Sensory Abilities of Horses and Their Importance for Equitation Science

Abstract

Vision, hearing, olfaction, taste, and touch comprise the sensory modalities of most vertebrates. With these senses, the animal receives information about its environment. How this information is organized, interpreted, and experienced is known as perception. The study of the sensory abilities of animals and their implications for behavior is central not only to ethology but also to animal welfare. Sensory ability, perception, and behavior are closely linked. Horses and humans share the five most common sensory modalities, however, their ranges and capacities differ, so that horses are unlikely to perceive their surroundings in a similar manner to humans. Understanding equine perceptual abilities and their differences is important when horses and human interact, as these abilities are pivotal for the response of the horse to any changes in its surroundings. This review aims to provide an overview of the current knowledge on the sensory abilities of horses. The information is discussed within an evolutionary context and also includes a practical perspective, outlining potential ways to mitigate risks of injuries and enhance positive horse-human interactions. The equine sensory apparatus includes panoramic visual capacities with acuities similar to those of red-green color-blind humans as well as aural abilities that, in some respects exceed human hearing and a highly developed sense of smell, all of which influence how horses react in various situations. Equine sensitivity to touch has been studied surprisingly sparingly despite tactile stimulation being the major interface of horse training. We discuss the potential use of sensory enrichment/positive sensory stimulation to improve the welfare of horses in various situations e.g. using odors, touch or sound to enrich the environment or to appease horses. In addition, equine perception is affected by factors such as breed, individuality, age, and in some cases even color, emphasizing that different horses may need different types of management. Understanding the sensory abilities of horses is central to the emerging discipline of equitation science, which comprises the gamut of horse-human interactions. Therefore, sensory abilities continue to warrant scientific focus, with more research to enable us to understand different horses and their various needs.

Enhanced Understanding of Horse–Human Interactions to Optimize Welfare

“…We are familiar with the idea that horses can see almost all the way around them, with a blind spot directly in front and behind them. The broad lateral view is enabled by the convex cornea paired with a horizontal visual strip [ 11 , 12 ], and despite not being able to see a full 360° field of view when motionless, the horse need only move his head slightly to achieve this [ 11 ]. We also know that horses have monocular vision except for the area directly in front of them.…”

“…We also know that horses have monocular vision except for the area directly in front of them. Because the eye is situated on the side of the skull sporting a long nose, binocular vision is limited to a narrow arc of 65–80° [ 11 ]. This narrow binocular field of view allows the horse to judge distance, for which the horse needs to raise its head.…”

Testing olfaction in equids: Age and gestational stage affects olfactory interest

“…7,8 )). How horses respond to odours is important 1) as it plays a key role in their everyday life 9 , and hence their welfare, and 2) as horse's reactions, and the ability to predict these reactions, are crucial for humans to ensure safety when handling and training horses 6 . An odour may be neutral to the horse, but it might also elicit either avoidance behaviour or have an attractive effect depending on the horse's perception of the odour.…”

“…Food flavour, foraging, and social behaviour 2,3 , mating and reproduction [3][4][5] but also in the evaluation of predation risk 1 to name but a few. It is therefore surprising how sparse research on the olfactory abilities of horses is 6 . The extent of this sparsity is noticeable when searching e.g.…”

Horses’ (Equus caballus) performance in visible and invisible displacement tasks is expressed in frustration behavior and heart rate

“…Collectively, this indicates that female horses are better instrumental problem solvers, while male horses outperform mares in visuo-spatial tasks. Coat colors is another individual characteristic described to be associated with greater sensitivity and reactivity e.g., chestnut colored horses (26). Although there is no research on the topic in horses, practitioners often report red or chestnut horses to be more reactive, and research from rodent studies show that red coat color is associated with greater pain sensitivity (27).…”