Natural Clocks: Cricket Chirps

1. Natural Clocks: Cricket Chirps Biology II—Mrs. Regina Chustz H.L. Bourgeois High School

2. The Snowy Tree Cricket • There are several natural phenomena - the rate ants walk, the rate fireflies flash, the rate of a terrapin's heartbeat, and even the frequency of human alpha brain-wave patterns - that follow the Arrhenius equation closely. We will look at one well-studied case, the chirp rate of the snowy tree cricket, oecanthusfultoni. This little cricket is familiar to outdoor enthusiasts as a chirping thermometer. (It is found in every US state except Hawaii, Alaska, Montana, and Florida.)

3. The Snowy Tree Cricket

4. The Snowy Tree Cricket • Outside magazine, in its June, 1995, issue, had a story on this cricket's thermometric ability. They state, "snowy tree crickets are more accurate than most [cricket species]; their chirps are slow enough to count, and they synchronize their singing." If you turn their chirps into sound intensity versus time graphs, you can see each individual chirp and immediately see how the chirp rate (and even each individual chirp) varies with temperature

5. Chirp Rate at Various Temps

6. The Arrhenius Equation • What does Arrhenius say? First, the Arrhenius equation is a fairly complicated function of temperature. It says the rate depends on the exponential of a constant quantity, –Ea/R, divided by the absolute temperature. The cricketeers propose a simple linear rate expression: • T/°F = (# chirps per 13 seconds) + 40 • or • Rate = Chirps per 13 seconds = T/°F – 40

7. Here is some actual data.