An evolutionary approach to perissodactyl vocalizations.

Abstract

Approximately 65 million years ago, dinosaurs were displaced by mammals. In a then highly forested world, the perissodactyls (odd‐toed ungulates) became the largest group of large mammals, consisting of an estimated 15 families. We hypothesize that they started to develop a melodic component in their tonal vocalizations in order to provide identity in this restricted visibility setting. With time, large areas shifted to grassland, favoring mammals with compound stomachs, namely, artiodactyles (sheep, cattle, etc.) and resulting in the decline of the perissodactyls to only three families (equines, tapirs, and rhinos) today. Although all the remaining perissodactyls still retain a melodic component in their vocalizations, it appears to be less developed in those that adapted to the open grassland environment, such as the plains zebra. There a simple tonal call (as the artiodactyles have, too) is sufficient to draw attention; additional information can be obtained visually. On the other hand, those that continued in a forested location such as the Sumatran Rhino have developed a more lyrical call to compensate for reduced visibility.