New research suggests horses communicate through facial expressions such as moving the eyes and ears.
The findings, reported in the Cell Press journal Current Biology on August 4, suggest animals communicate in more ways than humans give them credit for.
"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."
The new study also challenges earlier conclusions suggesting animals with eyes on the side of their heads cannot gain information from the direction of another's gaze. To make their findings the researchers took photographs of horses when they were paying attention to something. They used the photographs as life-sized models for horses to look at as they chose between two feeding buckets; this made it appear as if the horse was concentrating on one bucket and not the other. In some cases key features such as they eyes and ears were removed from the horse replica.
The team found horses rely heavily on head orientation of their peers to locate food. This interaction is disrupted when the eyes and ears are covered with a mask. The ability to correctly judge attention also varies from horse to horse.
"Horses display some of the same complex and fluid social organization that we have as humans and that we also see in chimpanzees, elephants, and dolphins," Wathan says. "The challenges that living in these societies create, such as maintaining valuable social relationships on the basis of unpredictable interactions, are thought to have promoted the evolution of advanced social and communicative skills. There is a general interest in studying species with this social structure."
