Enter Tucker, a rescue dog who bounds into the scientists’ boat and either stands over the bow with his nose down and pointing toward the slimy scat — or snoozes and then leaps up when his never-dormant nose hits on the poop scent. Tucker’s reward for a find? Playing with his tennis ball.
Tucker’s story is recounted in the new book “Being a Dog: Following the Dog into a World of Smell,” by the prominent canine cognition researcher Alexandra Horowitz. The book is a thorough examination of dogs’ incredible sense of smell, as well Horowitz’s efforts to boost her own olfactory aptitude. In it, she outlines the geography and biology of a dog’s snout and explores the world of detection dogs trained to sniff out explosives, human scent on detonated bombs, missing people, disease — and poop that humans want to find. Horowitz also explains why people cannot smell nearly as well as their pooches (though she did get good enough to catch a whiff of porcupine pee in a snowy forest).
Dogs, she said in an interview, have both anatomical and behavioral advantages over us when it comes to scent. They possess hundreds of millions more olfactory receptor cells of more varied sizes, which means they can sniff out minute quantities and “even the dimensions of smell” might be different to them, Horowitz said. Their oblong snouts warm, humidify, filter and speed air to the olfactory epithelium, a tissue in the nasal cavity where those receptor cells lie, and they have a relatively larger olfactory lobe in their brains.
Dogs also have a “beautiful way of exhaling,” Horowitz said, that pushes air out the side slits of their nostrils without shoving out odors. And then there is what Horowitz calls “the sniff.”
“Our way is not the best way. We sniff maybe once every one-and-a-half seconds, which is not much at all,” she said. “Dogs sniff about five to 10 times every second. So that allows them to get many more odor pictures of the world every second.”
Other animals, such as elephants, have strong senses of smell. What dogs have over them is being highly trainable. For thousands of years, humans have selectively bred dogs to work for us — and to like it. But although all dogs can smell well, Horowitz said, the best detection dogs are “high-drive dogs,” the kind that get so obsessed with a task — in this case, locating their assigned scent — that they cannot be satisfied until they succeed.
“I think of detection dogs really as the anti-pet,” she said. “The dog just will not stop until they find something. If they can’t find it, you have to plant something . . . They’re all the things you try to groom out of pets.”
That is the case with Tucker and his dog colleagues at Conservation Canines in Washington state, whose founder, Sam Wasser, told Horowitz that he selected young mixed-breeds from shelters that may seem uncontrollable but “never run away — because you’ve got their ball.” And it was also true for the “smelling experts” Horowitz visited at the University of Pennsylvania’s Working Dog Center, where litters of roly-poly puppies (often Labs and German or Dutch shepherds) evolve into elite detection dogs that can sniff out missing or dead people, drugs — even a diabetic’s dropping blood sugar — while ignoring other people, pooches or other scents in their path.
“They’re not training the dogs to smell. They can already smell it,” Horowitz said. “They’re training the dogs to tell you when they found it.”
They do this in steps, by learning a scent and being rewarded for alerting to it in increasingly difficult spots. Exactly what these dogs are smelling is in many ways still a mystery, she writes, particularly when it comes to detecting things like cancer — are they smelling diseased tissue, the body’s inflammatory or immunological response to the illness, or ailments that can accompany cancer, such as anxiety?
As for more typical pet dogs, such as the one by your fireplace, they, too, are good smellers, but probably not as good as they are allowed to be. We people, hurrying through our walks, often pull dogs away from the fire hydrants they sniff. We swat the snouts of dogs that lunge for human crotches or canine rear ends. “We cleanse them and our house to get rid of smells, and dogs, they kind of assent to it and start using smell less,” Horowitz said. “They might be smelling perfectly. But they’re not using it to problem solve, to navigate, to use it socially.”
Horowitz observed this in an experiment she carried out at the Dog Cognition Lab at Barnard College, which she runs. She presented 64 regular dogs with plates holding one or five chunks of hot dogs. Dogs will always choose the plate with more hot dog when they can see it, she knew from previous research. But would they do so when they could only smell it?
Nope. When the plates were covered, the dogs chose randomly, despite one plate’s clearly stronger hot dog scent, she said.
But she also observed her own dog, a mutt named Finnegan, relearn to use his sense of smell in a “nosework” training class. In little time at all, he was able to locate neutral scents, such as birch-scented essential oil, in progressively more challenging locations. Horowitz and Finnegan still practice the skill on walks and at home every day, she said, something she recommends to many dog owners.
“He had been a good sniffer before,” she said. “But he wasn’t finding his way by sniff. This has really changed his personality. In this context, he has a huge drive to find something by smell — and he really seems to love it.”