Dogs vs. Machine for Detecting Explosives

Nose to nose, when it comes to portability, dogs win

"If the dog is not here," says Falzon, "this is an excellent replacement."

His comment is telling.

Even at Toronto's state-of-the-art airport, machines haven't completely replaced dogs.

Checking for illegal foods that might carry foot-and-mouth disease, avian flu, mad-cow or any number of insect or microbiological pests falls squarely on the tiny shoulders of the CBSA's corps of beagles.

Drug, firearm and currency dogs patrol the agency's warehouses, the international postal facility and the airport. It's all part of a long tradition.

"Dogs have been used for hundreds, possibly thousands, of years to track animals and track men. It's a very short way to go to check for specific substances," says Stanley Coren, a professor of psychology at the University of British Columbia who has written a bestselling series of books on dogs, most recently How Dogs Think What the World Looks Like to Them and Why They Act the Way They Do.

"For dogs, the sense of smell is really what the sense of vision is for human beings. It's their most important single sense," Coren says.

Dogs have 300 million olfactory cells in their noses, while humans have 5 million, Coren explains. And the part of the brain processing smell is 40 times larger in dogs than in people.

Detector dogs have shut out machines for a lot of police work.

On "common detector dog day" at the Air Canada Centre, canine teams from Toronto's police dog services are taking turns practising their skills. The dogs specialize in drugs, firearms, explosives or cadavers.

Their officers work different shifts, but once every three months Sgt. Paul Caissie gathers them to train together. Caissie's own floppy-eared sidekick, Bandit, is a drug dog. "Most people look at my little springer spaniel and say, 'That's a police dog?' "

But the choice wasn't random. Bandit is compact and able to search small spaces. His cuteness helps, too. Offenders searched by Bandit have a hard time convincing the court that excessive force was used.

Const. John Gerrits strides down the fifth-floor hallway of the ACC. Alongside him is Buster, a yellow Labrador retriever trained to detect gunpowder and drugs such as heroin, hash and ecstasy.

Gerrits dons a pair of leather gloves as Buster looks on expectantly, his tail wagging in anticipation. Gerrits leads him by a leash onto a series of balconies overlooking the stadium floor.

"Come, come, come," the strapping officer urges in the high, lilting voice that people use with babies. Buster's nose sweeps to and fro and so does his tail, only faster. Gerrits directs him, moving chairs out of the way, until Buster pauses at a damaged part of the wall, sniffing intently. He sits down and scratches at it. That's where a bag of white powder has been concealed.

Caissie tosses Buster a small knot of towel, his favourite toy. The dog leaps and rolls, pawing and gnawing at the toy, his wagging tail a blur.

"A machine could not do what we (police dog services) do now," Caissie says firmly.

A machine can't subdue a suspect, for instance.

"When you find him, then what?" Caissie asks.

Though the police use dogs to hunt for bullet casings, forensics specialists use metal detectors. Those turn up various metal objects, Caissie says, "but I've never seen them find what they're looking for."

There are things dogs can't do. For instance, the Ionscan identifies substances while most detector dogs respond the same way to gunpowder and crack cocaine.

And dogs can only detect substances that release a vapour, says Ulli Krull, a professor of chemistry at the University of Toronto in Mississauga who does research and teaches on biosensors.

Machines, he says, can detect compounds that don't "smell."

"A dog has to go to the bathroom. A dog is distracted. A dog can only work for an hour or two before it needs a rest," Krull adds. "I've never seen one of these instruments sit down and say, 'Aw, give me a coffee break.'"

But Coren says dogs trump technology in significant ways. First, they do what's called gradient detection - they can lead you to the source of a scent.