Tracking a Dog’s Scent Ability


On a gorgeous, blue-sky day, often called a “bluebird day,” most pointers and setters have difficulty finding coveys of quail lying low after a soaking spring rain has passed through. One English Pointer, a seasoned 10X Open All-Age Champion with natural ability, had no trouble pointing birds, even on these days.

“‘Silverwood’ was an exceptional, once-in-a-lifetime dog,” recalls professional trainer Robin Gates of Leesburg, Ga., who handled him for owner Dr. Everett Crouch. “People used to say, ‘The field trial isn’t over until Silverwood runs.’”

Silverwood, who died last year at 17 years old, was blessed with innate ability and intelligence. He stood out among the better dogs. Following ground scent he quickly found the hidden places where quail had gathered hours earlier to feed on grain sorghum or soybeans. More than once, Gates watched him methodically use the old ground scent to catch wind of air scent and find birds.

“When he caught a whiff of hot scent, he would make a circle and take us straight to the covey,” says Gates, who has handled dogs to 98 Open All-Age Championship wins. “Silver­wood was a remarkable dog.”

No doubt some dogs have better noses than others, or maybe they just have the brains to know what to do with scent. Regardless, how talent and brains play out affects performance and separates good dogs from the others.

Whereas pointers and setters use body scent (air scent) to find birds, field trial brace beagles rely primarily on ground scent to track rabbits. Sometimes called “footprint runners,” brace beagles are judged for their accuracy in tracking a rabbit’s footprints. Air scent, which is affected by wind and can be several feet off mark, is unreliable in this precision sport where every inch is important.  

Tracking a rabbit’s often widespread jumps woven with turns and double backs tests the acumen of even the best-bred beagles. Long­time brace beagle breeder Ralph Gillum of Northville, Mich., has bred 63 Field Champions. “A good dog is extremely accurate on the line, works close on checks to recover the scent, and is independent,” he says.

Two memorable male beagles did exactly that, says Gillum. “FC Green Bay Scott did his own work and had all the traits a brace beagle should have. He could read the track, and he stayed close in the check. I was very proud of FC Gillum’s Canadian Ace. He read the track, then proceeded slowly and methodically, which made him extremely accurate with his work.”

The best brace beagles get enough scent from the track to read it. “They know exactly where the next jump is,” Gillum says. “Other dogs are not able to pick up directional scent, so they have to learn a rabbit usually moves forward. Unfortunately, they are not as accurate in their performance and are more likely to miss turns.”

All dogs have an amazing ability to detect scent. To begin with, dogs have from 125 to 300 million olfactory sensory cells compared to five to 10 million for humans. What’s more, the area of the canine brain devoted to assimilating scent — called the olfactory bulbs — is four times larger than in humans.1 Thus, dogs are believed to smell from 44 to 100 times better than humans.2

As a dog takes in scent, his nose screens the chemical smells converting them to electrical signals en route to the brain. Whether a dog primarily uses ground scent or body scent in trailing, both are processed in the same way. Why some dogs, such as brace beagles, primarily ground track, and others, such as pointers, follow air or body scent is not known. Likewise coonhounds trail the scent of raccoons with their heads up, moving fast as they drift and track the scent.

A good dog in the world of Gates and Silver­wood uses both types of scent when trying to find birds. The same is true for hounds running a track. The dog’s objective becomes more complicated, however, when weather, deer, other game, even humans, enter the picture.  

Factors That Affect Scent

Right before a front moves in birds feed more and scent is strong, Gates says. The best opportunities come on these days. After a storm passes and the front has moved through, barometric pressure decreases. Though it turns into a beautiful bluebird day as described earlier, such a day usually makes hard conditions for picking up scent.

Rainy weather is considered an all-right time to track game as animals often move during rain and then hold tight afterward. Hot, dry air makes scenting conditions worse. In contrast, optimal scenting conditions are when the ground temperature is slightly warmer than the air, usually early evening.

Spring and fall provide better conditions for trailing ground or footprint scent than does summer when the vegetation and cover are thick or winter when the ground is frozen or covered with snow. “Scenting conditions are hot and tough in the summer,” says Gillum. “Brace dogs do best in the spring before the cover gets high and in the fall when it has thinned out. It’s hard for them to be smooth and accurate when the cover is thick and high with no pathways.”

When the scent of other game or deer, even humans, gets mixed in with the scent being tracked, things could become confusing. In brace beagling, dogs that cannot differentiate the rabbit track from other dogs are called “dog trackers.” Bird dogs and coonhounds sometimes get off on “trash” scent, such as deer. Experience and age help some dogs to outgrow these problems.

Other factors can affect a dog’s olfactory senses, and thus his performance in the field. Among them are certain medications and illnesses. For example, tonsillitis, infection from tooth decay and fungal or tickborne diseases can impact scent ability. A dog’s overall health condition can play a role too. 

The exact mechanisms that come into play when dogs track or trail are not easily known. When dogs perform flawlessly and their scenting ability is right on the mark, these times are the ones that make for exceptional memories, particularly if they fall at a field trial or championship. These are the moments when it’s easy to remark, “It’s all in the nose.”  

The Anatomy of the Canine Nose

Dogs see the world through their noses. Everything they need to know comes from their sense of smell. While dogs have keen olfactory senses, it is how their brains process smells that is important.

Here is a glimpse at how the canine nose works.  

The dog’s nasal cavity is divided into two parts by a bone and cartilage structure known as the septum. The nasal cavity is made up of turbinate and cartilagelike bones. Those closest to the nostrils, called nares, warm and moisten incoming air. Further back in the cavity are turbinate bones covered by olfactory mucosa, a thick, spongy membrane.

The olfactory mucosa consists of millions of microscopic cilia, or thin, hairlike structures that sprout into passages. The olfactory mucosa and cilia trap dirt and foreign objects and prevent them from entering the respiratory system. Scent molecules are trapped in the mucus and processed by odor-detecting cells found on the tips of the cilia.

The vomeronasal organ (VNO) — also called Jacobson’s organ — is found on the roof of the mouth. This organ is an especially sensitive part of a dog’s sense of smell. An elongated structure, the VNO consists of two small, cigar-shaped, fluid-filled sacs that are filled with receptor cells, which are sensitive to chemical messengers such as pheromones (body scent).             

Once the receptor cells in the nose pick up scent molecules, messages are sent to the brain. The brain processes the information, identifying the scent and determining its significance. This is why the brain’s ability to discriminate between scents is important. With a bit of luck, training can help enhance a dog’s ability to distinguish scents and act on those that are important at field trials.

1 Coren S. Understanding the Canine Mind. (New York: Free Press, 2004.)

2  Hunt R. Focus on Forensics: The Benefits of Scent Evidence. FBI Law Enforcement Bulletin. November 1999.

This article originally appeared in Today's Breeder, a Nestlé Purina Publication Dedicated to the Needs of Canine Enthusiasts.

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