Snort acoustic structure codes for positive emotions in horses
While the vocal coding of human and animal internal states has been widely studied, the possible acoustic expression of “positive” emotions remains poorly known. Recent studies suggest that snorts (non-vocal sounds produced by the air expiration through the nostrils) appear to be reliable indicators of positive internal states in several ungulate species. Here, we hypothesised in horses that the acoustic structure of the snort could vary with the subjects’ current emotional state. Indeed, a preliminary sound analysis of snorts let us suggest structure variations related to the presence of pulsations. We recorded snorts from 20 horses living in a riding center. Auditory playbacks run with 20 humans first confirmed the existence of two snort subtypes, i.e. one pulsed and one non-pulsed. Observations were then conducted to compare the distribution of these two subtypes according to the location (stall/pasture) of the signaller as a contextual determinant of its internal state and to its ears’ position as a reflection of its emotional state. We found that both subtypes were preferentially observed in positive contexts, but that pulsed snorts were even more associated with highly appreciated situations (in pasture and with ears forward). This study is a step further in the identification of indicators of positive emotions in horses and more generally in the understanding of the acoustic emotions’ coding.
KeywordsSnort Unvoiced signal Pulsation Positive emotion Bioacoustics Horse
Authors are grateful to the riding school of La Touche in Ploërmel (France) and particularly to S. Gicqueau and all the staff for letting them observe the horses and for their help on site.
This study was funded by IFCE (Institut français du cheval et de l’équitation) (http://www.ifce.fr/), the Fonds Eperons (https://www.fondseperon.com/), the University of Rennes (https://www.univ-rennes1.fr/), and the CNRS (http://www.cnrs.fr/).
Compliance with ethical standards
The study was carried out in 2016 in accordance with the European Parliament and the European Union Council directive 2010/63/UE relative to the protection of animals used for scientific purposes and complied with the current French laws related to animal experimentation (decree no. 2013-118 of 1 February 2013 and its five implementation orders (JO of 7 February 2013), integrated in the Code rural and the Code of the maritime fishing under no. R. 214-87 à R. 214-137). Being only observational, our study did not require any further ethical authorization. The private owner of the riding school allowed our research to be conducted on his site. Animal husbandry and care were under the management of the riding school staff.
Conflict of interest
The authors declare that they have no conflict of interest.
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