Potential Sources of High Frequency and Biphonic Vocalization in the Dhole (Cuon alpinus)

Biphonation, i.e. two independent fundamental frequencies in a call spectrum, is a prominent feature of vocal activity in dog-like canids. Dog-like canids can produce a low (f0) and a high (g0) fundamental frequency simultaneously. In contrast, fox-like canids are only capable of producing the low fundamental frequency (f0). Using a comparative anatomical approach for revealing macroscopic structures potentially responsible for canid biphonation, we investigated the vocal anatomy for 4 (1 male, 3 female) captive dholes (Cuon alpinus) and for 2 (1 male, 1 female) wild red fox (Vulpes vulpes). In addition, we analyzed the acoustic structure of vocalizations in the same dholes that served postmortem as specimens for the anatomical investigation. All study dholes produced both high-frequency and biphonic calls. The anatomical reconstructions revealed that the vocal morphologies of the dhole are very similar to those of the red fox. These results suggest that the high-frequency and biphonic calls in dog-like canids can be produced without specific anatomical adaptations of the sound-producing structures. We discuss possible production modes for the high-frequency and biphonic calls involving laryngeal and nasal structures.

双发声（Biphonation），即叫声频谱中存在两个独立基频的现象，是犬型类犬科动物发声活动的显著特征。犬型类犬科动物可同时产生低频（f0）与高频（g0）两种基频。与之相对，狐型类犬科动物仅能产生低频基频（f0）。本研究采用比较解剖学方法，以探究可能与犬科动物双发声相关的宏观结构，对4只圈养豺（Cuon alpinus，其中雄性1只、雌性3只）及2只野生赤狐（Vulpes vulpes，雌雄各1只）的发声解剖结构进行了调查。此外，本研究还对本次解剖研究所用的同批次圈养豺的发声叫声的声学结构展开了分析。所有受试圈养豺均能产生高频叫声与双发声叫声。解剖重建结果显示，豺的发声形态与赤狐极为相似。上述结果表明，犬型类犬科动物的高频叫声与双发声叫声，无需发声结构出现特异性解剖适应性改变即可产生。本研究讨论了涉及喉部与鼻腔结构的高频叫声及双发声叫声的潜在产生机制。