By Lynne Gunville

At first, you might notice something wrong with your horse’s skin. He may start making unusual noises or being hypersensitive to your touch in the flank area – signs that would normally point to a medical issue such as a dermatological condition. 

But if you look closely at your horse’s behaviour, you’ll see a pattern, a repetitive chain of activity that indicates an altogether different problem. In veterinary medicine, this cluster of stereotypic behaviours is called self-mutilation syndrome.

If your horse is engaging in self-mutilating behaviour, you may notice him becoming hypersensitive when touched in the flank area. Photo: iStock/VM

“Stereotypic behaviour is an undesirable, repetitive and non-productive behaviour that serves no purpose and can actually cause harm to the animal,” explains Dr. Claire Card, a professor of theriogenology in the Department of Large Animal Clinical Sciences at the Western College of Veterinary Medicine (WCVM). 

In horses, the range of stereotypies includes cribbing or grabbing objects with the teeth as well as repeated movements such as weaving, stall walking, and head flipping or head shaking. But of all the actions, self-mutilation syndrome is the most alarming since it includes self-injuring behaviour. 

One common behaviour known as “flank biting” is often part of a chain of movements that includes an oral component. The horse turns and nips at its flanks repeatedly, often while kicking out with its hind legs. The horse may also bite at its limbs, chest, pectoral (girth) area and tail. 

In many stallions and geldings, the behaviour is triggered by factors such as the presence of females in heat, the smelling of manure or urine, the anticipation of being fed, or events such as storms or weather changes. Isolation can also have a huge impact, especially if the horse is in an unfamiliar place. Generally, stereotypic behaviours are also associated with high grain diets. 

While the condition only affects a minority of horses, Card sees the behaviour arise most frequently in stallions around the age of two when they reach sexual maturity. Since males typically express their dominance over other males by biting at their necks, bellies and limbs, there’s speculation that the self-mutilating behaviour results from a redirected expression of male aggressiveness. 

There may be a hereditary component as well, since the condition is more commonly seen in Arabian, Quarter Horse, Thoroughbred, and Standardbred stallions. Most significantly, Card says self-mutilating behaviours are almost always found in stabled horses.

“We’ve created the Swiss cheese phenomenon where you layer isolation with a high-grain diet, you create anxiety from the isolation, and you don’t have enough forage in the diet to keep the horse busy eating during the day,” says Card. “You end up creating the conditions for this inherited tendency to be expressed.”

She points out that stereotypies are common in stables and racetracks where horses with similar temperaments are housed in small stalls with no opportunities for socialization. In addition, they have a rigid feeding schedule and are further stressed by the stable environment where horses are constantly on the move.

Horses housed in stables and racetracks with smaller stalls, a strict feeding schedule, and no opportunities for socialization may become stressed by their environment and begin to exhibit stereotypic behaviours such as weaving, stall walking, head flipping, and self-mutilating behaviour. Photo: Canstock/Yokowikowitz

Horse owners who see these types of behaviours should first consult with their veterinarian to rule out any other physical problems. Their next step is to observe the animal — Card recommends they use a video camera to document the behaviour so their veterinarian can observe and evaluate the horse’s activity when no one is around. It’s the consistency of the behaviours that’s key to a diagnosis of self-mutilation syndrome – they’re performed over and over and in a very similar manner. 

Horses that have been diagnosed with the condition will often alter their behaviours once their environment is changed. Card recommends a low-stress environment that includes generous amounts of turn-out space. She also suggests changing their feed from high grain to high forage, and using devices such as slow-eating hay nets that make the horses work harder and longer to access their feed.

It’s also helpful for horses to have consistent social interaction with other animals. One solution is to provide a companion – a quiet horse or another animal such as a goat can help to reduce the anxiety level. Even providing a mirror so the horses can see themselves has proven to have a calming effect on stereotypic behaviours.

Horses exhibiting stereotypic behaviour will often benefit from a change of environment and the opportunity to socialize. Photo: Thinkstock/iMarley

“It’s almost always that environmental and social enrichment are the answer – things like providing a larger or double stall, and having some quiet ‘Joe’ pony in there as a companion,” says Card. “A lot of these animals are valuable show horses, and people may be resistant to allowing them to socialize, but that’s what ultimately keeps the horse psychologically healthy, and it has to be part of their general health.”

She points out that horse owners may also need to evaluate their own behaviour. In addition to changing the environment, she recommends that they try to ensure low-stress handling without a lot of arousal and excitement. 

Although there are medications available, Card advises against their use and considers some of them to be dangerous to both the horse and its owner. She particularly cautions against drugs such as fluphenazine (Prolixen), an anti-psychotic medication that can trigger hallucinations and make a horse dangerous to be around. 

While it’s easiest to provide an environment that prevents self-mutilation syndrome from developing in the first place, horse owners can often correct the behaviours by identifying and then eliminating the environmental stressors.  

“In our experience, changing the horse’s environment so it’s a more natural situation for them removes the environmental stressors that cause the behaviours,” says Card. “If you take a stallion that’s been expressing the behaviour and turn him out with a group of mares in a pasture, he will almost never repeat the behaviour once he’s busy eating and socializing and doing other things.”

Lynne Gunville of Candle Lake, Saskatchewan, is a freelance writer and editor whose career includes 25 years of teaching English and communications to adults.

This article was originally published in the March/April 2017 issue of Canadian Horse Journal.

Main article photo: Shutterstock/Anastasija Popova