Behavior Problems in Horses

Aggression is a common problem in horses and includes chasing, neck wrestling, kicks and bites, and other threats. Signs of aggression include ears flattened backward, retracted lips, rapid tail movements, snaking, pawing, head bowing, fecal pile display, snoring, squealing, levade (rearing with deeply flexed hindquarters), and threats to kick. Submissive horses respond by avoiding, lowering the neck and head, clamping the tail, and turning away from the aggressive horse.

Aggression toward people is usually seen in stalls, where the horse feels confined and can easily defend. The most common types of aggression towards people are due to fear, pain, sex hormones, dominance, and learning (the horse learns that being aggressive can help it to achieve its goals). Dominance aggression and fear aggression in horses are similar to what occurs in dogs, except that equine dominance aggression does not depend on the situation as it does in dogs. Fear can be caused by physical abuse, harsh treatment, and night blindness associated with confinement in a dark stall. Horses that are aggressive to people are sometimes too dangerous to keep. There have been cases of horses killing people in such circumstances.

The first step in managing equine aggression is to ensure human safety. The cause of the aggression should then be identified and, if possible, removed. Aggressive behavior can be modified using counterconditioning and desensitization (using rewards for nonaggressive reactions). Rewards could be frequent feedings of highly desirable foods (for example, molasses or apples), attention, grooming, or exercise. The purpose of the frequent feeding is to mimic the natural pattern of frequent grazing and to associate that with the person’s presence. It is also important to examine the horse's environment, making sure it has sufficient access to space, food, and water. All aggressive animals should probably be neutered because aggression may be hereditary, and removal of sex hormones reduces some types of aggression.

Aggression toward other horses is usually associated with breeding, sexual competition, fear, dominance, and territory (including protecting the group, food, or water). Horses have preferred grooming and grazing partners. The extent to which these preferences may be a factor in aggression to other horses is unknown. Aggressive horses should be separated from other horses. To minimize competition and stress, ensure that all horses have sufficient access to space, food, water, and other resources. Treatment may include castration, desensitization, and counterconditioning. This can be done gradually by introducing horses across 1 or 2 fences so that they do not injure each other. Two fences are best because they reduce the possibility that the horses could strike each other with their feet. Medications may also be helpful in some cases. However, punishment should be avoided because it may worsen the aggression.

Maternal aggression is aggression by a mare toward people during the first few days after the delivery of a foal. It is a normal behavior caused by hormones that usually lessens with time. Allowing the mare to become familiar with her caretakers prior to delivery and minimizing human contact afterward may help. Treatment is not necessary in most cases.

Aggression while breeding can occur when stallions are overused or used out of season. Stallions can prefer certain mares and may not be compatible with the chosen mare; changing the mare may help. Stallions may not want to mate with mares that they were stabled with when they were colts, and forced mating can result in aggression. The goal of treatment is to treat the main cause of aggression; changing the mare (because of preferences) or artificial breeding can also be attempted. Physical restraint (such as hobbles) and desensitization can help as well. Clicker training has been used successfully to desensitize stallions with this problem.

Wood chewing involves grasping wood with the front teeth and then swallowing it. The usual cause of the behavior is lack of roughage in the diet. Under free-ranging or pasture circumstances, horses graze 8 to 14 hours per day, whereas confined horses eat for less than 3 to 4 hours per day. Most wood chewing occurs in the winter, and it appears to take place more often in horses that are fed pelleted diets. Confinement, lack of exercise, and boredom can also lead to wood chewing. If a horse receives less than 1 kilogram of hay per 100 kilograms of body weight, wood chewing can become extreme. It is important to address the primary problem (that is, learn why the horse is doing it), rather than merely trying to prevent it. To treat this condition the owner should provide more roughage (hay, for example), exercise (through work or increased pasture time), stimulation, toys, or social contact. Eliminating or covering exposed wood may also help.

Coprophagia is the eating of feces and is a normal behavior in foals. It is most common in the first 2 months of life, after which it usually declines. The behavior is thought to provide foals with certain nutrients and intestinal bacteria. When it is seen in adults, it is usually associated with low roughage or a dietary deficiency. A veterinarian can help identify any dietary deficiencies. Treatment usually includes increasing the amount of roughage in the diet.

