Determinants of yawning are still uncertain. As yawning seems to be triggered by stress and emotional contexts, we investigated specific correlates of yawning and stereotypic behaviours in horses. Study 1 investigated correlations in time between yawning and stereotypic behaviour in stereotypic horses from the same facility; study 2, involving riding school horses, investigated the cooccurrence of yawning and stereotypic behaviour at the individual level and in response to environmental factors (feeding time). Results showed that (1) stereotypic horses yawned more than the nonstereotypic horses, (2) yawning increased at the same time periods as stereotypic behaviours did, and (3) yawning frequency was positively correlated with stereotypic behaviour frequencies (study1). Different hypotheses are discussed: direct/indirect causal relationship and other factors susceptible to trigger both yawning and stereotypies. This study, underlining for the first time a cooccurrence of yawning and stereotypic behaviour, opens a promising line of investigation of this puzzling behaviour.
BackgroundHow do we bond to one another? While in some species, like humans, physical contact plays a role in the process of attachment, it has been suggested that tactile contact's value may greatly differ according to the species considered. Nevertheless, grooming is often considered as a pleasurable experience for domestic animals, even though scientific data is lacking. On another hand, food seems to be involved in the creation of most relationships in a variety of species.Methodology/Principal FindingsIn this study, we used the horse training context to test the effects of food versus grooming during repeated human-horse interactions. The results reveal that food certainly holds a key role in the attachment process, while tactile contact was here clearly insufficient for bonding to occur.Conclusion/SignificanceThis study raises important questions on the way tactile contact is perceived, and shows that large inter-species differences are to be expected.
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