Division of Animal Welfare, Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Länggassstrasse 120, 3012, Bern, Switzerland.
Ethology and Animal Welfare Unit, Institute of Agricultural Sciences, ETH Zürich, Universitätstrasse 2, 8092, Zurich, Switzerland.
Sci Rep. 2017 Aug 18;7(1):8779. doi: 10.1038/s41598-017-09437-1.
Vocal expression of emotions has been suggested to be conserved throughout evolution. However, since vocal indicators of emotions have never been compared between closely related species using similar methods, it remains unclear whether this is the case. Here, we investigated vocal indicators of emotional valence (negative versus positive) in Przewalski's horses, in order to find out if expression of valence is similar between species and notably among Equidae through a comparison with previous results obtained in domestic horse whinnies. We observed Przewalski's horses in naturally occurring contexts characterised by positive or negative valence. As emotional arousal (bodily activation) can act as a confounding factor in the search for indicators of valence, we controlled for its effect on vocal parameters using a behavioural indicator (movement). We found that positive and negative situations were associated with specific types of calls. Additionally, the acoustic structure of calls differed according to the valence. There were some similarities but also striking differences in expression of valence between Przewalski's and domestic horses, suggesting that vocal expression of emotional valence, unlike emotional arousal, could be species specific rather than conserved throughout evolution.
情绪的声音表达被认为在进化过程中是保守的。然而，由于从未使用类似的方法比较过密切相关的物种的情绪声音指标，因此尚不清楚情况是否如此。在这里，我们研究了普氏野马的情绪效价（负面与正面）的声音指标，以查明在物种之间，特别是在马科动物之间，效价的表达是否相似，这是通过与之前在驯养马的嘶鸣声中获得的结果进行比较得出的。我们观察了在具有正性或负性效价的自然发生的情况下的普氏野马。由于情绪唤醒（身体激活）可能会在寻找效价指标时产生混淆因素，因此我们使用行为指标（运动）来控制其对声音参数的影响。我们发现，积极和消极的情况与特定类型的叫声有关。此外，叫声的声学结构也因效价而异。普氏野马和驯养马在效价的表达上存在一些相似之处，但也存在明显的差异，这表明情绪效价的声音表达，与情绪唤醒不同，可能是物种特异性的，而不是在进化过程中保守的。
