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Trailing Dogs: How To Read Negative Indications

Many people are already familiar with tracking dogs. Tracking is often used in dog sport, as well as to locate people who have traveled short distances and their dropped articles along the way. Trailing dogs, however, are often used by law enforcement and search and rescue teams to locate a specific individual in the shortest possible time or in difficult environments where exclusively following tracks is not possible. 

Tracking and trailing dogs work very differently, and it is important for K9 handlers to understand the differences between these disciplines, in addition to how to most effectively read the dog that they are working with.

What is the difference between tracking and trailing dogs?

A tracking dog is typically worked on a leash attached to their collar, and taught to follow footsteps or crushed vegetation to a missing person or suspect. By contrast, a trailing dog is worked on a harness and long line, and trained to follow human odor alone wherever it may fall. More specifically, the odor is the skin cells that human bodies are constantly shedding (did you know that we shed almost a million skin cells every single day?), and the bacteria that eats them as they land on the ground. These cells, and the bacteria-producing odor, are referred to as surfs or rafts. 

As the dog is following these rafts, they may deviate from the “track,” or exact location where a subject has walked. This is due to the fact that odor molecules are very light and constantly moving. Factors such as environmental conditions, wind, temperature and terrain can drastically move odor molecules and skin grafts, causing concentrated human odor to spread. 

Since trailing dogs are not specifically following vegetation trails and the small quantity of human odor sticking to them, their nose does not remain on the ground while they are working. Instead, handlers often see their dog using a combination of tracking (nose on the ground) and air scenting (head raised in the air). Since trailing dogs are working to follow the strongest concentration of odor, they will often move between the perimeters of an odor path. Working in this manner enables them to eliminate the directions where odor is not present, and identify the areas where odor is present. 

Trailing K9s can often cover ground significantly faster than a tracking dog can because they use an entire odor picture when attempting to locate a person, instead of relying on only a portion of it. As the dog works to eliminate the locations where the skin raft trail weakens or disappears, they will display a variety of natural behaviors which can indicate to their handler that odor is no longer present. These behaviors can also communicate the areas where odor is present, as well as the direction that an individual has traveled. Understanding these behavioral cues is often referred to as “reading” the dog.

trailing police k9

How to read a trailing dog

When reading a trailing dog, it is important to remember they are following skin rafts, where they become weaker and where they disappear entirely. Since such a significant aspect of trailing is accomplished through the process of elimination to determine where odor is not present, handlers will often witness their dog demonstrating negative indications

Negative indications are the behaviors demonstrated by trailing dogs to communicate that odor is no longer present. When odor is no longer present, trailing dogs will move back into the area where odor molecules are present. It is imperative that handlers understand how to read their trailing dog’s negative indications so they can identify when their dog is still working odor, and when they may need to re-cast the dog in instances where odor is completely lost. 

There are three primary types of behaviors that are most commonly demonstrated by trailing dogs exhibiting negative indications while working. These are known as head turns, flowing negatives and cutbacks.

Head Turns

Head turns are dramatic, sharp turns of just a dog’s head – either right or left. These can be witnessed when a dog is airscenting, but will also occur after a dog’s head has lifted back upright from the ground when they are tracking. 

When head turns occur, it can almost appear as though the dog is trying to look in that direction to see if the subject may be there. This indication can be a positive sign that odor is present in specific situations such as when the dog is first searching for the beginning of a trail. Most of the time, however, a head turn will occur because they have reached the edge of the raft trail, causing them to turn and sample odor in an alternative direction. 

Frequently, a dog will offer head turns as they move down a tree line or other physical barriers to eliminate the locations where a trail layer did not enter.

Flowing Negative

A flowing negative refers to the motion that a dog demonstrates when they bracket through the perimeters of odor. Oftentimes, this pattern resembles zig-zagging and it can range in distance from a few to many feet depending on how far odor has dispersed. 

Typically, when a flowing negative is occurring, a dog’s head is not held completely upright and their entire body will move consecutively in and out of a skin raft path. As the dog turns away from each edge of odor, their handler can confidently eliminate each direction in which the dog’s body turns away from.


Cutbacks frequently occur during dramatic changes in direction, such as when an individual has made a sharp turn, or during drastic changes in environmental terrain such as when pavement changes to thick brush. 

A cutback can be very small, or can cover a large amount of distance as a dog moves in a circular motion to locate the direction in which odor has traveled. The surrounding conditions will heavily affect how far a dog needs to travel to know exactly where a subject turned. Once the dog completes their cutback, they will resume a rhythm of head turns and/or flowing negatives as they continue along the trail. 

A cutback will eliminate every direction besides the one which the dog commits to. In more difficult conditions where odor is moving drastically, or when inexperienced dogs are working, the prevalence of cutbacks may occur more frequently.

trailing police k9

How can I get better at identifying negative indications?

For trainers and handlers, the most effective way to learn how to effectively recognize negative indications is to intentionally observe as many trailing dogs as possible in both blind and known trailing scenarios. If you are the one handling the dog, it is important that you are comfortable enough working with a longline that the dog may be observed without needing to worry about longline management. If you are not yet completely comfortable working with a longline, it is useful to observe dogs when you are not handling. 

It is also important to watch a variety of dogs and breeds trail during these sessions because some dogs are more obvious than others, and working styles can differ between dogs. By observing a wide variety of dogs, a handler can become very competent in identifying the behaviors of their own dog as well as other dogs. 

Other things that can be beneficial in learning to recognize negative indications are having another person videotape a dog that you are handling so you can watch the video back when you don’t have to focus on longline management, in addition to simply walking a dog on a longline so you can observe how a dog acts when they are not working.

Learning to correctly interpret negative indications is a crucial skill for every handler of a trailing K9. Effectively identifying these cues will enable a handler to know for certain when a dog is working, when a dog needs to be re-casted, and where exactly the direction of odor is moving.