Researchers are studying these behaviors and how they can affect equine health and welfare.
By Christa Leste-Lasserre, MA, The Horse: Your Guide To Equine Health Care
Cribbing, windsucking, weaving, stall-walking. These are all examples of equine stereotypies. Not to be confused with stereotypes—preconceived ideas about certain groups of individuals—stereotypies are any kind of repetitive behavior that appears to have no purpose. In horses, the most common stereotypies are oral (cribbing and windsucking) and locomotor (weaving and stall-walking).
To help you better understand what these behaviors are (and aren’t), what causes them, and what to do about them, we’ve gone to those who study them. We’ll also look at recent research on stereotypies and how they affect equine health and welfare.
Cribbing, aka crib-biting in some regions of the world, is the most common oral stereotypy, affecting about 5% of domestic horses, says Katherine Houpt, VMD, PhD, Dipl. ACVB, professor emerita at Cornell University’s College of Veterinary Medicine, in Ithaca, New York.
When cribbing, horses grab onto wood, metal, or any other available sturdy surface with their teeth. They then suck in air, producing a raspy, hoarse sound. Horses can also skip the grabbing part, exhibiting a less common stereotypy known as windsucking. In both cases, the behavior appears to be related, at least initially, to frustration—particularly food frustration, or a desire to eat when there isn’t food available, says Sabrina Briefer Freymond, MSc, a researcher at the Agroscope Swiss National Stud Farm, in Avenches.
“Horses naturally eat up to 17 hours a day, and if they only have access to food three times a day, it can cause high stress that can, in some cases, lead to an oral stereotypy,” she says.
The frequency of these oral stereotypies can vary significantly from one horse to another, Briefer Freymond adds. “Some of them will crib an hour a day, and others do it practically 15 out of 24 hours,” she says. “Our last study, where we filmed horses for 48 hours, showed one horse that was cribbing at 2 o’clock in the morning while all the other horses in the barn were sleeping.”
These behaviors include weaving and stall-walking—both apparently related to a frustration caused by a need to move, say our sources. Horses naturally travel several miles a day when not confined, so being locked in small enclosures can trigger such stereotypies.
When horses weave, they stand in one place, transferring their weight from side to side, sometimes shifting the front feet only, says Houpt. “This is often an escape behavior, which you’ll see at a door or gate, even in a paddock, coming from the horses wanting to get out,” she adds.
Stall-walkers pace their stalls relentlessly in circles, Houpt says, and each horse usually prefers one direction. This stereotypy is not to be confused with a frantic temporary state of panic, in which horses wheel around, even at a trot, in their stalls. Those horses whinny, defecate, and sweat, indicating a stress response to an event such as getting separated from a preferred stallmate, but do not display the stall-walking stereotypy, says Houpt. Rather, stall-walking is calmer and more monotonous and can occur in the absence of acute stress.
Other Stereotypylike Behaviors
Several repetitive behaviors have gained the reputation of being stereotypic, even though they’re not, says Briefer Freymond. “It’s not something everyone agrees on, but for me, most of these other behaviors are learned and rewarded.”
Many people consider pawing, for example, to be a stereotypy. But horses paw with a purpose, our sources say. “They paw before the food comes, and then the food comes, so they think they made the food come by pawing,” says Houpt.
Kicking a stall door also has purpose—maybe as a sign of aggression toward a neighbor or, more commonly, as a way to “bring on the food.”
Angelo Telatin, MS, assistant professor in equine science and management at Delaware Valley University, in Doylestown, Pennsylvania, has taught horses to play with a hanging ball instead of kicking their stall doors at mealtime. Because the horses can learn to replace one behavior with another, this indicates the kicking is learned, says Telatin, and not a stereotypy.
Headshaking, licking, and sticking out the tongue also seem to be learned behaviors with a purpose—typically, making food arrive. “Headshaking is also a frequent method of fly evasion, which would also be a learned behavior, with the reward of having fewer flies on the face,” says Houpt. It can also be a sign of discomfort or pain, as with allergies, infections, and some neurologic disorders.
Despite popular belief, wood-chewing isn’t a stereotypy, either. Houpt says a lack of roughage initially causes wood-chewing, and the behavior becomes problematic when the horse begins destroying fences and stall walls.
Physical & Chemical Brain Changes
Stereotypies are tied to dopamine overproduction in the brain, says Sebastian McBride, PhD, a lecturer in biological science at Aberystwyth University, in Wales. Dopamine is a neurotransmitter—a sort of chemical “messenger”—related to learning.
McBride believes stress is to blame, as it causes permanent structural changes in a learning center in the brain called the striatum that lead to dopamine overproduction.
These overdoses first cause “hypermotivation,” which he describes as a motivation level that exceeds healthy or useful limits. A hypermotivated horse might be inclined to chew and ultimately become a cribber or move and start weaving or stall-walking.
This explains why horses with stereotypies tend to have other signs of habit formation, as well, McBride adds. It’s part of their structural brain change—they get “stuck” in habits and have a challenging time accepting change.
“There’s clearly some dysregulated neurophysiology in the striatum,” he says. In other words, that dopamine center of the brain has gone through real physical, and probably permanent, transformations. “And that can cause these learning anomalies,” he says.
