Mouthy Mystery

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.

If we see no abnormal behavior in the stall video, we might then recommend that our sports medicine group systematically add pieces of tack and exercise the horse on a longe line, then incorporate the rider and the work the horse is asked to do--each perhaps with and without analgesia to see if we can locate and confirm a source of discomfort. If the video behavior evaluation revealed similar or other abnormal behavior when the horse was alone in his stall, we might recommend diagnostic imaging, such as nuclear scintigraphy (bone scan), radiographs (X rays), or MRI--again depending upon what type of discomfort seems most likely. From your description, we would probably be most interested in the head and neck area as the painful region.

We would also want to see the rider interacting with the horse, if possible, to get an idea if something in her riding and training style could contribute to anxiety at a level that would likely induce such a response.

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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