StereotypiesBack to Stable Stress





1. Types and definitions

Stereotypies have been studied in many animals, even bank voles (Cooper and Nicol 1991) but was first studied in autistic children (Hutt and Hutt 1970). They are repeated invariant sequences of movements, which have no obvious goal or function (Appleby and Hughes 1997), where an animal is frustrated or otherwise lacking in control over the world that impinges on it. If the movements are not necessary for locomotion to a particular place, food ingestion, cleaning the body, social communication or any other normal biological function, they are included by the above definition as stereotypies (Broom and Kennedy 1993). They also described any movement made by a horse necessary for locomotion, food, cleaning, social or any other biological function as "normal behaviour". Any other behaviour is a stereotypy. Manson (1993) however did not think that the distinction between normal behaviour and stereotypies was that clear, with the boundary between them being crossed regularly. Long established stereotypies become so ingrained and habitual that the animal incorporates them into otherwise other normal behaviour patterns.

FIGURE 3 - A Horse Crib biting (McGREEVY 1998).

Stereotypies rarely occur in individuals living in the relatively complex environment that is appropriate to the biology of the species, and where a wide range of the behavioural repertoire can be shown. They are described as abnormal and thought by many to indicate welfare problems for the animal displaying them (Lawrence and Rushen 1993).

The stereotypies shown by stabled horses are listed by Broom and Kennedy (1993) as being stall walking, crib biting, wind sucking, weaving, swaying, pawing, stall kicking, head shaking, head nodding, crib whetting and tongue dragging. They were probably seen the first time that horses were confined. They described them as a sequence of events repeated with little no or variation in form. "Stable vices" may include kicking, aggression, biting and ingestion of bedding material as well as stereotypies. They are behaviour patterns that interfere with management. These behaviours tend to cause more embarrassment to owners than concern (McGreevy 1995), and are considered aesthetically displeasing. Owners believe that the behaviour indicates the horse’s lack of interest in the environment.

Stereotypies in the stable are sometimes referred to as "stable vices" (Cudderford 1995). This is an incorrect description as it implies that the "vice" or stereotypy developed through some fault of the horse (Houpt 1986). Ironically the reverse is true; the stereotypy developed in the horse due to inappropriate stable management practices of the vast majority of owners (McGreevy 1995). Problem behaviour is any behaviour that does not fulfil reasonable human expectations (Ralston 1982). The term also lumps together stereotypies with what Miller (1996) terms simple learned misbehaviours.

TABLE 2 - The table below shows some of the stereotypies and their origin of behaviours (Luesher et al 1991).


2. Aetiology

Coping mechanism

Many researchers have proved that stereotypies result from a difficulty in coping with environment (Broom and Kennedy 1993), and that a horse may come to show stereotypies in its attempts to cope with the highly unnatural environment in which it finds itself (Houpt 1986, Broom and Kennedy 1993, Cooper and Nicol 1991). Confinement, some particular frustration, or some unpredictability in the environment makes it difficult for the individual to control its interactions with its environment (Fraser and Broom 1990, Mason 1991a).

Broom and Kennedy (1993) found that stereotypies were behavioural pathologies that were a consequence of trying to cope with a problem. However McCall (1993) described stereotypies as a normal behaviour that had resulted from keeping a horse in an unnatural environment. And it has been shown through the coping hypothesis that animals that perform stereotypies showed fewer physiological signs of stress (Wiepkema et al 1987). Animals have many different methods for trying to cope with adversity and there are many different consequences of failing to "cope" (Broom 1991, Broom and Johnson 1993).


Diet and Feeding

At present we know that horses at pasture seldom show stereotypies in comparison with stabled horses and that a high concentrate, low volume diet is more likely to result in stereotypies. McGreevy et al (1995a) found stereotypies were higher as the amount of forage fell below 6.8 kg/day and that horses offered forage types other than hay were less likely to perform abnormal behaviours (McGreevy et al 1995b). Low levels of feeding also increase the chances that stereotypies are shown by tethered gilts (Appleby and Lawrence 1987).

When a horse is stabled his diet is changed from pasture to hay and concentrates, the ratio of which depend on his requirements and workload. In physiological terms this dietary change alters oral stimulation, the pattern of ingestion and digestive function. Johnson et al (1998) studied how the effect of neutralising the acidity of the hind gut of stereotypic animals may affect the behaviour of the animal. They found that supplementing virginiamycin to reduce the fermentative acidosis in the hindgut also improved behaviour and lessened some behavioural problems.

