NOTHING BORING ABOUT YAWNING

The next time your horse yawns, pay attention---he could be signaling a significant change in emotions.

“Yawning is commonly considered to be the effect of boredom or drowsiness,” says Aleksandra GoreckaBruzda, PhD, of the Polish Academy of Sciences. “However, equine behavior research has suggested that yawning can also be closely related to frustration-provoked behavior in stall-kept horses, especially in arousalprovoking situations, such as before feeding.”

To explore the topic and learn how environmental factors may influence equine yawning, Gorecka-Bruzda teamed up with researchers at University of Rennes in France, to observe 16 domesticated horses living in a stable herd with extended turnout times and 19 Przewalski horses living on a preserve. During multiple daily five-minute observation periods, the researchers tracked and categorized each horse’s social interactions and counted the number of times he yawned. The Przewalski horses were observed for 10 hours, while the domesticated horses were observed for four hours.

The researchers found no difference in yawning frequency between the two groups, indicating that domestication alone has little influence on the behavior. There was, however, much less yawning in the domesticated herd in semi-feral conditions than in a comparable group of stall-kept riding school horses observed in a previous study. This, the researchers say, may be attributed to the options offered to the domesticated horses in the current study---primarily ample turnout time and unrestricted feeding.

“In the most recent study, the domestic horses lived in ‘good’ naturalized conditions and in this context they yawned little,” says Martine Hausberger, PhD. “This shows clearly that the very high frequency of yawning observed by earlier research was not related to domestication but to the restricted conditions the horses were kept in.” The frequency of yawning varied by individual, but stallions tended to yawn more than geldings or mares.

The researchers note that the Przewalski horses had more social interactions overall, which may have influenced the data, but both species showed a correlation between the frequency of yawning and that of social interactions. In the Przewalski horses, interactions preceding yawns tended to be agonistic, such as a threat to bite or a chase; in contrast, interactions among domesticated horses were positive or neutral, such as sniffing each other. “It can be proposed that, among other things, yawning can be related to the increase in arousal, in response to whatever positive or negative trigger,” says Gorecka-Bruzda.

“When a horse yawns a lot, the owner should not conclude that he is relaxed and well, especially if the yawn appears at high occurrence,” says Hausberger. “In some cases, it can indeed be related with drowsiness, but high frequencies of yawning should attract the attention of the owner, who should then observe the horse and the situation for signs of potential welfare problems.”

Reference: “Investigating determinants of yawning in the domestic ( Equus caballus) and Przewalski ( Equus ferus przewalskii) horses,” The Science of Nature, October 2016