What does my horse “see” and why does he react to something one day and a few days later he has no reaction at all?
An owl can see a mouse moving more than 150 feet away. A dragonfly has 30,000 lenses in its eyes. These lenses assist them with motion detection and, consequently, it’s very difficult for predators to kill them. Dogs can’t distinguish between green and red.
Presently, the belief is that horses, and other non-primate mammals, can only see two colors: blue and yellow. They only have two cones in their eyes, which allows them to see dichromatically (two colors).
Humans have three types of cone cells in their eyes and can see four basic colors: red, blue, green and yellow. Furthermore, we can also see many different hues in between these colors.
Horses see things in very dull shades. For example, what we see as bright red would appear to be a dull shade of grey to our horses. This leads us to have to think a little differently when considering our equine partners. For example, the orange cones, which some people use to train horses, may not be utilized the best when working on grass: Horses perceive orange as the exact hue of a young fir branch. Consequently, when riding on grass, horses have a difficult time seeing an orange object. The contrast is nowhere near what we perceive it to be. Also important to know and remember is the fact that three factors impact how a color is perceived: brightness, saturation and hue. So one particular hue tends to look very different depending upon its brightness and saturation.
Moreover, we need to remember that horses’ senses are much better than ours. A horse’s night vision is better, they hear sounds at much higher frequencies than we do and their sense of smell is better. It’s interesting to think about why most mammals only have two types of cones and limited ability to see colors. If we think back, early mammals were active at night, when color vision wasn’t of much use. Have you ever taken a picture of your horse with a flash and have the picture result with your horse having white eyes? This is caused by how their eyes reflect light off of a membrane at the back of the eye.
One can think of horses as seeing the world like people who suffer from red-green color blindness. Color vision deficiencies vary a great deal in people, but those with severe abnormalities probably still see more color variations than horses do.
Colors definitely break up the world, separating the earth and things in the sky. The color blue is distinctly different and horses watching for predators can see them well against the backdrop of a blue sky. Think of a prey animal — how it would stand out against the backdrop of a blue sky?
Most of our “assumptions” are based on scientific research. However, one thing is definite: the position and structure of a horse’s eyes are quite different than ours. This alone makes a difference in vividness, color and the visual field a horse experiences, and why something in particular might look different to them from one similar type of experience to another — and certainly different to us.