Expect it. Accept it. But understand it as well. Aggressiveness is part of every horse's behavioral repertoire to varying degrees, a normal phenomenon. Horses can behave aggressively – pin back their ears, kick, bite, or charge – to protect their foals, maintain their position within the herd, defend themselves, and compete sexually. But there is a limit; if your horse's aggressive behavior threatens the safety of other horses and humans, you'll need to step in and change that behavior. Before you try to create a “beauty” out of your “beast”, though, you need to understand why the animal is aggressive. Start with...
If you notice an increase in your horse's aggression level, whether sudden change or gradual, have your veterinarian examine the animal. Chronic pain – like the pain associated with navicular disease and arthritis, can make horses irritable and highly reactive to minor discomfort; so can sudden changes like that caused by an abscess.
Not all causes are quickly obvious; for example, aggressive behavior can stem from testosterone. Typically, only stallions produce measurable quantities of testosterone; however, crypt-orchids (males with an undescended testicle) may produce testosterone, as may geldings with a pituitary tumor, for example. Mares may also produce testosterone if they develop adrenal-gland tumors or ovarian tumors.
If your veterinarian can't find a medical cause for your horse's behavior, the animal's aggression could reflect dominant, fearful, sexual, or maternal instincts. To rein in your horse's aggression, you'll need to dig deeper to get to the root cause of the behavior.
If a horse is prevented from escaping a painful stimulus such as the jab of a needle or the sting of topical medication, for example, he may act aggressively out of fear. What's more, a horse may learn to associate pain with a certain touch, sound, or smell that coincided with pain in his past. For instance, as some trimmers and farriers can attest, if he once had an injured foot that required painful treatment, he may continue to show fear and aggression when one goes to pick up his foot – long after the pain is gone.
Try to avoid triggering pain and fear aggression by minimizing painful treatments and procedures and avoiding harsh reprimands. If your horse has preexisting fears, slowly accustom him to whatever triggers his fear response. For example, if your horse tends to object to your handling his foot, work your way toward picking up his foot by touching his back, then moving slowly down the limb. As long as your horse remains calm, reward him with a treat and keep telling him what a good boy he is. Reinforcing calm behavior, though a slow treatment, will help him control his fears.
DOMINATING OTHER HORSES
Horses use aggression against each other to maintain their social position in a herd, typically through threats or posturing. A higher-ranking horse pins his ears back and lashes his tail to warn a lower-ranking horse to move away. If it doesn't retreat, the higher-ranking horse can emphasize his point by biting or kicking the underling. Fortunately, for the most part, such displays of dominance aggression result in only mild injuries such as kick bruises or a patch of lost hair.
We can cut back on displays of dominance aggression by providing adequate pasture space and equal access to feed. It's always wiser to make sure food is widely dispersed and provide more feeding sites than there are horses. This strategy makes it harder for a high-ranking horse to monopolize multiple food piles. You'll know you have enough feed stations when you see the lowest-ranking horse eating peacefully. Of course, if one horse is very timid (or very aggressive), you may have to step in and feed it separately from the other horses.
Introducing a new horse to the herd often disrupts the established heirarchy. Herd members will show aggression not only toward the new horse but also toward each other as they jockey for new positions in the herd. Prevent it by pre-planning: turn out the same set of horses together so newcomers are not continually being introduced to the herd.
When you introduce a new horse, you can put a damper on aggressive acts by following a few guidelines. First, select an enclosed area with plenty of space, preferably an acre or more. Avoid sharp corners and dead-end spaces where a horse can be cornered. Put the newcomer in the enclosure first and give him time to become familiar with the surroundings, then bring in the members of the established herd one by one, allowing time for the newcomer to settle his relationship with each herd member before bringing in another horse. Take your time, you can't rush this. After the newcomer has interacted with each horse separately, you can turn out the entire group together.
Some horses display dominance aggression toward people to improve their social position just as they would toward a herd member. Owners often unwittingly reinforce this behavior. For example, when you arrive with a grain bucket, a stabled horse may pin back his ears as if competing with another horse. If you quickly dump in the feed, you reinforce the aggressive threat, and next time, the horse's aggressive display may escalate to wall kicking. If you respond by quickly giving it grain, the horse will then associate his pinning his ears and wall kicking with the speedy arrival of food. To prevent this behavior, give your horse grain only if his ears are forward and he's not kicking – invoke your reward option.
Foals too must learn the difference between acceptable and unacceptable behavior. When foals are raised as part of a herd, their mothers and other herd members are the disciplinarians – meting out punishment for unwanted aggressive behavior. If they don't, you'll have to do it, and it's much harder for you than for them. Owners who permit a foal to have its way are in for a rude awakening as the foal matures sexually (at about six months) and its hormone levels rise. Being children, colts and fillies will see how much they can get away with, and if they aren't discplined early on, they may begin to dominate people by nipping and charging them. To extinguish this type of behavior, set clear limits, defining the acceptable and the unacceptable. Then use positive reinforcement to reward acceptable behavior. Build a relationship based on the rule that “if you are nice to us, you get nice things from us”. Do it by rationing things the baby likes – such as treats or scratching its favorite spot – in return for good behavior.
Sexual aggression flares up in a number of situations: mares resisting unwanted sexual advances of stallions, stallions competing for mates, and mares in estrus competing with each other to get close to a stallion. To reduce sexual aggression, keep stallions in separate paddocks and promptly castrate colts that will not be used for breeding.
Mares instinctively defend their foals from people, particularly unfamiliar people. A protective mother may kick, charge, or bite anyone who comes too close to her foal. Timing is important: this maternal protectiveness can create difficulties for an owner who tries to handle a young foal early on to accustom it to people and various sensations.
To keep maternal aggression to a minimum, teach your mare basic obedience before she foals – and preferably before she is bred. The mare should lead quietly and allow you to enter her stall and handle any part of her body. And after the foal arrives, be sure your mare and foal are not disturbed from one “handling session” to the next. When you do handle the foal, allow the mare to stand close by and avoid placing yourself between the mare and her foal. This will help calm the mare and keep you out of the “line of fire” should maternal aggression flare.
Experts aren't certain why some horses tend to be more aggressive than others. Although the foals of high-ranking mares tend to dominate their peers, it doesn't necessarily mean that aggressive tendencies are genetically determined: a high-ranking foal can easily learn aggressive behavior by watching its mother.
Whatever the reason for aggressive behavior, you need to take quick action when aggressive acts get out of hand so your farm isn't overrun by a thousand-pound equine bully. If you nip unwanted aggression in the bud, you will help maintain a peaceable kingdom for you and your horses.