Understanding a Dog's Sense of Smell

By Stanley Coren, PhD and Sarah Hodgson from Understanding Your Dog For Dummies

A dog's nose not only dominates her face, but her brain, as well. In fact, a dog relies on her sense of smell to interpret her world, in much the same way as people depend on their sight. Although this contrasting world view may be hard to imagine, know that your dog interprets as much information as you do. However, she does much of this by smelling an object or animal, not by staring at it.

Born to sniff

To gain more respect for your dog's olfactory ability, compare it to a person's nose. Inside the nose of both species are bony scroll-shaped plates, called turbinates, over which air passes. A microscopic view of this organ reveals a thick, spongy membrane that contains most of the scent-detecting cells, as well as the nerves that transport information to the brain. In humans, the area containing these odor analyzers is about one square inch, or the size of a postage stamp. If you could unfold this area in a dog, on the other hand, it may be as large as 60 square inches, or just under the size of a piece of typing paper.

Though the size of this surface varies with the size and length of the dog's nose, even flat-nosed breeds can detect smells far better than people. The following table shows the number of scent receptors in people and several dog breeds.

A dog's brain is also specialized for identifying scents. The percentage of the dog's brain that is devoted to analyzing smells is actually 40 times larger than that of a human! It's been estimated that dogs can identify smells somewhere between 1,000 to 10,000 times better than nasally challenged humans can.

Table: Scent-Detecting Cells in People and Dog Breeds

*Species*	*Number of Scent Receptors*
Humans	5 million
Dachshund	125 million
Fox Terrier	147 million
Beagle	225 million
German Shepherd	225 million
Bloodhound	300 million

Your dog's unique nose

Your dog's nose has a pattern of ridges and dimples that, in combination with the outline of its nostril openings, make up a nose print believed to be as individual and unique as a human being's fingerprints. Companies even register nose prints as a way of identifying and helping to locate lost or stolen dogs, a system that is now being used by kennel clubs around the world.

If you want to take a nose print from your dog just for fun, it's quite simple: Wipe your dog's nose with a towel to dry its surface. Pour food coloring onto a paper towel and lightly coat your pet's nose with it. Then hold a pad of paper to her nose, making sure to let the pad's sides curve around to pick up impressions from the sides of the nose, as well. You may have to try a couple of times until you get the right amount of food coloring and the right amount of pressure to produce a print in which the little patterns on the nose are clear.

The food coloring is nontoxic and is easily removed. Never use ink or paint, or you may have to explain to your friends why your dog has a green or blue nose.