Solitary snowy tree cricket males typically maintain a very precise rhythm in their chirp rate. The plot on the left shows the distribution of a sample (from over one hour of calling) of chirp periods from a single male. The entire range is less than 15 ms and the standard deviation is less than 1% of the average chirp period. This behavior can be likened to a clock or oscillator having some natural period, T_o. One interesting feature of the snowy tree cricket is that when males call in groups, they synchronize their chirps. The synchrony is caused by the acoustic coupling between males in the chorus. That is, the period of a male’s chirp can be increased or decreased if the male hears the chirps of neighboring males.