Figure 7. Spatio-temporal structure in an actual frog chorus obtained by our field research on 15th June in 2011.

(A) A light pattern of the sound-imaging devices deployed at the paddy field. While the horizontal and vertical axes represent the time and device index, the colored plots represent the light intensities of the devices¹⁴. An index was placed on each device from one end of the edge, which was closer to the camera, to the other end. The attached right panel shows the summation of light intensity of each device. This data set represents the calls of 6 frogs numbered from 1 to 6. (B) Calling times and positions of male Japanese tree frogs. Each black dot represents the calling times and positions of the 6 frogs. We observed that some pairs of these frogs called synchronously. For instance, the 2nd and 3rd frogs stably synchronized in almost anti-phase π (see the two red arrows). (C) Time series data of the order parameters, R_cluster, R_wavy, and R_in, which were calculated from the calling times of the 6 male Japanese tree frogs. Red, blue, green, and black lines represent the time series data of R_cluster, R_wavy for k = 1 and k = −1, and R_in, respectively. R_cluster stably took considerably larger values than R_wavy and R_in, which meant that two-cluster antisynchronization was realized in this chorus.