Figure 6

Charts showing development of the male vocal pattern: (A) predicted values of the last form of a multi-modulation phrase (frequency Fm2) plotted against the log-transformed maximum frequency of calls emitted by the young males; and (B) predicted values of the last form of a multi-modulation phrase (frequency Fm2) plotted against the log-transformed age (months) of the young males. Values for each cases indicate the number of frequency modulations (two or more) in the second note of a mature form of the multi-modulation phrase (Fm2).