Figure 4.

The Exceptionally Low Call Frequency of Howler Monkey Vocalizations

(A) Log-log plot of body weight versus F0 for a range mammals, highlighting the low-frequency vocalizations of howler monkeys (adapted from [28] with permission from AAAS).

(B) Log-log plot of vocal fold length versus F0 for a range mammals (adapted from [29] with permission from Elsevier), showing that the low-frequency vocalizations of howler monkeys are to be expected, given their remarkable vocal fold length.

Data sources are provided in the Supplemental Experimental Procedures. See also Figure S1.