If whinnies, nickers and squeals are a universal equine language, Przewalski’s horses seem to express their emotions in a different way, according to a new study from Switzerland.
A wild species related to the domestic horse but distinct from it, Przewalski’s horses were preserved in captivity and reintroduced to the wild in the 1990s. To determine whether vocal expressions differ among species or may be affected by domestication, researchers from ETH Zurich and the University of Bern recorded the vocalizations of 23 Przewalski’s horses of various ages living in two different wildlife preserves.
The calls were recorded during affiliative interactions or when a food reward was anticipated, which the researchers presumed would be positive emotional experiences, and during aggressive confrontations with herdmates or when individuals were separated from the herd, which researchers presumed would be negative experiences. The various acoustic parameters of each call were analyzed and then compared to similar data collected from the vocalizations of domesticated horses in previous studies.
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Although the vocalizations of the Przewalski’s horses were found to be generally similar to those of domesticated horses, the researchers identified a few significant differences. Specifically, domesticated horses seem to indicate the valence (positive versus negative) of emotions through the duration of whinnies and frequencies in ways that Przewalski’s horses do not. These differences, the researchers explain, could be due to genetic differences between the species or may have developed as part of the domestication process.
Reference: “Vocal expression of emotional valence in Przewalski’s horses (Equus przewalskii),” Scientific Reports, August 2017
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