A Domestication Problem
It’s a fact: Equine stereotypies don’t happen in the wild. Feral horse herds show no signs of cribbing, wind-sucking, weaving, and certainly not stall-walking.
Stereotypies appear in domestic horses generally between six months and 2 or 3 years of age, says Briefer Freymond. This period coincides with major lifestyle and management changes, such as weaning and the start of training. Weaning often involves separation, along with a change of environment, food, and social setting. And when horses begin training at 2 or 3 years old (depending on breed and discipline), they might change owners, homes, living conditions, social environment, and, of course, workload.
However, stereotypies can develop at any age, Briefer Freymond says, following a major source of stress. Her own mare became a weaver after an operation on her leg that required three months of stall rest. “She’s out in pasture now, all the time, so she doesn’t feel the need to weave anymore,” she says.
Horses also develop stereotypies as a result of experiencing extreme chronic stress, she adds. “A lot of people think horses will pick up stereotypies from other horses in the same barn,” she says. “But the reality is, if you’ve got several stereotypic horses in the same stable, you need to consider what’s going on with the management there.”
To Stop or Not to Stop?
As owners we find equine stereotypies annoying. They grate on our nerves, and they can even lower a horse’s sale value.
But aside from being irritating, is a stereotypy really a bad thing? Not necessarily, say our sources. As stated above, many horses develop stereotypies as coping mechanisms for a chronic stressor. And that, they say, could be good.
“When you go into a barn, look at the cribbing horse in his stall, and then look at his noncribbing neighbor next door,” says Briefer Freymond. “Which horse is happier or better off? Can you really tell a difference?”
Except in extreme health-endangering cases, such as completely worn-down teeth or sleep deprivation due to a constant need to crib, Briefer Freymond believes it’s better to not prevent horses from carrying out their stereotypies.
Houpt disagrees. “If you’ve ever seen a horse with surgical colic (abdominal pain caused by pathology that requires surgery), you would vote for preventing him from cribbing,” she says, adding that she believes cribbing horses are at an increased risk of developing gastric ulcers and gas colic. Houpt also says cribbers can develop life-threatening epiploic foramen entrapment, an intestine-twisting kind of colic that requires surgery. “I did one study on 15 cribbers, and seven of those horses died (from colic),” she says. “That convinced me.”
For Briefer Freymond, however, the link between GI issues and cribbing is unclear. “Crib-biters might have these issues, but nothing proves that it’s the cribbing that causes them,” she says. “It’s possible that the cribbing and the ulcers are both related to a third, shared cause. Cause-effect has not been established.”
The same is true of musculoskeletal problems and stall-walking and weaving, Briefer Freymond adds. “We can’t say that locomotor stereotypies cause joint or hoof problems because that’s never been scientifically proven,” she says.
But Houpt says such constant in-stall movement could fatigue the horse. “They may be running their race before they race,” she says.
One thing Briefer Freymond and Houpt do agree on, however, is that it’s not easy to stop a stereotypy. But there are a few available methods, including cribbing collars and straps that fit around a horse’s neck, restricting the muscles at play and inhibiting the ability to crib. New surgical methods, such as laser-assisted revised modified Forssell’s procedure, are also proving to be effective in stopping cribbing.
One way to stop stall-walking is to tie the horse in his stall, “but this often converts a stall-walker into a weaver,” Houpt says. Mirrors can help, giving the horse the impression he’s not alone, though the effects could be temporary.
Because stereotypies are signs a horse has probably experienced a compromise in his welfare at some point and has developed a coping mechanism, our goal, then, shouldn’t be to stop them from performing their stereotypy, but to stop them from needing to do it, says Briefer Freymond. That’s best accomplished, she says, by changing the horse’s environment.
“Get them outside; let them graze if their mouths need to be busy,” she says. “Let them walk if their bodies need movement. Reduce the grain content (of their diet) and increase forage.”
But even more importantly, get to know your horse and his stressors. “Sometimes it’s just that particular environment he’s in, for whatever reason,” Briefer Freymond says. “Something in that stable—the other horses, certain smells, who knows?—makes him stressed. So sometimes just changing stables or even places within the stable can help.
“Each horse is unique, with a different personality and ability to handle certain sources of stress,” she continues. “And if we try different environments, we might find the one that makes him feel less need to carry out his stereotypy.”
Stereotypies can be annoying. Once they develop, changes in the horse’s brain have likely occurred that make them nearly impossible to stop. However, with good environmental adjustments, horses might not need to perform these actions as much. When a stereotypy is endangering a horse’s health, we can apply methods to force them to stop for their own protection. Most importantly, we need to stop thinking of stereotypies as “vices” and remember that affected horses aren’t “bad” and don’t have a reduced value, say our sources. They’ve just found a coping mechanism to deal with the stresses imposed on them.
“The horses are not evil just because they crib, or even if they do other repetitive behaviors like kick the stall door at mealtime,” Houpt says. “The vice is not with them, but with us, because we want to keep them conveniently in stalls.”
Reprinted with permission from The Horse: Your Guide to Equine Health Care/TheHorse.com. Find more veterinarian-approved horse care information at TheHorse.com.