Dog vs. Human: Who Smells Better?

22-02 four-dog-snouts

Photo above from:

22-01 human nose                     22-03 another Human Nose

Nose on left from:

 Nose on right from:

The post from March 9, 2016 (The Pug Smells!) focused on how dogs with small, short snouts, such as pugs and their brachycephalic brethren, cannot detect scents as well as dogs with large, long snouts, such as Basset hounds and bloodhounds. You may recall that pugs’ snouts simply don’t have enough space to accommodate as many scent receptors as those of bigger dogs. (With the sense of smell, size evidently does matter.)

Nevertheless, in comparison to my own ability to detect scents, even pugs excel. Their noses easily detect odors (particularly of edible items) that I don’t even notice. In fact, scientists have learned that a dog’s sense of smell is 10,000 to 100,000 times as acute as that of humans.

A couple of scientists put this difference into perspective:

Working from the lower estimate of a dog’s sense of smell being “only” 10,000 times better than that of humans, the former director of Florida State University’s Sensory Research Institute, James Walker, explained, “If you make the analogy to vision, what you and I can see at a third of a mile, a dog could see more than 3,000 miles away and still see as well.” (cited in Dogs’ Dazzling Sense of Smell by Peter Tyson, NOVA scienceNOW, posted 10/04/12 at

Another analogy is provided by Alexandra Horowitz, an animal behaviourist who studies dog cognition at Barnard College in New York City: “We might notice if our coffee’s been sweetened with a teaspoon of sugar;”22-08 coffee-cup

Photo from

[but] “a dog can detect a teaspoon of sugar diluted in a million gallons of water: two Olympic-sized pools full.”  (Inside of a Dog: What Dogs See, Smell, and Know. 2009. Scribner. p. 72.)

   22-09 swimming pool - Copy     22-09 swimming pool - Copy

Photos from

The difference in smelling ability between humans and dogs is partly due to the number of scent receptors: about 5 or 6 million for a human vs. 100 million or more for a dog. But a dog has other anatomic and physiological advantages as well. These advantages are explained by Tyson (cited above) and by Horowitz (cited above, pp. 67-74.) I’ll try to summarize these advantages here:

First, unlike a human’s nose, a dog’s nose stays wet.

22-11 wet nose   Photo from

Airborne odor molecules stick to the wet nose, and they’re easily licked into the mouth. From there, they’re carried on through the rest of the dog’s olfactory apparatus.

But before the scent molecules move much past the nostrils, the dog can sniff and snort and move the scent-laden air around. He can also widen or narrow his nostrils to help direct the air flow. A dog’s nostrils, unlike those of humans, are open at the sides; they look somewhat like vents.22-12 nose vents
22-13 nose vents

(Brown dog nose from and black dog nose from Black Dog’s Black Nose on the End of His Black Snout, by Quin, Liam R.E.: Mars and Reuben (2007) at×683.html)

The anatomy of a dog’s nostrils actually helps make it possible for him to know which nostril an odor enters from! So, from the very beginning, a dog has a great clue to which direction he should go to find the source of an incoming odor.

Moreover, as the air enters a dog’s nose, it doesn’t just go straight through the throat to the lungs, as ours does. Instead, it splits along two separate pathways: Part of it goes to the lungs for breathing, and part goes to the dog’s olfactory area, which is loaded with scent receptors. (You can find Brent Craven’s excellent copyrighted diagram of the two air flow patterns at

When the odor-laden air gets to the back of a dog’s nasal passage, it encounters the vomeronasal (or Jacobson’s) organ. This organ is especially sensitive to pheromones released by other animals, often in their urine. Pheromones are hormone-like chemical substances that convey information about the sex and sexual readiness of the dog who released them.

22-14 vomeronasal organ

Diagram from

(Obviously this diagram is not of a pug!)

A dog has still more advantages in the sense of smell. With vision and hearing, the input must be processed through intermediary organs (in the eyes and ears) before it goes to the brain. With the sense of smell, however, a dog’s nose receptors have a direct route to the specific area of the brain where olfactory data are interpreted. As Alexandra Horowitz says, “[The dog’s] nose is also the fastest route by which information can get to the brain.” (Inside of a Dog: What Dogs See, Smell, and Know. 2009. Scribner. p. 72.).

