Fig. 4. Vocal development under exposure to playback of low-frequency calls.

(A) Average fundamental frequency used by pups from the manipulated (black, n = 3), control (blue, n = 5), and isolated (red, n = 5) groups in the first month after the group assembly. *P < 0.05 (Mann-Whitney U test). Dashed line, the adult average. (B) Detailed distribution of the fundamental frequencies of bat calls. Lower panel: The vocalizations heard by the control group (adult vocalizations, light blue) and the manipulated group (playback, gray). Upper panel: The vocal production of the different groups: control (blue), isolated (red), and manipulated (black). Note the frequent use of low frequencies in the manipulated group, mimicking the distribution of the playback calls.