Ectotherms (ecto = outside, therm = temperature) such as toads and crickets do not have an internal mechanism of controlling their body temperatures. Thus the body temperature of a frog in the water is the same as that of the water and the body temperature of a cricket and a frog sitting near a pond are the same as air temperature. Male frogs and crickets use muscle actions to produce their calls. Because muscles work faster and more smoothly at warmer temperatures, one might expect that on cold nights, some aspect of the call such as its rate of repetition might be decreased over the pattern exhibited on warm nights. Where environments have this influence, females processing the male calls would either have to correct for air temperature (do the math) or their processing of the calls would have to be temperature-dependent as well. In this exercise you will calculate the effect temperature has on frog and cricket songs.

Exercise 5.1. Temperature and Frog Call Rates (3-12)

Frogs produce sounds by forcing air through the larynx (the upper end of a windpipe that contains vocal chords). The air vibrates the vocal chords and a special vocal sac is blown up like a balloon to amplify the sound (make it louder). What instrument does this remind you of? (A Scottish bagpipe perhaps?)

• Find out how temperature affects call songs by finding Exercise 5.1. on the Unit 10 Behavior CD (frog pictures) starting with an introduction on track 8
• You will need a piece of paper, a pencil and a ruler to complete this exercise.
• Listen to the instructions to the exercise on track 9.
• Complete the exercise presented on tracks 10-22.

Exercise 5.2. Temperature and Cricket Call Rates

The male cricket song consists of a series of chirps. The chirp is produced by a process similar to that of a person playing a violin. The wing moves over a comb-like structure (bow over strings) that is positioned on a sound-box filled with air. The sound box amplifies the sound (makes it much louder).
You will need a piece of paper, a pencil and a ruler to complete this exercise.

• Find the Unit 10 Behavior CD with the calling frog pictured on it.
• Go to track 23 for introduction to temperature effects on calls.
• Go to track 24 to listen to a cricket call
• Play tracks 25 - 38 for the activities associated with Exercise 5.2. At the end, you will be able to tell air temperature from the number of chirps a cricket makes in its call in a 10 sec interval.