From the June 2020 Decker Dispatch, the newsletter of the Back Country Horsemen of Montana.
Do You See What I See?
by Stacie G. Boswell, DVM, DACVS — originally published in the Decker Dispatch, June 2020
The text below is reproduced from the original newsletter so that this article can be found and read online. The full issue of the Decker Dispatch, including the article as it appeared in print, is reproduced at the foot of this page.
When working with our horses or mules, it is critical that we understand what they can see. Their ability to focus and to detect light, color, and distance is different from our vision. These differences can result in confusion about why a horse is afraid of something he sees. We need to be aware of the differences so that we can set our animals up for success in doing what we ask.
Horses’ eyes are different from human eyes, and from other animal eyes. The way they see is highly adapted for who they are – they are a prey animal, and spend the majority of their time grazing. Since other animals attack and eat horses, it’s critical for survival that he detect any new threats in his environment early.
Color Perception
Horses can see color, but not as vibrantly as humans. Generally, their world is muted. They also only see blues and greens or yellows. That bright red bucket – it looks brown to your horse.
Light Perception
Horses have a tapetum lucidum in the back of their eye. This is a specialized, reflective surface in the back of the eye. Light enters the eye, stimulates the sensory cells of the retina, then is reflected back by the tapetum in order to stimulate the retina again. This is how dogs, cats, and horses all see very well in low levels of light. When you shine a light in the dark at your pets’ eyes, you’ll see the bright reflection caused by the tapetum.
Although your horse’s ability to detect light is excellent, it takes a very long time for him to adjust to changing light. You know how it feels to step from bright sunlight into a dark barn – it takes a second for your eyes to adjust. Your horse needs about eight times as long to adjust. When he hesitates, it may be because he is temporarily blinded as his pupils adjust from bright light to darkness.
Eye Shape
Horses have eyes that are larger than any other land mammal, and they are set wide. They have horizontal pupils, which helps them see a wide range, almost the entire horizon. But, because they are set wide, horses do not have great depth perception. They cannot judge distance very well.
Focus
Focus is also known as accommodation. Because of the large size, focus takes more time. Much of what a horse sees at any given time is blurry. If he needs to see something up close more clearly, he may lower his head. For example, many animals need to lower their head and inspect footing before getting in a trailer. If given the opportunity to do so, trailer loading can be a smoother process.
Despite the world being somewhat fuzzy, there is a special cluster of cells in the retina that helps a horse detect motion. Motion is the first sign of a predator, so that is why horses will spook when something moves unexpectedly.
Check out this video: As Seen By The Horse (Horse Nation).
Next time you lead your horse in a new area, or have him hesitate on the trail, remember to be patient. Understanding how horse vision is different will help you work with your horse or mule more successfully, especially when loading in trailers or introducing new objects. Allow his eyes to adjust, or let him lower his head for closer inspection. He sees his world in an entirely different way!
Dr. Stacie G. Boswell and her husband Sid are members of the Gallatin Valley BCH. Look for her upcoming book, The Ultimate Guide for Horses in Need, a handbook to help with horse care tailored especially for rescue horses.
The full issue below — this article appears on page 4: