Figure 1. Example playback stimuli of a (a) grunt-only vocal sequence and derived call vocal sequences that include either a (b) moan, (c) wobble, or (d) yawn.

‘G’ refers to exhaled grunts, ‘I’ refers to inhaled grunts, ‘M’ refers to a moan, ‘W’ refers to a wobble, and ‘Y’ refers to a yawn. All of the vocal sequences include exhaled and inhaled call types. Spectrograms were made with Avisoft SAS Lab Pro.