Pica is the consumption of soil or sand or other nonfood items. This can lead to serious and even fatal digestive complications, and therefore should not be taken lightly. By nature, horses spend much of their time grazing and if this activity is curtailed, such as when stabled, they are likely to seek other materials to consume. Lengthy periods of confinement, often combined with concentrated feeds that are quickly consumed, can cause boredom and lead to abnormal eating behaviors. Texture may be important, and the addition of roughage, toys, and salt blocks may have a role in treatment.

Horses form friendships with other horses, and anorexia (loss of appetite) can be associated with changes in these relationships. For example, if a horse is separated from a companion it may stop eating. A submissive horse may not eat near an aggressive one that has previously attacked it. Addressing the social aspects of the problem is important. It is important to consult your veterinarian if your horse is not eating. Your veterinarian can determine whether it is a medical or behavioral issue and can prescribe drugs that stimulate appetite, if needed. In foals, poor appetite may be due to inappropriate weaning or an aggressive mare attacking a foal that tries to share the mother’s food. Barriers should be erected that safely permit normal development and feeding patterns. Foals may not eat the same plant or same plant part as the mare, and the part they choose may be based on the height of the plant. This problem should be addressed and creep feeders should be placed near the mare so that the foal does not have to choose between food and contact with its dam. Foals on pasture that are nursing do not drink water, but the mares need access to good, clean water.

Obesity can be the result of decreased exercise, increased palatable food, and understimulation (horses that eat in the absence of other activities). Food should not be abruptly removed from an obese horse. The amounts of food should be decreased gradually while increasing exercise and social contact with other horses and people. A veterinarian can evaluate the diet for nutritional content and make any necessary adjustments to achieve a more balanced ration. This will help the horse lose weight.

Stall walking or circling is a stereotypical behavior in which horses walk in circles around the stall. When released to a larger space (such as a pasture or barn), they continue to circle in a small area. Tying the horse to prevent walking will only transform the behavior into weaving (see below). Both behaviors are seen in confined horses, serve no purpose, are hard to interrupt, and are usually slower than other types of movements. Possible causes of stall walking include lack of exercise and social contact and claustrophobia (an intense fear of small spaces). Stress and anxiety appear to make the problem worse. Treatment should include increasing exercise, providing social company, allowing the horse to see other horses, and providing clean, thick bedding. Feeding frequently (more than twice daily), allowing more access to pasture, providing more open stalls, and providing better access to outside views can also help. Adding toys to the stall may help if the horse is young and active. In some cases, your veterinarian may need to prescribe medication to control the problem.

Weaving occurs when a horse that normally stall walks is tied or prohibited from walking due to restricted space. Because they cannot circle as usual, they will still move constantly, but in a weaving motion. The horse may lift its legs, shift its weight, and move its head from side to side. Treatment includes untying the horse, providing a larger stall, or best of all, turning the horse out onto pasture. Providing a large mirror in the stall in front of the horse can help decrease weaving. The other treatments recommended for stall walking (see above) can also help.

Pawing or digging can cause injury to the horse, damage the floor, and cause wear to the horse’s hooves. It is a normal behavior when horses on winter pasture are forced to dig for feed. When horses are confined and fed highly palatable foods, pawing can occur more frequently and more intensely than it would otherwise. Pawing can occur due to frustration, anticipation, or as a displacement behavior. The underlying cause of the pawing needs to be determined in order to successfully treat it. Specific treatments are similar to those for stall walking (see above). Changing the floors to concrete may stop pawing; however, it will not change the motivation to do so, and some horses (especially stallions) may rear up instead of pawing. Pawing should not be rewarded, which is what inadvertently happens when horses paw in anticipation of feeding. The food should be presented to the horse only when the horse is not pawing, or the horse should be brought to the food.