And – if that weren’t enough – the olfactory section of the brain is “approximately 40 times larger in dogs than in humans, relative to total brain size.” (from The Dog’s Amazing Nose! at ).

So it’s no wonder that our pugs astound me with their ability to out-smell me every day (not that I want to be able to smell everything that they can).

17-01 Sarah & Harley pee

But what do they really smell for when they search for the perfect place to pee?



The Pug Smells!

Do you know how a pug smells? If you’re expecting a discussion of the odor of a pug, that’s very simple: It depends on what the little critter has gotten into and how long ago he had his last bath. But today’s topic is the sense of smell.

Previously, I’ve focused on some health effects of the pug’s squished snout. That short snout also affects how well the pug can smell. That’s because the ability to detect odors is determined largely by the number of scent receptors in the nasal passages, and the number of receptors is largely determined by the size and length of the nose and snout; it’s a matter of the amount of space available for the receptors.

Obviously, a dog like the Basset hound has a bigger and longer nose than either the Boston terrier or the Pekingese, all shown below.

21-00 basset

Basset photo above is from


21-02 Boston terrier

Boston terrier photo above is from


21-03 Pekingese

Pekingese photo above is from

Dogs with larger noses and longer snouts have more nasal space and thus, room for more scent receptors. Therefore, such dogs are better able to distinguish smells than are dogs with smaller noses and shorter snouts – such as, of course, pugs.

21-04 Bloodhound

For example, scientists have determined that bloodhounds, being large, with long noses, have about 300 million scent receptors. (Bloodhound photo above is from

21-05 Benji

On the other hand, dachshunds, being small, but with long noses, have about 125 million scent receptors. (Dachshund in photo above is our pugs’ friend Benji, who is able to detect odors that they miss.)

Based on the facts above, I’d “guesstimate” that small, flat-nosed dogs like our pug Sarah may have as few as 100 million scent receptors. Here’s Sarah again (below), with a frontal view of her squash-nosed self:

21-06 Sarah cuddle bed crop 2

Lest you grieve overly much for Sarah and her brachycephalic kin, bear in mind that in a sniffing contest between a pug and a human, the pug always wins. Humans have only 5 to 6 million scent receptors, compared to my “back of the envelope” estimate of 100 million for pugs. Sarah may not be able to track an escaped convict through the Everglades, but she always knows when my pocket contains an empty plastic bag that once held dog cookies.

And whenever a morsel of food rolls under the stove or anywhere else that her truncated snout can’t reach, our pug Sarah knows it’s there. She places herself in front of the offending appliance or furniture and “points” her unpointed nose in its direction until she can get a human (usually me) to fish out the crumb for her.

21-07 Sarah smells

For more information about the dog’s sense of smell, read the chapter titled “Sniff,” pp. 67-88 in Inside of a Dog: What Dogs See, Smell, and Know by Alexandra Horowitz. (2009). Scribner.

Pugs’ Ears

Pugs have a number of different “styles” of outer ears (ear flaps), or pinnae. Take a look at the pinnae in the photos below.

19-01 Charlie ears Photo of our Charlie


19-02 pug2  Photo from


19-03 pug3Photo from×800.jpg


19-04 pug4    Photo from–1197386145.jpg


19-05 pug5  Photo from:

Whatever way they flop, pugs’ pinnae are near the top of the head (probably because there’s no room for them anywhere else). These cute little flaps cover the openings to the ear canals, which direct sound waves down to the eardrums.

The undersides of the pinnae should be kept clean, as in the photo below.


If the inside of an ear flap is red or inflamed, the pug may have an external ear infection (otitis externa) that probably warrants a visit to the veterinarian. Regular cleanings help you spot such an infection before it gets as bad as the one below.