There has been a lot of research into the relationship between crib-biting and diet. Marsden (1993) found that the time spent feeding was highly negatively correlated with time spent in abnormal behaviour. Crib-biters deprived of the opportunity to stereotype eat more than normal horses, suggesting that they have greater oral needs, and the link between foraging and crib-biting explains why restricted feeding is a management factor associated with an increase in abnormal behaviour in racehorses (McGreevy 1995). McGreevy (1995c) has shown that horses do not swallow air when they crib, air is taken into the mouth and pharynx but not swallowed.

There has also been a strong link with diet and other stereotypies. Marsden (1993) looked at wood chewing and stated that one of the major causes of the increased abnormal behaviour seen in housed horses is the effect of diet on time spent feeding. Increasing the hay ration in the diet was shown to increase the time the horse spends eating and decreases the time spent chewing wood. It was concluded that increasing the roughage content in the diet was probably the easiest solution to decreasing the incidences of wood chewing in horses that alleviates the problem rather than just preventing the behaviour.



Horses are a gregarious species and social isolation can have profound effects on many aspects of their behaviour. If people are kept in solitary confinement or are otherwise severely frustrated they may also show stereotypies (Broom and Kennedy 1993). In confinement in stalls, some sows are very inactive and unresponsive where as others show high levels of stereotypies and there are differences in their brain opioid receptor densities as a consequence (Broom 1987, Zanella et al 1992). Cribbing occurs less frequently in horses kept in tie stalls than it does in horses kept in box stalls, suggesting that isolation rather than confinement is the major contributing factor in the cause of cribbing (Miller 1996).



Stereotypies are most often observed when the animal is confined and there are constraints on their ability to perform certain behavioural patterns (Mason 1991b). Miller (1996) stated that most cribbing is due to confinement. The development of stereotypic behaviour is associated with the degree of confinement. Attention must be given to the amount of activity in the horse’s visual field and its contact with other horses. Due to insufficient stimuli, the animal turns to rewarding self-stimulation. There is much advice about stable design and construction to ensure physical health but rarely if ever do advisers consider the psychological needs of the horse. The time spent in a stable is correlated with an increase risk of abnormal behaviour (stereotypies) (McGreevy et al 1995a). Some horses get claustrophobia, just like humans.


Insufficient space for movements

Most reports of stereotypies in horses concern individuals confined in a relatively small space. Inability to carry out normal movements and to exercise causes frustration, leading to stereotypies. Stereotypies are rare in horses that are not confined, and are reduced in frequency or disappear completely when the horses are given more space.


Lack of exercise

Today’s horses have to exercise sporadically throughout a 24-hour day for short periods, followed by enforced immobility in confinement for long periods. However many long distance competitive horses are kept out at pasture during the competitive season to achieve the highest standards of fitness and endurance. Box walking could be a redirected escape response to the aversive stimulus represented by the stable (McGreevy et al 1995a).


Insufficient social and other environmental stimulation

Direct contact with social companions can reduce the incidence of stereotypies. McGreevy et al (1995b) found that visual contact between stable interiors was associated with a reduced risk of abnormal behaviour. Loose box designs that limit the amount of communication between neighbouring horses increase the risk of abnormal behaviour. "Free time" of the stabled horse may allow stereotypies to develop (McGreevy et al 1995b).


Other kinds of frustration

The mere fact of locking a horse up in a stable, by itself, when it is in fact naturally inclined to want to roam over large areas with other horses as company is the best example of conflict. Broom and Kennedy (1993) stated that stereotypies originate in a movement, which is relevant to the problem that the animal is encountering. Rushden et al (1993a) proposed that stereotypies result from the frustration of specific motivational systems, indicating that the animal is still motivated to perform the behaviour, that is, there is evidence for behavioural deprivation.

McGreevy et al (1995b) found the use of bedding types other than straw was associated with increased weaving but this may have been because the horses were eating their bedding. McGreevy (1996) gave an interesting explanation of the possible reason why in his 1995 study of stereotypies, endurance horses had a higher level of box walking than other stereotypies or horses from other disciplines. He described endurance horses as "marathon runners" of the horse world and suggests that the horses experience the same "jogger’s high", when endorphins are released after strenuous exercise. Endurance horses experience this when worked and recreate this feeling in the stable.


