Horses can use their facial expressions, specifically the direction of eyes and ears, to communicate with each other, a new study has found.
Horses are sensitive to the facial expressions and attention of other horses, researchers said.
"Our study is the first to examine a potential cue to attention that humans do not have: the ears," said Jennifer Wathan of the University of Sussex.
"Previous work investigating communication of attention in animals has focused on cues that humans use: body orientation, head orientation, and eye gaze; no one else had gone beyond that.
"However, we found that in horses their ear position was also a crucial visual signal that other horses respond to. In fact, horses need to see the detailed facial features of both eyes and ears before they use another horse's head direction to guide them," said Wathan.
The study challenges the notion that animals with eyes to the sides of their heads cannot glean information based on the direction of one another's gaze.
Wathan and the study's senior author Karen McComb took photographs to document cues given by horses when they were paying attention to something.
Then they used those photographs as life-sized models for other horses to look at as they chose between two feeding buckets. In each case, the horse in the photo was paying attention to one of the buckets and not the other.
In some instances, the researchers also manipulated the image to remove information from key facial areas, including the eyes and the ears.
The researchers' observations show that horses rely on the head orientation of their peers to locate food. However, that ability to read each other's interest level is disrupted when parts of the face - the eyes and ears - are covered up with masks.
The ability to correctly judge attention also varied depending on the identity of the horse pictured, suggesting that individual facial features may be important, the researchers said.
Wathan and McComb plan to continue to explore facial features related to the expression of emotion in their horses, noting that horses' rich social lives and close relationship to humans make them particularly interesting as study subjects.
The findings were published in the journal Current Biology.
