Sex Differences and Age Gradations in Vocalizations of Japanese and Lion-tailed Monkeys (Macaca fuscata and Macaca silenus)

Abstract

SYNOPSIS. Vocal repertoires of male and female non-human primates can differ by presenceor absence of sounds, acoustic form, and function or usage. Examples of sex-specificity in vocalizations are taken from field studies of two macaque species that differ in social organizationand habitat. They are used to illustrate sex-specific acoustic patterns and vocalizations thatare employed in socially different fashion by males and females. Some vocal sex differences develop from sounds shared in common by young animals of both sexes while others arise late in life by an acoustic pattern suddenly emerging only in males. Differences may be due to sexual selection, social suppression, morphological features, or because vocal sounds are linked to circumstances experienced by only male or female adults. The relation between social usage of some vocalizations by adults and youngsters affords insights into their signal value and into the underlying state of the vocalizing animal.