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The Science of Scent: How Hounds Smell | Understanding how hunting dogs use scent to track wild game

The Science of Scent: How Hounds Smell | Understanding how hunting dogs use scent to track wild game
March 14, 2023

By: Taylor Young, DVM for On Track Media Group

Photo By: On Track Media Group

“The coon’s right there!” I thought to myself as Belle ran right under the tree I’d seen eyes in; she was oblivious to its presence. “How can she not smell that?!” This was the final round of a full elimination competition coon hunt, and with the failure to tree that coon, my Blackmouth cur came in second for a National Kennel Club (NKC) Reserve World Champion title (yes, there were only nine dogs in the hunt, but it still counted to my 17-year-old self). Even if you know some of the science behind scenting like I do, it can still be baffling. Scenting is a complex activity with many variables and a basic understanding of how it works can make you a better hound hunter.

The Nose Knows

The canine olfactory system begins with the hound’s nose. The nose is specially formed to increase the turbulence of the air entering the airways, making it swirl around and contact the inside lining of the muzzle. The elongated muzzle of a hunting dog is filled with a curled system of cartilage covered by mucous membranes, allowing for much more surface area under the skin than is first apparent. These mucous membranes have somewhere around 200 million scent receptors (compared to a human’s 5 million), and are innervated by the olfactory nerve. The olfactory nerve connects to the olfactory lobe of the brain where scent is recognized and processed. Additionally, a dog has a vomeronasal organ situated just above their front teeth that allows additional scent differentiation. This organ has openings inside the mouth as well as the nasal cavity. The specialized anatomy of a dog’s nose allows scent to build up over time inside the nasal passages and is not immediately blown out while breathing through the nose.

How Hounds Use Scent to Hunt

What exactly is a dog smelling when they’re putting that nose to work? It’s theorized that it is pieces of the game animal left behind that are being detected. Skin cells that naturally fall off, hair, feces and urine, pheromones, and sweat may all play into the smell being recognized by the hound. On the ground, scent directly from glands in the feet, or cells that have settled on the ground can be captured in the dirt and debris where they are then stirred up as the dog sniffs them into his nostrils. A dog running with his head up is smelling these pieces caught up in moisture in the air or where the animal has brushed up against a tree or brush.

If you’ve ever watched a hound put his nose into the air for scent, you’ve seen the short, sharp intakes of air through his nose. As opposed to simply breathing through the nose, sniffing is an intentional activity that accumulates scent-rich molecules of air into the nasal passages. As the air passes through the nasal cavity, scent molecules attach to the moist surface of the mucous membranes, which bind to the scent receptors. This creates a signal in the nerve that travels to the brain, where the scent is then discerned. All of this happens within a split second! The strength of a smell is dependent upon many factors, but a hound is able to discern the direction of a track by the presence of more scent molecules (and therefore a “stronger” scent) in one direction versus the other.

Not only is there an anatomical and physiological component to scent, but also a behavioral one. Scent hounds like a beagle or coonhound are hardwired to put their nose into the dirt and follow it. A cur or feist, though, will usually rely more on scent drifting in the air, running with their nose up off the ground. Some dogs will even smell a scent drifting down from an animal who’s been sitting in a tree for a while (known as a “layup”). 

Why is it, for example, that the average cur won’t follow that 12-hour-old bear track, even though the hound will; is it because he can’t smell it, or because he doesn’t have the desire to chase that scent? More likely the latter, as the breeding programs and what they have been selected for has been so different over time.

What Conditions Affect Scent?

Though the dog’s ability is very important, the environment plays a large role in scenting. Moisture is thought to be the most important factor influencing scenting conditions while hunting. Rain, snow, humidity, or the lack of these can all play into scenting. Moisture helps scent to stay around longer, preventing it from drying out and fading away. This is why a dry-ground lion dog is such an impressive dog to watch and why those hound hunters in colder regions wait for snow. Other factors such as temperature and wind also influence scenting conditions on a daily basis.

There’s still much we don’t know about scenting, but the things we know through experience and observation are enough to leave me in awe of how it all comes together. It seems like magic when that dog follows a trail to a tree with game sitting in it. I know it still gets me excited, and I hope it does for you, too!

To learn more about the health and wellness of your hound, cur, or feist dog, be sure to follow Dr. Taylor Young (@treedogdoc) on social media.





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