In this article:
- How do dog noses work?
- Why do dogs sniff the way they do?
- How good is a dog’s sense of smell?
- Do some dogs have a better sense of smell than others?
- How do I give my dog smell-based enrichment?
- How do I keep my dog’s nose healthy?
In 2016, Matthew Staymates built an artificial dog nose. The nasal engineering project had a practical purpose: improving chemical detection technology.
“The dog is the gold standard in chemical detection,” said Staymates, a mechanical engineer and fluid dynamicist at the National Institute of Standards and Technology. Fluid dynamicists study the way liquids and gasses move. Staymates and his team published a paper on their faux snoot, modeled after a female Labrador retriever’s, in the journal Scientific Reports.
Staymates and his team turned to dogs for inspiration because of their keen sense of smell. Humans’ best friends are highly skilled sniffers, and we have been able to harness that ability for our own benefit. Some service dogs, for example, are trained to sense when somebody is about to have a seizure and help them safely prepare; others can aid medical diagnosis by detecting the scent of cancer cells.
Here are the details on what makes dogs’ noses so astounding—and why, when it comes to their olfactory powers, nothing beats the real thing.
How do dog noses work?
A dog’s nose boasts some astonishing features.
The design of the nose and the whole nasal cavity—the space inside and behind the nose—improves how dogs sniff up information. The nasal cavity includes a dedicated pathway for air intended just for smelling: Some of the air a dog inhales goes down one path to their lungs, and some flows up to a maze-like area deep in their skull called the olfactory recess. Even after the dog exhales, some air from that breath remains. This way, the scent compounds in that breath have “more opportunity to potentially bind with olfactory receptors,” which line the olfactory recess, so the dog can discern more information about that scent before the remaining air gets exhaled, said Nathaniel Hall, PhD, associate professor of companion animal science at Texas Tech University and director of the Canine Olfaction Research and Education Lab.
These receptors connect to a part of the brain called the olfactory bulb, which interprets aromatic information. This connection between the olfactory receptors and bulb is critical to understanding scent. “The nose does the initial sensing and sampling of odorants in the environment, which dogs can do much more accurately and efficiently than many other species,” said Lucia Lazarowski, PhD, research assistant professor and scientist of canine performance sciences at Auburn University’s College of Veterinary Medicine, “but their brain processes and interprets the identity, significance, and relevance of the odor.” She added that dogs use odor to form cognitive representations of objects—meaning that the way something smells helps them visualize it in their mind.
The slits on either side of a dog’s nose also contribute to their fantastic sense of smell. These slits play an important role in maximizing the amount of air inhaled, so the dog can smell as much as possible. When the dog exhales, the slits get smaller, shooting out a brief, potent air jet. This turbulent jet stream manipulates nearby air, stirring it up and then pulling it in with an inhale—so they’re able to pull more aroma back toward themselves.
Dogs are stereo sniffers—they can distinguish whether a scent was hoovered up in their left or right nostril, or which direction it’s stronger in. “This is why you see dogs, especially scent-following dogs, track left and right,” Staymates said. “They head one way, but then they stop and recalibrate. What they’re doing is determining left from right.”
Dogs also have a sense organ called the Jacobson’s organ (aka the vomeronasal organ) located in the roof of the mouth. Dr. Hall explained that this organ is part of why dogs can tell, just from sniffing a fire hydrant, who else peed there: They can detect the chemical cues, known as pheromones, left in a specific place. Compounds in the urine give the dog biologically important information, such as whether the other dog was in heat. And its potency tells them how long ago that other dog passed by.
Why do dogs sniff the way they do?
If you want to take a whiff of something, you might take one long inhale. Dogs, on the other hand, rapidly alternate between inhaling and exhaling—five times per second on average, to be exact, according to Staymates. This method results in a process fluid dynamicists call “entrainment.”
Watch entrainment in action in the video below. Staymates 3D printed a model dog nose, on the right, to simulate sniffing. On the left, a box emits a vapor. Between the box and the nose, you can see the vapor’s motion as the nose sniffs. The nose is able to more efficiently suck up the vapor through entrainment by creating an air current that pulls the vapor toward itself.
In the video below, you can see the model nose on the bottom left. When it’s simply “inhaling,” the swirling vapors drift all around; but when it’s “sniffing,” it manipulates the vapors to create an air current that pulls more of the odor in. This happens because as the artificial nose “exhales,” it creates two turbulent jet streams of air that stir up the vapors around it in an air current that flows back toward the nose on the “inhale.” These jet streams mirror those created by the slits in a dog’s nose.
Staymates created this model nose in 2016 to improve upon existing commercial vapor detectors that pick up certain chemical compounds in the air. He found that a dog-nose-inspired design was much more effective than what was already on the market. “The dog is this active aerodynamic sampling system,” Staymates said. “They’re reaching out and grabbing odor from extended distances.”
Copying designs found in nature and applying them to new technology is called biomimicry, and the novel detector Staymates and his team created is a textbook case of scientists imitating nature.
How good is a dog’s sense of smell?
You may have heard some astonishing figures illustrating the power of a dog’s sense of smell, like that some dogs can smell 10,000 times better than humans, that they have up to 300 million olfactory receptors compared to our 6 million, and that their olfactory bulb is about 40 times larger than ours.
Dogs are unmistakably remarkable smellers. But Dr. Hall warned that these particular claims come with caveats. Regarding dogs’ outsized ability, he pointed to a 2017 paper in the journal Science called “Poor human olfaction is a 19th-century myth.” Dr. Hall said this study showed that “if you directly compare dog [scent detection] thresholds to human thresholds, in about half of the cases the humans outperform the dogs.” This isn’t to say that dogs and humans smell at the same level—he added that “in many cases dogs do definitely still beat us”—but that we tend to underestimate human olfaction.
