Pet Care

Compulsive Behavior in Horses

Brown horse standing in a field

The term stereotypy describes a sequence of behaviors that’s repeated over and over with no apparent function. Stereotypies occur in all types of animals who live in the care of people. Because stereotypies become increasingly fixed—the behavior sequences all begin to look exactly alike—and because they take up more and more of an animal’s time, they can interfere with other aspects of an animal’s life.

Without treatment or management, stereotypies in horses can lead to health problems, damage to the stable area and a great deal of distress for the horse’s guardian. Most equine stereotypies develop when horses are stabled or kept where they can’t interact socially on a regular basis with other horses or don’t get enough exercise or grazing opportunities. However, studies show that horses sometimes develop stereotypies even when they live in a pasture with other horses. Also, once a horse develops a stereotypy—for whatever reason—she will continue to do it even after the original problem has been dealt with. The behavior is particularly likely to resurface if the horse is stressed—even in a small way, such as having to wait an extra few minutes for a meal.

Equine stereotypies are categorized by a horse’s actions. The following is a short list by category:

Oral Stereotypies

  • Cribbing - Horses who crib place their upper teeth on a stationary object—such as the feed bin, their stall door or a fence board—and then arch their necks, pull a big gulp of air into their upper throat and abruptly release the air with a grunt. Approximately 4% of adult horses crib. Wind-sucking is similar to cribbing, but the horse doesn’t use a stationary object to steady herself when she takes the air back into her throat.
  • Wood-Chewing - Horses who chew wood nibble on any available wood surface. Many people confuse wood-chewing with cribbing—probably because both cause damage to the horse’s stall—but horses who wood-chew don’t grab the wood with their teeth, pull back and grunt as do horses who crib. Approximately 12% of adult horses wood-chew.  

Locomotor Stereotypies

  • Weaving - Horses who weave rock back and forth against or in front of their stall doors or stall walls. If prevented from weaving against the stall door, they’ll weave wherever they are standing. Approximately 3% of adult horses weave.
  • Head-Bobbing - Horses who head-bob stand relatively still and bob their heads up and down repeatedly. 
  • Head-Weaving - Horses who head-weave stand still and repeatedly swing their heads from side to side. Similar to head-bobbing and head-weaving are head-shaking and head-nodding. Shaking and nodding can develop because of inadequate stimulation, but they can also be the result of improper bit fit or other problems associated with the horse’s mouth, or flying insects around the horse’s face.
  • Stallwalking or Circling - Stallwalking horses usually pace back and forth close to the front of their stalls, although some circle continuously around the entire stall. Approximately 2% of adult horses stallwalk.

Self-Mutilation

  • Self-Biting - Self-biting, sometimes referred to as “flank-biting,” describes repeated biting by horses at their flanks, legs or tail, or at the sides of their body and their lower shoulder blade area. Horses are very flexible and can bite at flies and other pests, of course, but horses who self-bite do so over and over when there is nothing touching their skin.
  • Wall-Kicking - Wall-kicking is common in horses, particularly at feeding times, but this behavior can develop into a stereotypy that occurs in the absence of specific triggers.

Comparing Stereotypies to Other Types of Behavior

Certain characteristics are associated, sometimes mistakenly, with stereotypical behavior. The following sections look at some facts and assumptions about these characteristics.

Horses with Stereotypies Are Persistent

Studies suggest that, compared to horses without stereotypies, horses with stereotypies have less self control and are more likely to persist in doing the same thing even when it doesn’t get them what they want. Studies also show they might have more trouble than other horses learning new things, but this is usually because they persist with an old response rather than trying something new.

Stereotypies Might Be an Addiction

Some horse stereotypies, particularly cribbing, cause a release of endorphins, the brain’s natural opiate. The release of endorphins is the body’s way of reducing pain, but endorphins can also cause a general feeling of well-being. This release of endorphins may maintain cribbing behavior with a horse similar to how an addiction is maintained in a person.

Are Stereotypies a Vice?

Some people refer to horse stereotypies as “stable vices.” However, most experts discourage the use of the term vice because it implies that a horse is being unruly or has some diabolical intent for engaging in the behavior.

Are Stereotypies an Obsessive-Compulsive Behavior?

Stereotypies are also often referred to as obsessive-compulsive behavior. Referring to stereotypies in horses as an obsessive-compulsive behavior also is not supported by some experts. This hesitancy is based on the fact that, in humans, obsessive-compulsive disorder is a diagnosis that suggests a cognitive component—particularly with regard to obsession—a component that can’t be assumed when assessing equine stereotypies. Labeling equine stereotypies as obsessive-compulsive implies that they all share a common cause and will benefit from the same treatment, which is not the case.

