussion, give a basic explanation of how echolocation works.
  2. Ask the students to form a large circle. This circle will represent the area in which a bat will be looking for food.
  3. Ask for a volunteer to be the hungry insect-eating bat. Have that student come into the center of the circle.
  4. Ask if anyone knows what kinds of insects are the prey for this predator. As students make suggestions (mosquito, gnat, moth, some kinds of beetles, and some kinds of crickets) have them also come into the center of the circle until you have three to five types of prey. (Lightning bugs are usually not bat food because they are poisonous.)
  5. Explain that when the game starts, the bat will be blindfolded not because it cannot see, but because its hearing will be most important. The bat will send out its sonar by saying "Bat!" often. Tell the insects that this represents the bat's sonar signal hitting them to see if anything is near. Although the insects may move around, they must return the signal each time by returning their echo, saying loudly what they are (example: "Mosquito!" of "Gnat!"). The bat must hear their echoes to try to catch them. Instruct the environment circle to remain quiet to allow the bat to concentrate on its echolocation skills. Have students hold hands to maintain their positions and provide a protected area in which the bat and insects must remain.
  6. After being blindfolded, the bat can start saying "Bat!". Remind the bat that it is hungry, and the insects that they must respond. The bat must tag the insect to "capture" it. The captured prey become part of the environment circle. Play several rounds to allow all students the chance to experience either the predator or prey position.

Note: With a mixed age group or a very aggressive bat, the insects might not stand a chance. A student acting as a tree or lamp post can be added in the middle of the circle and respond "Tree" or "Lamp post" to each bat signal sent. This stationary object will provide a little natural protection for the flying insects.

Evaluation

Variation for Young Students

Young students will have an easier time remembering their roles and responding if you have all the students inside the circle be moths (or any one type of appropriate insect). The insect type may vary in a future round.

Variation for Older Students

After completing one or two rounds, have the environment circle play an active part in returning signals each time the bat calls. Have the students look around and determine what else would return the bat's signal. If outside: trees, a fence, cars, buildings? If inside: the walls, chairs, tables? Assign two to four students standing beside each other a particular item they will represent and continue around the circle, with every few students representing different items in the bat's surroundings.. When the bat sends its signals out, each person in the circle will respond. You may introduce background interference by adding constant shuffling of feet of the students in the circle. It will add confusion and promote concentration by the bats to differentiate between prey and the natural surroundings.