Presence of other stereotypers

There is a belief that stereotypies are learnt by imitation, but when stabled horses show stereotypies they must have some problem, whether or not they initiate the behaviour by copying others. However there is only anecdotal evidence to show that stereotypies are copied. Sambraus and Radtke (1989) regarded it as a response to stressful situations and it did not seem to arise by copying from another horse. Social facilitation may also affect the incidence of abnormal behaviour; animals may be more likely to develop stereotypies if their neighbours already perform them (Cooper and Nicol 1994, McGreevy et al 1995b).


Genetic factors

Vecchiotti and Galanti (1986) concluded that a genetic component was important as a cause of such behaviour but this was difficult to ascertain because of the need to distinguish inherited effects from those learnt from older animals i.e. learnt by foals from their dams. There is little scientific evidence for this but McGreevy (1995) did find that stereotypies were especially prevalent in certain family groups. Genetic predisposition would explain why certain horses developed stereotypies while others kept in the same environment and managed identically did not. The heritibility of such a factor is unknown.

Leucher et al (1991) believed that horses inherit both sensitivity to stress and susceptibility to expressing a particular behaviour associated with obsessive compulsive disorders. Studies have shown horses are more likely to exhibit the same compulsive act if they are related.


3. Prevalence

Quantitative measures of horses performing stereotypic behaviours can either be the number of horses exhibiting stereotypies ant any one time of how much of the animal’s time is spent in the stereotypic behaviour. McGreevy et al (1995b) used this epidemiological approach on the abnormal behaviour of stabled horses. He studied weaving, wind sucking and crib-biting and found they were most common on yards where the horses were fed a high proportion of concentrates relative to natural forage like hay.

Horses allowed visual contact with one another between their stables also developed less abnormal behaviour, particularly wood-chewing. Results involving 4468 horses in training showed the prevalence of stereotypies to be 10.8%. He also discovered that stereotypies have never been recorded in feral animals. Prevalence of stereotypies rises with age and crib-biting was 5.5% in the Thoroughbred population (McGreevy 1995). Luesher et al (1991) gave a prevalence of over 15% of domesticated horses exhibiting stereotypies.

In a study on weaving the number of movements of the head and neck varied from under 400 to 18000 a day and 67 minutes a day average (Sambraus and Radtke 1989). Krzak et al (1991) found that wood chewing occurred primarily during the late night and morning and that exercise reduced the time that stabled horses spend chewing wood. Crib biting is normally seen at feed time and weaving is normally seen when the horse is disturbed or excited e.g. anticipating feed time.

Mason and Turner (1993) summarised "Individuals with a limited ability to generate a range of behaviour patterns spontaneously, or who readily restrict their attention…might be more inclined than others to develop stereotypies. That animals may differ in their propensities to develop or control behaviour in particular ways has welfare implications, for it suggests that an individual’s stereotypy levels are not just a product of how aversive it finds its current environment, but are also influenced by the readiness with which certain behavioural control mechanics come into play."

(McGreevy 1996)


TABLE 3 - Effect of diet on time spent feeding and time spent in abnormal behaviour in the horse (from Marsden 1993).

(A = ad libitum M = as required for maintenance and light work)


This shows that feeding practices have a greater effect than housing practices on the incidence of abnormal behaviour. It is interesting to see that the horses out at pasture showed no signs of abnormal behaviour!


TABLE 4 - The multi variable relationship between yard variables and the risk of an individual horse performing anomalous behaviours (adapted from McGreevy 1995b).


This shows there is an association with the amount and type of forage offered, number of times per day forage was offered, total number of horses in yard, type of training in which the yard was involved, design of loose-boxes, type of bedding used and the possession of an exercise area. Oral-based and locomotion stereotypies were more prevalent on those yards, which fed less forage per day, and the risk of horses performing abnormal behaviour increased when the total number of horses on the yard were fewer than 75. 13% of horses exhibit stereotypic behaviour.


TABLE 5 - Prevalence of the four behaviours in the horses trained for three disciplines (from McGreevy 1995a).

This shows that endurance yards have a lower prevalence of abnormal behaviours, except box walking. Overall there was an average prevalence of 13.66% of abnormal behaviours in competition yards.


