Click to Enlarge When a dog sniffs, it picks up scent from the air, ground and objects.   A Dog's Nose by Barbara Baird illustrations by David Besenger photography by Cliff White To a dog, the world makes perfect scents. Which of the five senses is most important to a hunter? If you said sight, you’re right. Dogs, however, rely more on their sense of smell than on their sight for hunting. “A dog’s nose is as important as our eyes are to us,” said Dr. Brian Janke, a veterinarian in Rolla, Missouri. “And, usually, the longer the nose, the better the sniffer.” Some dogs have been bred to develop their sense of smell. These dogs are often used for hunting or tracking. Some tracker dogs work in the field or woods to help hunters find game. Other dogs aid law enforcement officials by sniffing out drugs, food, flammable items or explosives. Dogs can even find people buried under earth or snow. A dog’s nose also contains infrared receptors that are sensitive to temperature. Some experiments have shown that dogs can even locate cancers in people by smell. Hunters often take advantage of a dog’s ability to smell game. Setters and pointers are really good at finding quail and pheasants. Beagles are good at sniffing out and following the trail of rabbits. Some sports, such as coon hunting, would be much more difficult without a hunting dog’s nose to help. You’ve probably noticed that dogs’ noses are usually wet on the outside. This moisture first attracts and then collects molecules from lots of places—the air, the ground and from objects. The reason a dog often licks its nose is to keep it moist. A dog’s nose also has lots of mucous inside. If unfolded and spread out, the surface area of the dog’s nasal membranes would be about the size of a handkerchief. The surface area of a human’s nasal membranes comparison would be about the size of a postage stamp. When a dog sniffs, it draws air up through the turbinate bones and to the back of the nose. An olfactory bulb at the end of each nasal passage then sends information about the scent to the dog’s brain. There’s a lot to tell about a scent, such as what type of animal was there, if the animal was male or female, and which direction the animal was headed. A dog’s olfactory bulbs are four times larger than ours—even though its brain is much smaller. Proportionally, a dog devotes much more of its brain to smell. In fact, it’s estimated that dogs can identify smells somewhere between 1,000 to 10,000 times better than humans can. A dog also can focus on a scent for a long time. A dog inhales through its nasal tubes, but exhales outward and sideward through slits at the sides of its nose. The exhaled air swirls to stir up the air near where the dog is smelling, helping the dog to inhale even more scent molecules. Even though a hunting dog may naturally have a good nose, he needs to be trained to use it properly. For best results, it’s important to make training fun for the puppy. Sometimes a coon hunter will take a coon hide and let the puppy smell it. Then, he’ll take the hide, touch places along a trail with it and put it where the puppy doesn’t see it. When the puppy finds it, he gets a reward, such as a pat on the head or a treat. Puppies can also learn from watching older, more experienced dogs work. The pup will excitedly run around trying to smell everything. Eventually, however, the pup will figure out what the older dog is smelling. During time spent hunting, a puppy naturally forms a bond with the hunter. Most hunters love their dogs, too, creating a relationship that is fun and productive. A real stinker A free-running dog will sometimes roll in manure or the rotting carcass of some animal. The dog almost seems pleased to have discovered and marked itself with such a stinky smell. Dogs may have it in their genes either to mark exceptionally strong-smelling spots with their own smell by rolling in them, or to camouflage their own scent by rolling in a strong smell.