Fig. 3From: Age related decline in female lar gibbon great call performance suggests that call features correlate with physical conditionCall quality index by caller age. The call quality index is based on rankings within the population in regards to four characteristics of the female great call: The maximum F0 frequency of the climax, the delta F0 frequency of the climax, the duty cycle of the climax, and the number of high notes producedBack to article page