Introduction
Dogs have an incredibly powerful sense of smell that allows them to detect scents unnoticeable to humans. Their olfactory abilities make dogs excellently suited for tracking, which involves following a trail using their nose. When tracking, dogs pick up ground scents and air scents which provide information about who or what passed through an area. This allows dogs to identify and follow a specific person or animal’s scent trail. With proper training, a dog can use its powerful nose to track anything from missing persons to shed antlers.
Olfactory System
Dogs have a highly advanced sense of smell thanks to the complex anatomy and physiology of their nose and olfactory system. Their noses contain up to 300 million olfactory receptors, compared to only about 6 million in humans (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8388720/). The olfactory epithelium, which contains the olfactory receptors, covers a large surface area inside a dog’s nasal cavity to allow detection of a wide range of scents.
When odor molecules enter the nose, they bind to olfactory receptors which send signals to the olfactory bulb and then to the brain for processing and identification. A portion of the dog’s brain devoted to analyzing smells is about 40 times larger than in humans. Dogs also have a special organ called the vomeronasal or Jacobson’s organ which detects pheromones and is used to analyze chemical communication between animals.
The complex olfactory system allows dogs to detect scents in miniscule concentrations, as low as 1 part per trillion. They can pick out individual scents from complex mixtures and locate the source. Their nose anatomy and sense of smell makes dogs excellent trackers.
Odor Detection
Dogs have an incredible sense of smell thanks to their sophisticated olfactory system. They have up to 300 million olfactory receptors in their noses, while humans only have about 6 million (How Dogs Use Smell to Perceive the World, 2022). These receptors allow dogs to detect and process scents at the molecular level.
When odor molecules enter a dog’s nose, they bind to the olfactory receptors which send signals to the olfactory bulb in the brain for processing and identification. The olfactory bulb has a large surface area which allows dogs to analyze smells in detail. Their nostrils also move independently which helps dogs determine the direction of a scent (Canine Olfaction: Physiology, Behavior, and Possibilities, Kokocińska-Kusiak, 2021).
Dogs use this highly advanced olfactory system to gather information from scents. Their brain can categorize and remember tens of thousands of different smells. Dogs can detect odor molecules in incredibly small concentrations, far below what humans can perceive. Their sense of smell is so keen that they can pick up scents that may be weeks or months old.
Tracking Scents
Dogs rely on their highly developed sense of smell when tracking scents and can detect and follow two main types of scents (Wikipedia, 2022):
Ground scents – These are scents that have been left by footprints and crushed vegetation. The scents from the ground can adhere to shoes and clothes. Dogs can detect these scents even after the person has left the area.
Air scents – These are the odors and particles released into the air from a person’s breath, sweat glands, and skin. Air scents create an invisible “scent cone” that extends downwind from the person. Dogs can detect air scents from over a mile away under ideal conditions (SitStay, 2022).
When tracking, dogs will follow a combination of ground scents and air scents left behind by an individual. Their ability to detect and discriminate between the intricate odors allows dogs to determine if they are following the track of their target scent or someone else.
Ground Scents
Dogs have an incredible ability to follow ground scents and footprint odors left behind by people or animals. As a person or animal moves across the ground, skin cells and microscopic particles containing their scent fall off and get left behind in their footprints and path of travel. Dogs are able to detect these microscopic scent particles using their powerful sense of smell.
A dog’s nose has over 300 million scent receptors compared to only 5 million in humans. Their nostrils even have folds and grooves that allow odors to linger longer in the nasal cavity, giving more time for scent detection (1). When tracking a ground scent, dogs will sniff the individual footprint odors, working to detect, separate and identify all the smells that make up the track (2).
As the dog follows the ground scent, they are able to determine the direction of travel based on the concentrations of odor deposited over time. Older scent deposits will have lower concentrations than fresher deposits. Dogs can also identify changes in gait or movement by analyzing the variations in footprint odors and scuff marks.
Sources:
(1) https://www.akcchf.org/educational-resources/library/articles/articles/tracking-a-dogs-scent.html
(2) https://en.wikipedia.org/wiki/Tracking_(dog)
Air Scents
Dogs use airborne odors, or scent that has become aerosolized, to locate targets while tracking. These odors are carried by air currents instead of being located on the ground, requiring dogs to follow the scent cone rather than a physical trail.
Air scenting dogs will hold their heads high, sniffing the air to detect the target odor. They use the intensity of the odor to determine direction, moving in the direction where the scent is stronger, following it to the source. The fresher the scent and the closer they get to the target, the stronger the odor will be.
