Mechanisms and evolution of roaring-like vocalization in mammals

Abstract Typical examples for roaring are provided by rutting red deer stags and male elephant seals, but also by both sexes of lions. Roaring is characterized by a low fundamental frequency and lowered vocal tract resonances (formants). The fundamental frequency depends on the mass and length of the vocal folds and, thereby, correlates with larynx size. A lowered dispersion of formants is decisively determined by vocal tract length that correlates with body size. Several species evolved pronounced larynx retraction causing vocal tract elongation and, therefore, acoustically simulating a larger body size. Roaring, however, remains an honest signal and it may prevent conflict escalation by acoustic assessment of a rival's quality. If roaring is restricted to the males of a species, it is directly linked to their reproductive success. If roaring occurrs in both sexes, it may improve intergroup spacing, territory defense, or communication in a densely forested habitat.