Platypus Touch

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life sciences






one class period


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Before their visit, students will learn about ... their abilities to respond to touch.

Background Information

Platypus [graphic] hunt under water for snails, shrimp and other animals they find along stream bottoms. To find food in murky waters, they have a special organ-- their duckbill. On a platypus bill are two kinds of sensitive receptors. One feels by touch, the other picks up minute electrical signals given off by the contracting muscles [definition] of its prey.

This activity gives your students a closer look at how the sense of touch provides clues to what's around them.



  • Blindfold.
  • 6 strips of balsa wood (1 inch by 2 inch strips, approximately 4 inches long).
  • Straight pins.
  • Ruler.
  • Paper and pencil.


Why do we have the sense of touch?

How is it useful?


  1. Carefully push two pins through each of the balsa wood strips. Position the pins in the following ways:
    • Strip A: 1 inch apart
    • Strip B: 3/4 inch apart
    • Strip C: 3/5 inch apart
    • Strip D: 2/5 inch apart
    • Strip E: 1/5 inch apart
    • Strip F: 1/10 inch apart

  2. Blindfold Student 1 and give Student 2 the strips of wood.
  3. Have the Student 2 lightly touch the back of Student 1's forearm, starting with the pins on Strip A.
  4. Ask Student 1 how many pins he or she feels.
  5. Have Student 2 record the results.
  6. Repeat steps 3 and 4 with the other strips until Student 1 feels only one pin. Record the results each time.
  7. Try this on the inside of the forearm. Record any differences.
  8. Have students switch roles and repeat the experiment.


Was it hard or easy to tell what you were feeling? What made it hard? What made it easy?

Was the skin on the back of your arm and the inside equally sensitive?

Can you think of any reasons they might be different?

How important is a good sense of touch?

Do you think it's more important to some animals than others? Why?

Which animals have a good sense of touch? Where do they live? How do they use that sense?

Adapted from

Abruscato, Joe and Jack Hassard. The Whole Cosmos. Santa Monica, CA: Goodyear Publishing Co., 1977.

Additional Sources

Burnie, David. How Nature Works. Pleasantville, NY: Reader's Digest Association, Inc., 1991.

Whitfield, Philip, ed. The Human Body Explained. First ed., New York: Henry Holt and Company, 1995.