19-07 Otitis externa    Photo from

However, it’s not sufficient just to clean the pinnae. It’s important to pour ear cleaning solution into the ear canal (as in the photo below), squish it around, and then soak it up (I use a rolled-up piece of cotton to do this). There’s an excellent article on how to clean pugs’ ears at

19-09 cleaning ear Photo from

I clean our pugs’ ears religiously – every Sunday, in fact. Weekly ear cleanings usually are needed to prevent pugs’ ear infections, or at least to minimize the number and intensity of such infections. This schedule also forces me to examine the undersides of our pugs’ pinnae, so I’m more likely to catch an external ear infection before it gets very painful.

But why are pugs so prone to ear infections? Would you believe that it’s because of that smushed-in snout? Think again of how the pug’s snout and all its anatomical components are shoved back, toward the skull. An earlier post, Beautiful, Beguiling, Bulging Eyeballs (January 25, 2016), explained how there are not quite enough “parking spaces” available for the anatomical components that belong inside a pug’s head; that includes the ear canals. The canals of a non-pug dog are shown below.

19-08 non-pug ear canal

Diagram from

Unfortunately, with a pug, the squished snout takes up a lot of head space.Therefore, a pug’s ear canals may not be as straight as this diagram depicts. The canals may have to wend – or wind – their way along a narrow, twisted route to find paths through any leftover space in the pug’s head. Thus, a pug’s ear canals are likely to be narrower and more crooked than those of a dog with a snout that extends forward, outside the main part of the skull.

So, with those floppy flaps blocking the entrances to the ears, and with the ear canals being circuitous or narrowed, it’s unlikely that a pug’s ears can get adequate ventilation; thus, moisture accumulates easily. Such conditions are akin to broadcasting an invitation for bacteria and yeast to move in, set up housekeeping, and raise large families in the pug’s ears. Therefore, it behooves the landlord (i.e., the pug’s human) to keep the premises as clean as possible, in the hope that doing so will cause the nasty interlopers to seek living quarters elsewhere, and not settle in the pug’s ears.

Our pugs are not quite as blasé about ear cleanings and ear medications as they are about eye meds, but they do keep themselves quiet and still during these ministrations. I think that’s because they know they’ll get a special jackpot-size serving of one of their favorite dog treats afterward. (I don’t know whether this is positive reinforcement or bribery; but whatever it is, it works for me.)

19-10 Sam, Charlie, Sarah lightThese three pugs wait for their after – ear-cleaning treats.

More About Pugs’ Eyes

You may recall that the original breeders of the pug wanted a dog with large, front-facing eyes, like a human infant’s (see How Did Pugs Lose Their Snouts? Posted October 27, 2015). In the same tradition, today’s dog show judges and pug breeders put a high value on eyes that are “very large, bold, and prominent.” Without a doubt, without a snout to detract from them, our own pugs’ eyes look very large and prominent, indeed.

Here’s Sarah (below), her “very large” and “prominent” eyes bulging a bit more than usual, as she waits for a treat.

0-Xylitol Oct 4


Pugs’ eyes also appear to be “bold.” Pugs are helped along in this by the fact that their eyes are encircled by dark pigment that has the appearance of eyeliner. Like eyeliner make-up for humans, this pigment emphasizes the eyes. This natural eyeliner is worn by all pugs, but it’s more visible on fawn pugs like Sarah (below).

Sarah cuddle bed crop


On a black pug, black eyeliner just isn’t very noticeable.  Below, even though Duchess has gotten very gray, you can still see the “eyeliner” on her lower eyelid.

Ch1-03 Duchess

Those big, bold bug eyes may be just what pug breeders and dog show judges look for, but a pug’s eyes are sitting targets for all kinds of loose fluff and stuff blowing in the wind, such as pollen, dirt, or other debris, as well as any pug-level swishing weed or vine. The assault by such foreign matter irritates the outer covering of the eye, and then the irritated area provides a great place for germs to enter and multiply.

Because of such assaults on their eyes, our pugs have learned that daily applications of various medicinal eye drops and ointments area normal part of life. In fact, Sarah even voluntarily tilts her head from one side to the other, making it easier for me to apply the drops to each eye.

