title: Investigating determinants of yawning in the domestic (Equus caballus) and Przewalski (Equus ferus przewalskii) horses.
abstract: Yawning is rare in herbivores which therefore may be an interesting group to disentangle the potential function(s) of yawning behaviour. Horses provide the opportunity to compare not only animals living in different conditions but also wild versus domestic species. Here, we tested three hypotheses by observing both domestic and Przewalski horses living in semi-natural conditions: (i) that domestic horses may show an elevated rate of yawning as a result of the domestication process (or as a result of life conditions), (ii) that individuals experiencing a higher level of social stress would yawn more than individuals with lower social stress and (iii) that males would yawn more often than females. The study involved 19 Przewalski horses (PHs) and 16 domestic horses (DHs) of different breeds living in large outdoor enclosures. The results showed that there was no difference between the PH and DH in yawning frequency (YF). PHs exhibited much higher levels of social interactions than DHs. There was a positive correlation between yawning frequency and aggressive behaviours in PHs, especially males, supporting the idea that yawning may be associated with more excitatory/stressful social situations. A correlation was found between yawning frequency and affiliative behaviours in DHs, which supports the potential relationship between yawning and social context. Finally, the entire males, but not castrated males, showed much higher levels of yawning than females in both species. The intensity (rather than the valence) of the interaction may be important in triggering yawning, which could therefore be a displacement activity that helps reduce tension.
authors.affiliation: Department of Animal Behaviour, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzębiec, Poland. a.gorecka@ighz.pl.
authors.forename: Aleksandra
authors.identifier: http://orcid.org/0000-0002-2770-2278
authors.initials: A
authors.lastname: Górecka-Bruzda
authors.affiliation: CNRS UMR 6552 Ethologie Animale et Humaine, University of Rennes 1, Rennes, France.|School of Veterinary Sciences, University of Bristol, Langford House, Langford, Bristol, BS40 5DU, UK.
authors.forename: Carole
authors.initials: C
authors.lastname: Fureix
authors.affiliation: CNRS UMR 6552 Ethologie Animale et Humaine, University of Rennes 1, Rennes, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Ouvrard
authors.affiliation: CNRS UMR 6552 Ethologie Animale et Humaine, University of Rennes 1, Rennes, France.|UMR CNRS 5263 Cognition Langue, Langage, Ergonomie, Laboratoire Travail et Cognition, University of Toulouse Jean Jaurès, Toulouse, France.|Association pour le cheval de Przewalski: TAKH, Station biologique de la Tour du Valat, Arles, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Bourjade
authors.affiliation: CNRS UMR 6552 Ethologie Animale et Humaine, University of Rennes 1, Rennes, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Hausberger
mesh_terms: D000374:Aggression / Q000502:physiology*; D000818:Animals; D000829:Animals, Domestic; D000835:Animals, Wild; D001522:Behavior, Animal / Q000502:physiology; D001947:Breeding; D005260:Female; D006736:Horses / Q000502:physiology* / Q000523:psychology; D008297:Male; D009919:Orchiectomy / Q000662:veterinary; D012737:Sex Factors; D013045:Species Specificity; D013315:Stress, Psychological / Q000503:physiopathology; D015000:Yawning / Q000502:physiology*
keywords: Domestic horse; Przewalski horse; Sex; Stress; Welfare; Yawning