Looking at receptors and brain size, he said, the absolute size and number is less important than the amount of real estate they take up in gray matter. “Dogs are not, in terms of their sense of smell, special [among] mammals,” said Dr. Hall. “Dogs are not the best mammals in the world for scent.” But, as Dr. Lazarowski said, they’re up there—their sense of smell is only rivaled by rodents and elephants. Rodents and elephants have brains of vastly different sizes, but both have extraordinary senses of smell. So it’s less about brain volume and more about how much of that brain space is devoted to a certain skill. “Dogs definitely have a higher proportion of their brain essentially dedicated to olfactory pathways [than humans],” Dr. Hall said.
And research shows that dogs certainly can smell things that humans can’t. A recent study in the journal Scientific Reports demonstrated that dogs can perceive emotional odors from other dogs, and behave differently when presented with odors generated after joyful, stressful, or relaxing events. And dogs may be able to gauge how much time has passed based on a smell’s strength.
In another illustration of the role smell plays in the way dogs see the world, Alexandra Horowitz, PhD, a cognitive scientist and senior research fellow leading the Horowitz Dog Cognition Lab at Barnard College, has written that—in what may be a canine equivalent of recognizing one’s reflection in a mirror—dogs can distinguish between their own smell and one that belongs to another dog.
Do some dogs have a better sense of smell than others?
Dogs of various breeds are gifted sniffers—but a suite of factors influence how well they can track and detect scent. “For the most part there has been very minimal research that has truly demonstrated detection capability differences across different breeds,” Dr. Hall said. He led a study, published in 2015 in the Journal of Comparative Psychology, comparing German shepherds, greyhounds, and pugs in an odor-detection task. The pugs outperformed the German shepherds, while the greyhounds “showed a general failure to participate.” This isn’t because pugs are better at smelling than German shepherds, whom you might espy sniffing luggage at the airport, but because there are likely other factors besides sense of smell, such as attentiveness to scent and trainability. (See: unmotivated greyhounds.)
Scent hounds, Dr. Hall said, may be more attentive to the smells around them, and are already low to the ground where they can track odors. Breeds’ unique physical features may even help them scent better. Staymates said that if you’ve ever seen a bloodhound or basset hound follow a scent, “you’ll notice their ears create this cocoon around their head.” Not only do these hounds’ noses entrain the air around them, but now the scent particles swirl entrapped beneath those floppy ears. “Now the dog’s got this plethora of airborne particles they can inhale and analyze.”
In other words, it’s not necessarily that some breeds have a better sense of smell, but they may have other traits that enhance this ability.
The sweet smell of enrichment
Knowing what makes your dog’s sense of smell so extraordinary, you may wonder if the quickest way to their heart may be through their nostrils.
And scent-based enrichment can provide a dog with ample mental stimulation. Consider taking them on “sniffaris” where you go for a walk geared toward exploring as many smells as possible—as opposed to taking a certain number of steps or reaching a particular destination.
Snuffle mats, too, can entertain a dog through their sense of smell. And if you’re looking for a structured activity, some dogs will take to barn hunts and scent work, both of which make extensive use of their natural affinity and ability for olfaction.
How to keep your dog’s nose healthy
For what fine instruments dog noses are, they’re relatively low-maintenance. If your dog’s nose gets dirty from digging or eating, wipe it with a damp cloth. If your dog has a pink nose, apply dog-safe sunscreen (not the kind for humans, which can harm them) and limit time in direct sun—because dogs with pink noses are more prone to sunburn than dogs with black noses.
And make sure you pay attention to any changes to your dog’s nose. You may find that your dog’s typically cold, wet nose is sometimes dry—but most of the time there’s a benign reason behind this change, said Brian Collins, DVM, Diplomate of the American Board of Veterinary Practitioners, with the Cornell Richard P. Riney Canine Health Center. “Dog noses may normally vary in dryness or moistness throughout the day,” he said, “so it’s good to watch for patterns to see if there may be a problem developing.” Knowing when your dog’s nose is usually dry makes it easier to catch when something unusual breaks that rhythm.
Dry climates, or even just having spent a few hours sleeping can be cause for a dry nose.
But in some cases, a dry nose may develop a thickened, scab-like outer layer made of a protein called keratin. This is a skin condition called hyperkeratosis, which occurs when the dog’s body produces too much keratin. While hyperkeratosis is rarely an emergency, more severe cases may lead to bleeding and discomfort. Untreated, the superficial cracks increase the risk of secondary infection caused by bacteria or fungi. Your veterinarian can suggest appropriate treatments for managing hyperkeratosis, such as balms, ointments, or medication.
Dryness of the nose that’s accompanied by dryness in other places, like your dog’s elbows or paw pads, may indicate a broader problem. Persistent dryness of the nose accompanied by other abnormal signs—such as bleeding lesions, lethargy, poor appetite, or unusual nasal discharge—may speak to underlying illness, in which case Dr. Collins recommended contacting your vet as soon as possible.
And speaking of unusual nasal discharge, he said that thick grey, yellow, green, or bloody fluid from the nose ought to be brought to your veterinarian’s attention—as should any bleeding or discharge from the nose’s surface.
We can all agree that dog noses—and furthermore, dogs—are incredible, and must be treated with care and respect. And we’re still understanding the full extent of their noses’ power. “We don’t really know what the limits of dogs’ detection abilities are,” Dr. Lazarowski said. There’s still plenty more to learn—but we know for certain that a dog nose is always better when there’s a dog attached to it.
The post The Science Behind Dogs’ Powerful Noses appeared first on The Farmer’s Dog - Digest.
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