Natural Stallion Behavior

Q: I own a Lusitano stallion that has been stabled at the same barn for four years. Within the past four to six months, he has shown increasingly aggressive displays toward two stallions that walk in front of his stall. He kicks and bashes his face full-force into the bars. I've lined the stall walls with rubber mats and put padding on the bars. His feed, exercise level, and location have not changed. My situation is such that I cannot move him to a stall with less horse traffic or turn him out.

When I'm in front of his stall I can curtail this behavior, but unmonitored he goes nuts, and now I fear for his safety.

I have read many of your articles in The Horse, and I am hoping you can suggest a form of behavior modification that will alleviate this problem.     Georgette, via e-mail


A: I know this behavior well, and I have seen it accelerate quickly to worrisome levels.

The basis of the behavior is that natural tendency of harem stallions to aggressively repel intruding stallions. In fact, this is very adaptive behavior for a harem stallion. And if there are other mares in his area of the stable, your stallion might actually perceive himself as the harem stallion. But as you have experienced with your stallion, regardless of the natural basis of the behavior, in a stall this reaction to passing horses can reach dangerous levels.

In breeding facilities, you sometimes see stallions with this behavior pattern get so worked up that they displace their thwarted aggression onto the intervening barriers, not just slamming into them, but viciously attacking or gnawing in frustration at the bars or stall doors, breaking teeth, or injuring lips and gums, not to mention bending bars and trashing the woodwork. I've seen some in frustration back right into and double-barrel kick the stall door. You not only worry about the stallion inside the stall, but it's an unnerving handling challenge to get by with the other stallion. Stories over the years of stallions that one day just took the stall door off the rail and came on through with the door haven't done much for my confidence when placed in this situation.

This is one of those behaviors in which once the cycle gets going, the intensity of the behavior usually accelerates rather than extinguishes. That's because just as with car-chasing dogs, the behavior is reinforced every time by its pure and simple effectiveness. The stimulus animal approaches, the enclosed stallion threatens and attacks, and the stimulus stallion goes away. Stimulus-response-reinforcement. Stimulus-response-reinforcement. It's a perfect conditioning model. So, in essence, this natural behavior is reinforced.

You didn't mention punishment, but I'll start off here by saying that it often seems tempting to blame the animal and, thus, to feel justified in reaching for punitive methods to modify the behavior. But appreciating this as a natural behavior that inadvertently has been reinforced, I think the humane approach to behavior modification is to try to remove the motivation or stimulation rather than to punish the trained behavior.

I have worked with stallions that people tried to stand beside and punish whenever another horse passed, then the stallion started "attacking" the bars whenever a person approached or passed. Just as with children who are not yet verbal, it is very difficult to get the timing and intensity of punishment just right so as not to confuse an animal. A stallion can end up being unpredictably dangerous.

If you have exhausted all options for moving your stallion away from this traffic area, or for having those two stallions take another route to the arena, then you might be able to take steps to reduce the level of stimulation as they pass, with the goal of at least reducing the intensity of your stallion's response to safer levels.

This scenario comes up as an urgent matter sometimes in the hospital here at New Bolton Center. For certain injuries, it is not safe for a colt or stallion to get all excited and bounce around the stall or climb the walls every time another stallion or a mare passes. And at times there are just not enough low-traffic stalls available to relocate the patient. Our nurses have found that simply eliminating the visual stimulation of the passing horses can sufficiently temper the reaction of many patients. They just curtain off the view by taping up sheets or a tarp on the outside of the stall front. The colt or stallion patient still seems to appreciate that animals are passing, but his response is less animated and focused.

I'd recommend trying just a tarp or sheet at first, and if it works, maybe get a more permanent setup that can be efficiently closed just when those stallions pass. It could be as simple as a shower curtain-style arrangement with an inexpensive tarp that could easily be drawn closed just before the stallion walks past, then reopened. I would not recommend keeping the stall front blocked all the time. A stallion usually gets stir-crazy when boxed in visually 24/7.

You didn't mention what you do at the front of the stall that curtails your stallion's response, so I'm imagining your presence with maybe some verbal interaction is enough to distract him. If that is the case, then I would expect that visually blocking the view will likely be quite effective.

In terms of other general management factors that can help temper a stallion's general reactivity when turnout is not an option, diet and work are probably the two most worthwhile issues to explore. An all-grass hay diet can do wonders in mellowing some individuals, and it's rare not to appreciate some behavioral benefits of going from grain and hay to an all-hay diet. Again, in the case of this natural stallion behavior that has been systematically reinforced over a period of months, changes in diet alone or increased exercise and work alone--or even together--are not likely to significantly lower the threshold or the intensity of the response. The same would be true for medications or hormone treatments that might be recommended to subdue stallion behavior. Short of castration or sedation, any of these alone are not likely to bring satisfactory reduction in this particular response. A package of management changes might add up to some meaningful benefit. And just for the general welfare of your stallion, I certainly would pursue all that you can, in addition to reducing the provoking stimulation.

About the Author

Sue McDonnell, PhD, Certified AAB

Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.

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