Searby Amanda, Jouventin Pierre
Behavioural Ecology Group, CEFE-CNRS, 1919 Route de Mende, F-34293 Montpellier Cedex 5, France.
Proc Biol Sci. 2003 Sep 7;270(1526):1765-71. doi: 10.1098/rspb.2003.2442.
Ewes of the domestic sheep ( Ovis aries ) display selective maternal investment by restricting care to their own offspring and rejecting alien young. This trait relies on individual recognition processes between ewes and lambs. Whereas identification at the udder is only olfactory, distance recognition is performed through visual and acoustic cues. We studied the effectiveness and modalities of mutual acoustic recognition between ewes and lambs by spectrographic analysis of their vocal signatures and by playbacks of modified calls in the field. Our results show that ewes and their lambs can recognize each other based solely on their calls. The coding of identity within the vocal signatures, previously unknown in sheep, is similar in lamb and ewe: it uses the mean frequency and the spectral energy distribution of the call, namely the timbre of the call. These results point out a simple signature system in sheep that uses only the frequency domain. This engenders a signal with low information content, as opposed to some highly social birds and mammal species that may integrate information both in the temporal and spectral domains. The simplicity of this system is linked to the roles played by vision and olfaction that corroborate the information brought by the vocal signature.
家养绵羊（Ovis aries）的母羊通过将照料行为限制在自己的后代身上并排斥外来小羊来表现出选择性的母性投资。这一特性依赖于母羊和小羊之间的个体识别过程。虽然在乳房处的识别仅靠嗅觉，但远距离识别是通过视觉和听觉线索进行的。我们通过对母羊和小羊的声音特征进行频谱分析以及在野外播放经过修改的叫声，研究了它们之间相互听觉识别的有效性和方式。我们的结果表明，母羊和它们的小羊仅通过叫声就能识别彼此。声音特征中身份编码在小羊和母羊中相似，此前在绵羊中并不为人所知：它利用叫声的平均频率和频谱能量分布，即叫声的音色。这些结果指出了绵羊中一种仅使用频域的简单特征系统。这产生了一个信息含量较低的信号，这与一些可能在时域和频域都整合信息的高度社会化的鸟类和哺乳动物物种形成对比。这个系统的简单性与视觉和嗅觉所起的作用有关，它们证实了声音特征所传达的信息。
