Fig 1. Egyptian fruit bat vocalizations.

(A) Isolation call—produced by newborn pups. (B) A modified isolation call—the first non-isolation social calls of pups (appearing around the age of 20–40 days). White dotted lines in (A) and (B) mark the F0; notice the drop in F0. (C) Adult multisyllabic vocalization. One example, out of a diverse repertoire, containing a low F0 call (179 Hz). (D) Another example of an adult vocalization containing a high F0 call (1,431 Hz). Notice how in the first call in the sequence the harmonics are clearly separable due to the high fundamental. (E) The distribution of adult calls’ F0. Calls with F0 lower than 250 Hz were designated by us as “Low-F0,” and calls with F0 higher than 1,315 Hz were designated as “High-F0” (see Materials and methods for details). (F) The distribution of F0 among the 3 playbacks: Blue represents Low-F0 playback, red represents High-F0 playback, and black represents Control playback. Distributions are plotted as smoothed and normalized histograms. Numeric data for (E) and (F) are given in S1 Data. F0, fundamental frequency.