Search results

Vision in the Equine

The horse is a prey animal, relying on their senses to assess their environment. Prey species are designed for scanning the environment compared to picking out sharp details. By scanning larger areas, prey is safer from a surprise attack from a predator. Horses use vision to orientate themselves, detect motion and distance, and evaluate the consistency of the environment. The equine eye is eight times larger than human eyes placed on the sides of their head (figure 1). The position of the eyes on the horse’s face accounts for differences in how horses see, dictate visual range, peripheral motion detection and depth perception. A horses’ ability to see depth is limited because their eyes are set so far apart. From most angles, horses cannot get a left-eye and right-eye view of the same object in one glance. Unlike humans, the horse is able to see images to the left and right at the same time due to the eyes being at the side of the head.

Vision in the Equine Compared to Humans

The horse is a prey animal, relying on their senses to assess their environment. Prey species are designed for scanning the environment compared to picking out sharp details. By scanning larger areas, prey is safer from a surprise attack from a predator. Horses use vision to orientate themselves, detect motion and distance, and evaluate the consistency of the environment.

The horses eye

Compared to humans, horses vision has the following characteristics:

  • Horses can detect the appearance of objects within an almost fully encompassing circle and are able to identify objects within most but not all of their panoramic field of view.
  • The horse may startle when an object passes from the field of vision from one eye to the other eye. For example, you take your dog with on a trail ride. The dog falls behind and jogs to catch up. The horse recognizes the dog on the left but when the dog moves over to the right side the horse jumps unexpectantly.
  • Horses are less able to distinguish details and contrast colors
  • Horses can see longer distances and can view the horizon and ground at the same time
  • Horses are easily blinded by bright light but can see better in dim light
  • Horses recognize patterns or outlines. For example, a horse is trail-ridden down a gravel road with no problem. The next time the horse is ridden down the gravel road there are garbage cans out by each drive and the horse spooks at the garbage can. This is most likely due to the garbage can being out of place. It was not there before and now it is a new item to be assessed.
  • Horses detect movement quickly. For example, you and a horse are trail riding, when a deer quite a way down the trail runs across the trail. The horse sees the movement of the deer and may react by trying to turn the other direction, or even taking off at a run.

Check out Vision in the Equine for more information on how horses see

The Horse's Ears and Hearing

Horses’ ears are a means of communication and listening for sounds. Using ten muscles, a horse can rotate each ear independently, up to 180 degrees, to locate, funnel, and magnify sounds. This allows the horse to position itself towards the sound that is making the noise.  Horses hear sounds over a wider range of frequencies than we do. In general, horses are good at hearing both higher and lower frequencies than humans. Horses can experience a reduction in hearing as they age. Hearing loss can be reflected in changes in behavior, such as not responding to voice cues or being more anxious. .

Horses ears tell a story. Humans can easily evaluate the ears to assess the horse’s behavior. When a horse is attentive to happenings all around him, the ears will actively move in all directions. A relaxed or drowsy horse has ears that are almost loose and drooping. The ears are held loosely, with the openings facing forward or outward. Neutral ears are held loosely upward, openings facing forward or outward. Ears pointed forward indicates the horse is interested in what is in front of them. Ears stiffly, pointed forward with flaring nostrils indicates the horse is anxious and extremely interested in what is ahead of him. Ears angled backward (with openings directed back towards a rider): usually mean attentiveness to the rider or listening to commands. Ears laid back tightly against the top of the neck indicates aggression or annoyance. This is also a warning to other horses or people. It is best to use caution when a approaching or working around a horse with tight, laid back ears.  Examples of positions of a horse’s ears are shown below.

Examples of Horses Ear Positions
Drooped ear

Drooped ears indicate drowsiness, mild sleep, or at ease

Resting ears
Drooped ears, lowered head, relaxed eyes indicates the horse is resting
Half back ears

Half back and flat are submissive and relaxed

Ears back while being ridden
Ears back while being ridden indicate the horse is attentive to the rider or listening to commands
Ears pricked forward Fjord ears forward

Ears held stiff with openings pointed directly forward indicate concentration, the horse is alert or focusing in front.

Ears back Horses ears turned back

Ears turned back are submissive, frightened, listening to noises behind them

Ears pinned back

Ears flat and pinned back indicates territorial protection. These ears should alert the handler or rider that the horse might be angry or irritated. 

Aggressive ears

Alarmed horse illustrating a tense neck, raised heads and ears pinned backwards. The horse may act in a hostile manner towards people or other horses.

Resources

  1. Beaver, B. 2020. Equine Behavioral Medicine. Academic Press.
  2. Williams, C. A. Basics of Equine Behavior. Extension Horses.

Horses Have A Highly Developed Sense of Smell

Olfaction (smell) is important for horse’s survival. Smell helps horse select what they eat (horses are sensitive to poisonous plants, moldy forage and grain, dirty water, etc.). Horses use smell to detect other horses by smelling feces, urine, and body odors. Smell is very important in detecting the sex and stage of estrous in mares.

Horses only breathe through their noses, or they can’t breathe through their mouths. The term for this is an obligate nose breather.  Horses have a large nasal cavity with structures called turbinate bones. Within the turbinate’s, inhaled air is mixed, warmed and distributes scents. Olfactory receptors are positioned towards the top of the nasal cavity. Olfactory epithelium lines the inside of the upper nasal cavity and connects olfactory neurons held in the turbinate’s to olfactory bulbs in the horse’s brain. The olfactory bulbs are relatively large in size and include numerous folds that increase the surface area over the receptor cells. Horses are thought to have about 300 million olfactory receptors, which is considerably higher than humans (five or six million olfactory receptors).

The horses nasal cavity
The horse's nasal cavity

Horses have an accessory olfactory system known as the vomeronasal organ that detects pheromones and volatile odors. When a horse breathes in strong odors, the vomeronasal organ expands, contracts, and sends the aroma to the brain. In response, the horse will display the flehmen response where they extend their neck, raise their nose, open their mouth slightly and curl the upper lip. The flehmen response is commonly demonstrated by stallions, but mares and geldings may also demonstrate the response. The flehmen behavior can appear as early as the first day of life in foals.

Flehmen response in horses
A horse displaying the flehmen response

Remember, odors can be used to smell predators, stage of estrous cycle, and social recognition of other horses and even people. It is beneficial to allow the horse to smell your hand, tack, or whatever is causing them to be anxious when working around a horse.

Resources

  1. Beaver, B. 2020. Equine Behavioral Medicine. Academic Press.
  2. Rorvang, M V., B L Nielsen, and A N McLean. Sensory Abilities of Horses and Their Importance for Equitation Science. Front. Vet. Sci 2020 7:633