Stereotypic behaviors are defined as repetitive, relatively unvarying patterns of behavior with no obvious goal or function.¹ A horse that displays stereotypic behavior tends to perform the behavior in nearly the exact same way every time, and many horses also perform the behavior in a preferred location, e.g., in a specific area of the stall. The performance of stereotypic behavior has been used as an indicator of poor welfare, although it is often difficult to determine whether the behavior is the result of poor welfare in the past or due to current unfavorable conditions. This presentation will introduce horse owners to stereotypic behaviors in horses, what has been learned about stereotypic behaviors through science, and how this information can be applied in order to better manage and thus improve the welfare of horses with stereotypic behavior.

Stereotypic behaviors (STBs) are often referred to as “stable vices”, e.g., in popular press equine publications and in older equine textbooks. However, we are now moving away from using this terminology to describe stereotypies, as research studies aimed at further investigating STBs in horses are demonstrating that these behaviors are not simply the result of boredom. These behaviors are not attempts by the horse to be a nuisance to their owner and should not be considered to be the fault of the horse. Although the exact underlying cause(s) of STBs remain unknown, we have gained a better understanding of how, or rather why, stereotypic behaviors develop in horses. The development and continued performance of stereotypic behaviors appear to have a physiological or psychological basis.

Oral Stereotypies

Most survey studies conducted to date⁴ show 4–5% of the average horse population engage in an oral STB, such as cribbing, crib-biting or wind sucking. The typical cribber places its front teeth on an object, such as a fence board, pulls back while sucking air inward, and then emits a grunting noise. This behavior is distinctive both to see and to hear. Some evidence suggests that these behaviors are the result of ‘feel good’ neurotransmitters in the horse’s brain, which may be why the behavior seems so addictive and so challenging to stop once started.

It should be noted that cribbing and wood chewing are not the same thing. Wood chewing is actually a normal, natural behavior that even horses in the wild will perform. On the other hand, feral horses have never been observed cribbing. Wood chewing is sometimes classified as a redirected grazing behavior, particularly in horses on limited forage diets. There is a possibility that wood chewing behavior will precede a horse becoming a cribber, but evidence of this is limited.

Locomotor Stereotypies

There are two reasonably common locomotor STBs observed in horses. One is called weaving, where horses shift their weight back and forth on their front legs (a repetitive, side to side swaying motion). This is often performed when standing at the front of the stall or next to a paddock gate. It often coincides with anticipation of something; e.g., awaiting morning turn out or while waiting to receive feed. The second is called box walking or stall walking, and it literally means to walk part or all of the horse’s box stall (or paddock) perimeter.

Risk Factors for Developing STBs

Though direct cause and effect research on this topic is limited, multiple studies involving thousands of horses have consistently found the following factors to be associated with increased likelihood of engaging in a STB:⁴ Insufficient/very limited turnout time, insufficient/very limited opportunities to socialize with other horses, insufficient/limited grazing/foraging opportunities—this factor often goes hand-in-hand with high concentrate diets, which have also been implicated.

Stressful weaning, particularly an abrupt method with individual housing, has been associated with increased STBs in several studies.³ Additionally, there has been evidence that young stock with gastric ulcers are more likely to be crib-biters. Some differences in brain physiology responsible for goal directed and reward seeking behavior have also been demonstrated between horses with STB and horses who do not show these behaviors.

Commonly Held Beliefs

Contrary to popular opinion in the industry, there is no scientific proof that horses learn STBs from one another. Anecdotally, when stereotypic horses are turned out to pasture with non-stereotypic horses (those horses who do not display a STB), the non-stereotypic horses do not pick up the STBs. There is, however, less consistent evidence when it comes to housing non-stereotypic horses next to or across from stereotypic horses in environments involving the risk factors mentioned above.

Do STBs Cause Damage?

Cribbers may cause damage to their teeth, and as such may need additional dental care. Cribbing can be hard on fencing and stall boards. Weavers and stall walkers may cause more wear and tear to their feet, thus potentially needing more farrier care. They may also cause ruts or wear in the flooring in their stall or paddock. In general, though, these potential damages tend to be exaggerated by many in the horse industry leading to some horses with STBs being turned away from certain boarding or training centers. Hopefully, with increased understanding of STBs, this bias will subside.

Should I Try to Stop It? And, If So, How?

If you own or manage a horse with a STB, the recommendation is to learn as much as possible about that particular behavior. Stereotypic behaviors are recognized as both a welfare and a management concern, and many owners attempt to physically prevent the behavior. Attempts to physically prevent STBs can result in reduced welfare for the horse and additional strain on the owner’s pocket book. Therefore, strategies aimed at addressing the behavior should include consideration of potential causal factors and implementation of management practices known to help reduce the behavior (e.g., increased opportunities to socialize with other horses and to graze/consume forage).

Always remember that somewhere along the way, the horse developed this STB because it was likely trying to ‘cope’ with a suboptimal husbandry situation. If we view it as a coping mechanism, how certain are we that we should take away the horse’s ability to cope? Multiple studies have shown that, when presented with a stressor, the horses who handled it least well were crib-biters who were prevented from cribbing; non-cribbers did fine, and cribbers who were allowed to crib were fine, but cribbers who were thwarted were more stressed.²

With respect to the locomotor stereotypies, some owners have had success in reducing their horse’s weaving or box-walking by increasing the visual horizons; e.g., placing the horse in a stall with a window to the outdoors or with an acrylic/shatter-proof mirror, adding an anti-weave stall front that allows the horse to have its head and neck out to the aisle, or simply keeping the horse out at pasture more of the time. Based on the authors’ experience and anecdotal reports from owners, it appears much easier to reduce the time a horse spends engaged in a locomotor STB than an oral STB.

Conclusion

Just because your horse performs a stereotypic behavior, such as cribbing or weaving, does not mean its current state of welfare is suboptimal, but more likely, that at some point in the horse’s history, the horse was trying to cope with stressors outside the behavioral demands of the horse’s nature.

Managing stereotypic behaviors can be very challenging. The best management strategy continues to be prevention by trying to optimize turn out time, social interaction and grazing/foraging opportunities. Minimizing stress during the weaning process is important, and working hard to enhance natural behaviors when horses are on stall rest for injuries or illness can help reduce the chance that your horse will develop a STB.

References

1.  Mason GJ, Latham, NR. 2004. Can’t stop, won’t stop: is stereotypy a reliable animal welfare indicator. Animal Welfare. 13, S57–S69.

2.  Nagy K, Bodo G, Bardos G, Harnos A, Kabai P. 2009. The effect of a feeding stress-test on the behavior and heart rate variability of control and crib-biting horses (with or without inhibition). Applied Animal Behaviour Science. 121, 140–147.

3.  Nicol CJ, Davidson HPD, Harris PA, Waters AJ, Wilson AD. 2002. Study of crib-biting and gastric inflammation and ulceration in young horses. Veterinary Record. 151, 658–662.

4.  Wickens C, Heleski CR. 2010. Crib-biting behavior in horses: a review. Applied Animal Behaviour Science. 128: 1–9.