Q: When my friend rides her Thoroughbred gelding in the arena, after doing several side passes over and over again, he opens his mouth and arches his neck. He will stay in that position (standing still) for several minutes. He is not chewing while doing this. What do you make of this behavior? She insists that he is totally comfortable and is showing her he enjoyed himself.

Tamara Wilson, via email

A: Because arching the neck and opening the mouth is an unusual behavior, not associated with relaxed comfort, I would be suspicious that this horse is experiencing either some sort of physical discomfort or, if psychological, fairly extreme fear or confusion. If the cause is physical discomfort, you should be able to pinpoint what it stems from more easily than other behaviors indicating discomfort, such as tail swishing or gait abnormalities.

If our clinic was asked to evaluate a horse with unusual behavior such as this, we would likely recommend starting by looking at the horse when he is not being ridden and just standing in the stall to see if everything looks normal there. We do this by evaluating the behavior during a 24-hour video sample of the horse in a stall or small paddock. Then, depending upon that evaluation’s results, our team might recommend proceeding in any number of directions