Apr 24 2009
Skin Rafts, Vegetation, and Your Trailing Dog
The difference between tracking and trailing is twofold. Part of the difference is in how soon the tracklayer’s scent stuck to the surface covered. Most of the difference is in what the primary source of scent is.
A trailing dog works on stuck-down scent sources, skin rafts primarily, from the human (or other scent source) she is following. She may go up the sides of trees or stones to check for skin rafts caught in bark. She may work quite far from where the person actually walked, depending on the location of the trail. Since nobody can avoid shedding skin rafts, this is a highly effective method for the dog in most situations. However, there’s a big however.
For skin rafts to produce scent, they have to be either extremely fresh from the person or subject to decay from bacterial action. This is where the “A dog can’t follow a trail more than an hour old” line comes from. At an hour, the soil bacteria are still in lag phase, not yet responding to the new food supply of the skin rafts, and the skin bacteria have digested all their metabolisms can digest, becoming largely inert. The trail scent isn’t altogether gone, but it’s at its lowest ebb and will stay low for quite some time.
The tracking dog has a different tool in the toolbox. She’s trained to follow the line of crushed vegetation left by the person walking. Now, this has limitations; the person she’s following may not stay on the grass, for a start. On a newly-mown lot, she may have trouble telling the crushed from the cut. In a heavily-trafficked area, she’s going to need some trailing skills in her tool set to sort out the exact crush pattern of her target. However, the track scent of crushed vegetation is strongest in that one-to-four hour window where the bacteria needed for trailing are least active. Some rafts will be stuck into the footprint for clearer identity of the tracklayer, but primarily what the dog is smelling is plant-based.
The dog who learns to trail first may hit a problem when she first discovers that window. She stops, looks up, looks around, and says to her handler, “Sorry, but I think this person flew away.” In warm weather, when the skin bacteria work fast and fade fast, this moment can be quite dramatic. Dogs who are started on track scent first, on the other hand, tend to get overenthusiastic on their first trailing problems, apparently drunk on this overwhelming quantity of human scent. Once they’re over the first hurrah, though, they become pretty steady workers, and when the trail scent becomes thin, their first impulse is to shove their noses deep in the grass to look for trapped scent there instead of casting about with their heads high. Since skin rafts can blow an amazing distance (which is how air scent dogs are so effective for searching large areas) this is more likely to keep the dog near the trail’s actual line.
Working with Dustin on tracking, I’ve learned a great deal about the plants in my yard. Crushed old pine needles tend to put him off track altogether. Crushed grass, he says, is not at all the same as crushed flowering plant. It’s an imperfect lawn, to understate wildly, and he’s learning a great deal about different scents under the same feet. Going from shade to sun, he sometimes loses focus where the faint residual trail scent is baked away. He’s also beginning to notice the difference in remaining trail scent when the grass is taller or shorter; skin rafts trapped in tall grass can keep smelling fresh for quite some time. At those places, his tail goes higher and his focus improves. The grass smells more like the articles there, and he hopes for more cheese soon. In future, this communication from my dog will be handy on harder tracks, where I may have to help him solve the problem of just where exactly the elusive person might have gone.