4. As indicators of poor welfare

Mason (1991) stated that the development of a stereotypy indicates that well being had probably been poor, with the animal motivated to show a behaviour pattern that it could not perform normally, or to completion. Whether the stereotypy reduces the adverse impact of the environment on the individual at that time, or just shows that the individual is psychology damaged, the problem must be there, and the stereotypy is an indicator of poor welfare (Broom and Kennedy 1993).

The continued performance of the stereotypy may also indicate suffering, but the degree of stereotypy does not necessarily correspond to the degree to which its wellbeing or welfare is impaired. Lower levels of stereotypy do not necessarily reflect better wellbeing and not all animals in a given situation show stereotypies (Broom and Kennedy 1993). However the welfare is worst if the stereotypy dominates the life of the individual (Broom and Kennedy 1993).


The links with stereotypies and welfare have been analysed in three main ways:

  1. By identifying the types of environment in which they are most common,

  2. By identifying the motivational bases of the behaviour,

  3. By looking for links with other welfare indicators such as physiological signs of stress.


They are termed abnormal behaviours and their implications for welfare are controversial. The literal meaning of abnormal is "away from the norm", statistically rare, or different from chosen population. All stereotypies have some energetic cost, which may be high enough to result in deterioration of body condition and in some cases injury or disease results (Broom and Kennedy 1993). "The moment a behaviour is labelled "abnormal" it can become almost impossible not to assume the animal doing it must be suffering, because "abnormal" is such an emotionally loaded word" (Dawkins 1980). This is because the term is sometimes used specifically to mean pathological, either causing harm to the animal or the product of damage or illness (Schmidt 1982). When not performing these "statistically unusual" behaviours, the animals are likely to seem normal, healthy and unaffected by any mysterious pathology.

Abnormal behaviour has been equated with poor welfare because it is often prevalent in environments judged to be poor, often develops from frustrated motivation, and sometimes correlates with other signs of poor welfare. Abnormal behaviour especially stereotypies is a reliable indicator of poor welfare. Individuals with low levels of stereotypy are better off than those with high levels of stereotypy. Similarly environments that elicit high levels of stereotypy are worse than those that result in little or none of this behaviour.

Behavioural changes associated with housing of horses often give rise to concern for their welfare (Marsden 1993). If animals that show stereotypies are put into better conditions, they usually show a reduction in occurrence of the stereotypy, but long established stereotypies may continue (Ödberg 1987, Cooper and Nicol 1991).


5. Prevention and cure

So what should be done about stereotypies in horses? As mentioned the existence of stereotypies can be an indicator of poor welfare in horses as in other species. Any horse showing stereotypies has a real problem therefore any attempt to prevent the stereotypy will have no beneficial effect on the animal’s real problem. Examples of this are removing the object of attention of a crib-biter, or by restriction neck muscle movements in a wind-sucker, or by severing muscles or nerves. Miller (1996) gives 3 options for a crib biter’s owner, "cribbing straps, a more stimulating environment or by simply ignoring the habit." In fact this will cause additional frustration for the animal in most cases and unnecessary pain and suffering in those horses subjected to surgery. The practice of myectomy and neurectomy of structures in the neck may be associated with compromised welfare and should be questioned on humane grounds (McGreevy 1995). He discovered that when crib-biters are prevented from stereotyping, their motivation to perform the behaviour rises.

The horse is unlikely to benefit from most attempts to block stereotypies and horse welfare should be the primary consideration. The positive action, which should be taken in the long-term to prevent the occurrence of stereotypies, is to improve the housing and management of horses. Genetic selection is unlikely to have a substantial effect. All horse management should take into account the needs of the horse. Nutrition should be adequate. Housing for horses should provide sufficient opportunity for movement and variety of stimulation. Social contact between horses should be maximised, preferably by being kept in groups.

Releasing horses that perform stereotypies from the stabled or confined situation to conditions which allow freer movement and contact with more horses, will often produce a changed and improved animal. Traditional methods of prevention were physical methods like grills, collars and surgery. Short term methods were a flute bit for wind suckers and for crib biters, "comforters" which was something for the horse to crib on that did not wear its teeth down, like covering surfaces with rubber. There are drugs available like naloxone that blocks the endorphin action of the stereotypy. There are different ones for different stereotypies.

