New study has identified 17 discrete expressions in horses (three more than chimpanzees) which may give researchers insight into their emotional states

A horse doesn’t have to pull a long face, it has one already. But it can and does look down its nose at you. It can be insistent, if not a nag. Horses are expressive, but those who want to decipher their expressions have a few hurdles yet to jump.

But the chase is on. Scientists at the University of Sussex have compiled a directory of facial expression in one of humanity’s oldest four-legged friends. Their Equine Facial Action Coding System (EquiFACS for short) has identified 17 discrete facial movements in horses that may indicate mood or intention or just bafflement.

This is at least three more than the facial expressions identified in chimpanzees. Dogs can get a message across with 16 different expressions. And human faces have 27 different ways of speaking silently, with the lips and eyes and the occasional wrinkled nose.

“Horses are predominantly visual animals, with eyesight that’s better than domestic cats and dogs, yet their use of facial expression has been largely overlooked. What surprised us was the rich repertoire of complex facial movements in horses, and how many of them are similar to humans,” said Jennifer Watham, a doctoral researcher and one of the lead authors.

“Despite the differences in face structure between horses and humans, we were able to identify some similar expressions in relation to movements of lips and eyes. What we’ll now be looking at is how these expressions relate to emotional states.”

She and her colleagues report in PLOS One that they dissected a horse’s head (it came from Pennsylvania andthe horse had been put down for clinical reasons) to identify, sketch and photograph all the elements of facial musculature. The researchers then recorded 15 hours of natural behaviour in 86 horses, aged from four weeks to 27 years taking in both male and female and a range of breeds . The search for variety embraced rescued horses, riding schools and farms. And then the team charted all possible twitches of their horse-faced subjects.

Facebook Twitter Pinterest Horses and humans can both raise the skin above their eyes, as seen in this video.

Wild horses roamed across Europe, Asia and North America during the Ice Ages, between 2.5 million and 12,000 years ago. They were hunted for food, but then were first domesticated around 5,000 years ago. Bythe mid-20th century, the species Equus ferus had become extinct in the wild. The horse changed human society – it delivered mounted cavalry, the notion of chivalry, and the original measure of horsepower for economic development. It became a draught animal, a farm worker, a military steed, a sporting hunter and the foundation of one of the world’s oldest and biggest gambling industries.

But the research by the Sussex scientists, with collaborators from the University of Portsmouth and Duquesne University in Pennsylvania, turns history on its head. It is the commencement of a long cool look at how humanity might have changed the horse, and how the look in a colt’s eye, or a frisky glance from a filly, or a Clydesdale’s curling lip – could answer complex questions about the social, cognitive and physical characteristics of biology on the hoof. The Sussex study – a catalogue of eye, lip, nostril, chin and other movements - is just a beginning.

It could tell the riders a lot more about how their runners view the human race. “Horses and humans can both raise the skin above their eyes, which seems to happen in negative emotional states,” said Watham. “Another example is the retraction of lip corners, which seems to be part of a submissive gesture in horses. Our paper has only identified the movements horses can make – the challenge now is to document what contexts these occur in, and then we will be able to make more informed comparisons.”

Horses are social animals: most of their behaviour must have evolved to help keep family groups together during seasonal migration in search of changing food sources, and to warn of possible predator attack. But the range of possible expression remained a surprise.

“It was previously thought that, in terms of other species, the further away an animal was from humans, the more rudimentary their use of facial expressions would be,” said Karen McComb, professor of animal behaviour at Sussex, and the other lead author.

“Through the development of EquiFACS, however, it’s apparent that horses, with their complex and fluid social systems, also have an extensive range of facial movements and share many of these with humans and other animals. This contributes to a growing body of evidence suggesting that social factors have had a significant influence on the evolution of facial expression.”