Could snorts inform us on how horses perceive riding?

Several previous studies have shown that working conditions (including riding) can induce stress in horses. Riders' actions and postures, when inappropriate, induce stress and conflict behaviours during riding and welfare impairment and negative emotional states outside work. Optimistic biases have been found in leisure horses, which, amongst positive management factors, were ridden with loose reins and low hands. Thus, one can wonder whether horses may positively perceive work or parts of it. Indicators of positive emotions are poorly known yet but we recently found that, out of the working context, a non-vocal acoustic signal, snorts, could reflect mild positive emotions in horses. We hypothesized that snorts could help identifying the working phases and actions appreciated by horses. An overview of snort production in 127 horses spread over 16 riding schools was first conducted to highlight a potential site effect. Results show a great difference in snorts frequency between facilities which may be due to different riding techniques. In order to test this hypothesis, we then focused on 37 horse-rider dyads by scoring horses' postures (neck) and riders' positions (hand, reins) during, but also out of the context of snort production. Results show that snorts were particularly associated with phases when the rider technique, i.e. long and loose reins, allowed more comfort for the horse, especially while walking. Results were more mitigated for higher paces since the association of snorts with signs of comfort was less clear-cut. Snorts could therefore be useful tools for identifying better practices, especially at slower gaits. However, care has to be taken at higher paces.