This same dog would go on to nearly blind Coren in one eye the week before we spoke in October 2011. Coren had fallen asleep in his favorite chair. The nine-month-old Ripley, being both a lap dog and a face-licker, took advantage of the moment and, in the process of enthusiastically slathering Coren’s face, got one of his nails lodged in the inner margin of Coren’s left eye. The dog, unable to extract it, used his other paw to press against Coren to dislodge it. When I interviewed him, Coren’s eye had ruptured, the iris and the lens were gone. He’d had two surgeries, with two or three more to go “before they give up,” he said. He takes it in stride. He would have started to go blind in that eye from a progressive eye disorder within a couple of years anyway, so he says the dog just speeded up the process. I wondered if maybe the dog had some sense of his eye problem and was trying to help him, like dogs I have read about who try to chew away cancerous moles. Coren, perhaps not surprisingly, does not give Ripley any accolades as a diagnostician or surgeon.
A handy way a dog’s olfactory sensitivity manifests itself is with something called odor layering. This enables a dog to separate a chosen scent from the “background noise” of all the other scents, much as humans could visually sort a bunch of miscellaneous items spread out on the ground. Dog handlers have variations of analogies for odor layering, and they’re all based on food. Probably the most common: We humans can smell the pizza. A dog can smell the dough, the sauce, the cheese, and all the spices and toppings. A dog might even be able to smell the components of each of those. Not just dough, but flour and yeast. Not just sauce, but tomatoes and basil and oregano. Some handlers and dog trainers use chocolate cake as an example, others use stew. But it all boils down to the fact that dogs have very sensitive noses that are capable of teasing apart scents as you and I could never dream of doing.
As Navy Lieutenant Commander John Gay was driving me to the submarine in Norfolk to see little Lars do his detection work, he told me that even his late boxer, Boris, was adept at odor layering in his heyday. (Boxers are generally not renowned sniffers.) Gay’s wife used to bake all kinds of muffins and cookies, and Boris would show no interest. But when she made a particular kind of cookie that Boris was allowed to eat, he waited eagerly by the oven door, even though she gave no indication the cookies were for him. Oh, and the dog could also smell flies. Flies.
We humans have, not surprisingly, found plenty of ways to put this exquisitely sensitive olfactory apparatus to work in detecting odors of importance to us. Some of them seem nothing but miraculous.
Dogs are proving very adept at sniffing out a variety of cancers, including lung, ovarian, skin, and colon malignancies. Specially trained dogs can predict seizures in those prone to them, or sense dangerous changes in blood sugar levels in diabetics. Dogs can detect pests, including bedbugs and termites. They’ve been used to sniff out cell phones in prisons, oil and gas pipeline leaks, flammable liquid traces in arson investigations, toxic molds, diseases in beehives, and contraband foodstuffs. They can tell when a cow is going into heat. They can even use their noses to find cash. Jake has shown no talent for this I’m afraid.
Former Marine Sergeant Brandon Liebert, whom you may remember from an earlier chapter (his dog, Monty, found six hundred rounds of antiaircraft ammunition), was stationed at Cherry Point, North Carolina, in 2005. One day he sent out a dog team to sweep the convention center in Morehead City prior to a Marine Corps Ball. The team went out on what was a formality. But a few hours later Liebert received a call to say that the dog had responded to something in one part of the convention site. Verification was required. Liebert was the only handler available, so he got Monty and rushed off to investigate.
“When we got to the area of where the other dog had responded, Monty began to circle the room multiple times and then finally stopped in the middle of the room. I asked the handler what his dog did, and the handler stated that his dog had responded on the tables behind me. We got out of the area and informed the local authorities.”
It would later turn out that there had been a Ducks Unlimited show the previous weekend and that there were a lot of guns and ammunition for sale. The vendors had placed the ammunition on tables, and so it was a residual odor the dogs had picked up on. The ball went on as planned.
31
A TOUR OF A DOG’S NOSE
Not all dogs have the same genius for sniffing. Dogs with longer snouts generally have more sensitive noses than dogs with stubby noses, like bulldogs. This is one of the reasons why you will probably never see a pug as a military working dog, unless the military decides it needs something rather amusing-looking to distract the enemy.
