Written by Michael Pumilia
I have discussed a human’s scent in Part 3 and the dog’s nose in Part 4. That’s two parts of this scenario that makes up this sport called Tracking. The next part is the tracklayer. That is who the dog is meant to follow. You as the handler get to follow the dog. That’s right, you plod behind the dog. I introduced FRED, the “Fairly Reliable Emission Device”, in Part 3. Now I’m going to explain how Fred creates the track in detail.
Fred represents the typical person and is surrounded by his molecules of scent flakes. The shape of the distribution is a bell curve. You might remember from your schooling “being graded on the curve”. Figure 1 shows this curve. We are viewing the skin flakes that the tracklayer has shedded in a instant of time. This is just a snapshot of what is going on. To better understand how a track is created, I’m going to use the curve in a different manner.
Figure 1. Typical Scent Distribution of a Person
The snapshot of Fred in Figure 2 is changed so that we see the intensity of the scent as it decreases by the distance from the centerline of where he is standing. This particular view assumes the wind is not blowing. The centerline is at zero feet on the horizontal axis. The distance shown is theoretical as is the intensity; I’m showing what Fred’s scent would do. Each person on a given day may have a different strength of odor. The intensity depends on what makes up the scent that day. A person could have freshly showered or applied cologne, deodorant or used a cleaning product in the kitchen prior to leaving. There are many variables. The distance each odorant travels from the centerline depends on its volatility. Your skin flakes are different than liquid bleach which is different than ammonia. Each of these travels at a different speed. Also the wind speed affects how far the scents will travel. Even the pace that Fred uses to travel across the field affects the spread of his scent. So we have two ways to consider Fred’s bell curve of scent distribution and its effect on the dog.
Figure 2. Scent Intensity v.s. Distribution from a Centerline
The vertical axis is the Intensity of the scent. I’ve divided the area under the curve to highlight certain aspects related to various dogs. Figure 3 shows a variety of dogs and where they fall on the bell curve. A Good Tracking Dog needs a high amount of scent intensity in order for it to locate and follow a particular track. When the scent level falls below this intensity, the dog will “lose” the track. The Better Tracking Dog is one with more experience for tracking or could have a better nose than the Good Tracking Dog under consideration. It can follow a given track further than the Good Dog or a track that is older. The Best Tracking Dog requires very little scent in order to find the odorant and follow it. This track could be much older than any other tracks that the Better Dog could follow, even days older. For each type of dog, you see that the track spreads out based on intensity of scent. The lower the amount of scent is, the wider it is found on the ground. In the figure, we are in a no-wind situation so the scent is evenly spread around Fred. See figure 4.
Scent intensity decreases as time passes. The lighter-than-air scent molecules will have blown away after about 30 minutes. The intensity will be so low that only extremely talented dogs would be able to find them. See figure 5.
The skin flakes are heavier than air so they fall around the human as shown in these figures which are no wind conditions. Fred represents the average human. The scent distribution bell curve does change for certain situations. For example, the average tracklayer is not wearing a heavy jacket, waterproof boots, gloves and hat, and cold weather pants or coveralls. You probably recognize this as a Winter scene. This bell curve then would be thinner and not as tall because so much off the odorants would not escape the garments. A Summer day means short sleeve shirts and shorts and perhaps light weight sneakers. So plenty of skin flakes would be spread around and a sweaty condition would mean heavier flakes due to perspiration. The bell curve would be huge with greater intensity and greater spread of the molecules around Fred.
Figure 3. Scent Intensity Identifies Different Types of Tracking Dogs
Figure 4. Scent Disribution in a No-Wind Situation
Figure 5. Approximate Result as Time Goes By
There is a second way to look at the scent distribution. Instead of using the y-axis (scent intensity), I’ll use the x-axis which is distribution from the center of Fred. As Fred moves forward in this no-wind condition, his scent distribution will move forward with him. There is very little wind disturbance of the skin flakes leaving Fred, no upwind or downwind effect. See figure 6. There are eddy wakes of scent molecules created by Fred’s pace.
Figure 6. Fred’s Scent Molecules Create a Wake in a No Wind Condition
In any snapshot of time, the scent distribution bell curve seen in figure 2 can be pictured along the path that Fred walks. Remember that he is the tracklayer. This is how the track is built figuratively to the dog’s nose. See figure 7.
Figure 7. Scent Distribution Along the Track with No Wind
The width of the track is determined by the experience of each type of tracking dog shown in figure 3. Figure 8 shows how you should consider the track in your mind. For any given dog they usually follow the track in one of two ways – straight line or weaving. A dog that is considered a straight line tracker means it tends to follow right down the centerline of the scent path. Notice I didn’t say centerline of the track. In a no wind situation the two centerlines (track and scent path) fall on each other. If there is a wind, the scent path is not necessarily centered on the track. The track is where the tracklayer walked, the scent path is where his scent landed.
I have a wonderful example to explain this. The late Dr. Arnold Korn had one of his Dachshunds entered in a tracking test I was judging in Memphis, TN. The site was a sod farm where the grass was perfect and cut to 1/8th of an inch. It was like a billiard table. Arnold had the first track in the morning. The weather was cloudy, the ground was damp and there was a slight wind. The first leg of the track turned out to be straight into the wind. So the dog was moving straight along where the tracklayer walked. The second leg turned 90 degrees to the right. The dog took the turn about 2 feet before the track turned. The other judge and I got into position so we could see the length of the leg. There before us we could see Dr. Korn’s footstep’s to the left of the tracklayer’s and 2 feet to the right of the tracklayer’s were the dog’s steps.
Figure 8. Scent Distribution Along a Track
We saw three perfectly parallel lines of steps in the dew. At the turn, the track went left. All three lines merged into one as the track went into the wind.
A dog that weaves along a track is one that moves from side to side as it follows along the track. Sometimes the dog will go to the edge of where it loses the scent and then turn back towards the centerline. In figure 8, the better tracking dog would go from one green line then across the black centerline to the other green line, all while moving forward. Or it could be a dog that favors a certain amount of scent intensity to be its imaginary edge, meaning it would not go all the way to the minimum scent strength shown by the green lines. This dog’ weaving path would be narrower than the dog that goes all the way from the minimum to minimum.
A weaving dog runs a greater risk to miss a corner than does the straight tracking dog. The problem is where the weaver is located when the turn comes up and whether it’s a uphill or down hill track and how much of a cross wind is involved. I’ll talk more about this when I’m discussing “turns” training.