The effect of choice on horse behaviour, heart rate and heart rate variability during human-horse touch interactions

Touch interaction between humans and horses is a feature common to almost all equine-assisted services (EAS) although less is known about how horses perceive this tactile stimulation during human-horse interactions. The current study assessed the effect of three types of touching (patting, stroking, scratching) on three anatomical body locations (neck/shoulder, body, hindquarter) of therapy horses (N = 10) on horse behaviour, heart rate (HR) and heart rate variability (HRV) under forced and free-choice touch treatments. Human participants (25 experienced and 24 less experienced with horses) each interacted individually with four horses in both treatment conditions while in a familiar round pen. During the forced touch treatment, the horse was tethered for the duration of the test (4.5 min) and the participant was instructed to touch each body location with each type of touch, switching every 30 s. During the free-choice touch treatment, the horse was loose in the pen and the participant, standing in the centre, was instructed to touch the horse only if the horse came within arm’s reach. A Generalized Linear Mixed Model with repeated measures examined the effect of treatments, touch type, location and human experience with horses on horse behaviours, HR and HRV. Oral behaviours, restlessness and tail swishing were more frequent, while head shaking behaviour was less frequent during forced than free-choice touch treatments (all p < .0206). Tail swishing was less frequent when touching the hindquarters in comparison to touching the neck/shoulder and body (p < .0001). Free-choice touch treatments resulted in lower odds of high (OR = 0.10, 95 % CI (0.05, 0.20)) and even (OR = 0.04, 95 % CI (0.03, 0.06)) head positions and higher odds of low head positions (OR = 9.75, 95 % CI (7.84, 12.12)) compared to forced touch treatments. Horses were less likely to keep their ears oriented toward the participant during free-choice touch than forced touch treatments (OR = 0.19, 95 % (0.15, 0.23)). Horse HR was higher during free-choice touch compared to forced touch treatments (p = .0007). Horse HRV was lower during interaction with experienced than with less experienced participants (p = .0293). The results demonstrated that forced touch treatments were not perceived positively by therapy horses highlighting the importance of providing choice and agency for therapy horses during EAS. The findings could be reflected in the guidelines of therapy horse organizations to minimize human risk of injury and ensure a good life for horses.