Can Dogs See Colors?
Moderate Vision, Better Hearing, and an Incredible Sense of Smell
Our dogs may be deprived of common sense, but when it comes to the five senses, we should be in awe and understandably envious, with a couple of exceptions. We have a better sense of taste, possessing about 6 times as many receptor cells on our tongues as do dogs. If they had as many taste buds as we do, they wouldn’t (you finish the sentence) . . .
I’d also rather have my eyesight than a dog’s. They see better in dim light and hold a slight advantage over us when it comes to seeing beside and behind themselves, but their color perception is very weak.
I’ve seen their color vision likened to our color vision at dusk, which if it's true, isn't very good at all if my testing of the theory is accurate. At dusk, I can't tell if that house has black trim or green trim, or if that bike in the driveway is dark red or brown.
You may remember from your grade school science class that eyes contain two types of receptor cells, rods and cones. What you may not remember is which do what. It's the cones that detect colors, and dogs' eyes are about 90% rods.
A dog’s hearing is better than ours, though. Not only is the frequency range of sounds they can hear wider than ours, but dogs with upright outer ears are able to funnel fainter sounds into the hearing mechanisms of the inner ear.
The outer ear, besides acting sort of like a satellite dish, is also capable of independent motion (floppy-eared dogs are disadvantaged here).
By rotating the ears, dogs are better able to determine where a sound is coming from and can do so in about 6/100 of a second. Isn't it a hoot watching your dog's left ear and right ear move in different directions simultaneously, and don't you wish you could do that? You'd be invited to every party in town.
The main difference between a dog’s sense of touch and that of a human is the fact that they have specialized hairs (back on the block we just called them vibrissae) on their muzzles, eyebrows and lower jaws.
These stiff hairs, which are embedded deeper than those common other hairs, can detect air currents, subtle vibrations, and objects in the dark. I've read that it's possible that they also direct food and other objects to the mouth.
Distinguishing the Component Parts of the Whole
Saving the best for last, there’s no comparing a dog’s sense of smell to that of the Homo sapien. Heck, a dog can detect butyric acid, a component of sweat, from 1 million to 100 million times better than we can. Jealous?
When we walk by a pizza parlor we smell pizza. Dogs smell yeast, tomatoes, oregano, etc., which is why a trained dog can walk along an airport baggage carousel and from among scores of bags filled with soiled underwear, cosmetics, toiletries and souvenirs, pick out a baggie containing a small amount of cocaine.
In humans, the area of olfactory receptor cells that communicate to the brain covers about one square inch. In a dog, depending upon the length of its muzzle, that area can be up to 60 square inches.
And here’s where those “hearing compromised” floppy-eared dogs make up for it. Those floppy ears allow for more scent to be directed to the nose. What’s more, dogs and other animals possess a functioning vomeronasal organ (VNO) also known as Jacobson’s organ. We have one, too, but it doesn’t work anymore.
The Vomeronasal Organ and Marking
The VNO’s specialized receptor cells detect pheromones, which are abundant in dog pee and poop, providing a lot of information, including, but not limited to, another’s social status and reproductive state.
And that is why Boomer sniffs everybody in their nether parts. It's also why dogs sniff surfaces where other dogs have "marked" and why they sniff piles of poop left on the ground by thoughtless dog walkers. They can even detect echoes of scent left by poop that was responsibly scooped.
By doing that, they can tell who was there, how long ago, what they ate, and if they're ready for love. Aren't we glad that all we have to do is look at our dogs to know all that stuff?
You may from time to time see an interesting behavior in dogs, known by us laypersons as tonguing. Scientists call it the flehmen movement. They’ll click their tongue against the roof of the mouth, the teeth may chatter and there may be a little foam on their upper lip. They’re essentially directing molecules of scent to the VNO to interpret data. You'll also notice that they do it right after sniffing something or someone. A friend of mine says her dog is checking his peemail.
Dogs lift their legs to deposit their urine high up on vertical surfaces so that the scent can be better carried by air currents to the VNO's of others. The higher the deposit, the better to prevent other dogs from over-peeing the spot. They also do it simply to relieve themselves. The differences is, when they're scent-marking, they release small amounts of urine at a time. To relieve themselves, they pretty much empty their bladder, although it seems they retain a little . . . just in case an urgent scent-marking opportunity suddenly presents itself.
Questions & Answers
© 2012 Bob Bamberg