HORSE SENSES

The senses are an important partof what makes horses behaviorallydistinct. Animals share the fivebasic senses: vision, audition(hearing), olfaction (smell), gustation(taste) and touch. The sensesare the tools that an animal uses tointeract with its environment. Assuch, the senses can be consideredstarters of behavior. There is a temptation to relatehuman senses to horses, but horsesand people have basic differences inhow they see, feel, taste, smell andhear their environment. We do notcompletely understand horsesenses, but the things we havelearned have greatly added to ourhorse knowledge. A review of thisinformation can be helpful inunderstanding horses.

VISION
Did you ever look at a horse eye to eye?If you have, you probably noticed a fewthings. First, they have a very large eye and avery large pupil. Second, the eyeball is placedmore to the side of the head, which giveshorses a wider field of vision. Predator species, such as dogs and coyotes,have eyes placed toward the front oftheir head. This narrows their total field ofvision but it increases their binocular (usingtwo-eyes) visual field. Binocular vision givesthe predators better depth perception and amore concentrated field of vision. Preyspecies, such as horses, sheep and cattle, havea much wider visual field. With only slighthead movement, horses can scan their entiresurroundings. If there is a threat, the behavioralresponse is generally to flee. Much of the width of the visual field thathorses see is observed with only one eye.This is called monocular vision. When ahorse sees an object with its monocularvision, it will tend to turn toward it so thatboth eyes can see it (with binocular vision),and the ears can better hear it. There issometimes a brief visual shift as the horseswitches from monocular to binocular vision,which sometimes causes an unexplained“spooking” of the horse . The size of the pupil improves the abilityof a horse to pick up movement. The large head to observe close objects.Conversely, a horse tends to lowerits head to observe faraway objects. In spite of the wide field ofvision, there is a “blind spot”directly behind the horse. Peopleshould avoid approaching a horsefrom behind, because their presencemay not be detected until they areclose, and this could startle thehorse. Some horses may instinctivelykick in this situation. Ifapproaching a horse from the rearcannot be avoided, make a soothingnoise to announce your presence.Do not “sneak up” on a horse frombehind. Another question often asked isdo horses have color vision? Formany years it was believed thatboth horses and cattle were colorblind. If horses can distinguishcolors, it is unlikely that horses’ability to see color is equal to otherspecies, such as humans.
HEARING
In spite of its importance, thereis limited information about theauditory (hearing) sense of horses.We know horses are sensitive tohigh-pitched noises and the releaseof stress-related hormones inresponse to sudden loud noises suchas firecrackers or barking dogs.Horses become nervous and difficultto handle when stress hormonesare elevated, so it may be useful toavoid loud or shrill noises whenhandling or moving horses. The horse can amplify andpinpoint sound with its ears. Soundarrives at each ear at slightlydifferent times, which allows thehorse to use sound as a means totell where the sound came from.The horse can then move its ears,head or its entire body to tell moreabout the source of the sound. Thisskill is probably as important assight and smell for keeping thehorse, as a prey species, alive.
SMELL
The horse’s sense of smell(olfactory) may be the most difficultfor humans to understand.Horses have a more highly developedsense of smell than humans,and they use their ability to distinguishdifferent odors more in theireveryday lives. Horses use their sense of smellin a number of ways. Horses usesmell to identify other horses,particularly when a mare uses smellto pick out her foal from a group.Another common use of smell isduring mating. The stallion constantlychecks mares to detect theones in heat (estrus). The classichead-raised, lip-curling behavior ofthe stallion (bulls and rams, also) ashe smells females is called theFlehmen response. This trait,which may be occasionally observedin females, is due to aspecial organ (vomeronasal organ)above the roof of the mouth, whichhumans do not have.
Horses probably use theirolfactory sense to locate water andidentify subtle or major differencesbetween pastures and feeds. Smellalso triggers behavioral responses.There are, for example, horses thatdo not like the smell of tobaccosmoke or may react negatively tothe odor of certain medications. Some people believe that horsescan sense when a person is afraid— which is probably true — andthis is often referred to as horses’ability to “smell fear.” It is possiblethat the horse can smell some smallchange in the fearful human, but itis equally likely that the horse cansense the human nervousness viaother senses.
