The yawn is a unique and highly recognizable behavior: The jaws open wide and facial muscles tighten, the head often tilts and the eyes close, then the jaw relaxes and closes again. Yawning usually triggers a deep inhalation, followed by a short exhalation.
Yawning is considered an innate, fixed action pattern behavior, meaning:
- It’s triggered by something internal or external to the animal.
- It occurs in a consistent, predictable way each time.
- It cannot be interrupted once it starts.
- Animals of the same species perform it in the same way.
All vertebrate animals, including horses, perform yawning behaviors. Horses, however, yawn less frequently than some other species, such as primates.
You might have heard a number of theories about why horses yawn—for example, boredom, stress, or tiredness. In some training circles, yawning is theorized to be a sign the horse has learned something positive. While yawning has not been extensively studied in horses, some research looks at potential causes.
Why Do Animals Yawn?
As mentioned, specific stimuli unconsciously trigger yawning. For example, yawning might occur when an animal switches between arousal states—from dozing to greater alertness, for example. To date, scientists have not identified one apparent reason an animal yawns. They do, however, have several theories. For clarification, theories in this context don’t mean a “best guess” based on feelings or a few observations. Rather, theory means an established explanation for something, based on facts that have been confirmed repeatedly through experimentation. Let’s look at two theories that have been studied in horses.
The Brain Cooling Theory
One of the most popular theories about yawning is that it occurs as a way to cool down the brain. When an animal yawns, the act of inhaling, coupled with the facial muscles tightening, helps draw warm blood away from the skull, allowing cooler blood to move to the brain. Numerous studies in other species have shown that before an animal yawns, the temperature of its brain and the surface of its skull are warmer than after the yawn. In horses, research has shown that horses yawn more in hot, sunny conditions than they do in the shade. While yawning alone cannot cool an overheated horse, yawning in this context might help cool the horse’s brain and aid in localized thermoregulation.
The Stressor Theory
Another theory about yawning is it occurs during or after an animal faces exposure to a stressor. Research has shown that horses living in highly managed conditions yawned more than those living under natural conditions. Bachelor stallions that frequently engage in aggressive encounters with other stallions yawn more than their filly and colt counterparts that have fewer such stressful encounters with others.
This yawning theory could explain why it is common to see horses yawn after horse training demonstrations where a trainer tries to rapidly address a specific behavior problem, such as reluctance to load in a trailer. During the session, the trainer might punish unwanted behaviors, such as balking in front of the trailer. The nature of punishment involves creating an unpleasant consequence to discourage unwanted behavior, and these consequences are usually stressful or painful for the horse. When the horse feels relief after the stressful training session has ended, he might yawn.
Yawning has also been observed when horses have crank nosebands and double bridles removed. Yawning increases in frequency in managed horses before feeding events, suggesting factors such as stress, discomfort, anticipatory excitement, or frustration might trigger it.
Summary
Research looking specifically at why horses yawn is limited. However, what we do know suggests that if we are consistently seeing yawning in certain contexts with our own horses, we might be wise to pay attention to the behavior.
Related Reading:
- From Body Language to Behavior: How Horses Communicate
- Snooze or Lose: Understanding How Horses Sleep
- What Does it Mean When a Horse Nickers?
Lauren Fraser, MSc, FFCP, has helped people understand horse behavior problems since 2006. With a background working as a horse trainer, an MSc in clinical animal behavior, and more than a decade working as an equine behavior consultant, Lauren’s approach gets to the heart of why horses behave the way they do and addresses issues using low-stress methods. Lauren also guest lectures at universities, presents at conferences, and creates educational programs for horse owners and equine professionals.
Are you enjoying this content? Sign up for My New Horse’s FREE newsletter to get the latest horse owner info and fun facts delivered straight to your inbox!
