Two Tracking: Horses show a great variety of motor patterns other than those already mentioned (see Table 3.2). For example, during a walk or slow trot, a horse can shift from a direct line of travel (single track) to a sideways motion of varying degrees in what is often called two tracking.
With sideward flexion of the back, such locomotion can occur in the direc-tion of flexion (traver or renver) or with the convex curve of the body leading (i.e., shoulder-in). Some degree of leg crossing occurs in such maneuvers.
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Table 3.2: Motor Patterns, Postures, Emissions, and Other Behavior Patterns Characteristic of the Horse Ethogram
(see text and illustrations for clarification)
Ethologists who have especially developed equine ethogram material with illustrations include Feist and McCullough (1976), McDonnell and Haviland (1995), Bettina (von Goldschmidt) Hughes, and Angela Glatthaar.
Circling: Turning during locomotion, especially continuous tight turns (circling), can involve leg crossing. Turns can be pivotal primarily around the forelegs or around the hindquarters (e.g., pirouette). In the pirouette the forelegs describe a larger circle than the hindlegs (Seunig 1956).
Piaffe and Passage: Leg motion can occur with little or no forward move-ment of the body. When a horse maintains a lofty, sustained trot-like action while remaining in place, showing springiness in its leg movements, it is called piaffe.
When similar leg motions create a slow forward floating movement, it is referred to as the passage (the parade step of the ancient Greek horses).
Swimming: Horses while swimming maintain leg movement in a sequence resembling the trot. The head is elevated, keeping the eyes and nostrils above the water surface.
Jumping: Horses exhibit jumping over high elevated obstacles as well as over ditches and similar obstacles requiring broad jumps. In both cases, the forelegs are raised clear of the obstacle while the animal con-tinues to propel forward with a final push by fully extending the hindlegs (Figure 3.4a). At take-off the hindfeet are commonly at the site where the forelegs left the ground (cf. Leach and Ormrod 1984). The forelegs flex close to the chest as elevation is gained, extending subsequently to alight either simultaneously or sequentially as the hindlegs are momentarily flexed clear of the obstacle. The animal is fully off the ground during the jump. Occasionally while jumping, horses rotate the hindquarters to one side as the hindlegs reach maximum flexion. Although jumping can occur from most gaits, the running jump occurs usually from a canter or a mod-erate gallop.
Rearing Motions: Rearing is a motor pattern where the hindlegs remain on the ground while the forequarters raise high into the air (Figure 3.4b).
Two rearing horses with their chests in contact or nearly so are said to be dancing. A controlled movement by one horse where the forelegs are tightly flexed as the forequarters are moderately raised placing the spine 30–45˚ above horizontal is called the levade (Figure 3.4c). The weight is borne by the deeply flexed hindquarters. The greater this flexion the longer the horse can maintain the position. The mezair is a series of levade move-ments combined with forward motion accomplished by smooth jumps where the forelegs alight briefly followed by the abrupt alighting of the hindquarters.
An in-place leap or hop upward in a rearing-like attitude from the lev-ade is called a crouplev-ade (Figure 3.4d), whereas a similar leap on the hindlegs where forward advance occurs is the courbette (Figure 3.4e).
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More than one leap may be induced before the forelegs again contact the ground. Such gymnastics are achieved by extensive development of mus-cle and coordination through training. Two other in-place leaps can be obtained from highly schooled horses. The ballotade is a high leap where the legs are flexed underneath with the hindlegs retracted as if ready for a kick (Figure 3.4f). In the capriole (Figure 3.4g) the hindlegs do kick pos-teriorly during the leap (Seunig 1956).
Bucking: A sudden humping or arching of the back with head and neck quickly lowered is called bucking (Figure 3.4h). Kicking with both hindlegs may follow. Frequently the horse also leaps or bounds clear of the ground, exhibiting what is called a buck-jump (Figure 3.4i). A horse usually per-forms these movements to rid itself of something on its back, as riders some-times discover. A series of these motions can occur with leaps in erratic directions. Exuberant, playful horses while galloping at liberty sometimes exhibit bucking followed by a kick.
Kicking: Kicking with one or both hindlegs, while the forelegs remain in contact with the ground, is a common aggressive pattern of horses (Fig-ure 3.5a). The suddenly flexed and elevated hindleg or legs are thrust quickly posteriorly as the weight is shifted over the forelegs. The neck may be lowered in the process. Two related motor patterns occur. One is knock-ing of the substrate (Figure 3.5b) with a hindleg. (A similar raisknock-ing and low-ering of a foreleg is called stomping.) The other is a hindleg lift used often by mares to block or bump away a foal, using the stifle to prevent access to the udder. Each of these movements can be forceful.
Striking: Striking is the often swift motion made by one or both forelegs in an anterior direction (Figure 3.5c) usually to hit or threaten another indi-vidual. Often it occurs with one leg while the other foreleg remains in con-tact with the ground. The neck is usually elevated. Striking can be done also by a horse during rearing; when two horses interact in this fashion it is called boxing.
