A. To best answer a question specific to a particular horse, it would be helpful to know how old the horse is and what his behavior has been with cats and small dogs in the past. When a problem is completely new and escalating, you have to consider that something has changed. The most obvious reason could be that he has had a recent bad experience with little critters. Your horse—being mature with no previous history of fear of cats or dogs—would have to have had a fairly dramatic and threatening event to develop an aversion sufficient enough to kick out after a single bad experience. It could also result from a series of ongoing negative events.

In any case, a horse’s fear behavior should extinguish rather than escalate if the dramatic single negative experience hasn’t been repeated. If he did not have a bad experience with small animals, something as seemingly off-the-wall as a change in vision (in that the horse perceives the animals’ movement differently than he did in the past) could lead to fear-related behavior changes. Vision and perception deficits can be challenging to diagnose, let alone treat. But you might discuss this with your veterinarian. If that is the case, and any perception changes stabilize and the cats or dogs never respond aggressively or further scare the horse, theoretically he should acclimate—as horses do to most novel stimuli—with diminishing fear-related aggression.