Department of Behavioral Biology, University of Bielefeld, Morgenbreede 45, 33615 Bielefeld, Germany.
J Acoust Soc Am. 2011 Mar;129(3):1631-41. doi: 10.1121/1.3531944.
Elucidating the information content of vocal signals is fundamental to the understanding of animal communication. Acoustically distinct calls produced in specific contexts allow listeners to predict future events and choose adequate responses. However, the vocal repertoires of most terrestrial mammals consist of a limited number of call types that vary within and between categories. These "graded signaling systems" are thought to be rich in information, at the cost of increasing uncertainty regarding call categorization. In this study, patterns of acoustic variation in grunts of wild chacma baboons (Papio ursinus) were assessed in relation to different contexts, callers' arousal, the presence of listeners, and individual identity. Although overall production specificity was low, and sensitive to the number of contexts under consideration, grunts given in three contexts could be statistically distinguished from each other. Contextual differences remained when controlling for caller arousal, suggesting that these differences cannot be explained by variation in arousal. No audience effect was detected, but individual identity was found to have an influence on acoustic structure. Overall, these results support the view that, in comparison to other signaling systems associated with hazardous conditions, lower production specificity might evolve under relaxed circumstances where unambiguous signaling is less important.
阐明声音信号的信息内容是理解动物通讯的基础。在特定情境下产生的具有独特声学特征的叫声可以让听众预测未来的事件，并选择适当的反应。然而，大多数陆地哺乳动物的叫声 repertoire 仅由有限数量的叫声类型组成，这些类型在类别内和类别间存在变化。这些“渐变信号系统”被认为具有丰富的信息，但在叫声分类的不确定性方面有所增加。在这项研究中，评估了野生狒狒（Papio ursinus）呼噜声的声学变化模式与不同情境、呼叫者的唤醒状态、听众的存在以及个体身份之间的关系。尽管总体产生特异性较低，并且对所考虑的情境数量敏感，但在三种情境下发出的呼噜声可以在统计上彼此区分。当控制呼叫者唤醒状态时，仍存在情境差异，表明这些差异不能用唤醒状态的变化来解释。未检测到听众效应，但发现个体身份对声学结构有影响。总体而言，这些结果支持这样的观点，即在与危险条件相关的其他信号系统相比，在不太重要的明确信号的放松环境下，较低的产生特异性可能会进化。
