Analysis of rhesus monkey vocalizations: Maturation‐related sex differences in clear‐call frequency

In the first of two studies six like‐sexed pairs of rhesus macaques early in their third year of life were observed for two days, then separated for two days, and finally reunited for two days. In the second, about nine months later, the same animals were paired across sex and were separated in a similar fashion to that in the previous study. The number of distress‐related clear calls uttered by females remained stable through both studies, but the males showed a decrease with age in this behavior. The results of these two studies are compared with other research in which maturation‐related sex differences have become apparent. These comparisons suggested that decreases in the production of clear calls accompany the onset of puberty. Since the females which were involved in our research reached puberty shortly before the time of our first study and the males did so shortly before the second, the decreases in male clear‐call rate which we observed across these two studies appears to have been linked with peri‐pubertal influences.