The New York City subway has more than four hundred stations, eight hundred miles of track, six thousand cars, and, on any given weekday, five million passengers. It’s an antiterrorism unit’s nightmare. To sweep this teeming labyrinth for bombs would take an army of explosives experts equipped with chemical detectors. Instead, the city has gone to the dogs. Since 2001, the number of uniformed police has dropped by 17 percent. In that same period, the canine force has nearly doubled. It now has around a hundred dogs, divided among the narcotics, bomb, emergency-response, and transit squads.
A good dog is a natural supersoldier: strong yet acrobatic, fierce yet obedient. It can leap higher than most men and run twice as fast. Its eyes are equipped for night vision, its ears for supersonic hearing, its mouth for subduing the most fractious prey. But its true glory is its nose. In the 1970s, researchers found that dogs could detect even a few particles per million of a substance; in the 1990s, more subtle instruments lowered the threshold to particles per billion; the most recent tests have brought it down to particles per trillion. “It’s a little disheartening, really,” Paul Waggoner, a behavioral scientist at the Canine Detection Research Institute, at Auburn University, in Alabama, told me. “I spent a good six years of my life chasing this idea, only to find that it was all about the limitations of my equipment.”
Just as astonishing, to Waggoner, is a dog’s acuity—the way it can isolate and identify compounds within a scent, like the spices in a soup. Drug smugglers often try to mask the smell of their shipments by packaging them with coffee beans, air fresheners, or sheets of fabric softener. To see if this can fool a dog, Waggoner has flooded his laboratory with different scents, then added minute quantities of heroin or cocaine to the mix. In one case, “the whole damn lab smelled like a Starbucks,” he told me, but the dogs had no trouble homing in on the drug. “They’re just incredible at finding the needle in the haystack.”
The New York police have two kinds of canines: detection dogs and patrol dogs. The former spend most of their time chasing down imaginary threats: terrorist attacks are so rare that the police have to stage simulations, with real explosives, to keep the dogs on their toes. Patrol dogs, on the other hand, have one of the most dangerous jobs in public life. Canine police are often called when a criminal is on the loose, and they’re far more likely than others to have a lethal encounter. “The crimes I get called out on are always in progress,” one officer told me. “The suspects are armed. They’re known to be violent. So, by the mere nature of that call, it’s going to be more dangerous.” He shrugged. “I guess I’m an adrenaline junkie. I got into canines to hunt men.”
The dogs in the Long Island City training facility are heirs to an ancient and bloodthirsty line. Their ancestors, descended from the great mastiffs and sighthounds of Mesopotamia, were used as shock troops by the Assyrians, the Persians, the Babylonians, and the Greeks. (Alexander the Great’s dog, Peritas, is said to have saved his life at Gaugamela by leaping in front of a Persian elephant and biting its lip.) They wrought havoc in the Roman Colosseum, ran with Attila’s hordes, and wore battle armor beside the knights of the Middle Ages. In 1495, when Columbus sailed to what is now the Dominican Republic, he brought Spanish mastiffs almost three feet high at the withers and greyhounds that could run down an enemy and disembowel him.