Animal Behavior Graduate Group, University of California-Davis, Davis, California.
California National Primate Research Center, University of California-Davis, Davis, California.
Am J Primatol. 2020 Jun;82(6):e23134. doi: 10.1002/ajp.23134. Epub 2020 Apr 16.
As social animals, many primates use acoustic communication to maintain relationships. Vocal individuality has been documented in a diverse range of primate species and call types, many of which have presumably different functions. Auditory recognition of one's neighbors may confer a selective advantage if identifying conspecifics decreases the need to participate in costly territorial behaviors. Alternatively, vocal individuality may be nonadaptive and the result of a unique combination of genetics and environment. Pair-bonded primates, in particular, often participate in coordinated vocal duets that can be heard over long distances by neighboring conspecifics. In contrast to adult calls, infant vocalizations are short-range and used for intragroup communication. Here, we provide two separate but complementary analyses of vocal individuality in distinct call types of coppery titi monkeys (Plecturocebus cupreus) to test whether individuality occurs in call types from animals of different age classes with presumably different functions. We analyzed 600 trill vocalizations from 30 infants and 169 pulse-chirp duet vocalizations from 30 adult titi monkeys. We predicted that duet contributions would exhibit a higher degree of individuality than infant trills, given their assumed function for long-distance, intergroup communication. We estimated 7 features from infant trills and 16 features from spectrograms of adult pulse-chirps, then used discriminant function analysis with leave-one-out cross-validation to classify individuals. We correctly classified infants with 48% accuracy and adults with 83% accuracy. To further investigate variance in call features, we used a multivariate variance components model to estimate variance partitioning in features across two levels: within- and between-individuals. Between-individual variance was the most important source of variance for all features in adults, and three of four features in infants. We show that pulse-chirps of adult titi monkey duets are individually distinct, and infant trills are less individually distinct, which may be due to the different functions of the vocalizations.
作为社交动物，许多灵长类动物使用声音交流来维持关系。在许多灵长类物种和叫声类型中都记录到了声音的个体差异，其中许多叫声可能具有不同的功能。如果识别同种个体可以减少参与高成本的领地行为的需要，那么听觉上识别邻居可能会带来选择性优势。或者，声音的个体差异可能是不适应的，是遗传和环境独特组合的结果。特别是配对的灵长类动物，经常参与协调的声乐二重奏，这些声乐可以被附近的同种个体听到很远的距离。与成年叫声相比，婴儿的叫声是短距离的，用于群体内的交流。在这里，我们对铜长尾猴（Plecturocebus cupreus）的不同叫声类型中的声音个体差异进行了两个独立但互补的分析，以测试不同年龄类别的动物的叫声类型是否存在个体差异，这些动物的叫声功能可能不同。我们分析了 30 只婴儿的 600 个颤音叫声和 30 只成年长尾猴的 169 个脉冲啁啾二重奏叫声。我们预测，鉴于它们在长距离、群体间通讯中的假定功能，二重奏的贡献将表现出更高程度的个体差异。我们从婴儿的颤音中估计了 7 个特征，从成年脉冲啁啾的声谱图中估计了 16 个特征，然后使用带有逐个样本交叉验证的判别函数分析对个体进行分类。我们正确地将婴儿分类为 48%的准确率，将成年个体分类为 83%的准确率。为了进一步研究叫声特征的变化，我们使用多变量方差分量模型来估计个体内和个体间两个水平上特征的方差分配。个体间方差是成年个体所有特征和婴儿个体四个特征中三个特征的最重要方差源。我们表明，成年长尾猴二重奏的脉冲啁啾具有独特的个体差异，而婴儿的颤音则不太具有个体差异，这可能是由于叫声的不同功能。
