Language-like efficiency in whale communication

Abstract

Human language and other animal communication systems tend to be optimized for efficiency—the benefits that they bestow relative to the costs of learning and producing them. One of the clearest manifestations of communicative efficiency is Menzerath's law, which predicts that longer sequences (e.g., songs) will be comprised of shorter elements (e.g., notes). In this study, I assessed the evidence for Menzerath's law in cetaceans by analyzing vocal sequences from 16 baleen and toothed whale species and comparing them to spoken data from 51 human languages. The vocalizations of 11 of the 16 whale species included in this analysis adhere to Menzerath's law to an extent that is comparable to, and sometimes far greater than, what is observed in spoken human language data. Humpback whales exhibit Menzerath's law both at the level of notes within phrases and phrases within songs. There is also a broad tendency for vocal shortening—elements or intervals getting shorter over the course of sequences—which may point to simple energetic constraints. Overall, the results of this study suggest that the vocalizations of a wide range of whale species have undergone compression for increased communicative efficiency.