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A Batty Mapping Activity: A Study of Echolocation

Lesson Objectives
Related National Standards
Tools and Materials Needed
Estimated Time to Complete Lesson
Teaching Strategy
Procedure
Helpful Web Sites
Assessment Recommendations
Extensions/Adaptations
 

Lesson Objectives

Students will find how bats use echolocation to find their prey by using echoes to map the direction and distance to various echo sources in their surroundings. Science skills are used in the collection of data as echoes are timed and math skills used to calculate the distance to the echo sources. Geography is used in the construction of the map of the area and math skills are used for a scale drawing.

By the end of this activity, students will:

  1. Determine the minimum distance at which an echo can be heard.
  2. Determine the distance to a distant echo source by using reflected sound waves.
  3. Draw an area map with echo sources and approximate distance located.
  4. Explain how bats find prey at night without the use of eyesight.

Related National Standards from the McRel Standards Database

http://www.mcrel.org/standards-benchmarks/

Science

  1. Knows that an organism's patterns of behavior are related to the nature of that organism's environment (e.g., kinds and numbers of other organisms present, availability of food and resources, physical characteristics of the environment).
  2. Knows ways in which species interact and depend on one another in an ecosystem (e.g., producer/consumer, predator/prey, parasite/host, relationships that are mutually beneficial or competitive).
  3. Knows that vibrations (e.g., sounds, earthquakes) move at different speeds in different materials, have different wavelengths, and set up wave-like disturbances that spread away from the source.

Tools and Materials Needed

  1. Copy of the program "Borneo: Island in the Clouds."
  2. Stop watches (1 for each student is ideal).
  3. Sharp noise source (whistle or firecracker).
  4. Tape measure (100 foot) or meter sticks.

Estimated Time to Complete Lesson

Approximately one week. One class period to watch the video. One class period to discuss the concepts and to use the bat resources on the Internet. One period to determine the distance for echoes, and draw a rough area map and determine the speed of sound. One period to take area echo readings and determine the distance to echo sources and apply to the map.

Teaching Strategy

Background Information: Bats are a paradox that inspires both fascination and revulsion. Depending on the culture, they are seen as either a symbol of good luck or of evil. However, bats have been found to be of great importance to the ecology of an area as they consume huge swarms of damaging insects and pollinate trees and plants. In Borneo, the bats leaving the cave consume over 6 tons of insects each night.

Bats are not the blind creatures of myth. However, they are night feeders and rely on echolocation to find their prey. Each bat sends out a series high-pitched cries that reflect from the bodies of the insects and gives the bat an idea of the distance and direction to that insect. Using a series of cries, the bat is able to hone in on the prey in pitch-black conditions and avoid running into obstacles. The police use a similar technique when identifying speeding cars with a radar gun.

Students can use echoes from a sharp, short sound to identify the distance to stationary objects outside of the school building. While the best results are obtained by using firecrackers, acceptable results may be obtained with short blasts from a police whistle. Be sure to check regulations in your area.

Sound travels approximately 340 meters/sec (1100 ft/sec). If a sound produces an echo in 4 seconds, the object producing the echo would be half that distance away (the sound takes half the time to get to the object and half the time to return). The distance for an object with a 4-second echo return would be 2 sec X 340 meters/sec or 680 meters (2200 feet). By applying the distance found to a sketch of the area, students can identify the distance to various suspected echo sources and build a scale map. The distance allows students to discriminate between possible sources and to eliminate other possibilities. The direction to the objects is usually estimated but could be determined with a compass if more accuracy is desired.

Video Segments

18:40-22:15 Segment describing the bats and how they prepare for hunting for insects. Make special mention of the bat ears shown about 20 seconds after the segment begins.

Procedure

  1. Watch the "Living Edens: Borneo" video. Discuss the food sources for a number of the animals. Note that some eat only vegetation, others eat only other animals and still others will eat both. Discuss the bat flight and the search for insects. An example of bat sounds can be found on the Bat Conservation International site.
  2. Take students to an outside area with a flat wall. Have students line up about five feet from the wall and have one student in the middle clap once loudly. Ask students if they could hear an echo from the wall (the answer will be no). Back up from the wall in several meter intervals until an echo is heard by a majority of students. Reposition the line until the class determines the approximate distance at which an echo can first be heard. The distance will be about 17 meters or 50 feet. By dividing the distance to the wall by the speed of sound, it is found that a human must have a delay of about .1 seconds to hear an echo. Bats are much better than this.
  3. Have from a point in the center of the area to be mapped, have students draw a rough sketch of the area with buildings and other large, flat objects that may be echo sources identified.
  4. Have the students take the timing devices and tell them to click the watch on when they first hear the sound and click it off when they hear an echo. The person making the sound should do a countdown to when they will make the sound. Students should collect a fairly large number of times, about 40 or 50.
  5. Place the numbers in order from smallest to largest and a pattern should occur that identifies echo sources. If the groupings are hard to identify, take more readings. Some of the values will not fall in the groupings and may be discarded as inaccurate readings.
  6. Students should average the groupings and determine an average time of echo for each of the echo sources. By taking the value, dividing by 2 and multiplying by the speed of sound, the distance to each source may be found.
  7. Apply the distances to the sketch maps of the area. The maps may be redrawn on graph paper using a standard scale.
  8. Apply the activity to bats and the use of echolocation.

Helpful Web Sites

Bat Conservation International
http://www.batcon.org/index.html
Bat Conservation International is an organization that promotes understanding of bats. This site has bat information, a place to ask questions, samples of bat sounds and more.

Jim Buzbees Bat Links Page
http://www.nyx.net/~jbuzbee/bat_house.html
This is probably the most extensive list of bat links on the entire Internet. There is information on bats, hat houses, bat house temperatures, school sites, information site and educational activities.

"How Stuff Works: Radar and Echoes"
http://www.howstuffworks.com/radar.htm
"How Stuff Works" is a large site that explains how many common things work. This is the section on radar and echoes.

National Federation of the Blind
http://www.nfb.org/kids.htm
This is the NFB resource page for kids. It has general information on blindness, information about the causes and treatment, and links to companies and organizations.

Assessment Recommendations
Students may be assessed through their participation in the class discussions. Calculations may be graded for correctness. The map would be assessed by evidence of student application of the calculation results to the finished map. Depending on the age of the student, the map may be drawn to scale.

Extensions/Adaptations

  1. The local police department can be used as an outside source to come and discuss both traffic safety and the use of radar to identify the speed of cars. Most police departments will provide a demonstration and will use hand-held radar devices to determine the distances to objects that the children identified in their echo experiment.
  2. Students may investigate how the blind are able to navigate in their surrounding by the use of a cane. The cane is used both to find objects by touch and to allow the detection of more distant objects by echoes.



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