Tag Archives: vision

Dear Dr. Warford, What Can Dogs See, Anyway?

11 May

Dear Dr. Warford:

So what can dogs see, anyway? I’ve heard they are colorblind and only see black and white. Is this true? And why don’t they care about the tv? 

Signed- Just wondering

First let’s talk about what colors dogs can see. You’ve probably heard dogs are color blind. Well, that’s kind of true. Dogs have the same kind of colorblindness as most people who are colorblind. It’s called deuteranopia.  You see, we humans normally have 3 different type of cone cells in our eyes. These cells are responsible for the detection of color. In dogs, and some colorblind people, they only have 2 types of cone cells, yellow and blue.  As a result, they see red as a brownish-gold,  orange as lighter shades of gold-yellow, and green as shades of yellow-grey. They also can’t see violet, which to them appears as shades of blue or grey. This means dogs see the world in shades of brownish/gold, yellow, blue, and grey.  So it’s pretty impressive that they can fetch that red ball on the green grass, but we’ll get into why they are so successful at that a bit later.

Not only do they not have as many types of cones, they also don’t have the same number or concentration of cones as compared to people, so the intensity/brightness of the colors they see is also diminished. It is speculated that all of this happened with evolution. As we primates evolved, it was important that we could distinguish the full range of colors because we needed to be able to see them when foraging for food to distinguish what was safe to eat. In contrast, dogs hunted mainly at night, so the ability to distinguish color wasn’t as important as the ability to see well in low light, which brings us to the other type of cells in our and our canine friends’ eyes: the rod.

Dogs have many more rod cells in their eyes than humans. Rods can only discern black and white, not color, but they make dogs sensitive to many more shades of grey than humans and enable them to have much better vision in the dark. They also allow dogs to detect much tinier movements than we can and from much further away. They also have a reflective surface on the back of their eye called a tapetum lucidum, which reelects light, acting like a mirror allowing more light transmission and better night vision.  So you can see how these traits would be preferable in animals that needed to be able to catch their prey at night.

Dogs’ vision is estimated to be 20/75. This means they are unable to see as clearly as we are at a distance. A dog may clearly see an object only 20 feet away that a human could see clearly from 75 feet away.  But don’t feel too bad for our canine friends, because while we can only see about 180 degrees around us without moving our eyes, dogs can see an average of 240 degrees, more or less around themselves, which means they have a much better sense of what’s nearby.  Add that to their keen ability to detect movement from a distance and see more clearly in the dark thanks to those plentiful rods, and their ridiculously acute sense of smell, and it’s no wonder they are such great hunters.

Which brings us to the biggest question of all: Can my dog see what’s on TV? Well, yes, but is it the same? Until the new fancy high resolution TVs, it was likely that instead of seeing a continuous image, dogs only saw constant flickering, due to our differences in “flicker resolution.” I imagine this was not only not interesting, but pretty annoying for dogs to look at. Now, with the advent of higher resolution screens, dogs are likely able to see a continuous image, and more dogs do seem to “watch” tv, especially animals that are moving. But, keep in mind their limited color vision, decreased ability to discern detail, and the fact that tv has no smell, they often don’t associate the movements seen on tv as anything of interest, or at least not for very long.  So don’t worry, our advanced technology shouldn’t turn Rover into a soap opera addict while you’re away at work.

So next time you and Lola are playing fetch in your back yard with a tennis ball or a bright red/orange toy, be a bit more impressed! She (or he-no judging here) is relying much more on the movement and scent of the ball than the ability to see it.  Plus, you’ve gotten her off the sofa and out from in front of the TV! That deserves a treat!

Coming soon:

What Can Dogs Hear? What Can Dogs Smell? What Can Dogs Taste?

Also: What Can Cats See? What Can Cats Hear? What Can Cats Smell? What Can Cats Taste?

Subscribe to the blog today so you don’t miss it!

*JD Warford, DVM, is the owner and operator of DC MetroVet. Check us out at www.dcmetrovet.com.

*Photos by Jen Sizer at https://www.facebook.com/FuzzyFacePhotography