Licking and Chewing – Submission or Stress?

 they found that the majority of the behaviours before chewing were tense and the majority of behaviours after chewing were relaxed. The chewing behaviour occurred when the horses transitioned from a tense to a relaxed state.

The researchers concluded that chewing could be associated with a switch from a dry mouth caused by stress (sympathetic arousal) to salivation associated with relaxation (parasympathetic activity).

The results of this study suggest that non-nutritive chewing was not used as a submissive signal by horses in the contexts observed, but it occurred after a tense situation, likely as a response to a dry mouth.

The research team acknowledge that further research is required to measure the stress responses associated with non-nutritive chewing. However, this study does highlight that licking and chewing likely occurs after a stressful situation and may be used as a behavioural indicator that the previous situation was perceived as stressful by the horse.

From researcher Margrete Lie: “We looked at feral horses living with as little human interference as possible to see how they behaved in their natural habitat,” says researcher Margrete Lie. “It was important to look at completely natural behaviour and therefore we wanted to see horses living without restriction. These horses were living in a 334 square-km national park, and in the area we observed there were a little under 200 horses. No stallions had been removed from the population as is so common in domestic horses.

“It was interesting to see how often the horses performed the chewing behaviour and also how clear it was that all individuals did chew – not only ‘submissive’ individuals.

“The study showed that the horses were chewing between calm and relaxed situations, but it does not say if chewing comes as a response to relaxing or if chewing helps them relax. To able to look at this more closely I believe a more controlled study with stress measurements is needed.”