Pawing: Pawing is similar to striking with a single leg except pawing is slower and the toe is dragged posteriorly in a digging or scraping motion (Fig-ure 3.5d). When used during investigation, the nose is usually oriented toward the substrate or object. Pawing is commonly repeated several times in succession. In addition to its use in scraping, Ödberg (1973) noted that paw-ing is occasionally exhibited as a displacement activity by horses restricted in forward locomotion. During such occasions, contact with the ground may be incomplete and the head and neck often remain elevated.
Figure 3.4:Jumping,rearing,and leaping motor patterns of horses (see text for details). Continued on next page 03 (36-62) Chap.03.Horses 10/21/02 2:34 PM Page 51
Figure 3.4:Jumping,rearing,and leaping motor patterns of horses (see text for details). Continued on next page
Figure 3.4:Jumping,rearing,and leaping motor patterns of horses (see text for details).
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Scratching: Scratching with a hindfoot is often done by young horses and occasionally by adults, such as ponies. The body is flexed to one side and the hindleg on that side is extended forward so the hoof rubs the lowered head or neck (Figure 3.5e).
Pushing: Pushing is where a horse presses against something in an attempt to displace it. For example, the neck, shoulder, or thigh is used to push other organisms; the chest is often used to push against barriers. A head bump is a variation of pushing.
Lying Down: Lying down is the process of going from a standing to a recumbent position. It is a continuum of motor patterns (Figure 3.6a) that may commence with the horse investigating the substrate with nostrils near the ground. Sniffing, circling, and trampling may ensue. If rolling is to occur, pawing of the substrate often takes place. Next the legs gather close together, often with a piaffe-like movement, with the head remaining low. Having positioned the legs, the forelegs begin to bend at the knees.
Figure 3.5: Additional leg movements of horses: (a) kicking, (b) knocking, (c) striking, (d) pawing, and (e) scratching.
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Figure 3.6:Motor patterns of (a) lying down to sternal and then lateral recumbency, (b) rolling,and (c) getting up.
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As the forequarters slowly sink, the neck and head move forward. The body weight is concentrated on the somewhat flexed hindlegs. The fore-quarters continue to sink, and the head is kept well forward. As the knees are about to contact the ground, the hindlegs fold, the neck elevates, and the body is abruptly lowered to the substrate. At this point, the horse is in sternal recumbency, resting somewhat on one side in such a way that the sternum and abdomen rest on the ground to either the right or left of the midline with head and neck upright. The legs remain flexed with only one hindleg extended free of the body.
To go completely prone to lateral recumbency, the horse rolls further onto its side and somewhat extends its legs while lowering the neck and head to the substrate. The upper foreleg is commonly anterior to the lower forelimb which is often slightly flexed at the carpal and fetlock joints (Lit-tlejohn and Munro 1972). Either of the extended hindlegs can be slightly anterior to the other.
Rolling: Rolling is accomplished while recumbent by rotating onto the back with flexure of the legs (Figure 3.6b). The head and neck appear to assist in the effort to roll by providing leverage for the sudden body twist.
The extent of the roll commonly stops along the back with muzzle point-ing skyward; however, the animal may roll over completely onto its other side. If the latter occurs or the roll is inadequate, the horse often attempts to return to its back where it may rub against the substrate with legs thrash-ing as the back flexes laterally back and forth. After a few seconds, the horse returns to sternal recumbency.
Getting Up: The process of getting up onto the feet begins with the posi-tion of sternal recumbency. The weight is shifted posteriorly by elevating the neck as one foreleg then the other extend anteriorly lifting the fore-quarters clear of the substrate (Figure 3.6c). As one or both forelegs become stabilized, the neck lowers allowing the weight to shift anteriorly, and the hindquarters are raised by the hindlegs. On rare occasions, a foal varies the process and stands by first raising the hindquarters, reversing the sequence of lying down.
Shaking: Shaking is where the surface of the body as well as head and neck are rotated or vibrated rapidly. This frequently occurs after rolling. The entire animal vibrates momentarily casting away dust and other matter from the pelage. Localized quivering of the skin (skin twitching) occurs in response to localized stimulation of the skin, for example, by insects. Insects and other annoyances around the head and ears cause head shaking.
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Rubbing: Rubbing can occur, for example, by a horse moving its lower jaw surface or muzzle against its forearm or by moving any part of the body back and forth or up and down against some object. Licking with the tongue and nibbling with the incisors are other motor patterns often directed at the pelage during grooming.
Mouth Movements: Biting motions are often directed at another horse by extending the head and neck while opening the mouth and directing the incisors at the other individual. If contact is made, a bite occurs; if main-tained, it is a grasp. The feigning of a bite without making contact is a bite threat. An acoustical variant of bite threat used by mares toward their nursing foal is called smacking; the mare, with ears laid back, turns the head and neck toward the foal while the mouth is abruptly opened creating a smacking sound (Crowell-Davis 1985). Cribbing is the pushing of the upper incisors against a fixed object and involves the musculature of the neck and head (see Chapter 25).
