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Scientists probe how horses communicate with their faces

Photographic stimuli was used in the study, including manipulations that incorporate fly masks to cover key internal features of the face to see which facial indicators the horses approaching the two buckets used.  The photographs were reproduced at life size for the experiment.  Figure A shows the three experimental conditions: all cues visible; ears covered; eyes covered.  Figure B shows the percentage of horses choosing the congruent bucket for each condition.

Photographic stimuli was used in the study, including manipulations that incorporate fly masks to cover key internal features of the face to see which facial indicators the horses approaching the two buckets used.  The photographs were reproduced at life size for the experiment.  Figure A shows the three experimental conditions: all cues visible; ears covered; eyes covered.  Figure B shows the percentage of horses choosing the congruent bucket for each condition.

Horses are all ears when it comes to paying attention to one another,  fresh research has shown.

British researchers found that horses used a variety of visual cues to work out what may be going on in a stablemate’s head, with one of the most important factors being the direction of a horse’s ears.

Mammal communication experts Jennifer Wathan and Professor Karen McComb, from the University of Sussex in England, set up an experiment to see which cues horses relied on to judge the direction of another horse’s attention in a task in which they had to choose where to feed.

Each horse was individually led to a point where it was released and allowed to choose between two buckets. On a wall behind the buckets was a life-sized photograph of a horse’s head facing either to left or right.

The researchers, whose findings have been published in the journal, Current Biology, found that if either the ears or the eyes of the horse in the picture were obscured, the horse being led made a random choice between the two buckets.

However, if the ears and eyes were visible, then the horse used these directional cues to guide their choice.

The findings suggest that both a horse’s ear position and its gaze each convey important information.

“Previous work investigating communication of attention has focused on cues that humans use – body orientation, head orientation and eye gaze. But no one had gone beyond that,” Wathan says.

“We found that in horses, their ear position was also a crucial visual signal. In fact, horses needed to see the detailed facial features of both eyes and ears before they would use another horse’s head direction to guide their choice.

Scientists begin to uncover how horses communicate with their faces

Scientists begin to uncover how horses communicate with their faces

“Most people who live and work alongside animals with mobile ears would agree that the ears are important in communication, but it has taken science a while to catch up.

“We naturally have a human-centric view of the world and, as we can’t move our ears, they get rather overlooked in other species.”

McComb, director of the university’s Mammal Vocal Communication and Cognition Research group, says the study emphasises that animals other than primates are aware of subtle differences in facial expression and can use these to guide the decisions that they make.

“Fine scaled facial movements can indicate important changes in attention and emotional state and are likely to be crucial in determining social behaviour in a wide range of animals.”

Wathan and McComb noted in their research that experimental work on facial indicators had tended to focus on cues that humans use, in particular, head orientation and eye gaze, potentially overlooking a wealth of other available information.

“Animals with a different facial morphology — particularly those with large, mobile ears — may have other means of signaling.”

Which bucket will they choose? The ears and eyes were crucial elements, researchers found.

Which bucket will they choose? The ears and eyes were crucial elements, researchers found.

They also noted that the cues available — whole head visible, eyes covered, or ears covered — influenced the time spent looking at the photographs.

“Planned comparisons revealed that horses looked for significantly longer when all the information was visible, compared to when the ears or the eyes were covered.

“However, there was no difference in looking time when the ears were covered compared to when the eyes were covered, nor was looking time influenced by the identity of the model horse,” they said.

“Our results provide the first evidence from an animal with laterally placed eyes that cues from this area convey important information.

“Eye gaze is difficult to isolate in animals with eyes positioned at an oblique angle, and it had been suggested that non-primates cannot use eye gaze independently of head orientation.

“However, we demonstrate that the eyes do carry information, even when laterally placed in an animal far removed from the primate lineage.

“Horses, along with other ungulates, have a white sclera that is visible in various situations. This plus other cues, such as dilation of the pupil and movement of the facial muscles surrounding the eye, could be informative of attentional state, as they are in humans.”

Most significantly, they said, our results showed that animals with large, mobile ears can use these as a visual cue to attention.

“While anecdotal accounts of this exist in the literature, the potential role of the ears in signaling has been overlooked in previous experiments.

“In animals that have evolved a differently shaped face it is important to consider cues that humans do not have, and novel paradigms that incorporate these will be crucial in developing a full understanding of attentional mechanisms across species.”

The paper is entitled, “The eyes and ears are visual indicators of attention in domestic horses.”

The study can be read here

 

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