Forget talking horses like Mister Ed—when it comes to horse communication, the ears have it.
A new study revealed that a horse's large, highly mobile ears can help tell another horse where to direct its attention, which may help the observing animals locate food and evade predators.
As one of the first studies to examine communication avenues that humans lack—movable ears, for example—it's an important step in understanding how social animals interact, said study leader Jennifer Wathan, a Ph.D. student at the University of Sussex in the U.K.
Traditionally, Wathan explained, scientists studying how animals communicate with one another focused on traits that humans also have, such as body language. (Watch a video that explores the minds of animals.)
But by thinking about the world as a horse experiences it, Wathan said, scientists can gain more insight into how these animals share information.
Like humans, horses are social animals. While living in large groups of other members of your species has its downsides, the arrangement also has benefits. Animals can watch each other's backs, keeping a lookout for potential predators while others are busy eating or looking for food.
To make this system work, however, animals have to have ways of communicating information to other members of the species.
"Horses have really good vision—better than dogs or cats—but the use of facial expressions has been overlooked," Wathan said.
So Wathan hypothesized that horses could use ear direction as a cue for where to look and if they should pay attention to something in the environment.
To test this idea, Wathan and her adviser Karen McComb first photographed horses in a pasture looking at one of two buckets of food.
In one set of photographs, the horse's ears were covered by a mask. In a second set, the horse's eyes were covered. A third group of photos showed the horse's head as normal. Then, Wathan and McComb turned these photos into live-size pictures for a horse to look at as it chose between one of two buckets of food.
Preliminary experiments established that the horses were able to recognize that they were looking at another horse in the photo. (Read "People of the Horse" in National Geographic magazine.)
When horses looked at a photo from the third set, where both eyes and ears were uncovered, they picked the bucket of food the horse in the photo was looking at about 75 percent of the time.
When either the eyes or ears were covered by a mask in the photo, the observing horse selected between the two buckets of food more or less randomly. However, the horses performed slightly better when the photo showed the ears uncovered than when it showed the eyes uncovered, according to the study, published August 4 in Current Biology.
"The horses actually looked at the photographs of the [horses with masked eyes] less, which indicated there was less information there, and not enough to change behavior," Wathan said.
Helpful for Horse People
The study represents the first evidence that horses can signal information about food to each other, even though they evolved in an environment where "one blade of grass is as good as any other," said Katherine Houpt, an emeritus professor of veterinary medicine at Cornell University in Ithaca, New York, and a horse expert.
Since the study provides such a unique insight into how the animals think, "these results are really important to anyone who works with horses," Houpt said. (Read "Kentucky Horse Country" in National Geographic magazine.)
"Experienced riders know to pay attention to a horse's ears to help figure out what it's thinking, so I'm not surprised that the ears were the most important cue," she added.