A horse has the largest eye of any land mammal. The lateral placement of his eyes is consistent with that of most prey animals high in the food chain and is particularly suited to an animal that spends most of its time grazing and that must be constantly on the lookout for predators.
The first known horses had much shorter noses. The modern horse’s elongated nose might have evolved so that while grazing he has a higher field of vision and therefore is more likely to spot predators.
A horse sees with monocular vision, which means that each eye can work independently to relay separate messages to her brain. She also sees binocularly, wherein both eyes might focus together on the same object.
Monocular sight affords a horse a panoramic view of her world. She has three blind spots. The first is a couple of inches directly in front of her face. The second is directly behind her. The third is directly under her. Excluding these blind spots, her field of vision is nearly 360 degrees.
Binocular sight allows for a modicum of depth perception, or “stereoscopic” vision. This ability is very poor in horses. Her faculty of binocular vision expands to about 65 degrees directly in front of her. In order to increase this advantage, she need only to turn her head toward whatever she is looking at.
A horse possesses two external eyelids and one inner eyelid.
The eyelids together help keep her eye safe from debris or foreign objects that are ever present in her environment and keep the eye lubricated.
A horse’s ability to focus on objects that are close up is generally poor. However, a horse possesses a high degree of acuity, which is the ability to distinguish the details of objects at a distance. Their acuity is about one-third worse than a human’s, and about one-third better than a dog’s.
Horses have excellent night vision due to an abundance of rods, which are the ells of the retina that are sensitive to dim light, in the eye. Night vision is increased by the tapetum, a group of cells behind the retina, which reflects light back to it. An excess of rods comes at a cost of cones, the cells that allow an eye to see color. The jury is still out on whether or not horses can see in color.
Some researchers suggest that horses might be able to see shades of yellow, green, blue, and red.
Horses have trouble adjusting to sudden changes of light conditions because of a lack of cones, the cells that capture bright light and color. This should always be considered when leading a horse from low light to bright, or vice versa.
A horse’s hearing is exceptional. The outside ear is mostly cartilage, with the ability to move independently and in all directions, controlled by sixteen different muscles. Along with its wide, funnel shaped opening, the ear, like a horse’s vision, is designed to pick up sound from a 360 radius. A horse’s ears are uniquely sensitive to a wide range of both low- and high-frequency sounds and can discern between near or faraway sounds.
A horse’s keen sense of smell is her best aid to memory. It helps her in the wild to detect predators, and remember where the best grasses grow and where water can be found. A domestic horse uses smell to determine if his grain, hay, grass, and water are fresh and not poisonous. They are particularly attracted to sweet smells and tastes, such as apples, carrots, bananas, candy, and even beer.
The flehmen response is when a horse curls his upper lip in reaction to an odd smell or taste, or even a mare in season. It is thought to heighten his sense of smell.
Touch is said to be a horse’s most acute sense. He gathers information with his lips, skin and hair, and his nose, which is mostly cartilage and soft tissue. Their bodies are so sensitive that they can feel a fly anywhere on them, isolate the muscle, and twitch to dispel the fly.
Touch is of great importance to a horse socially as well. They are herd animals.
As such, they need the contact with other horses that comes with daily rituals of grooming, nudging, or horse play for their happiness, sense of security, and general well-being. If you cannot provide your horse with the company of another horse, then a farm animal, such as a goat or pig, will often suffice. Your human contact and affection is important too, but probably not constant enough for sufficient companionship. The horse’s practice of mutual grooming, nudging, and general horsing around demonstrates their need for the intimacy of touch.
Besides communicating by touch, horses have a vocal language that communicates a wide range of needs, desires, and emotions to their herd mates and to you as well.
- •The Snort. The snort signifies curiosity, fear, or a cross between the two. It also acts as an intimidation to a possible predator or challenger.
- •The Squeal. The squeal is a warning or sign of defensiveness, telling another horse to beware. Two horses getting to know each other will squeal.
- •The Nicker. The nicker is a low-pitched sound meant as a greeting or beckoning to other horses or humans in close proximity.
- •The Neigh or Whinny. This is the loudest of the horse’s vocalizations.
- It is often used as a location call from horses that are out of visual range from each other.
How and when your horse uses these vocalizations will often point to strong characteristics of her personality. If you pay attention to what your horse is telling you, your mutual bond will deepen.
A Sixth Sense?
What you attribute to a horse’s uncanny abilities to read your mind, anticipate your actions, or just know things that seem outside of the realm of sensory perception is mostly due to the horse’s extremely acute senses that work together to form intuition. When a horse seems to know that a rider is nervous, or a handler inexperienced, it is more likely that he smells sudden perspiration, feels the vibration of tense muscles, recognizes improper actions and responses, or all of the above.