Horse Mouth Behaviour Related to Selected Kinematic Variables Representing Horse- Rider Interaction: a Pilot Study 2 3 4 Introduction

19 The objective of this pilot study was to investigate the influence of rein contact and 20 the movement of the rider’s hand on the horse’s behaviour, analysing data on horses ridden 21 in two different head and neck positions. We hypothesized that the rider’s hand movements 22 and rein tension generate behavioural responses from the horse, and more so when ridden 23 on the bit compared to free and unrestrained. Data were collected from seven dressage 24 horses/riders in sitting trot on a high-speed treadmill. Kinematics were recorded using a 25 12-camera, infrared-based opto-electronic system. Behavioural recordings were made from 26 video and three horses wore a rein tension meter. After stride split, data were standardised 27 to 0-100% stride duration. Mixed models were used to analyse how the behaviours varied 28 over the stride cycle; trial within horse was treated as a random effect, while percentage of 29 stride, rein tension and kinematic variables mainly related to the rider’s hand were entered 30 as fixed effects. Behaviours discerned were lip movement, mouth movement, open mouth, 31 ear position, head tilt and tail movement. Mouth movements were associated with the 32 suspension phase of the trot and percentage of stride was highly significant (P<0.0001). 33 Head and neck position was non-significant in the final models, while rein tension and the 34 distance between the rider’s hand and the horse’s mouth affected the amount of mouth 35 movements. The results from this preliminary study convey the large variations between 36 horses and riders, as well as the complexity of the interaction. 37 38