FRONT ROYAL, Va. -- Abbey loved to play, so much so that her distraught owner gave her to a dog pound. Who, after all, wanted a Chesapeake Bay retriever whose notion of fun was chewing up the curtains?
The U.S. Customs Service did. It recruited Abbey, who otherwise might have been destroyed, and taught her to sniff out illegal drugs. During her three-year tenure at Miami International Airport, Abbey, or more accurately, Abbey's nose has been responsible for more than 155 seizures of smuggled cocaine and heroin, worth $25 million on the street.
How dogs like Abbey can find anything in the confusion of an airport terminal is explained not just by their keen sense of smell, developed over thousands of years of hunting for food and fleeing predators, but also by scientists' increasing understanding of this olfactory ability, and the sophisticated training techniques developed to exploit it.
Looking for a towel
Customs trains its dogs to respond to a variety of odors, all of them associated with a rolled towel saturated with the scent of a pseudo-narcotic. "In their mind, they're looking for the towel," said Tim Spittler, another canine enforcement officer. "They don't think they're looking for narcotics."
The Customs Service recruits about 1,000 dogs a year, 90 percent of which are plucked from animal shelters. Most are Labrador retrievers, golden retreivers and other breeds that are inclined to hunt and fetch and are large enough to jump onto cargo and baggage carousels.
"The dog that sits in front of the fireplace is a dog we can't train," said Spittler, who recruits from animal shelters and kennels in Ohio and Michigan. "We want the dog that wants to play hide and seek."
The affability of the favored breeds, he said, makes them less threatening to travelers. Customs rejects dogs that look aggressive or are spooked by loud noises and sudden movements.
At the Customs Canine Enforcement Training Center in Front Royal, in the rolling foothills of the Appalachian Mountains, the dogs undergo 12 weeks of repetitive training. The first two weeks are largely spent playing with the rolled towel, as the dogs get to know their handlers.
Rewarding the dog
The towel is then doused with a narcotic scent and hidden inside junk cars or in suitcases rotating on a carousel. Whenever the dog finds the towel, it is rewarded with lavish praise and a tug of war that the handler deliberately loses.
"Any time the dog smells the odor, he thinks the towel is here," said Carl A. Newcombe, the director of the training center.
"But we can't make a dog smell," he added. "You've got to create the environment that makes the dog want to do it."
Clearly, dogs use their noses far more than humans. But how much better is a dog's sense of smell?
"Nobody knows," said Dr. Lawrence J. Myers, an associate professor of psychology and pharmacology at Auburn University's College of Veterinary Medicine. "It's going to be different for different odors."
Myers, who has been investigating the sensory abilities of detector dogs since 1982, is convinced their olfactory abilities far outstrip those of humans. But are they "20, a thousand or a million times better? I don't know," he said.
When scientists dissected the nose of a German shepherd, Myers said, they found 20 times as many olfactory receptor cells as in a human nose. These complex sensory organs reside within mucous membranes in the canine nasal cavity and are connected to the brain's olfactory bulb.
Sniffing, he said, increases sensitivity to an odor by widening the dog's nostrils to pull in more air. "A sniff straightens the nasal cavity so the odorant hits straight to the olfactory mucosa," he said.
But Myers seemed more impressed by a dog's ability to sort out scents. "That discrimination capability has to be something phenomenal, because they're doing this task around a lot of contaminating odors," he said.
The customs training center teaches dogs to recognize heroin, cocaine, methamphetamine and marijuana.
"If dogs are trained in all these odors, they can differentiate between them," Newcombe said. "The dog identifies the individual odor. As long as the odor is present, the dog will be able to respond to it."
They respond so well that the training center stopped using detergent to wash the towels used by the dogs for fear they might home in on the laundry of returning travelers.
Some dogs specialize in detecting smuggled United States bank notes by identifying the scent of currency paper and ink at amounts of around $10,000. "We're training the dog on various levels of currency," Newcombe said, adding that the customs service uses shredded money from the Mint in training exercises.
Other dogs learn to sniff out explosives and weapons for the Bureau of Alcohol, Tobacco and Firearms.