Breeds like Bloodhounds are known for their exceptional air scenting abilities. Their large, folded ears help to waft odors towards their nose as they track. Other breeds like Labradors can be trained for air scent tracking as well. The ability to detect a specific human scent in the air over long distances makes air scent dogs excellent for search and rescue operations.
Overall, air scents allow dogs to locate targets like missing people or escaped criminals even without a physical trail to follow. Their sensitive noses detect and interpret odors carried on the wind or by air currents.
Scent Cones
When tracking a scent, dogs follow what are called “scent cones.” A scent cone is the area where the odor from an object or person extends outwards and disperses in the environment.[1] As scent particles travel through the air or across the ground, they spread out in the shape of a cone, with the strongest concentration of odor in the center near the source.
Within the scent cone, the scent is strongest closest to the center and gradually diminishes and becomes more diffused further away from the source. The size and shape of the cone varies based on environmental factors like wind and terrain. Wind can make scent cones elongated in the downwind direction as scent is carried along. Dogs use their sensitive noses to smell and follow the strongest concentration of scent along the cone to track down the source.
When following a scent cone, dogs will zigzag back and forth across the cone to find where the smell is most intense, which guides them along the track. If they lose the scent, they may double back or cast out in wider circles to reacquire the cone. By smelling which direction has the strongest odor concentration, dogs can follow scent cones to successfully track down the source, whether it’s a missing person, fugitive, or lost item.
Scent Discrimination
Dogs have an incredible ability to discriminate between scents. Their olfactory system allows them to detect minute differences between smells that humans would perceive as identical. When tracking, dogs rely on scent discrimination to follow a specific person or animal’s trail, even if it crosses paths with other scents.
Dogs can be trained to ignore certain smells and focus on the target scent. For example, a tracking dog can learn to distinguish its handler’s scent from all others and follow it exclusively. Through repeated training with target scents, dogs hone their scent discrimination skills. Trainers use exercises like scent lineups, where dogs must identify the correct human scent sample amongst several distractions. This taps into the dog’s ability to detect subtle differences between similar odors.
A key to scent discrimination is understanding how air currents disperse scents in “cones” from their source. Dogs detect minute scent particles within these cones and use slight changes to determine direction and proximity. Their ability to pick out specific smells amongst scent cone overlap allows dogs to stay on track. With rigorous training, dogs’ natural scenting talent can be honed to pinpoint and follow a particular scent, even days or weeks after the original trail was laid.
Sources:
https://dokumen.pub/how-to-train-a-police-bloodhound-and-scent-discriminating-patrol-dog-the-kocher-method-secondnbsped-0578069865-9780578069869.html
https://books.google.com/books?id=z7hEAwAAQBAJ&pg=PT146&lpg=PT146&dq=%22dog+scent+discrimination+ability%22&source=bl&ots=_NuHXZ2j5K&sig=ACfU3U0-DL1RC8qIo55_lXrK5FkzD50Q2g&hl=en&sa=X&ved=2ahUKEwj8q7WGjdODAxXwDTQIHQG7D5MQ6AF6BAgREAM
Tracking Training
Dogs need to go through extensive training in order to track scents effectively. This often starts when they are puppies to get them used to focusing on scents. Professional tracking dog training involves positive reinforcement methods like rewarding with treats when the dog correctly identifies and follows a scent. Trainers will start with having dogs follow very short scent trails and work up to longer, more complex routes. Dogs learn commands like “Find” to start tracking and “Show me” when they locate the target item or person. Training focuses on real-world scenarios like finding lost people in parks or wilderness areas. With consistent daily practice, dogs can become reliable trackers for various settings. It takes great skill and patience to train a dog for tracking, but the result is an amazing ability to follow scents.
According to canine expert Tobias Gustavsson, “Tracking dog training – methods and techniques for a reliable result.” (https://tobiasgustavsson490.clickmeeting.com/tracking-dog-training-methods-and)
Conclusion
In summary, a dog’s incredible sense of smell allows it to detect and follow specific scents used in tracking. A dog’s olfactory system, with over 200 million scent receptors, is extremely sensitive to odors. When tracking, dogs use both ground scents and air scents to follow a specific person’s trail. They detect microscopic particles and scent cones that allow them to discriminate between individual scents. With proper training, dogs can learn to methodically follow a track and alert their handler when the trail is found. A dog’s ability to recognize and trail a particular scent is invaluable for tasks like search and rescue, law enforcement, and hunting. Their extraordinary olfactory capabilities make dogs uniquely skilled at scent tracking.