Vocal tract length and acoustics of vocalization in the domestic dog (<i>Canis familiaris</i>)

TLDR

The physical properties of the vocal tract generate formants, and in species such as humans listeners can infer body size from formant patterns; in dogs, selective breeding has produced wide head‑size variation, implying vocal‑tract length differences may influence interbreed communication. The study measured vocal‑tract length in dogs of diverse breeds using lateral radiographs and recorded growling acoustics to analyze formant dispersion. Vocal‑tract length, body mass, and formant dispersion were significantly correlated, indicating that formant dispersion conveys body‑size information, while the weak link between vocal‑tract length and the first formant suggests a non‑uniform vocal‑tract shape.

Abstract

ABSTRACT The physical nature of the vocal tract results in the production of formants during vocalisation. In some animals (including humans), receivers can derive information (such as body size) about sender characteristics on the basis of formant characteristics. Domestication and selective breeding have resulted in a high variability in head size and shape in the dog (Canis familiaris), suggesting that there might be large differences in the vocal tract length, which could cause formant behaviour to affect interbreed communication. Lateral radiographs were made of dogs from several breeds ranging in size from a Yorkshire terrier (2.5 kg) to a German shepherd (50 kg) and were used to measure vocal tract length. In addition, we recorded an acoustic signal (growling) from some dogs. Significant correlations were found between vocal tract length, body mass and formant dispersion, suggesting that formant dispersion can deliver information about the body size of the vocalizer. Because of the low correlation between vocal tract length and the first formant, we predict a non-uniform vocal tract shape.