To modify this unwanted and potentially dangerous behavior, it helps to understand why a horse might be grumpy in this situation. One reason is that other horses passing in the barn aisle are physically close, and less distance generally equates to a greater threat. Another reason is that horses are usually fed hay and grain in their stall, and food is a valuable and dependable commodity.
Even more problematic is that once it begins, the aggressive behavior often persists because, from the horse’s perspective, it works every time! When the stalled horse lashes out with pinned ears and a sour face, the other horse always moves away as he continues down the barn aisle. An association between the aggressive display and “intruder” retreat has been forged in the horse’s brain. Thus, aggression is unintentionally reinforced and likely to be repeated.
Decades ago behavioral scientists confirmed that this type of superstitious aggressive behavior can be created through inadvertent negative reinforcement. Offensive social aggression can be triggered when a horse asserts ownership over a valuable resource such as food, but the situation you describe is more consistent with a defensive “keep your distance” message. At 24 years old, age-related physical changes such as arthritis and muscular stiffness could reduce your horse’s comfort and mobility, which might explain her increasing grumpiness when other horses approach. But how can this be changed?
Here are a few ways:
1) A veterinarian can help identify and provide treatment for any physical and medical issues that might be contributing to the aggression.
2) If you suspect the aggression is due to resource guarding, it can be reduced by providing 24/7 hay access, putting food in multiple areas (e.g., in several haynets or spread around the stall), and using a puzzle feeder for grain, such as a Nose-It!
3) Using positive reinforcement to train an alternative response can also improve your horse’s attitude because she’ll learn that something pleasant happens when other horses walk past her stall.
