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Study Reveals Distinct Facial Expressions by Horses

Horses use similar facial muscles to humans, suggesting an evolutionary parallel in how horses and humans use the face to communicate. (Credit: Jennifer Wathan)

Horse owners know that the creatures are very social by nature. Their emotions may also be written on their faces, just as they are with humans.

British researchers studied video images of horses and report in the journal PLoS ONE that equines make at least 17 “action units,” or facial expressions.

The muscles in the human face allow us to make some 27 facial expressions, reflecting such feelings as anger, jealousy and amusement.

Chimps, in comparison, make 13 different facial gestures, and dogs have been found to have 16 discrete looks, which any dog owner will tell you can convey happiness, sadness or what looks like guilt at stealing table scraps.

An entire index of horsey faces called the Equine Facial Action Coding System, or EquiFACS, has been developed by researchers at the University of Sussex, along with fellow researchers at the University of Portsmouth and Duquesne University.

Animal behaviorist Jennifer Wathan, who led the study, said horses can move their faces in a surprising number of humanlike ways.

"They can move the skin above their eyes, to raise that skin a little bit like humans can," she said. "And they’ve got a really extensive set of muscles in the lower face about the mouth that they can use. … I mean, they do use their mouth to explore their environment, because mostly their hoofs aren’t very good for that. But they also use their mouths to make facial expressions, and we think that that’s for communication, perhaps for emotional communication, but that’s another study in itself.”

Investigators watched videos of horses in a variety of situations, including interacting with other horses and with veterinarians, to catalog all of their facial expressions.

Wathan said researchers want to try to relate the facial expressions of horses to emotions they might be feeling, and discover whether horses can communicate those feelings to one another through their faces.

The goal is to see "if we can sort of get the horse’s opinion on what information they might get from these expressions, what’s important to them and how that helps them in their environment,” she said.

Another interesting question to be explored is whether horses can use those expressions to communicate with other species, like we can ... and whether we can understand them.