Exploration of the acoustic structure and contextual occurrence of affiliative vocalisations in red wolves (Canis rufus)

Abstract

The purpose of this study was to determine the structure and nature of tonal vocalisations produced by red wolves. Video recordings of captive wolves from a breeding facility were analysed. Vocalisations were composed of 1--30 sound units. Linear units included squeaks (2600--9600 Hz) and wuhs (100--1600 Hz); non-linear units accounted for 22% of sounds and included between-type frequency jumps, harmonic and pure-tone biphonations, squeaks with sidebands, and squeak jumps. Five tonal vocalisation types were identified based on unit composition: squeaks 48.4%, wuhs 19.3%, and three mixed vocalisations 21.9%. Vocalisations occurred primarily during affiliative interactions and were relationally directed: squeaks were the most common vocalisation in individual activities and were distributed across relational states; wuhs were common in interactions, and directed toward pen-mates; and mixed vocalisations occurred at moderate rates across activity states, and were relationally directed. Tonal vocalisations were common, affiliative in nature, and differed in contextual occurrence by type.