The vocal communication of the mongoose lemur (<i>Eulemur mongoz</i>): phonation mechanisms, acoustic features and quantitative analysis

We recorded vocalisations of wild <i>Eulemur mongoz</i> groups in Madagascar and the Comoros Islands, as well as from habituated captive groups housed in European and Madagascan zoos. Each vocalisation was quantitatively described by means of an acoustic analysis procedure implemented in Praat, and vocal types were distinguished both by ear and by the visual screening of spectrograms. Vocal signals were then associated with the context in which they were produced, to explore whether they occur only in specific behavioural contexts or are uttered in a range of situations. We found that mongoose lemurs possess highly context-specific aerial alarm calls and territorial calls, while the ‘croui-croui’ is usually emitted to communicate between individuals regrouping at sunset. The other calls we recorded, such as those including low-pitched pulse trains sometimes followed by harmonic elements, were not tightly associated with a particular context. Mongoose lemur utterances included calls produced with closed mouths and the involvement of nasal resonance, or with constant degrees of mouth opening or mandible ‘articulation’ during phonation. We observed 15 vocal types, nine of which were entered into a multivariate model that classified vocal types with a high degree of reliability. The second and third formants played an important role in discriminating among types of calls.本研究记录了栖息于马达加斯加与科摩罗群岛的野生蒙戈狐猴（Eulemur mongoz）种群的发声行为，同时采集了饲养于欧洲及马达加斯加动物园内、已习惯化的圈养种群的发声数据。每一条发声样本均通过Praat软件内置的声学分析流程完成定量描述，发声类型则通过人耳听辨与声谱图可视化筛查两种方式共同区分。随后将发声信号与其产生的行为情境进行关联，以探究这些发声行为是否仅局限于特定行为情境，或是可在多种场景中发出。研究发现，蒙戈狐猴存在高度依赖情境的空中掠食警报叫声与领域叫声，而"croui-croui"叫声通常用于日落时分重新集结的个体间通讯。本研究记录的其余叫声，例如包含低频脉冲串、后续有时带有谐波成分的叫声，则未与特定情境形成紧密关联。蒙戈狐猴的发声涵盖了闭口发声且伴随鼻腔共鸣的叫声，以及发声过程中保持恒定口腔开度或下颌活动的叫声。本研究共观测到15种发声类型，其中9种被纳入多元分类模型，该模型可对发声类型实现高精度分类。第二和第三共振峰（formants）在区分不同叫声类型中发挥了重要作用。