Horses are expressive animals. Their eyes, ears, and body language can tell us a lot about how they feel. But what about those wrinkles that form above their eyes?
Sara Hintze, DrMedVet, MSc, a PhD student at the University of Bern, in Switzerland, recently evaluated whether there’s a link between horses’ emotional state and the amount and type of wrinkles over their eyes. She presented her findings at the 11th International Society of Equitation Science Conference, held Aug. 6-9 in Vancouver, British Columbia.
“Wrinkles above the eyeball are common in horses but differ in number and shape between and within individuals,” she said. “In the horse community, ‘worry wrinkles’ are often associated with negative reactions, but there’s no evidence to support this.”
She hypothesized that horses experiencing positive emotions would exhibit few eye wrinkles, while horses experiencing negative emotions would have increased eye wrinkles.
In her study, Hintze exposed 15 stallions and one mare to two positive situations—anticipation of a food reward and petting—and two negative situations—food competition and fear (waving a plastic bag). Each situation lasted for 60 seconds, preceded by a 60-second control phase during which the horses were not confronted with any stimulus. Throughout all phases Hintze took photographs of the horses’ eyes, collecting 512 images, and developed a scoring scale based on overall impression, eyelid shape, eye whites, number of wrinkles, markedness, and angle between a horizontal line through the eye and the highest wrinkle.