Causes

Insufficient Grazing

Given the opportunity, horses will graze almost continually. Pastured horses spend about 8 to 12 hours a day grazing. Most scientists believe horses require this amount of grazing time not to satisfy nutritional needs—something that can be achieved through grain supplements—but to satisfy their behavioral needs. Unfortunately, stabled horses can’t be provided continuous daily grazing time, either for management reasons or because it isn’t practical or safe to do so. In the usual stable situation, where horses are given a morning and evening feeding of hay and grain, stabled horses spend approximately 15% of their time eating. This drastic difference between their natural behavior and their stabled behavior is thought to be very stressful for horses and one reason for the development of stereotypies. .

Limited Social Exposure to Other Horses

Horses are a social species, and a horse’s natural desire to be with other horses is very strong. Studies show that horses who have limited social contact with other horses, especially limited visual contact, engage in more stereotypies than horses who socialize regularly with other horses.  

Excess Energy

As might be expected, horses with high energy levels, such as thoroughbreds and warm-blood breeds, engage in stereotypies more than other breeds of horses. It has been estimated that as many as 10% of racing thoroughbreds exhibit stereotypies, and most stereotypies remain when a horse is taken in as a companion following her racing career.

High-Concentrate Feed

Racing thoroughbreds are weaned relatively early in their lives, and some experts think the stress of early weaning might contribute to the development of stereotypies. However, one study of thoroughbred horses in the United Kingdom suggests cribbing might be influenced not by early weaning, but by the feed the foals eat. This study found that some foals began cribbing at the age of 20 weeks while they were still out in the pasture with their dams. These foals all had access to their dams’ concentrate feeds. Many experts now believe the high-concentrate foods contributed to the cribbing rather than the early weaning. High-concentrate feed can increase stomach acid, and cribbing might somehow reduce this acid.

Low Fiber

Scientists who observe stabled horses during the day find that horses engage in stereotypies more often in the afternoon than in the morning. In one study, horses received less hay in the afternoon meal, and this finding might indicate that reduced fiber contributes to stereotypies. However, fiber content versus amount of time grazing was not evaluated.

Genetics

Horse owners have long noticed that some families of horses are more prone to developing stereotypies than others. Recent studies in the United Kingdom of captive Przewalski horses support this observation, because although all the horses had the same care, some families of Przewalski horses had more stereotypies than others. However, it’s important to note that genetics don’t cause stereotypies, they simply increase the likelihood that certain stressors will produce stereotypies in certain families of horses.

Frustration

Frustration and stress are the two factors most likely to produce stereotypies in horses. Studies show that, in general, horses with stereotypies have higher levels of stress hormones than their stable mates, even when they aren’t practicing their stereotypy. Some experts suggest stereotypies might simply reflect overall frustration caused by such things as training and riding styles that are confusing for the horse. But most experts agree that the frustration is related to the horse’s feeding, social and leisure-time activities. In an evaluation to determine whether increasing the number of meals a horse eats might decrease stereotypies, half of the horses in a large stable were fed their normal ration of concentrate divided between two, four or six equally sized meals while the other horses continued to eat two meals per day. Oral stereotypies such as cribbing, wind-sucking and wood-chewing decreased as the number of meals increased, but weaving and nodding prior to feeding increased. At the same time, the horses who weren’t given more meals also showed increased weaving and nodding and an increase in oral stereotypies as their stable buddies received their extra meals. This tells us that frustration is a key trigger for stereotypies.     

Consider Other Possible Causes of Your Horse’s Behavior

Photic Headshaking

Recent studies have found that some headshaking in horses is actually induced by bright light. The disorder is likely similar to photic sneezing in people (sun sneezing) and is more common in the spring than during other times of the year. Light—and sometimes sharp sounds as well—appear to over-stimulate the cranial nerve responsible for sensation in the face, resulting in the horse experiencing an uncomfortable stinging or pricking sensation in her nasal cavities.

The photic headshake is a relatively abrupt and violent toss, whereas stereotypic headshaking is rhythmic. Unlike stereotypic headshaking, photic headshaking generally worsens during work and can occur while the horse is trotting or even cantering, and it will stop abruptly when the horse gets back to the darkened barn. Covering their eyes will also stop the shaking. Photic headshaking is also usually accompanied by snorting and attempts by the horse to scratch her head on anything handy, including her foreleg or even the ground.