Let’s see why size matters. If you have more odor analyzers in your nose, you are going to be more sensitive to smell. We humans have about five million odor receptors in our noses. The area these take up if unfurled would be about the size of a postage stamp. Dogs with long noses have far more of these scent receptors. Dachshunds have 125 million. But German shepherds have 225 million of them. So do beagles, which is pretty amazing considering they’re half the size of shepherds. Bloodhounds have the most, with three hundred million. A bloodhound’s olfactory receptor area is about the size of a handkerchief. (You will not see bloodhounds in the military, though. Doc Hilliard explains that while they have great noses, and can be excellent trackers, most do not retrieve or play with Kongs or balls the way they need to for the training. I wonder if another reason could be that their droopy, drooly countenances don’t seem very “military.”)
Smell is the dominant sense in dogs—even in those with less prominent snouts. From the outer nose (known as a dog’s “leather”) to the brain, a dog’s olfactory system makes ours look like it needs to go back to the manufacturer. (But our eyes have all the grandeur of their noses, so it all works out.)
Here’s a quick look at what happens when a military working dog we’ll call Sam, a German shepherd, sniffs an odor of interest; let’s say ammonium nitrate. Sam is close to a scent, but not sure quite where it is yet. He sniffs more rapidly, so the air coming into his nose is more turbulent and more of it can be distributed onto his olfactory membranes. He can sniff up to twenty times for every exhalation if he’s really interested in a scent. He can even pull a neat trick of inhaling at the same time he exhales. And he can move his nostrils independently, which helps him figure out just where a scent is coming from. When Sam thinks that he may be quite near the source, he will sniff more deeply, actively drawing air over the source to confirm its location. At this point he may even be able to compare the concentration of odor between left and right nostrils, which will both confirm that the source is nearby and further help to pinpoint its location.
As he sniffs, scent molecules stick to the moisture on Sam’s nose. (The moisture is actually mucus, which helps snortle the molecules all the way through the olfaction process.) Scent molecules dissolve in the mucus, and the sniffing carries them into the nose, to two bony plates called turbinates. This is the home of those millions of scent-detecting cells discussed earlier.
Adding to Sam’s nasal prowess is a body part that doesn’t seem to exist in any functional form in humans: an extra olfactory chamber known as the vomeronasal organ, aka Jacobson’s organ. It’s located above the roof of a dog’s mouth, just behind the upper incisors. It has ducts that open to the nose and mouth so scent molecules can be processed. Most mammals and reptiles have a vomeronasal organ. It’s used primarily to detect pheromones (not terribly helpful for Sam on the job), but some scientists think it may have other functions we’re not yet aware of.
The brains of dogs and people and most vertebrates contain two structures called olfactory bulbs, which help us decode smells. The olfactory bulbs of dogs are about four times as big as those of people, despite the fact that dogs’ brains are far smaller than ours. Between this and his 225 million scent receptors, Sam is able to find the ammonium nitrate quickly. He sits, stares, and is called back by his handler, who gives him his cherished Kong and praises him up
like mad.
All in a day’s work for a good nose.
Oh, and lest you think it’s all about sniffing and letting nature take it from there, a dog also has to do a great deal of legwork to locate an odor. Bradshaw explains that a dog’s first strategy is to run cross-wind to figure out whether or not he is directly downwind of the source. But wind spreads scent in unpredictable ways, so this may not be very informative. If the scent is continuous, the source must be very close by, so the wind direction is an unreliable clue, and visual cues may provide the best indication of the source. If the scent is discontinuous, its source is probably some distance away, so the dog will briefly switch to proceeding upwind; if the scent is quickly lost, he will switch back to running cross-wind to try to position himself more precisely in the odor “corridor.” Then, switching between upwind and cross-wind running will bring the dog, somewhat crabwise, to within close range of the source.
But what if the scent itself is moving?
