Figure 2
From: The progression pattern of male hyrax songs and the role of climactic ending
Progression plots of (a) standardised peak frequency and (b) standardised peak amplitude of vocal element and their proportional location through the signal. The trend lines show linear slope estimates with CI as shaded areas. Bachelor songs were performed by males without stable association with a female group. Resident songs were performed by males that were regularly observed associating with a female group. Induced songs were performed following an external trigger event. Spontaneous songs were performed without any observable trigger. N i denotes number of individual males and N s denotes number of songs in a corresponding category.
