What Makes a Horse Yawn?

Q. I would like to know what makes a horse do his mouth like he is yawning. Does this help the horse get lots of air in his lungs like with people? Is it a sign of anything in particular?

Via e-mail


A. Unfortunately, there is no simple answer that explains why a horse "yawns." There are some veterinary medical professionals that firmly believe that the behavior we attribute to yawning in the horse is actually a manifestation of pain or discomfort. Some believe that so strongly that they propose that a horse only "yawns" when he is uncomfortable. Certainly, many horses will "yawn" when experiencing colic pain, but no one knows precisely why the horse responds this way or what the "yawn" might do to make him feel better.

Horses also might "yawn" if they have oral pain, and some horses "yawn" just after removing the bridle, presumably to stretch jaw muscles. At one time, many hypothesized that the horse might be trying to equalize pressure inside the inner ear much like humans often do when driving in the mountains or riding in airplanes. This has not been proven.

We have all seen our horses "yawning" while seemingly happy and quiet in their stalls or pens. And sometimes horses will "yawn" close to meal times as if they are anxiously anticipating their hay or grain. With so many seemingly contradicting triggers, it is very hard to imagine a single cause for "yawning."

About the only thing we're fairly sure of is that the trigger is not the same as that of a yawn in humans, which is in response to transient drops in blood oxygen levels. That big intake of fresh air increases oxygen in the lungs and therefore in the vascular system. However, horses do not appear to be inhaling when they "yawn."

The most important thing to keep in mind if your horse seems to be yawning inappropriately is that it can often be a sign of abdominal pain. Take quick stock of the situation and make sure there are no other signs of colic. If you have doubts, observe your horse closely for a few minutes and if you still have questions, call your veterinarian. Most times when your horse "yawns," however, he is likely to be just fine and doing what horses do.

About the Author

Mary DeLorey, DVM

Mary S. DeLorey, DVM earned her veterinary degree from University of Missouri in 1992. Since 2000, she has devoted her entire professional energies to equine dentistry. Her practice, Northwest Equine Dentistry, Inc. serves the states of Washington and Idaho and is based near Seattle. Dr. DeLorey has traveled internationally to instruct veterinarians in equine dentistry techniques and speaks to horse owners nationwide. She trail rides and raises sport ponies from her ranch in Eastern Washington when she's not on the road.

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