Equine stereotypic behaviours are repetitive behaviours involving a constant sequence of movements that have no obvious or apparent function. [2]

Examples of common stereotypies include cribbing, wind-sucking, weaving, stall walking and head shaking. Sometimes referred to as stall vices, these behaviours are estimated to affect 10-20% of domesticated horses.

These abnormal behaviours may emerge as a response to stress, confinement, isolation or other sources of discomfort for your horse. While the exact cause of stereotypies is not well understood, they appear to be coping mechanisms or expressions of frustration.

Correctly diagnosing abnormal equine behaviour and understanding what it means is an important skill for every horse owner. In the past, it was not uncommon to dismiss behavioural abnormalities due to a lack of understanding. Only recently has stereotypic behaviour received significant attention from the scientific community.

Once you have identified a stereotypic behaviour in your horse, you can take steps to address the root cause of the behaviour. Improving your horse’s overall welfare through care, feeding and management practices is the best way to prevent stereotypies from occurring.

What is Stereotypic Behaviour?

Stereotypic behaviours in horses are defined as, “stylized, repetitive, apparently functionless motor responses or sequences.” [6] It is hypothesized that these behaviours are designed to reduce stress in the animal.

There is not a clearly defined categorization of stereotypies. For example, identification criteria are subjective and it can be difficult to distinguish a behaviour that is functional versus functionless.

Behaviours described by some researchers and behaviourists as stereotypic are classed differently by others. [2]

However, these behaviours are generally divided into two categories:

  • Locomotor stereotypies involving movement
  • Oral stereotypies involving the mouth

Sometimes, there is a clear cause of the behaviour related to the horse’s environment or routine. The behaviour may appear on a regular or predictable schedule. Other times, the behaviour may appear sporadically or unprovoked.

Some horses may display these behaviours intermittently, while others persist in the activity for long periods of time and devote considerable effort towards it. [6]

Horses that exhibit these behaviours may be otherwise healthy and able to be ridden. On the other hand, some horses with stereotypies are unrideable, have anxious temperaments or other health problems.

They may also develop related issues such as poor appetite, weight loss or poor performance as a result of increased energy expenditure or disruption to normal feeding and foraging. [6]

These behaviours can be a minor nuisance to horse owners, but they can also lead to long-term physiological problems depending on the severity and the behaviour exhibited.

Stereotypies may be referred to as “unsoundness” by horse owners conducting pre-purchase exams, thus reducing the value of the horse.

This article aims to help you identify common stereotypic behaviours in horses and learn about the concerns associated with these behaviours.

Functionless vs Conditioned Behaviours

Stereotypic behaviours lack function meaning that there is no beneficial consequence to the horse. These behaviours are purposeless. [3]

It is often difficult to ascertain whether a repetitive behaviour is stereotypic because some unique and abnormal behaviours do have a purpose.

For example, pawing and kicking may be repetitive, but operantly conditioned and not stereotypic. A horse may paw or kick at feeding time if it can see its food to receive more immediate attention from the caregiver.

The horse is fed after performing this behaviour, which results in positive reinforcement. [4]

In this case, pawing and kicking are not a stereotypical behaviour, as they have been learned and reinforced by feeding.

Displacement Behaviours vs. Stereotypic Behaviours:

Another important distinction is between displacement behaviours and stereotypies. Displacement behaviours are behaviour patterns characterized by an inappropriate or irrelevant reaction to a given situation. [5]

Self-grooming in an inappropriate situation is an example of a displacement behaviour. These behaviours are often immediate responses to a stressful situation.

If an abnormal behaviour appears during a stressful or unique situation, it is most likely a displacement behaviour. In contrast, stereotypies develop over longer periods of time. [2]

Displacement activities may appear in unusual contexts but typically subside as the stressful environmental conditions or stimuli resolve. [6]

The context of the behaviour is important. Inappropriate self-grooming is considered a displacement behaviour in stressful situations but would be classified as stereotypic behaviour (self-mutilation) if it occurred on a repetitive, perpetual, rhythmic basis in a stalled horse. [1]

Vices vs. Stereotypies:

Historically, stereotypies were referred to as stall or stable vices. [1] The use of the phrase vice is now viewed as incorrect because it suggests that something is morally wrong with the horse performing these behaviours.

This is an anthropomorphic concept, involving the attribution of human traits, emotions and intentions onto horses. Using the word “vice” implies that the horse is choosing to act in this manner and wouldn’t exhibit these behaviours if it had more willpower.

Stereotypic behaviour is usually an automated coping response for a horse in a non-species appropriate environment. The expression of these behaviours is out of the horse’s control. [4]

Risk Factors for Stereotypies

Stereotypic behaviour is believed to develop in response to a frustrating environment. Feeding practices, stable conditions, weaning methods and other management factors have been studied for their role in contributing to these behaviours. [25]

Between 10-40% of stabled horses experience stereotypic behaviours. In comparison, these behaviours are rarely observed in wild or free-ranging horses. [7]

Stereotypies are also reported to be more common in racehorses. There may also be genetic or neurological factors that contribute to the performance of stereotypic behaviour. [25]

Housing horses together with horses that are displaying stereotypies can result in copying or mimicry of the stereotype. For this reason, many horse owners avoid housing stereotypic and non-stereotypic horses together.

