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Understanding The Science Behind the “Licking’ and Chewing” in Horses
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Understanding The Science Behind the “Licking’ and Chewing” in Horses

If you’re curious about this, you are probably one of many people who misconceive the meaning of the horse behavior of licking and chewing. Rather than being a taught gesture that connotes relaxation or that your horse is processing something, the behavior simply indicates a change in autonomic nervous system tone. This results in more saliva release, stimulating the horse’s licking and chewing actions.

Horses can exhibit this lick/chew reflex in a wide number of situations. It is usually to reflect some kind of stress or tension release and typically follows any unusual encounters, threats or disturbances that lead to higher anxiety.

According to Dr. Sue McDonnell, a certified animal behaviorist and founding head of the University of Pennsylvania’s program in horse behavior, the licking and chewing can be explained by the state of the nervous system when stimuli are introduced.

When an organism (human or animal) is in a relatively relaxed state performing normal activities such as eating or resting, its nervous system is mostly being controlled by the part called the parasympathetic nervous system. If this person or animal encounters any acutely stressful situation, the sympathetic nervous system takes over by making the switch into flight, fight or alert mode depending on the situation.The sympathetic system is triggered by pain, fear or confusion and any of these emotive states cause stressful pressure on the nervous system.

Once the situation or problem at hand is resolved, or at least when the horse feels it is, the nervous system allows the parasympathetic nervous system to have its usual control back.

It is usual for horses to indicate these same signs of back-and-forth switching in states. Horse behavior is characterized by the licking and chewing gestures and typically occurs during this switch back to parasympathetic after some moments of needing the sympathetic, as a sign that the tension is released or situation has changed.

In horse behavior, this is the reflex observed simply because salivation ceases when the animal is in high anxiety state and needing his sympathetic control. When the stressful encounter is over the horse’s response to the change and his dry mouth and lips is to acknowledge that salivation has resumed. Effectively in a way, the licking and chewing behavior indicate that the horse is relaxing, but not just in a normal way rather it is typically as a direct result of some direct spell of pain or extreme stress that has just ceased.

McDonnell cites the medical term for why this happens as sympathetic attenuation; the exact same release that most people refer to as a feeling of relief. The same “relief” behavior can be seen in humans after going through some kind of traumatic moment. For example, a young woman who thinks she is about to get pulled over by a police car when speeding, but rather sees the car pass by with its flashing lights and a loud siren. In this case, the reaction that indicates relief may differ from person-to-person and could be a quick sigh or a deep breath. In many situations, when humans experience that same emotional change from a place of higher anxiety to lower anxiety, it could also be a case of licking or swallowing when salivation is resumed.

Common signs that a horse is getting anxious or increasingly stressed include faster breathing, widening of the eyes, total muscle brace, unusual fixation on objects or uneven movements of facial muscles. When it is unclear why a horse licks or chews, it had probably indicated higher anxiety with one of these signs prior to its sympathetic state. Watching a horse’s behavior can help identify the typical causes of discomfort over time.

Image source: Thespruce.com

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  1. Of Horse Support
    Of Horse Support
    This is news to me! Thanks for sharing, Philip. Great post.
    Log in to reply.
    1. Philip
      Philip
      Cheers!
      Log in to reply.

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