32
A CLOUD OF SCURF
In the silence of the vast desert, you can hear the chop-chop of the marine UH-1 helicopter (aka a Huey) approaching for miles. It comes near and veers suddenly, looping in quick semi-amusement-park fashion, circles overhead again, and descends. As it nears the ground, a fast-moving cloud of dust and tiny pebbles races toward Gunny Knight and me, dinging my camera lens and making it impossible to keep our eyes open for the next several seconds.
The air remains thick with dust when out of the helicopter, whose rotors are still churning, run a dog and handler, followed by another dog team. The handlers hunch forward slightly as they run, to better protect themselves from the churning sand and air. They race off into the distance, then stop. The dogs sniff the ground with great interest, but just then the helicopter lifts off, and we lose sight of everything again.
Gunny and I catch up with these teams, and a few others, while they’re resting up after having tracked a “bad guy” varying distances at the Yuma Proving Ground. The dogs are combat tracker dogs. While explosives dogs find bombs, these dogs find the people who plant them. (In friendly operations, they can track down lost people.) The dogs here today are training for real-life combat missions, which often involve these rapid helicopter drops. The dogs need to get used to these so they’re ready when they deploy.
One of the dogs was so scared of the helicopter this day that he put the brakes on as he approached it and had to be nearly carried aboard. He spent the ride with his head tucked firmly into the crotch of his handler, who had to move her rifle to make room for him. (Once off the helicopter, though, he tracked his man beautifully, I’m told.) Most dogs stayed very close to their handlers, and hunkered down and strapped in, for the ride. One veteran dog took in the view from the helicopter’s edge while firmly grasped by his handler.
These dogs are trained to track human odor over distances. They pick up a scent where a handler “suggests” (near an IED, for instance, or the last place an insurgent stood) and follow it. Tracks can be miles long and hours—or even days—old. Recall James Earl Ray, who broke out of a Tennessee prison in 1977 and was pursued by sister bloodhounds named Sandy and Little Red. They started their manhunt days after his escape, but within a few hours they had found him a mere three miles away. (Now there are a couple of hound dogs who could do the job.)
Tracking dogs keep their heads down and follow the scent on the ground. The track is a combination of human scent and crushed vegetation or stirred-up dirt or sand. Disturbed environments, like crushed grass (the grass “bleeds,” in a sense), give off unique smells. But nothing as unique as the smell of the person being pursued.
You may think that if you shower well and wear deodorant, you smell like just about everyone else out there. But our individual scent fingerprints are unique. As Horowitz says, “To our dogs, we are our scent.”
Anyone who is thinking of outwitting a tracking dog one day should read what she has to say about our scents:
Humans stink. The human armpit is one of the most profound sources of odor produced by any animal; our breath is a confusing melody of smells; our genitals reek. The organ that covers our body—our skin—is itself covered in sweat and sebaceous glands, which are regularly churning out fluid and oils holding our particular brand of scent. When we touch objects, we leave a bit of ourselves on them; a slough of skin, with its clutch of bacteria steadily munching and excreting away. This is our smell, our signature odor.
Coren likens our shedding skin cells to the Peanuts character Pigpen, who always has a visible billow of dirt around him. It seems humans have the same billow, only it’s made up of skin cells, which when in this flake form are known as rafts or scurf. We shed fifty million skin cells each minute. That’s a lot of scurf. “They fall like microscopic snowflakes,” Coren says. Thankfully, we can’t see this winter wonderland ourselves. But these rafts or scurf, with their biological richness, including the bacteria that sheds with them, are very “visible” to dogs’ noses.
Where a dog begins on a track is naturally where the scent is weakest, because it’s been there longest. As the track progresses in the right direction, the scent should get stronger. The increasing strength of a track is something dogs rely on. “They start at the farthest point in the past and work their way up, we hope, to the present moment, where they find who they’re tracking,” says Marine Corporal Wesley Gerwin, course chief/instructor supervisor for the combat tracker course. “It’s sort of like a dog’s version of time travel.”
