10/07/2025
Licking and chewing is probably the most misunderstood and ambiguous behavior in horses, being very often mistaken for the moment when horses relax or focus on what is being done, as if it was something good to aim at.
In reality, licking and chewing is a sort of involuntary reaction being activated by the attenuation of a stressful situation.
This process is well explained by Dr. Sue McDonnell, animal behaviorist and founder of the Equine Behavior Program at the School of Veterinary Medicine at the University of Pennsylvania, who clarifies that the action of licking and chewing simply reflects the transition from a sympathetic nervous system response to a parasympathetic nervous system one.
In fact when horses are relaxed and engaged in normal activities such as eating or resting, their parasympathetic nervous system is the one being in control, with it being the part of the nervous system that is responsible for each activity occurring when the body is at rest, like sexual arousal, salivation, tear production, urination, digestion, defecation and so on.
But when instead horses feel threatened or severely stressed by something, then their nervous system switches to an alert or fight-or-flight mode with the sympathetic nervous system, that is the system being in charge of regulating and activating any reflexes and reactions about pain, fear or confusion.
So, when the stimuli that had activated the sympathetic system is finally resolved because the stressful moment is over, then the parasympathetic system comes back in control again and the relaxation returns.
Well, horses show some observable behavioral signs of this shift just by licking and chewing, sometimes swallowing too: this happens precisely when the shift from the sympathetic to the parasympathetic system occurs, because when the sympathetic system is activated salivation stops and consequently the mouth and lips dry quickly, while when the unpleasant moment subsides and calm returns, then salivation comes back too.
Consequently licking and chewing is precisely that simple involuntary response to deal with the resumption of salivation after a period of dryness of the mouth and lips.
So whenever we see horses doing it we should ask ourselves why they are doing this, being aware of the fact that they have just been put in a difficult concerning situation, as their licking and chewing is just the sign of them going from a high level of stress to a slightly lower one, as a sort of relief: not something to aim at, but just something to possibly avoid by trying as much as possible not to make them experience any highly stressful situation.
