What Colors Can Horses See? How Horse Vision Works

How does horse color vision work?

Color vision depends on light-detecting cells in the retina called cones. Most people have three types of cone, tuned to blue, green and red light, which gives us trichromatic vision. A horse has only two types.

A 2001 study by Joseph Carroll and colleagues in the Journal of Vision measured these cones directly. One type is most sensitive to short-wavelength light, around 428 nanometers, which we see as violet-blue. The other is most sensitive at about 539 nanometers, in the yellow-green part of the spectrum. With only these two, horses separate colors along one main axis, from blue to yellow.

In practice, this means:

• Blue stands out strongly and looks clearly different from other colors.
• Yellow looks bright and distinct, especially against green.
• Red and orange lose their punch and may look like muddy yellow-brown or gray.
• Green is hard to tell from red, orange and some grays of the same brightness.

Behavioral experiments, in which horses learn to choose a colored panel over gray ones to earn a food reward, agree with these findings: horses reliably pick out blues and yellows but struggle with some reds and greens.

Why do horses have two-color vision?

Two-color vision is the normal pattern for most mammals, including dogs, cats, cattle and deer. Only humans, apes and some monkeys have evolved full three-color vision. For a grazing animal, spotting movement and shapes in low light matters more than telling ripe red fruit from green leaves.

The same is true of cattle, which is why the waving of a red cape does not enrage a bull. Read more in Do bulls hate red?.

How wide can a horse see?

A horse’s eyes are among the largest of any land mammal and sit on the sides of its head. Together they give a field of view of about 350 degrees, almost a full circle. This is ideal for a prey animal that needs to notice a predator creeping up from any direction while it grazes.

Only about 65 degrees of this field, straight in front, is seen by both eyes at once. This binocular vision gives the best depth perception, so a horse raises or lowers its head to bring an object into that zone. You can see this when a horse approaches a jump or inspects something on the ground.

Where are a horse’s blind spots?

The wide view comes with two blind spots:

• In front of the face: a cone-shaped area just in front of and below the nose, reaching roughly 1 m (3–4 ft) ahead. A horse cannot see food right under its muzzle or the ground directly below its head, and relies on its whiskers, smell and touch there.
• Directly behind: a narrow zone behind the tail, hidden by the horse’s own body when its head faces forward.

This is why horses may startle when someone approaches from straight behind without speaking, and why riders say a horse loses sight of a fence in the last moments before it jumps.

How sharp is horse vision?

Horses see detail less sharply than most people. Studies that test how fine a pattern of stripes a horse can recognize suggest its visual acuity is roughly 20/30 on the human eye chart. That means a horse must be about 20 feet away to see what a person with normal vision sees from 30 feet. This is better than dogs and cats, but worse than many birds of prey.

Horses have a horizontal band of densely packed nerve cells across the retina, called the visual streak, rather than a single point of sharpest vision like ours. It gives a sharp, panoramic view of the horizon, ideal for scanning open grassland. Horses are also very sensitive to movement at the edges of their vision, which is why a plastic bag flapping in the wind can send a horse leaping sideways.

Can horses see in the dark?

Horses have good night vision. Their large eyes and pupils let in plenty of light, their retinas contain many light-sensitive rod cells, and a reflective layer behind the retina, the tapetum lucidum, bounces light back through it for a second chance. This layer causes the greenish-blue eyeshine you see when a flashlight catches a horse’s eyes at night.

On a moonlit night, horses can move confidently across a field. Their eyes do, however, adjust more slowly than ours when moving from bright sunlight into darkness. This helps explain why some horses hesitate before stepping into a dark trailer or stable.

What horse vision means for racing and riding

Because horses see the world differently, the colors people choose can matter. A 2020 study by Sarah Paul and Martin Stevens at the University of Exeter, carried out for British horse racing, modeled how racecourse fences and hurdles appear to horses. The traditional orange take-off boards and markers were among the least visible to horses, while fluorescent yellow, white and blue stood out far more clearly against grass.

Myths and facts about horse vision

Myth: horses see only in black and white. Horses have true color vision with two cone types; they simply see a narrower range of colors than we do.

Myth: horses must tilt their heads because of a “ramped” retina. It was once believed that the horse’s retina was sloped so that different parts focused at different distances. Later research did not find such a ramp. Horses move their heads mainly to use their binocular zone and the visual streak.

Fact: horses can see almost all the way around themselves. With 350 degrees of view, a grazing horse can watch most of its surroundings without lifting its head, which helps herd members stay alert even while resting, as explained in Can horses sleep standing up?.