Dog’s Sense of Smell Compared to Humans

Understanding a Dog’s Sense of Smell. A Dog’s nose Dominates not only his face but also his brain. While the human brain is most strongly oriented toward analyzing data from the eyes and information gathered through light, the dog’s mind is designed with an emphasis on gathering information from scents.

The part of the dog’s brain that is devoted to analyzing smells is proportionally forty times greater than that of humans.

Dog’s Sense of Smell facts

dog sense of smell distance

Dogs work more actively than humans to gather scents. They don’t let smells casually drift into the nose but use certain abilities that humans don’t have.

To start with, dogs can move or wiggle their nostrils independently, which helps them determine the direction a scent is coming from. Dogs also have a special sniffing ability that is quite different from their normal breathing.

When your dog pushes its nose in the direction of ascent, he actively interrupts the normal breathing process so that the material he has sniffed passes over a bony shelflike structure in the nasal cavity that is designed to trap the odor-containing air and protect it from being washed out when the dog exhales.

This mechanism allows scent molecules to remain in the nose and accumulate to the point that there are enough of them for the dog to recognize.

Dog’s Amazing Nose

Dog's Amazing Nose

The bony plates in the dog’s nose are covered with a thick, spongy membrane, which contains most of the scent-detecting cells and the nerves that will take the information up to the brain.

For humans, the area containing these odor analyzers is about one square inch, the size of a postage stamp. If we could unfold the corresponding area in the dog’s nose, it might be as large as 60 square inches, or just about the size of a piece of typing paper.

In part because of this difference in the number of scent-detecting cells, it has been estimated that dogs can identify smells somewhere between a thousand and ten thousand times better than humans can.

Although dogs are more sensitive than humans to virtually all scents, their noses are particularly attuned to animal-related odors. You might have expected this to be the case since dogs are hunters and should be tuned to the kinds of odors their prey would tend to leave behind.

How good is a dog’s nose?

curious cute puppy

We see one example when we compare the human sensitivity for butyric acid, which is a component of sweat, to that of a dog.

Humans are pretty good at detecting this odor at the reasonably low concentration of about one five-millionth of a gram evaporated into a cube of air that is one-meter square.

Although that sounds pretty impressive, consider the fact that if we dissolved this same amount of butyric acid in 250,000 gallons of water, a dog would still be capable of detecting it.

If we took 1 gram of butyric acid and let it evaporate in the volume of a ten-story building when you opened the door your human nose would be only just barely able to smell it.

How strong is a dog’s sense of smell? If we evaporated that same gram of butyric acid in the air and dispersed it over a 135-square-mile area and up to a height of 300 feet in the air, a dog would still be able to smell it.

This is approximately the same size as the area covered by the entire city of Philadelphia! Since that city contains about one and a half million people, all of whom sweat (especially on typically hot, muggy summer days), it is interesting to speculate what that metropolis must smell like to a dog.

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