Figure 2. The amount of signalling in the private and public mode depends on nocturnal light conditions.

The amount of calling vs. tremulations (hatched and black bars, respectively) (A), the time spent signalling (B) and the ratio of calls vs. tremulations (C) differs significantly between new-moon and full-moon nights. (D) The overall sound-pressure level is significantly reduced by 13.6 dB under full-moon conditions compared to under new-moon conditions.