Motor patterns commonly involved in feeding are upper lip movements to separate and help lift food material, biting and cropping food with the incisors, use of the tongue to move the food into the mouth (tongue manip-ulation), chewing the material with cheek teeth by crushing and lateral grinding motions of the lower jaw, and finally swallowing. While chewing dry roughage, some stabled horses periodically immerse a mouthful into water using a motion called hay dunking, apparently to moisten the food (Waring 1974). Some horses acquire an abnormal trait of tongue rolling, where the mouth opens and the tongue is maneuvered, often in exagger-ated fashion, on one side and then the other.
The sucking pattern of a foal is displayed by extending the head and usu-ally elevating it above horizontal while protruding slightly the receptive tongue flattened against the lower incisors. Sucking readily occurs once the tongue makes contact with a teat or surrogate object. Occasionally neonates exhibit sucking in mid-air prior to successful nursing.
Immature horses especially, during submission or when apprehensive about the nearness of another individual, occasionally display an up and down movement of the jaw while the lips are retracted at the corners of the mouth. This nearly-silent display has been called snapping, teeth-clapping, Unterlegenheitsgebärde, champing, jaw waving, and so on. It is often dis-played by a submissive individual who is in a conflict situation of wanting the closeness of the more dominant individual, yet is timid and apprehen-sive at the same time.
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Head Movements: The head is capable of a variety of other motor pat-terns, some of which will be covered later under communicative behaviors.
Nodding is the oscillatory movement of the neck in the vertical plane, caus-ing the head to change elevation; an arched neck is often involved. Some horses are taught to momentarily hold a lowered neck position in what is called bowing. Head tossing is a similar motion up and down but head flex-ion and extensflex-ion is primarily involved. Weaving is a repetitious, relatively-slow, lateral motion of the head and neck, where commonly the weight is shifted alternately from one foreleg to the other.
The behavior pattern called flehmen (Figure 3.7) is where the head is elevated and the upper lip is raised, wrinkling the nose and exposing the gums. Such motor patterns occur in a variety of mammals, including most ungulates and felids (Schneider 1930; 1931; 1932a; 1932b; 1934). In the horse, flehmen begins with extension and elevation of the head, usually after sniffing something. As the head approaches extreme extension, the upper lip is lifted maximally exposing the upper incisors and adjacent gums. The jaw is usually closed or nearly so. The ears and eyes generally rotate to the side (Dark 1975), and the third eyelid (nictitating membrane) appears as a whitish area covering the anterior portion of the eye. At its peak, the head is raised above horizontal. In less than one minute, the head posture and facial features return to normal.
Figure 3.7: Sequence of the flehmen response. (Adapted from Dark 1975)
Horses also yawn. The yawn begins from a relaxed head position while either standing or recumbent. The mouth starts to open, and a deep inhala-tion occurs as the head is raised and extended. The eyes roll and close, at least somewhat, as the yawn reaches its peak (Figure 3.8). The elevated head sometimes turns and rotates slightly. The lower jaw may shift laterally when the mouth is wide open, and the otherwise relaxed ears may shift forward momentarily. Exhalation occurs quietly as the yawn regresses (Dark 1975).
Stretching a portion of the body occurs most often by either moving one hindleg (hindleg stretch) posteriorly fully extended, often while raising and lowering the back, or by elevating and sometimes extending the head (the head stretch). Such movements often occur after a yawn or a period of rest.
Eye and Ear Movements: Eye and eyelid movements occur. Eye rolling is where the eye rotates downward or posteroventrally and retracts expos-ing white scleral tissue above the pigmented iris. Durexpos-ing eye rollexpos-ing, the light colored nictitating membrane often moves over the anterior portion of the eye blocking some of the dark pigmentation of the iris. Although the nictitating membrane can be quickly raised and lowered, blinking normally involves the eyelids per se.
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Figure 3.8: Sequence of the yawn. (Adapted from Dark 1975) 03 (36-62) Chap.03.Horses 10/21/02 2:34 PM Page 59
Ear movements are versatile and are controlled by the complex interac-tion of some fifteen auricular muscles (Sisson and Grossman 1953). When the ears are pricked, they are forward in a vertical position with their open-ing directed forward. When the ears are laid back, their openopen-ing faces pos-teroventrally and collapse occurs to some degree as they are pressed back against the upper part of the neck. The ears can be rotated individually to varying lateral positions between the fully pricked and the extreme poste-rior facing positions. The open portion of the each ear rotates approximately 180˚ through this lateral arc.
The nostril openings can change diameter depending on the physiolog-ical and psychologphysiolog-ical state of the animal. Flared nostrils are those maxi-mally dilated.
The attitude of lowered neck, extended head, laid back ears, and forward locomotion is a head threat. And when the neck slowly oscillates from side to side this display becomes snaking. It is usually exhibited by stallions when attempting to drive or move other horses (i.e., herding), whereupon the other horses may show avoidance-retreat.
Tail Movements: Tail switching as well as tail depression (pressing the tail against the perineum) and tail raising occur by the interaction of five muscles. More will be said about motor patterns and postures of the tail and other parts of the body in subsequent chapters.