Kicking the walls of the stall damages horses’ legs and stalls. Horses may kick due to boredom, aggression, or frustration. When it is due to aggression, kicking can occur when another horse is nearby or when the horse perceives that another horse is nearby. Kicking can also occur in anticipation of food. When the horse is then fed, the behavior is reinforced because the horse associates kicking with being fed. It may also occur when the horse cannot achieve its goals (for example, exercise or a chance to breed). It is possible that the behavior is a form of self-mutilation (see below). Many horses that kick and make holes in the walls of a stall also eat wood from these holes. For successful treatment, the underlying causes of kicking should be determined and addressed. Treatment for aggressive kicking is discussed earlier (see Aggression toward People), and for most other causes the treatment is similar to the treatment for stall walking (see above). It may also require rearranging the social grouping in the barn. Owners should never reinforce kicking by providing food when the horse kicks. Providing more social contact, exercise, and stimulation can also help.

Cribbing (windsucking, crib biting) is a distinct behavior, different from wood chewing, that involves grasping a horizontal surface (such as a fence or water bucket) with the front teeth (incisors), flexing the neck, and sucking air. Some horses swallow or breathe in the air, while others suck air without grasping any objects. The activity produces strange, nonflatulant sounds. Cribbing is associated with feeding highly palatable foods (such as grain or molasses), lack of exercise, and confinement. It is more likely to occur in Thoroughbreds, other racehorses, and dressage horses. Cribbing is most easily diagnosed by noticing the missing U‑shaped pieces from the available fencing. Horses that crib have worn teeth and develop thick neck muscles. Treatment options include increasing roughage in the diet, increasing exercise and stimulation (such as toys), changing companions, and providing greater access to pasture. Placing a strap around the horse’s neck behind the poll can help by applying pressure each time the horse tries to flex its neck. Keeping stalls free of horizontal surfaces and objects that the horse can grasp can also help minimize cribbing.

Self-mutilation occurs when a horse hurts itself by biting (usually the legs, chest, or flanks) or kicking its abdomen with its hindlegs. Some horses vocalize at the same time. It may be due to a medical problem, such as a digestive disorder (for example, colic), skin disease, or pain. Your veterinarian can help differentiate a medical problem from one that is primarily behavioral. Self-mutilation can appear in sexually frustrated (usually male) or socially incompatible horses. It can also occur as a displacement activity. The problem is more common in males less than 2 years old and may possibly be triggered by environmental stressors. Treatment should include correction of the underlying problem. Self-mutilation associated with sexual frustration can be addressed by castration, pasturing with a mare, removing all mares, increasing exercise, increasing roughage, and decreasing grain.

Stallions have poor libido (are unwilling to mate) if they are overused for breeding, are inhibited because of the use of anti-masturbation devices, are used out of season, or are injured while breeding. Masturbation is a normal equine behavior. There is no truth to the myth that masturbation depletes semen value because horses that masturbate rarely ejaculate. Stallions that have poor libido should be rested if they have been overused. Submissive stallions that are presented to aggressive mares may also be unwilling to mate. Another cause of poor libido can be a poor breeding environment. Many stallions are “picky” about the environment in which they are collected and may exhibit signs of poor libido if the environment is not right. Distractions such as yelling, rapid and unexpected movement, and rough handling can lead to a stallion that has no interest in the situation at all.

Letting a stallion that exhibits poor libido watch other stallions mate may have a beneficial effect on their libido. Using an artificial vagina or medications may also help. Providing them with a variety of mares, including "teaser" mares, can also stimulate their interest. Pasturing with a mare may also help. Stallions should also be well rested and fed.

Nymphomania is excessive sexual behavior that is seen in mares usually due to changes within the ovary. Nymphomaniac mares “wink” (show the clitoris), squat, and urinate frequently, often when they are not in heat. Mating behaviors and those involved in solicitation are not considered abnormal if they occur every 21 days when the mare cycles. Nymphomaniac mares should be checked for underlying medical problems. Mares that are not in heat but show sexual receptivity to males may also have psychic estrus. The treatment for nymphomania and psychic estrus depends on the cause and includes hormone medications, increasing exposure to daylight (more than 16 hours per day), or surgery.

It is common for mares to exhibit a silent heat, especially during the first estrus cycle. The ovary responds as it should for estrus (that is, the ovary produces a normal follicle and ovulates), but the mare will not accept a stallion. Causes include stress and mating preferences. It may help to present her with several stallions. If she is nursing a foal, weaning may also help.