Injury or Medical Condition

Horses can engage in repetitive behavior or produce unusual movements when they are in pain, or as the result of neurological disorders. If your horse has no history of stereotypic performances and suddenly begins to do things such as head-bobbing, self-biting, foot-stomping or other behaviors that might indicate distress, have your veterinarian come out to your barn to rule out medical causes.

What to Do About Your Horse’s Stereotypic Behavior

Different stereotypies require different changes in a horse’s care to manage. However, as suggested by the causes listed earlier, you can take some general precautions to reduce your horse’s stereotypies:

  • Increase the amount of forage to at least 15 pounds per horse per day.
  • Use a variety of forage. In addition to your horse’s usual hay, you can feed commercial fiber cubes, whole carrots and other varieties of hay.
  • Feed flake hay up to six times per day.
  • Bed the stall with straw. Horses generally won’t eat straw, so it is excellent bedding in which to scatter hay and other grasses to increase your horse’s foraging time. Studies have also shown that horses prefer straw to other types of bedding, such as paper or wood chips.
  • Feed concentrates from a foraging apparatus, such as an Equiball. This choice is inappropriate for beddings where your horse could ingest sand or other fine particles.
  • Exercise your horse regularly. You can help your horse get adequate exercise by regular training, lunging or round pen work. Because stress increases stereotypies, be certain to include casual rides with your horse’s more stressful daily work sessions.
  • Provide access to other horses. The best way to do this is to increase pasture turn-out time with other horses because that will also increase forage intake. But simply increasing paddock turn-out time with barn buddies or increasing the number of turn-outs per day can also reduce stereotypies. If barn management or the horse’s monetary value prevents communal turn-out, creative barn adjustments such as installing bars in place of walls between stalls can help. Even increased opportunities to see other horses can help, so leaving the stall door open and installing a stall-guard can help.

Physical Management of Oral Stereotypies and Horse Welfare

Although treatment of any stereotypy begins with providing your horse adequate exercise, foraging opportunities and contact with other horses, management options are available to prevent horses from engaging in oral stereotypies. For instance, wooden fences coated with creosote can deter chewing, cribbing and sucking. An electric wire on the fence will prevent access to the wood. Cribbing and sucking wind can be prevented in some horses through the use of a “cribbing collar.” However, it is important to realize that these practices simply manage (avoid or prevent) the behavior. They do not remove the underlying motivation, and while they might decrease stress in horse guardians, they have been found to increase stress in horses. Studies have shown that stress hormones are highest in horses that perform stereotypies just before they begin to do the stereotypic behavior and lowest just after they’ve done the behavior. This tells us that performance of stereotypic behavior probably reduces stress for the horse. With this in mind, you’ll find it is better to treat stereotypies with changes in your horse’s management—changes that reduce your horse’s frustration levels or diet—rather than by using devices that simply prevent the horse from cribbing or wind-sucking. As mentioned, guardians should consider ways to increase foraging, decrease concentrate feed, increase contact with other horses and increase the amount of time the horse is out of her stall on a regularly basis.

Please see our article on Cribbing for more information on managing cribbing in your horse.

Management of Locomotor Stereotypies

Because almost all locomotor stereotypies are displayed while the horse is stabled, allowing your horse more time out of her stall can greatly decrease these behaviors. Social access to other horses is most important in reducing locomotor stereotypies, and keeping horses in a herd setting on pasture is the best treatment (and prevention). If increasing your horse’s access to other horses isn’t possible or your horse must be stalled for extended periods of time, providing social interaction with other horses in an adjacent stall as described earlier can help you meet her social requirements. Also, daily structured exercise will help ease frustration and boredom. Because horses are very social, they enjoy the company of not only other horses but other animals as well. So if there are no other horses in your barn, you can provide a different companion animal. Ponies and goats are the most common companions for horses because their size reduces the risk that they’ll be stepped on by the horse.

Studies also show that a mirror placed in a horse’s stall that allows her to see her own reflection can reduce locomotor stereotypies. Mirror size should be gauged by the horse’s size, but a mirror approximately 4 ½ feet x 3 feet is standard. For safety, mirrors should be acrylic, and acrylic mirrors made specifically for horses are available commercially. The mirror should be mounted where the horse can see into it at a natural relaxed head height. Avoid hanging the mirror near the feed manger to prevent perceived food competition. 

As with oral stereotypies, you cannot always eliminate a locomotor stereotypy by correcting the deficiency. Care should be taken to provide your horse with a highly enriched environment so as to prevent behavior problems. For other tips on environmental enrichment for horses, see our article on Enriching Your Horse’s Life.