Horses' behavior and heart rate in a preference test for shorter and longer riding bouts

Abstract

A Y-maze preference test was used to investigate whether horses prefer a shorter riding treatment over a longer riding treatment. In a pilot study (n = 4 horses), the maze was positioned with the 2 arms each pointing toward one of the short sides of the indoor arena, and in the main study (n = 14), the maze was rotated by 90°. Horses were 11 ± 4.4 years old and ridden regularly for at least 5 times/wk. They were conditioned to associate 1 exit of the maze with 1 lap of riding (R1), covering a distance of approximately 40 m at the walk or trot according to a predetermined schedule, and the other exit with 2 such laps (R2). Immediately afterward, riders dismounted, horses were led into the maze, and horses were let loose to make their choice in the maze. After exiting the maze, the rider mounted again and rode according to the chosen treatment. This procedure was repeated on the same day until statistical significance (P < 0.05) of preference was reached or up to a maximum of 35 trials. In addition, behavioral observations and heart rates were recorded. In the pilot study, all horses, regardless of the associated treatment, chose the left arm, which, unfortunately, pointed toward the arena's exit door. If horses were not caught immediately after exiting the maze (n = 5 occasions), they walked or trotted straight to the door. In the main study, 4 horses significantly preferred R1, 2 horses significantly preferred R2, and 8 horses had no significant preference. Heart rates were significantly (P < 0.05) higher during R2 (87.4 ± 2.6 bpm) than during R1 (79.5 ± 2.4 bpm). Except for tail swishing, no significant differences were found for the frequency of occurrence of behavior patterns between R1 and R2. Over the course of repeated trials, some horses became increasingly reluctant to enter and walk through the maze, and most showed increasing resistance to being remounted (e.g., sidestepping). Overall, the experimental setup did not seem to be appropriate to answer the research question. It is likely that the repeated mounting and dismounting caused discomfort or confused many of the horses to an extent that they did not actively select a treatment but rather searched for ways to evade further mounting (and riding). In conclusion, horses did not show a clear preference for either shorter or longer riding bouts, but their behavioral reactions indicate that they perceived mounting as uncomfortable and that their motivation to rejoin their herd-mates and/or to obtain feed in the barn was greater than their motivation to being ridden at all. Nevertheless, pronounced individual differences also seem to exist, with some horses showing little aversion to, and perhaps enjoyment of, being ridden, whereas others clearly preferring not to be ridden.

Introduction

Many riders believe that their horses enjoy being ridden. Also, the Fédération Equestre Internationale (FEI, 2006) calls the objective of dressage in their international rulebook “the development of the horses into a happy athlete through harmonious education.” However, scientifically, there are serious difficulties in complying with this request, as it is not known under which conditions, if any, horses get pleasure from riding. On the one hand, it is suggested that horses have a behavioral (i.e., psychological) need for locomotion itself. For example, the development of repetitive locomotor stereotypies is thought to be potentially linked–among other factors—to deprivation of exercise (Bachmann et al., 2003; McGreevy et al., 1995; Mills et al., 2005), which may lead to frustration from the behavioral motivation for exercise (Mills et al., 2005). Access to exercise opportunities can also reduce the occurrence of stereotypic behavior, as shown in horses in a study by Krzak et al. (1991) or in hamsters in a study by Gebhardt-Henrich et al. (2005). Thus, there may be a motivation for locomotory activity itself that does not have an immediate function or use to the animal (Fraser, 1992), such as in the case of play behavior (McDonnell and Poulin, 2002). Besides, there is a necessity for locomotion to maintain physical well-being (e.g., by walking while grazing or by fleeing from predators). Depending on the nature of their environment and availability of forage, free-ranging horses spend between 55% and 75% of their day in locomotion, which consists mainly of moving at a slow walk to graze (Duncan, 1980; Keiper, 1980; Salter and Hudson, 1982; Boyd and Bandi, 2002). Thus, a strong behavioral need for walking is likely to exist, and in horses that were observed after being exercised on a high-speed treadmill, walking (besides eating, elimination, and self-grooming) was not significantly influenced by exercise (Caanitz et al., 1991). Also, Houpt et al. (2001) pointed out that mares housed in tie stalls showed a compensatory increase of locomotion in turnout areas after being deprived of free exercise. The same compensatory effect was observed by Kurvers et al. (2006) and by Chaya et al. (2006) in foals, despite the fact that their horses were ridden on at least 5 d/wk. Therefore, exercise seems to be important to horses, and the possibility to express locomotory behavior after deprivation of exercise might result to some degree in the experience of pleasure in horses.

On the other hand, riders also frequently complain that their horses are “lazy,” that is, that they are disinclined to activity. Indeed, it seems likely that horses have mainly evolved to save energy. Horses are considered very cost-efficient movers (Minetti et al., 1999). For example, gait transitions in horses are suggested to occur at a speed that maximizes metabolic economy, presumably triggered by a system of biomechanical and metabolic factors (Wickler et al., 2003; Griffin et al., 2004). In each gait, horses move at a preferred speed that correlates with the minimum cost of transport (i.e., energy spent per unit body mass and distance moved) for that gait (Hoyt and Taylor, 1981; Wickler et al., 2001; Griffin et al., 2004), with walking being the overall cheapest gait in horses (Reilly et al., 2007). Also, even though Walker and Liem (1994) rightfully consider unguligrade to be an adaptation for speed, Reilly et al. (2007) suggest that it seems to have evolved in horses to make walking more cost-efficient rather than making running gaits cheaper, as unguligrade limbs serve as supreme pendulums. Behavioral studies on domestic horses housed in confinement showed that opportunities for exercise strongly influenced general activity. Jørgensen and Bøe (2007) found that daily forced exercise in a walker significantly reduced activity of stall-housed horses in turnout paddocks. Also, both the aforementioned studies that observed a compensatory effect (Houpt et al., 2001; Chaya et al., 2006) also found that horses that had daily access to free exercise significantly decreased their activity in the paddocks. Thus, it seems that after compensating for the deprivation of exercise, horses show relatively little motivation to spend more energy than necessary. Also, in recent studies with similar setup, compared with the present study, most horses seemed to prefer treatments involving lower workload rather than higher workload, both under a rider (Górecka-Bruzda et al., 2011) or on a treadmill (Lee et al., 2011). Therefore, from an evolutionary and ecological standpoint, it can potentially be concluded that although horses likely have a pronounced requirement for exercise, they have mainly evolved to save energy. These considerations lead to the questions of how much and what quality of locomotion fulfils the physical and psychological needs for exercise in riding horses (which are typically kept in a confined environment and provided with food), what role riding can play to satisfy locomotory requirements, and how that affects animal welfare. Therefore, the aim of the present study was to use a preference test to investigate whether horses prefer shorter over longer riding bouts. We hypothesized that horses would choose a lower workload if given the chance. We further hypothesized that horses with less energetic temperament, as assessed by their owners, will show a more pronounced preference for lower workload.