If you’re a dog owner, here’s an experiment you can try, courtesy of the veterinary eye specialists at Animal Eye Associates: during the next session of “fetch” with your furry friend, use a red ball and a blue ball instead of the single ball you normally play with. Throw the blue ball first and watch your dog react as she always does, by joyously launching at it, grabbing it in her jaws, and bringing it back to you post haste. However, watch what happens when you throw the red ball next — your pup may sit there with a confused look in her eyes, or she may run after the ball only to pass by it several times in a failed attempt to locate it. What’s going on here? Is your dog not as well-trained as you thought? Is she distracted by something?
The answer lies in the color of the ball. While dogs can easily see various shades of blue, they only see red as a grayish color that doesn’t stick out very much from the rest of what their eyes are showing them. Don’t worry; your dog is not dumb, just confused!
The vast, vast majority of animals on our planet (except the Skate fish, which has no color-absorbing cones in its eyes) see the world around them in color. Butterflies see a dazzling array of color in order to discern between flowers and the different kinds of pollen they carry. The mantis shrimp can not only view ten times more colors than humans, it can see infrared, ultraviolet, and polarized light. Woolly lemurs can see a particular shade of green that lets them identify high-nutrient leaves on trees and bushes.
How Vision Works For Mammals
Before we dive too deep into this topic, we should probably describe how vision works in mammals, specifically in relation to color. When light reaches our eyes, it bends upon hitting the cornea. This allows the light to pass easily through the pupil and to the iris, where it is picked up by millions of photoreceptors called cones and rods. The photoreceptors then convert the light waves into information that can be processed by the brain in the form of color, motion, and shape.
Essentially, the cones in the iris interpret colors, and the rods interpret light. Animals that are colorblind lack cones, and those that can only see during the daytime lack rods. For mammals, which have both of those present in their eyes, that means the world is viewed in a combination of light, dark, and a variety of colors. For the rare animals that are missing either rods or cones, the results are much different.
Unlike other mammals, both cats and dogs — along with their undomesticated relatives — have a layer of reflective cells, called the tapetum, located directly behind the retina. When light passes through the retina, it reflects off the tapetum and passes back through the retina so that the rods and cones stored there can receive even more light. This reflection is what makes a dog’s or cat’s eyes shine in the dark when struck by a light source.
Dogs And Color
Contrary to popular belief, dogs can see colors, just not nearly as many as humans or some other mammals. However, their color palette is extremely limited when compared to our own — dogs of any breed only see around 10,000 colors, while humans see a wider range of 1,000,000 colors. This is because canines have just two types of color-receptor cones in their eyes, whereas humans have three.
What does this mean for your dog’s vision? While a dog does have a limited number of colors to view — grays, blues, and versions of yellow, to be exact — they make up for it by being able to detect motion with exact detail, and by having vision that is works well in low-light situations. When you drop a treat right in front of your dog’s face, he won’t be able to see it immediately, but when you throw a treat into the air, he will be able to trace its movement and calculate where it’s going to land on the ground. With their heritage as ancient hunters, it’s no surprise that being able to track movement effectively is so important to canines.
Cats And Color
Similar to dogs, cats only have two types of receptors in their eyes, and they can only see shades of gray, blue, and yellow. Also similar to dogs, cats are limited to a range of 10,000 shades of those specific colors, which means they have a hard time focusing on objects that are red, orange, and green.
The ability to precisely define movement is just as important for cats as it is for dogs. Back when your kitty’s ancestors were hunting for food, they had to do it at the hours when their prey was most active, which was most often during dawn or dusk. Being able to see the smallest movement in low-light conditions was imperative for ancient felines, and the common house cat has evolved to this point because of that. It’s also why cats are more active during those times of the day.
Why are cat toys always so brightly colored, then? That’s so we can easily find them under the fridge or behind the oven. For the most part, cats just don’t care what color their favorite toys are — all that matters is that they move.
Birds And Color
Birds are a different matter entirely. In fact, the difference between how birds interpret colors and how other animals see them is quite stunning. In a 2007 study, scientists found that birds are capable of seeing a whole range of colors that are far beyond what humans and other animals are able to view.
The study found that birds possess two advantages in the area of color clarity:
- Birds can see colors in the ultraviolet spectrum due to an additional color receptor in their eyes. This receptor gives them access to a vast color range that is found only in the feathers of most bird species, especially songbirds. Mammals can’t normally see these colors because we don’t have the biological filter necessary to view them with the naked eye.
- Birds also have a special retinal filter made of colored oils that allow for an increase in the number of colors they can discern within the normal and ultraviolet spectrums. Because of this, birds are able to see an almost endless number of colors in the feathers of their fellow avian friends — and enemies.
The robin perched in the tree right next to your window may not look very spectacular to your eyes, but to another bird, that robin’s feathers are made up of a whole assortment of hues and shades, only visible in the ultraviolet spectrum. Access to this spectrum is what allows birds to differentiate between species during the mating season. Pretty neat, eh?
THE TOP RATED LOCAL® VETERINARY OPHTHALMOLOGISTS IN FLORIDA
If your furry friend is suffering from eye discomfort and you’re not sure what to do, look no further than animal eye care services from the pet ophthalmologists of Animal Eye Associates. We specialize in the diagnosis, treatment, and care of eye problems in animals, and we would be happy to help. Schedule an appointment online today!