Abstract

In animal vocal communication, the development of adult-like vocalization is fundamental to interact appropriately with conspecifics. However, the factors that guide ontogenetic changes in the acoustic features remain poorly understood. In contrast with a historical view of nonhuman primate vocal production as substantially innate, recent research suggests that inheritance and physiological modification can only explain some of the developmental changes in call structure during growth. A particular case of acoustic communication is the indris’ singing behavior, a peculiar case among Strepsirrhine primates. Thanks to a decade of intense data collection, this work provides the first long-term quantitative analysis on song development in a singing primate. To understand the ontogeny of such a complex vocal output, we investigated juvenile and sub-adult indris’ vocal behavior, and we found that young individuals started participating in the chorus years earlier than previously reported. Our results indicated that spectro-temporal song parameters underwent essential changes during growth. In particular, the age and sex of the emitter influenced the indris’ vocal activity. We found that frequency parameters showed consistent changes across the sexes, but the temporal features showed different developmental trajectories for males and females. Given the low level of morphological sexual dimorphism and the marked differences in vocal behavior, we hypothesize that factors like social influences and auditory feedback may affect songs’ features, resulting in high vocal flexibility in juvenile indris. This trait may be pivotal in a species that engages in choruses with rapid vocal turn-taking.

中文翻译：

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为歌唱而生！会唱歌的灵长类动物的歌曲发展

 抽象的

在动物声音交流中，像成人一样发声的发展是与同种动物适当互动的基础。然而，引导声学特征个体发生变化的因素仍然知之甚少。与非人类灵长类动物发声本质上是天生的历史观点相反，最近的研究表明遗传和生理修饰只能解释生长过程中叫声结构的一些发育变化。声音交流的一个特例是蝾螈的歌唱行为，这是链球菌灵长类动物中的一个特例。经过十年的大量数据收集，这项工作首次对歌唱灵长类动物的歌曲发展进行了长期定量分析。为了了解这种复杂的声音输出的个体发育，我们研究了青少年和亚成年蝾螈的声音行为，我们发现年轻人开始参与合唱的时间比之前报道的要早几年。我们的结果表明，频谱-时间歌曲参数在生长过程中经历了本质的变化。特别是，发声者的年龄和性别影响了 indris 的发声活动。我们发现频率参数在不同性别之间表现出一致的变化，但时间特征显示男性和女性不同的发育轨迹。鉴于形态上的性别二态性水平较低以及发声行为的显着差异，我们假设社会影响和听觉反馈等因素可能会影响歌曲的特征，从而导致幼年蝾螈具有较高的发声灵活性。对于一个以快速声音轮流进行合唱的物种来说，这一特征可能至关重要。