Stereotypic behaviours are safety valves that allow the horse to survive stress without life-threatening psychosis; attempts to curb the behaviour may be more harmful than the behaviour itself. If behaviours like box walking and weaving are prevented, the unacceptability of the environment is further enhanced and more pathological behaviour may result. The first step in prevention is designing an environment to accommodate the animal’s needs.

It is quite possible to compete horses in suitable environments. It would only take one generation of proper environmental conditions to eliminate stereotypies. Once developed the stereotypy can persist even in horses that are no longer stabled. It is as if the horse is scarred, with the stereotypy telling us something about the horse’s past (Mason 1991). Stereotypies can act as warnings that the horse has been in an unchanging and frustrating environment and that its welfare has probably been unsatisfactory.

McCall (1993) said that wood chewing could be prevented in the field by physical means like placing fencing around the trees or wrapping trees in wire. Fences and stalls could be coated with unpalatable solutions or an electric wire could be run along the inside of fences. However the problem with these strategies is that the horse’s desire for roughage is not reduced and the horses the may simply begin consuming other inappropriate materials like manure or another horse’s tail. One simple method to prevent stereotypies is to feed small frequent meals and slow the rate of the horse’s food consumption (McCall 1993). Relieving boredom by giving the horse more time to exercise and socialise with other horses may also decrease wood chewing behaviour (KRZAK et al 1991).

The problems of stabling horses could be reduces if a few horses were housed together. Isolation can be avoided in all types of horses by maintaining them outside in freely associating groups or with family groups in free housing systems. Horses living together for the majority of their lives in familiar groups rarely injure each other. Visual contact through bars although better than no contact is apparently not sufficient to prevent stereotypic behaviour. Horses in groups are able to hear, touch, and smell each other and interact frequently, on average 4.5 times per hour (Kiley-Worthington and Wood-Gush 1987). Other management techniques that can help are allowing free contact with other individuals for some part of each day in exercise rings or yards, or allowing the maximum amount of contact between animals in their boxes. Loose housing can be designed to prevent bullying with many feed and water points in the environment.

Any attempts at environmental enrichment to lower the incidence of stereotypies should be adopted at and continued from an early age (McGreevy 1995). Artificially formed groups can lead to aggression and injury (Houpt 1981). Houpt (1981) notes that the majority of horses adapt to unnatural conditions but a few do not and these should be removed from the environment, no matter how fast they run or how high they jump (Kiley-Worthington 1983).


6. What should be done in the first place?

Obvious steps are to turn the horse out, increase the time the horse spends feeding and making the horse work for what food he is given like small holed haynets. Houpt (1995) stated that it is possible to change a horse’s environment or diet without interfering with its function as a performing animal but in many cases it is not. She goes on to suggest the "greatest need of the owner" is suitable medication for these horses. However she does conclude "The goal should be to reduce the horse’s motivation to crib bite or stall walk rather than to sedate the horse."

The environmental conditions horses are kept in are not natural. Majority of horses adapt but some do not. Houpt (1981) suggests that stereotypers should not breed from. Horses should be able to live with out crib strap, but the answer must first lie with redesigning stables with the horses behaviour in mind e.g. so can see other horses. Every effort should be made to ensure naturalist environment. Attempts to eradicate an established stereotypy by increasing the time that a horse spends out of the stable may have little effect on its behaviour in the stable (McGreevy et al 1995a).


7. Stable Toys

There has been a relatively new introduction of "toys" for horses to benefit their welfare. The two described below are the market leaders and part of the information given to help market the toy is interesting and worrying as it is treating the symptom and not the cause. Boyle (1997) carried out a study to see if stable toys reduced the incidences of stereotypic and undesirable behaviour patterns in the ponies studied. It was concluded that stable toys are of little value in improving the welfare of stabled horses.


The Equiball Feeder is claimed to:


The Equiball is a behavioural enrichment device, which increases the time the horse spends consuming its food ration and encourages its natural foraging behaviour. Research has shown that the use of an Equiball can lead to a reduction in the performance of established "stable vices" in most horses.

The Horseball is approximately 12 inches in diameter and has two handles. It serves as a therapeutic friend for confined or recuperating horses. They will nose it and play with it in the stall and is used to reduce stable vices.