Division of Natural Sciences, New College of Florida, Sarasota, Florida 34243, USA.
Department of Animal Biology and Physiology, University of Yaounde I, Yaoundé, Cameroon.
J Acoust Soc Am. 2021 Oct;150(4):3028. doi: 10.1121/10.0006734.
Even among the understudied sirenians, African manatees (Trichechus senegalensis) are a poorly understood, elusive, and vulnerable species that is difficult to detect. We used passive acoustic monitoring in the first effort to acoustically detect African manatees and provide the first characterization of their vocalizations. Within two 3-day periods at Lake Ossa, Cameroon, at least 3367 individual African manatee vocalizations were detected such that most vocalizations were detected in the middle of the night and at dusk. Call characteristics such as fundamental frequency, duration, harmonics, subharmonics, and emphasized band were characterized for 289 high-quality tonal vocalizations with a minimum signal-to-noise ratio of 4.5 dB. African manatee vocalizations have a fundamental frequency of 4.65 ± 0.700 kHz (mean ± SD), duration of 0.181 ± 0.069 s, 97% contained harmonics, 21% contained subharmonics, and 27% had an emphasized band other than the fundamental frequency. Altogether, the structure of African manatee vocalizations is similar to other manatee species. We suggest utilizing passive acoustic monitoring to fill in the gaps in understanding the distribution and biology of African manatees.
即使在研究较少的海牛目中，非洲海牛（Trichechus senegalensis）也是一种了解甚少、难以捉摸且脆弱的物种，难以被发现。我们首次利用被动声学监测来探测非洲海牛，并对其发声进行了首次描述。在喀麦隆奥萨湖进行的两个为期 3 天的监测中，至少检测到了 3367 次个体的非洲海牛发声，大多数发声发生在午夜和黄昏时分。我们对 289 次高质量的音调发声进行了特征描述，这些发声的最低信噪比为 4.5 dB，其特征包括基频、持续时间、谐波、次谐波和强调频带。非洲海牛的基频为 4.65±0.700 kHz（平均值±标准差），持续时间为 0.181±0.069 s，97%的发声包含谐波，21%的发声包含次谐波，27%的发声除基频外还有强调频带。总的来说，非洲海牛发声的结构与其他海牛物种相似。我们建议利用被动声学监测来填补了解非洲海牛分布和生物学的空白。
