Because smoke particles are approximately equal in size to those particles shed by the human skin, some of the most interesting evidence we have about the dissipation of scent comes from watching the discharge of smoke bombs. Even on a calm day with minimal air movement, visible smoke takes on a life of its own. It attaches to bushes and rocks, springs upward along the sides of inclines or buildings and lingers in depressions and areas of long grass. When the ground is cool, smoke clings thickly to the earth. When the ground is heated by direct rays of the sun, the smoke expands, thins and dissipates upward.
The second type of scent is the track scent. This is the odor that a person, animal or object leaves behind after coming in contact with the earth’s surface. It appears that this contact with the ground changes the scent of the disturbed area in some way. Track scent dissipates very slowly in comparison with body and airborne scent.
Which kind of scent should the dog follow? That depends upon what sort of tracking you are doing.
The normal criterion for success in police scent work and search and rescue is simple: Does the dog find what we are looking for or not? In service dog work we are not concerned with style or appearance, only with efficiency and results. Therefore, tracking dogs that are used for police work and search and rescue are trained to trail—encouraged to use both air and track scent. They follow the track rather loosely and will freely cast about for body and airborne scent, exploiting it in order to draw nearer to their goal.
Schutzhund is a competition. In the tracking phase points are awarded, and there must be a winner. One dog must track better than the rest, and in Schutzhund this means more exactly, more precisely on top of the footsteps of the tracklayer. Because body scent is widely dispersed and blown easily about by the wind, a dog that searches for body scent will quickly take to quartering. It will zigzag back and forth, working the fringes of the scent path, much the way blind people feel their way down a hallway by touching first one wall and then the other. Air scenting therefore leads to very inexact tracking.
In addition, air scent appears to be transient. Depending upon conditions and terrain, some fifteen to forty-five minutes after the tracklayer has passed, his body scent has lifted and become so dispersed or discontinuous that a dog cannot easily follow it. Because the track scent lasts far longer and because it is much less affected by wind conditions than body scent, it is therefore more reliable and much more closely associated with the actual track itself. This is the scent we must teach the Schutzhund dog to follow.
An exquisitely trained competition dog actually footstep tracks in good conditions. This animal follows the track as if it were on rails, making geometrically precise turns, its head weaving from side to side across a six-inch area as the dog locates and checks each of the tracklayer’s footsteps.
Because of the importance of track scent, the type of terrain and vegetation strongly affects how the dog will track. Hot sand, frozen ground, asphalt and stone are all difficult and nearly impossible for the dog to follow a track across. However, the veteran tracking dog eventually must be able to adapt to virtually any type of terrain and all weather conditions.
For teaching Schutzhund tracking, tracks on short, pastem-length grass or soft dirt are the most suitable, as they retain the scent well. Tall grass retains odor all along its blades and the dog therefore tends to practice tracking with a high nose. Tall grass also shelters body scent from the wind and sun, so it dissipates slowly. When in an area of knee-high grass, the tracklayer’s body scent will remain for a surprisingly long time dispersed in a wide area about the track. The resulting low-hanging cloud of air scent among the grass stems will greatly confuse the novice tracking dog. Thus it is a good idea to avoid this type of vegetation during training sessions.
Hills can also have a pronounced effect on the dog’s performance because of the gentle uphill and downhill air currents that distract the animal from the track scent.
By causing the scent to drift, wind also affects the dog on the track. For example, if the animal is tracking into the wind toward a turn, it will tend to make its move before the actual turn. When the wind is at its back, the dog will turn slightly past the turn. Because of these and other factors we spend much time encouraging the competitive tracking dog to utilize primarily the track scent.
The age of the track affects the dog’s performance as well. On a fresh track where there is a great deal of body scent, many dogs do extremely well. (We conjecture that police dogs are often highly effective in following fresh tracks because of the intense aroma emitted by a frightened fugitive.)
Under normal weather conditions the track scent and body scent are approximately equal in intensity at about thirty minutes of age. After that time, however, the track scent begins to dominate.
The amount of time the track retains body and airborne scent varies with the weather and terrain. Any extremes in these conditions can cut down on the tracking dog’s effectiveness, but none of them need totally defeat its ability to perform.
Contrary to popular lore, the shape of the dog’s head has little effect upon its ability to track. Bloodhounds, for example, do not excel in tracking and tailing because of any special anatomical equipment they possess, and theoretically a Boxer has as much absolute ability to detect scent as a German Shepherd. The difference between an outstanding tracking dog and a mediocre one is not physical but behavioral—an innately greater desire to track and a gift for concentrating single-mindedly upon a task for long periods of time.
Therefore, the most critical aspect in the success of a particular dog in tracking appears to be its motivation to track at the time its handler desires. Apathy, lack of concentration and refusal to work are all usually indications of incentive problems rather than an inability to perform. While we cannot easily change the style of a dog’s tracking, we can increase its incentive to do it. A slow tracker can become a slow, methodical worker. An overexuberant tracker can become a controlled, eager worker.
Basically there are three ways of motivating the dog to begin tracking. The most traditional method makes use of what old-time German trainers called the dog’s pack drive—the animal’s desire to be with its master. Because of this desire, when its handler is hidden the dog will actively search him out. Von Stephanitz, and more recently Davis, as well as many police dog trainers have used this approach to training. With a highly motivated dog that has a natural talent for tracking, this method can be highly effective.
For a dog possessing less natural incentive, food often proves helpful. Some Germans do their training with a smelly piece of meat dragged behind the tracklayer to encourage the dog to put its nose to the ground and track. Glen Johnson, a well-known Canadian authority on tracking, uses a food-drop approach to begin all the dogs he trains. He uses the food drops to increase the dog’s motivation to track and to provide a reward for it when it is correct—when the dog is right on top of the track. It is also an excellent way to teach the dog to take scent in each footstep. However, the food drops are not intended to be continued indefinitely. They are eventually phased out.