Horses will use their sense ofsmell to select fresh feed in preferenceto spoiled feed. The next timeyou are tempted to dispose ofmoldy feed or hay by feeding it to ahorse, try smelling it yourself. Thenremember, if it smells bad to you, itmay smell worse to the horse. (Thismay not always work, however,because some molds, such as highlypoisonous aflatoxins, cannot bedetected by humans.)
TASTE
The sense of taste in horses isprobably not as important as thesense of smell, and it is difficult toseparate behavioral responses thatare due primarily to taste fromresponses caused by the olfactorysense. Using their sense of taste,however, is part of why horses cantell one feed from another. Whenpresented with a variety of feeds,horses will select certain feeds overothers. In practical situations, suchas under grazing conditions withmultiple forage species present, thehorse will select different types andspecies than either sheep, goats orcattle.
There have been experiments todetermine if animals have “nutritionalwisdom.” This is based onthe premise that horses will attemptto eat feeds that provide them withthe nutrients needed. In most cases,however, horses are unlikely tobalance their own ration whenprovided a variety of feeds. Ifpossible, they will consume feeds ata level far higher than necessary toprovide essential nutrients. Forexample, salt is often provided tomeet horses’ requirement forsodium; however, horses will oftenconsume many times the amount ofsalt needed to meet the requirement.Fortunately, there is no evidencethat over consumption of salt willcause health problems if adequatewater is available.
TOUCH
The sense of touch is certainlywell developed in horses, and is oneof the most important senses interms of human interaction withhorses. The nose, lips, mouth andpossibly the ears are the mostsensitive areas to touch and, consequently,most readily lend themselvesto feeling behavior. Althoughhooves do not respond to touching,they should not be regarded aswithout feeling. In fact, variousparts of the hoof are able to feeltouch, as anyone who has shodhorses or trimmed hooves canrelate
Other areas of the body are alsosensitive to touch. The flanks forexample, are particularly sensitive,and can pick up a light signal fromthe rider. The ribs are also sensitive,as are the withers and back. Understanding the degree towhich horses are sensitive to touchcan be valuable to the trainer. Forexample, knowing that horses canfeel the slightest touch with theirlips underscores the importance ofdeveloping “a light touch” on thereins, and making certain thatbridles be correctly fit to the horseshead and mouth. Knowing that thehorse can feel the slightest shift ofweight in the saddle illustrates whythe rider’s position is important asthe mount is guided toward a jumpor other maneuver. Poor position,exaggerated movement or excessiveforce are confusing to horses andresult in poor performance.
The sense of touch is undoubtedlyimportant in interactionbetween animals. Foals seek bodilycontact with their dams (mothers),and mares respond to the touchingbehavior of their foals in variousways, including milk let-down inresponse to the nuzzling/sucklingstimulus of foals. Another example of horses’sensitivity to touch is related to electric fences. Anyone who hasused electric fences with a varietyof grazing animal species knowsthat horses are very sensitive toelectricity. To use electric fenceswith horses, the wire should beplaced approximately at noseheight. High-quality, well-groundedchargers should be used, and horsesshould be trained to the fence byintroducing them to a well-constructedpermanent electric fencefor their first experience.The Role of the Sensesin Training The horse must rely on its sensesin order to perceive the signals(often called cues) that the rider isgiving. Touch and sound are theprimary senses which are used This is not a horse trainingmanual. There are a number oftraining publications, often developedby breed organizations orsuccessful trainers, which canprovide more detailed informationabout how to train your horse.However, understanding thebehavioral basis that the horse hasfor recognizing cues through itssenses can be helpful in training.The basic steps for using sensesin training are:Stimuli – The trainer / rider initiatesa cue, thus providing a stimulus tothe horse.Sense – The horse “senses” thestimulusResponse – The horse responds tothe stimulus with an actionReinforcement – The trainer “reinforces” in a positive way byrewarding the correct response andin a negative way by discouragingan incorrect response. Good trainers recognize that eachhorse has its own “combination”and will develop at its own pace.Intelligence, individual energy level,previous experience and many otherfactors may affect response. Patience,repetition and building insmall increments of success willgive the best results. Over-use ofnegative reinforcement may yield ahorse that is prone to nervousness.Use positive reinforcement morethan negative if long-term developmentis desired. Do not expectreasoning powers that are beyondthe powers of the horse to give. An extremely well-trained horsethat was trained by a professional islikely to “come untrained” whenridden by a novice if reinforcementschedules are not maintained.