Snorts — non-vocal signals produced by the air expiration through the nostrils — are associated with more positive contexts and states in horses, according to a new study published online in the journal PLoS ONE.

Assessing positive emotions is important for improving animal welfare, but it has been challenging to identify reliable indicators.

Physiological markers often give contradictory results, and many behavioral signals are ambiguous.

Anecdotal reports have indicated that horses frequently produce snorts in positive situations.

Following up on this evidence, Université de Rennes researcher Mathilde Stomp and co-authors evaluated snort production by horses that lived either in restricted or naturalistic conditions.

“We observed 48 horses living in two ‘extreme’ conditions: restricted conditions (riding school horses that spent much of their time in individual stalls) and naturalistic conditions (stable groups in pasture),” they explained.

“The immediate place (e.g. stall/pasture) and the behavioral/postural (behavior performed/ears positions) contexts of snort production were observed.”

“We additionally performed an evaluation of the welfare state, using validated behavioral (e.g. stereotypies) and postural (e.g. overall ears positions) welfare indicators.”

Snort production was significantly associated with positive situations and with a positive internal state, as indicated by ears positioned forward or sideways.

For example, riding school horses produced twice as many snorts in pasture than when they were in stalls.

In addition, horses living in naturalistic conditions emitted significantly more snorts than riding school horses in comparable contexts.

Taken together, the findings suggest that snorts are reliable indicators of positive emotions in horses.

“Our results lead us to believe that acoustic signals constitute a potential marker of positive emotions, suggesting a new breakthrough in research evaluation of positive emotional states in horses,” the scientists said.

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M. Stomp et al. 2018. An unexpected acoustic indicator of positive emotions in horses. PLoS ONE 13 (7): e0197898; doi: 10.1371/journal.pone.0197898