Geldings that act like stallions will mount mares, attack foals, fight with other males, or self-mutilate. These geldings may also disturb other social relationships. Laboratory tests may be helpful to exclude underlying medical problems, although about 50% of normally castrated geldings will retain some stallion-like behavior. Treatments include separation from any targeted horses and medications.

Foal rejection is seen in 3 main forms: mares that will accept the foal but will not let it suckle, mares that are fearful of the foal and run away, and mares that exhibit stallion-like behavior and attempt to kick or bite the foal. The first two forms are mainly seen in mares that are first-time mothers or those with a painful udder. The aggressive form may be hereditary in Arabians and Morgans. Mares may paw at foals to stimulate them to rise from recumbency, which is different from rejection. Mares can kill their foals if they are underweight and not getting enough to eat, and this can be a normal, although uncommon behavior. The first step in treatment is to protect the foal. If the mare will accept the foal but not let it suckle, the mare should be helped through several nursings until she learns that suckling is pleasurable. Holding her in such a way that she cannot injure the foal may involve either cross-ties or partial barriers through which she can see and smell the foal but that prohibit her from reaching for it. Avoiding any disturbances while the mare is nursing the foal is essential for successful nursing. The mare should be checked to make sure there is nothing wrong with her udder, such as mastitis or sores that could be causing her pain, which can explain an aversion to nursing. Pressure in the udder resulting from infrequent nursing can be treated using warm water baths and soaks, light massage using a hose, and milking the mare.

Mares that are afraid of their foals should be treated in the same manner, but the addition of relaxation cues such as darker, quieter stalls and food treats may help. Dogs have been used to evoke maternal “herding” behavior by stimulating the mare to protect the foal from a potential threat. Mares that attempt to injure their foals must be restrained with barriers or by tying. At the same time, the mare can be counterconditioned using positive rewards. If the mare cannot be retrained or trusted, a replacement (“nurse”) mare should be sought or other arrangements made (hand nursing) so that the foal can be adequately nourished.

Horses can have fears and phobias. Fear is a normal response to a real or perceived threat. Phobia is an exaggerated fear response that is sudden and profound and results in panic. The two most common phobias in horses are associated with noise and location. Horses naturally have a fear of new things (called neophobia), which may be responsible for some behavior issues, such as trailer-related problems (see below). The first step in managing fears and phobias is to identify the trigger. It may help to avoid, if possible, situations in which the fear or phobia occurs. Treatment includes changing the horse's emotional response to the trigger through desensitization and counterconditioning. For example, treating a noise phobia may involve playing a recording of the problematic noise at a low volume that does not evoke fear while the horse is rewarded with gentle petting or a highly desired treat. The volume of the recording can then be slowly increased over time as long as the horse remains calm. Desensitization and counterconditioning take time and patience and may require your veterinarian's help. Never use punishment in response to fears or phobias because it will make the problem worse. Medications may also be necessary.

Problems with trailering include refusing to enter or leave the trailer and scrambling while traveling. Horses may be afraid to load into a trailer because of natural fears (such as fear of new things, a dark interior, instability of the trailer, or noise) and/or learned factors (such as a previous accident, motion sickness, or previous punishment while loading). A horse may load into a trailer just fine but then misbehave while inside. This could be because the horse finds it difficult to keep its balance while the trailer is moving, anticipates a stressful event (such as a race after the trailer ride), or has motion sickness. All of these problems can be potentially injurious to the horse and are best addressed early. The best longterm approach to managing trailering problems is desensitization and counterconditioning using rewards, such as treats. However, these techniques take time and must be performed long before the trailering occurs. Foals should be taught at a young age to load into a trailer with their mothers. Punishment should never be used because it will make the problem worse. Often, treatment can be as simple as backing the horse into the trailer (using a platform rather than a ramp), walking the horse slowly around and then into the trailer, or using another horse that trailers well as a “buddy.” Trailers can be designed to allow bidirectional entry and exit and a walk-through option. Walking through the trailer may help demonstrate that the horse is not walking into a dark, uncertain area. Once the horse is calm, the gate can be raised. If these techniques do not work and the horse must be transported, your veterinarian may prescribe a sedative. However, sedatives will not help the horse learn for future travel and will make them less stable during the drive.

Also see professional content regarding behavior problems in horses.