Differential patterns of vocal similarity in tolerant and intolerant macaques

Abstract

The investigation of vocal similarity between individuals has provided evidence of the flexibility of communication signals. This study evaluates the impact of group membership, affiliative bonds, kinship and dominance on acoustic similarity in two primate species with different social styles, intolerant rhesus macaques and tolerant Tonkean macaques. We focused on the fundamental frequencies of the contact calls emitted by adult females. Close kinship promoted vocal similarity between individuals in both species, and also group membership in Tonkean macaques, indicating the involvement of experiential and/or genetic factors. In rhesus macaques more similarities were observed between partners with strong or weak dominance asymmetry than between those with medium asymmetry, which again points to the role of experience. No evidence was found that dominance influences vocal similarity in Tonkean macaques. Our results provide additional evidence to the flexibility of vocal signals produced by macaques, and reveal that it is influenced by social style.