Research Institute for Humanity and Nature, National Institutes for the Humanities, 603-8047 Kyoto, Japan.
J Acoust Soc Am. 2011 Jun;129(6):3623-9. doi: 10.1121/1.3586791.
Dugongs (Dugong dugon) produce bird-like calls such as chirps and trills. The vocal responses of dugongs to playbacks of several acoustic stimuli were investigated. Animals were exposed to four different playback stimuli: a recorded chirp from a wild dugong, a synthesized down-sweep sound, a synthesized constant-frequency sound, and silence. Wild dugongs vocalized more frequently after playback of broadcast chirps than that after constant-frequency sounds or silence. The down-sweep sound also elicited more vocal responses than did silence. No significant difference was found between the broadcast chirps and the down-sweep sound. The ratio of wild dugong chirps to all calls and the dominant frequencies of the wild dugong calls were significantly higher during playbacks of broadcast chirps, down-sweep sounds, and constant-frequency sounds than during those of silence. The source level and duration of dugong chirps increased significantly as signaling distance increased. No significant correlation was found between signaling distance and the source level of trills. These results show that dugongs vocalize to playbacks of frequency-modulated signals and suggest that the source level of dugong chirps may be manipulated to compensate for transmission loss between the source and receiver. This study provides the first behavioral observations revealing the function of dugong chirps.
儒艮（儒艮）发出鸟类般的叫声，如啁啾声和颤音。研究了儒艮对几种声刺激回放的发声反应。动物暴露于四种不同的回放刺激下：野生儒艮的记录啁啾声、合成下扫音、合成恒频声和静音。与恒频声音或静音相比，播放广播啁啾声后，野生儒艮的发声频率更高。下扫音比静音引起更多的发声反应。广播啁啾声与下扫音之间没有发现显著差异。在播放广播啁啾声、下扫声和恒频声时，野生儒艮的啁啾声与所有叫声的比例以及野生儒艮叫声的主频均明显高于静音时。随着信号距离的增加，儒艮的鸣叫的声源级和持续时间显著增加。在信号距离和颤音的声源级之间没有发现显著的相关性。这些结果表明儒艮对调频信号的回放会发出叫声，并表明儒艮的鸣叫的声源级可能被用来补偿源和接收器之间的传输损耗。本研究首次对儒艮的鸣叫功能进行了行为观察。