This may lead to isolation of the stereotypic horses, potentially exacerbating the behavior. [8]

Common Stereotypies

It is not uncommon to see conflicting information regarding what is classified as a stereotypy.

Some colloquial names for stereotypic behaviours include “chewing, lip-licking, licking environment, wood-chewing, crib-biting, windsucking, stall-walking, weaving, pawing, tail-swishing, door kicking (front foot), door kicking (back foot), rubbing, self-biting, head-tossing, head-circling, head-shaking, head-nodding, head extending, [and] kicking stall.”

We will divide these behaviours into eight broad categories below: [1]

  1. Cribbing / Windsucking
  2. Weaving
  3. Box (Stall) Walking / Pacing
  4. Wood Chewing
  5. Pawing
  6. Self Mutilation (including stall kicking)
  7. Stereotypic Licking (and other oral behaviours)
  8. Stereotypic Head Movements

Individual stereotypies present their own inherent risks for the animal, which are addressed below.

Some behaviours are commonly displayed in conjunction with others, and it is not uncommon to see a horse with more than one stereotypic behaviour.

#1: Cribbing / Windsucking:

Crib biting or “cribbing” is an oral stereotypic behaviour. A horse grips onto a fixed object, usually around chest level, with its incisor teeth.

The horse will lean back on its hindquarters, contract the muscles on its neck, and bring its head into an arched position. Air is drawn into the cranial esophagus, producing a grunting sound.

Cribbing occurs on a variety of solid surfaces. A horse may even crib on barbed wire or electric fencing if no other surfaces are available. [9]

Windsucking, which is less common than cribbing, displays the same characteristics without holding onto a fixed object.

Crib-biters may become windsuckers if there are no available surfaces for them to crib on or if the grasping behaviour is punished. [1]

Both cribbing and windsucking involve a quick intake of breath often accompanied by a grunting noise. This behaviour is sometimes referred to as aerophagia, but little to no air is actually swallowed. [7]

Concerns:

Horses that crib will often have clear erosion on the incisor teeth and pronounced hypertrophy (increase in muscle growth) of the neck muscles.

Cribbing has also been linked to weight loss and poor body condition. This may be connected to the amount of energy required to repeatedly crib-bite and to reduced time spent foraging, eating and grazing. [10]

Cribbing is associated with gastric inflammation and ulceration in young horses. [11]

 

Quiz: Assess Your Horse's Ulcer Risk

There is also a correlation between cribbing and temporohyoid osteoarthritis (THO). THO is a progressive disease of the temporohyoid joint, characterized by excess bone growth and decreased range of motion. [12]

Another concern for horse owners is environmental damage caused by cribbing behaviour. Fences, buckets and ledges may become damaged if the horse grips them with its teeth.

#2: Weaving:

Weaving is a locomotive stereotypic behaviour that involves lateral movement of the neck and head from side to side. It is a repetitive motion in which the horse alternates its weight between forelegs. [9]

Weaving typically occurs with the horse’s head over a stable door but can be observed in other locations. [13]

The horse may average 30-90 repetitions of weaving behaviour per minute and may weave for up to 3 hours a day. [6]

Concerns:

Weaving can lead to orthopedic problems such as strained ligaments, loss of body condition and poor performance. [9]

Horses that weave will have more wear on their feet. For horses that are shoed, the shoe will be worn down and need to be replaced sooner. [13]

Weaving can lead to weight loss and lethargy due to energy depletion during the process. [14] This behaviour is also likely to cause uneven muscular development within the horse’s neck. [15]

#3: Stall Walking or Pacing:

A horse who Stall Walks or Box Walks will repeatedly walk around the stall in a circle. [9] The size of the stall does not affect the behaviour. Horses that are given a larger area will often circle in one corner.

Restraining a horse that stall walks or preventing the circular walking pattern will likely result in the expression of weaving behaviour.

Some horses will circle for hours a day, at a rate of several repetitions per minute (depending on the stall size). [4] Stereotypic stall walking patterns are unique from horse to horse. Some horses will circle over and over in one direction while others will form specific and consistent patterns within the stall. [16]

Pacing refers to stereotypic movement along a barrier, usually at a walk or trot. Horses that pace may also move in a figure 8 pattern between parts of the enclosure; these turns will occur at a specific and consistent location.

Horses that pace in a straight line will often turn when they reach a barrier and change direction. [17] The consistent pacing may result in a trench along the fence or near the gate.

Most horses will periodically circle in their stall or pace down a fence or at a gate, especially when it is time for feeding. Pacing and circling are only considered stereotypic behaviours if they become excessive and replace other activities such as eating, foraging or resting. [6]