Variation in strepsirhine infant isolation calls and its evolutionary implications

Abstract

Infant cries (isolation calls) are ubiquitous among mammals. Their contribution to infant survival suggests a strong role for natural selection, making it appropriate to consider the cries of strepsirhine infants in an evolutionary context. Infants provide an opportunity to study vocal mechanisms without the complications of hormonal factors or complex vocal repertoires. The isolation calls of strepsirhine infants exhibit a diverse array of acoustic features, and infants of some species produce short-duration "click" vocalizations indicative of vocal tract specializations unique among primates. We report on several subtypes of vocalizations produced by infant strepsirhines when separated. The clade-speci fic nature of some of these subtypes leads us to propose that the isolation calls of infant prosimians constitute a particularly useful behavioral category for comparative studies.