Figure 4

Set-up of the frequency and call rate experiments. Schematic representation of the playback experiments (call rate and frequency). All measurements are in cm. Two speakers (S) were located in a triangle of 45° at the ends of a plank. A 50 cm long stick (dark-grey line) was used to obtain the correct distance of 1 m between the female and the plank. Two nails (dark-grey circles) acted as a makeshift to obtain the triangle of 90° between the female and the plank. The triangle was formed when the head of both nails were in line with the female.