Behaviour 2019
Mouth opening as an indicator of emotional state in ewes
Lucie Barluet de Beauchesne1, Nolwenn Risser1, Matthieu Keller2, Nicolas Mathevon1, David Reby1. 1Equipe de Neuro-Ethologie Sensorielle ENES / CRNL, University of Lyon / Saint-Etienne, CNRS UMR5292, INSERM UMR_S 1028, Saint-Etienne, , France; 2Laboratoire de Physiologie de la Reproduction & des Comportements, INRA/CNRS UMR 7247, Université de Tours, , Tours, , France

While the capacity for articulation is generally considered to be highly limited in nonhuman mammals, simple vocal tract movements are increasingly identified as contributing to the vocal diversity of a diverse range of species. Ewes produce two main types of vocalizations: “low” bleats which are produced with a closed mouth when the lamb is at close range and “high” bleats, produced with an open mouth when the lamb is further from the mother. Here we investigate whether the degree of mouth opening encodes information about the emotional state of the ewe. We analyse vocalizations of 28 ewes in different arousal contexts. Our hypothesis is that ewes will modulate the degree of mouth opening accordingly to their arousal level. We predict that more aroused ewes will produce calls with high degree of mouth opening. Identifying simple precursor of the articulations responsible for the high phonetic diversity of human speech (e.g. mouth opening, lip rounding, laryngeal movements) in species that lack speech and language improves our understanding of the selective pressures that may have contributed to the origins of these abilities.