Dry heat and ultraviolet light can cause a track to disintegrate quickly. Moisture and lack of sun help preserve tracks. Even if someone tries to throw a dog off the scent by going through a stream or river, there’s still likely to be a track. In most cases, if the dog is not too far behind, the water will not erase the scent. In fact, breezes can waft a person’s scent to a moist riverbank, where it can remain for a long time. (If a river is flowing very quickly and is relatively shallow, though, the scent dissipates far more swiftly.)
There aren’t many combat tracking dogs in the military. The numbers are in the low dozens, but security concerns preclude a more precise count. CTD handlers have to have been military working dog handlers for a minimum of a year; they then spend six additional weeks in a CTD course—four weeks at Lackland, two weeks at Yuma. The dogs are trained as combat trackers from the start. They begin tracking at distances of a foot or two (a second or two old) and work their way up. The oldest recorded track since the CTD program started in its most recent incarnation a few years ago is seventy-two hours, in Al Anbar Province, Iraq. Gerwin says he’s heard talk of a track up to five days old, but it’s not official.
33
DOG SENSE
In addition to their stellar noses, combat tracking dogs, like all military dogs, rely on other senses to do their jobs. Phenomenal as their noses are, soldier dogs can’t go purely by scent. A combat tracker, for instance, will use his eyes and ears to pinpoint his target as he approaches it. Patrol dogs depend a great deal on hearing and eyesight as well, especially when it comes to detecting the subtle movements or sounds of a suspect.
Like their noses, dogs’ ears are significantly more sensitive than ours, especially at high frequencies. “Dogs would describe us as having high-frequency deafness,” writes Bradshaw in his book Dog Sense. In the Pacific Islands during World War II, soldier dogs could sometimes detect the thin wires on booby traps by the very high-pitched whine produced when air moved over them. Some dogs ended up being trained in just this sort of sound detection. (The sound was utterly inaudible to any humans nearby.)
Canine ears have a reputation of being able to hear sounds up to four times farther than ours can. The mobility of their ears plays a role in helping locate and focus on sounds. As anyone who has ever watched a dog listen to something of great interest will tell you, a dog’s ears almost seem to have minds of their own. It’s no wonder: Dogs have about eighteen muscles helping them swivel and tilt their ears in response to sound. It’s pretty en
dearing to watch. Jake is adept at this ear maneuver whenever he begs for food or sits in the backyard listening for the cat.
Dogs have poor color vision compared to ours, decent night vision, and generally see a wider picture than we do because of the placement of their eyes. But how a dog sees the world is highly dependent on what a dog looks like. Dogs with longer noses, like most military working dogs, tend to have more photoreceptors crowded together in a horizontal streak across the eye. This “visual streak,” as it’s called, makes for better panoramic vision, with a field of vision that extends up to about 240 degrees (as opposed to our full frontal 180). Dogs with this kind of vision can even have some awareness of what’s going on behind them. But don’t ask them to focus on anything closer than ten to fifteen inches in front of their noses. Their eyes aren’t set up for that kind of vision. Dogs with shorter noses likely do better with closer vision. Their vision cells are packed in more of a circular shape, making for a narrower field of vision and more visual acuity up front.
This may explain why retrievers retrieve and lapdogs, with their big forward-looking eyes and their small snouts, like to sit on your lap and look at you.
Scientists are continuing to investigate the eyes, ears, and noses of dogs. And beyond the realm of these senses, they’re reaching out to get to know more about dog psychology, including how dogs think, feel, solve problems, and why they behave the way they do. Canine cognition is a relatively new field that’s burgeoning with enthusiastic scientists eager to plumb dogs’ minds for things we’ve wondered about but never explored before.
34
PLUMBING A DOG’S MIND
The heart of the Duke Canine Cognition Center is the dog lab. Unlike many laboratories that use dogs as guinea pigs for research, there is no pain in this lab. There aren’t even cages. In fact, the lab looks like a small dance studio. The white floor is striped with an assortment of tape colors; red, green, yellow, and blue. The dogs who come here enter with their owners, stay within feet of their owners, leave with their owners, and inevitably get treats and lots of attention during the studies. It’s Center Director Brian Hare’s idea of “an awesome place to learn about dogs.”
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