The Dog’s Nose Knows

Dogs “see” the world through their noses. My first direct experience with this almost mystical ability came early in my zoo career. Those were the days when my wife insisted that I disrobe in the laundry room and jump in the shower when I got home from work. It was not because of some unknown contagion, as with today’s medical professionals. It was because—not to put too fine a point on it—I often stank.

Simba, the guard dog

One evening when I was leaning against the washing machine, exhausted from a day of manhandling a herd of antelope for a medical procedure, my dog Simba—a big brown rescue-dog of unknown lineage—wandered in wagging her stump of a tail. She licked me on the hand, sniffed my leg, and snarled at my pants as she jumped back barking. Simba was warning me of unseen danger in our midst.

For humans, smell is often considered our least important sense. I didn’t smell anything on this particular evening, but Simba sure did. After nearly half a century of working with animals in zoos, I have become desensitized to smells. During my career, I have shoveled wheelbarrows full of elephant poop, hosed urine-soaked tiger cages, and had angry chimpanzees splatter me with their feces. After a while, I just learned to turn off my smeller. My wife also overcame her aversion to animal aromas. She helped foster a baby gorilla when I was deputy director of the Toledo Zoo and thirty years later, she still remembers the strong, earthy, old-fruit smell of the gorillas.

Karen and baby gorilla, August 1999

It was, I suppose, not that difficult for me to block certain smells since the human sense of smell is somewhat rudimentary. The inside of our nose is lined with specialized tissue which can receive air-born molecules that our brains process as scents. The tissue inside a human nose is covered with five or six million receptor sites, all clustered in one spot at the back of our nasal cavity. That might sound impressive until we consider that a dog’s nose has forty times as many receptors—two or three-hundred million. They line the entire internal surface of the dog’s nose from the nostrils to the back of the throat. In addition, the dog’s brain devotes much more capacity to processing those smells. The smell experience for a dog is exponentially more acute than ours. Simba had never seen an antelope, but she knew that whatever she smelled on my pants did not belong in her house.

We humans have recognized the power of a dog’s nose for millennia. A third-century scholar, for example, mentions “a hound of unrivaled scenting powers, so intensely devoted to his work that he could not be pulled off the trail until his quarry was found.” Perhaps this was an early version of the modern bloodhound.

According to the American Kennel Club, bloodhounds as we know them were perfected in Western Europe about a thousand years ago. During the centuries since, they have earned a reputation as trackers without equal. Police departments around the world have relied on bloodhounds to follow the scent of criminals, lost children, and confused seniors. But we have come to learn that the dog’s ability to identify a scent may be less about the breed and more about desire and training. Dogs can not only sniff out a quail in deep grass or follow the days old trail of an escaped outlaw. Dogs can also be trained to detect drugs, explosives, and even cancer. What if they could detect the coronavirus? Well, perhaps they can.

According to recent news reports, dogs have, in fact, been trained to detect COVID-19 by sniffing human sweat. European airports have been using dogs for months and, in January, Florida International University announced it would be using dogs to scan classrooms and labs for traces of coronavirus. That same month, the Miami Heat basketball team had COVID-19 detection dogs sniffing its fans as they entered the arena for a game.

Science tells us that a scent is a chemical particle that floats in through the nose and is processed into a form that’s readable by the brain. Brain cells then carry that information to the amygdala—the same area of the brain that processes emotions—before taking it to the adjoining hippocampus, where learning and memory formation take place.

Scents are the only sensations that travel a direct path to the emotional and memory centers of the brain. That results in an intimate connection between emotions, memories and scents. Perhaps that is why we can use specific scents to sell. Realtors have suggested sellers bake cookies just before a home showing. Bakeries have been known to exhaust the smell of cinnamon buns baking in the oven to entice customers into the store. And this is why memories triggered by scents (as opposed to other senses) are experienced as more emotional and more evocative. A familiar but long-forgotten scent can even bring people to tears.

When I worked with elephants, I discovered a scent so strong that I brought it home infused into my clothing and hair. Even a long, hot shower sometimes failed to rinse it off. Elephant smell was best described by John M. Kelley, of the Ringling Bros. and Barnum & Bailey Circus when he said:

“You cannot see it or feel it, yet it clings like a mother’s love. Its vaporized essence is so real that you cannot dilute it, dissolve it, liquify it, freeze it, smother it, counterfeit it, cut it, shake it, or lose it. Elephant smell is the fourth dimension.”

When I am driving the mule wagon on a quail hunt, my passengers spend the day watching dogs use their sensitive noses to sniff out tiny birds in acres of deep grass. In contrast, when the mules a few feet in front of us defecate, the pungent earthy smell barely registers with we humans. It is the sight of what they are doing, not the smell, that causes us to recoil. But let an over-excited hunting dog poop in the wagon box behind us and our threshold for smelling kicks into high gear. That’s a “vaporized essence” that triggers some evocative emotions—emotions that have all of us on the wagon ready to abandon ship.

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