Body size and vocalization in primates and carnivores

D L Bowling,J C Dunn,J C Dunn,W T Fitch,K-H Frommolt,R Ruprecht,M Garcia,M Garcia,A Stewart

doi:10.1038/srep41070

Abstract

A fundamental assumption in bioacoustics is that large animals tend to produce vocalizations with lower frequencies than small animals. This inverse relationship between body size and vocalization frequencies is widely considered to be foundational in animal communication, with prominent theories arguing that it played a critical role in the evolution of vocal communication, in both production and perception. A major shortcoming of these theories is that they lack a solid empirical foundation: rigorous comparisons between body size and vocalization frequencies remain scarce, particularly among mammals. We address this issue here in a study of body size and vocalization frequencies conducted across 91 mammalian species, covering most of the size range in the orders Primates (n = 50; ~0.11–120 Kg) and Carnivora (n = 41; ~0.14–250 Kg). We employed a novel procedure designed to capture spectral variability and standardize frequency measurement of vocalization data across species. The results unequivocally demonstrate strong inverse relationships between body size and vocalization frequencies in primates and carnivores, filling a long-standing gap in mammalian bioacoustics and providing an empirical foundation for theories on the adaptive function of call frequency in animal communication.

Highlights

Two facts about this combination of source and filter constrain the frequency content of vocalization
The proportion of variance explained by the carnivore ordinary least squares (OLS) regression could be improved considerably by excluding the two greatest outliers but we know of no a priori reason to exclude these species and reexamination of their data confirmed the accuracy of their exceptional status
Together with the overall greater dispersion of the carnivore data, these results show that the DF of a vocalization is generally a good predictor of body length, the relationship is much stronger for primates than it is for carnivores

Summary

Introduction

Two facts about this combination of source and filter constrain the frequency content of vocalization. Wallschäger (1980), for example, focused on male “song” in birds, whereas Gingras et al.[11] focused on male frog “advertisement calls”[10,11] This approach is not adapted to comparably diverse samples of mammals, where interspecific variability in vocal behavior is arguably greater and vocal repertoires often exhibit acoustically graded rather than discrete structures[19,20,21]. We use a novel algorithm to capture spectral variability and standardize vocalization selection, giving rise to data prepared for interspecific comparison These data are compared to body size data using both traditional and phylogenetically controlled regression techniques, resulting in the derivation of empirical size-frequency allometry in primates and carnivores

Methods

Results

Conclusion