Modem military and police organizations worldwide use dogs trained in scent work to locate narcotics, weapons and bombs. In America, hundreds of law enforcement agencies employ police service dogs. Every night in cities and towns all over the United States criminals hoping to escape detection are found and apprehended through the scenting powers of police K-9s.
Officer Jack Lennig of the Lakewood, Colorado, police department shared two of his favorite nose-work stories with us: The first occurred one night while Officer Lennig was cruising his beat. He saw a young man in an alley who fled the moment he saw the police car, disappearing into the rabbit warren of alleys and lots behind a major red-light district. On the assumption that anyone who ran like that had something to hide, Officer Lennig started his dog Beau on the man’s track. The animal led him perhaps a quarter of a mile through backyards and trash-choked lots, and across a four-lane highway. Finally, Beau turned a comer onto a major thoroughfare and followed the sidewalk a short distance to the door of a bar. Officer Lennig went inside and described the man to the bartender, who said that the fugitive had just been there and bought a drink, but left by the back door without finishing it. Officer Lennig started his dog again out back, and another quarter of a mile of alleys and asphalt parking lots later, the dog led him to the front door of a residence. The officer knocked at the door and the suspect answered it, protesting that he had been asleep in bed and hadn’t been out all night. Officer Lennig made a call on the radio, found that the man had several outstanding warrants and arrested him on the spot.
A more violent situation involved a woman walking home from work. A man jumped out of the bushes, dragged her to a nearby field and raped and robbed her, taking her diamond ring off her finger. Panicked by her screams, he pitched the ring into the field and ran off. The woman managed to flag down a Lakewood policeman and they returned with a K-9 unit to the field. The dog tracked the suspect down, finding him hiding in his nearby home. Then the dog was cast out into the field to search for any additional evidence. Unbelievably, after a few minutes of intense searching, the dog returned to its handler and spat out the diamond ring that had been lodged deep in the grass of the field.
Officer Lennig has enough anecdotes of this sort to fill a book of his own. Like any experienced K-9 officer, he is absolutely convinced of the value of a good scenting dog in law enforcement.
Officer Kenny Mathias of the Raleigh, North Carolina, police department, an authority on the subject, told us how a Dutch police tracking dog solved the famous Heineken kidnapping in Holland, in which a member of this wealthy beer-brewing family was abducted. When the kidnapping vehicle was found, the police still had no suspect. So they laid a piece of gauze on the driver’s seat of the car, left it there for twenty-four hours, and then sealed it in a jar. The gauze rested in the jar for two years while investigators developed a suspect. The Dutch police then performed a scent lineup, in which the suspect and four others impregnated sections of steel pipe with their scent, and the dog compared the scent of the gauze with that of the pipes. The dog matched the suspect’s pipe with the gauze and, confronted with the evidence, the man confessed to the kidnapping.
This anecdote amazes the authors and probably the reader as well. Two additional pieces of information are equally remarkable.
Glen Johnson, a well-known expert on tracking, trained dogs to search out gas leaks on the Canadian pipeline. One of his dogs detected a wooden clothespin impregnated with gas odorant (used for training) that had lain buried underground for three weeks. The chemistry department of the University of Windsor, where Johnson teaches, estimated the odorant remaining on the clothespin at less than one part per trillion.
Search and rescue dogs are sometimes used on searches for victims of drowning. The animals are rowed back and forth across the water in small boats, and indicate their finds over the side. These dogs have discovered bodies in dozens of feet of water.
The inevitable question that arises is: How do the dogs do it? The authors have no idea how they do it, and we note with some amusement that the experts in olfaction do not know either. In fact, the physiological basis of scenting is simply not fully understood. Scientists are amazed at the diversity and the sensitivity of even the human nose.
Unlike taste, which is divisible into only four modalities (sweet, sour, salty, bitter), many thousands of different odors can be distinguished by people who are trained in this capacity. …The extreme sensitivity of olfaction is possibly as amazing as its diversity—at maximum sensitivity, only one odorant molecule is needed to excite an olfactory receptor. (Stuart Fox, Human Physiology, 2nd edition. Dubuque, Iowa: William Brown Publications, 1987.)
Fox makes these comments in relation only to the human nose. We can only guess at the rich experience of the world that a dog’s nose gives it, because a dog’s nose is so different from a human’s. A human being’s nose contains approximately five million olfactory receptor cells dispersed across about one square inch of area. In contrast, the average German Shepherd Dog possesses approximately 150 million olfactory receptor cells distributed in about six square inches of nasal epithelium (Pearsall and Verbruggen, 1982).
Not only is the nature of the dog’s “smell” experience different from ours, but it is behaviorally far more significant to it. In humans, primates who began eons ago as tree dwellers, the primary aims of behavior are accomplished visually. Primates use their eyes to locate food, avoid contact with predators and motivate sexual activity, whereas dogs rely to a great extent upon their noses for the same purposes. Yet a human can differentiate among some 4,000 different odors (Pearsall and Verbruggen, 1982). Only our observations of scent-detection dogs give us any conception of the unimaginable abilities of a dog in this realm.
Since the exact physiological mechanism of olfaction is unknown, much of the process of tracking is still a mystery to us. We are not exactly certain what it is that the dog follows when it tracks a human. According to Pearsall and Verbruggen in Scent, a track is:
the imprint we leave whether traveling through a room, a field or over a road. The track is influenced by such variables as wind, temperature, humidity, rain, snow, terrain, grasses and trees. Our track also is affected by the immense variety of living creatures that share the world with us.
There appear to be two ways that a dog is able to follow a track. First, it can follow the body scent. This scent is the unique aroma that each person or animal emits. The components of this unique aroma in part include skin particles, perspiration, oils and gases and also, in animals, scent glands. This scent follows the individuals and is carried in the air currents around where they have walked. Noted obedience and tracking trainer Milo Pearsall describes scent as “slightly-heavier-than-air gas, very easily blown about by the wind, yet sticking tenaciously in part to everything it touches.” Some of this odor settles in a corridor around the footsteps while another part remains airborne.