The training of and science behind
SAR dogs is a quite interesting and well developed field...
Some dogs, like this one, use the
airscenting techniqueto find any living human scent within a search grid.
These dogs generally operate off lead, covering a wide search area in a short period of time. These dogs do not generally require a
scent article (caution PDF) from the missing person. (However, discerning airscent dogs do exist.)
Airscenting dogs run quickly, with their heads in the air, working back and forth as directed, trying to find the
scent cone. As you can visualize, a scent cone is a triangular shaped field of scent dissapation that spreads out along the wind and water from the source of an odor, in this case the human. Once the canine realises she is inside the cone, she works frantically back and forth, pushing forward, as the cone gets narrower and narrower, eventually winding up at the point of origin.
Obviously, issues arise when sudden wind shifts, extreme weather, and elevation change occour within the search grid.
They may operate as far as 1-2 acres ahead of their handler. Some even wear loud
field bells. Once they find their subject, they generally let the person know they've been seen, and return to their handler and perform an alert. Like any detection dog, this can be a
passive alert or an
active alert. The point is that the handler knows, without question, that the dog has found something. "Show me!" and the dog leads the way back to the subject.
Other dogs are tracking or trailing dogs. These dogs operate on-lead, and are generally quite
excited and insane, often yelping, barking, and pooing frequently along the trail. This particular video shows a young dog in the "runaway" stage of training, where the dog physically watches someone run away.
Tracking dogs move quickly too, dragging their handler down the exact path taken by their subject. In many cases, dogs have custom,
hand-tooled harnesses for maximum comfort and safety. Unlike airscenting dogs, they detect the decay of
skin rafts left by the subject. These dogs generally require a scent article and a point of origin, however a well trained dog will find the track of the offered scent within a couple acres fairly quickly. The dog instinctively follows the scent in the correct direction, detecting minute changes in the age of scent to detect direction of travel. Some dogs, like
Bloodhounds , have been specifically bred so that their physiology makes them more adept at their scenting role. You can see the flaps around his mouth, and imagine how they capture scent and direct that scent to the nasal passage. I can't readily find the source outside of the book below, but a bloodhound can have up to 400 million scent receptors, compared to the measly 5 million present in the best human nose. A typical German Shepherd will have approximately 220 million. There is some evidence which suggests that dogs with darker noses have better scenting capacity, but the research is inconclusive.
Cadaver dogs can operate on land or water. These are dogs specifically trained to discover decaying human remains. While it sounds macabre, too many times a missing subject becomes a cadaver search, and families and authorities appreciate having the remains. Cadaver dogs are also used in law enforcement to detect and uncover the bodies of missing persons and murder victims who might have been burned, buried, or otherwise hidden. Interestingly, and perhaps counterintuitively, cadaver dogs are often trained with an active alert, which might involve digging. Mouthing is specifically forbidden, however.
What makes a dogs scenting skill remarkable isn't the volume of smell detected, but rather the ability to discern the individual elements of the odors percieved. This is why a skilled tracking dog will follow 1 trail from a room with dozens of people inside.
Want to learn more? The most widely accepted and generally acknowledged work in this field is
"Scent and the Scenting Dog", by William G. Syrotuck. Alternatively, you can follow the link in the post title to visit NASAR and find a group near you.
This is my first post to the blue, and I apologize for its length. Maybe next time I'll discuss operational command and the role of the Incident Commander, mapping, the ideal search environment, and the motivation of the dogs in question.
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posted by snofoam at 6:46 AM on June 24, 2009