Sarah eye drops crop

Sarah does this so blithely and automatically that you’d almost think that this, too, is a trait that pugs are born with – but she’s the only pug who helps me out this way.

Beautiful, Beguiling, Bulging Eyeballs

In this blog (and in my yet-to-be-published book), besides describing the delightful antics of pugs, I include information about the not-so-wonderful aspects of life with pugs. As a volunteer with Pug Rescue of North Carolina, I see many pugs who are surrendered because their owners don’t know how to care for them or can’t afford their medical expenses. I’d hate for that to happen to any of my readers! So, today I’ll introduce you to some facts about the pug’s eyes. (Warning: A couple of the photos may be upsetting.)

Pugs and other flat-faced (“brachycephalic”) dogs,such as the ones below, are especially likely to develop eye problems. You can blame this on the dog’s squished-in snout.

Some brachycephalic breeds. Photos from:×368.jpg

A dog’s snout is not just an empty shell; it contains important stuff, like the mouth, mucosal tissue, nasal passages, and scent receptors, to name some. The “stuff” inside that mashed-in snout takes up space, even if it’s not visible from the outside, and the pug’s eyeballs have to compete for that space.

Think of it as a matter of real estate, or parking places. With all the body parts competing for space, there’s barely enough room for those beguiling eyes to fit inside the pug’s head. With so little parking space available in the eye sockets, the pug’s eyes tend to bulge out, like a frog’s. (You’ve noticed, huh?)

Photo from

Also, the placement of the eyeballs causes some pugs to have a cross-eyed view of the world, like the one below.

15-02 crossed eyes

Photo from

Some pugs’ protuberant eyeballs look like they’ll actually fall out. Indeed, they can, but the eyeballs won’t just happen to plop out onto the sidewalk while you’re out for a walk. To cause an eye to prolapse, or pop forward out of its socket, it usually takes a hard knock on the head, such as getting banged against a wall while rough-housing with other dogs. Excessive restraint on the pug’s head and neck also can cause a prolapse. Usually the eyeball won’t fall out completely, but stays attached in the back, where the optic nerve is.

15-03 Eye prolapseA pug with the right eyeball prolapsed, from

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Another dog with a prolapsed eyeball. From

In the rare event of a prolapse, it’s a surgical emergency. According to our veterinarian, you must get the pug to a vet within 15 to 30 minutes. In the meantime, keep the eye wet with sterile saline, wetting solution, or plain water. Wet the eyeball and also wet a gauze bandage. If the eye hasn’t popped out all the way, you can try to push it back in, but rush the pug to the vet anyway. Tape or hold the wet bandage over the eye until you get to the vet. The degree of damage to the optic nerve, which attaches behind the eyeball, determines how much the pug’s vision will be affected. Unfortunately, blindness can result, and sometimes the eye must be removed.

A post-surgical eye patient. From

So – I’m glad that I got that out of the way! A prolapse is probably the scariest thing that could happen with a pug’s eyes. Next time, I’ll continue with some less gory eye issues that I’ve learned about, courtesy of our pugs. Until then, I leave you with a photo of Sarah, who has dealt with a number of eye problems, but none as awful as a prolapse.

Sarah abt2006


Lost and Found

At our former home in the country, grass refused to grow in a large shady patch in the back yard. Seeing that we could not win the battle to grow a green lawn there, my husband Bill and I decided to cover the area with mulch, plant a few flowers, and declare victory. A landscaper built an enclosure around the shady section and dumped a mountain of mulch in it. Bill conveniently (for him, not me) managed to be unavailable, so I recruited our pugs Harley and Sarah to help spread the mulch in the boxed-in area.

14-01 S&H on leaves 2004

The pug landscapers dug in energetically and gleefully. They were, perhaps, more industrious than accurate in their shoveling, but they did work at it – and with their bare feet, no less. In fact, they made more progress than I did; it was clear that I’d need to hire a human landscaper to finish the job. But the pugs didn’t know that, and they toiled away enthusiastically all morning.

After all that exertion, my pugs joined me for a nap.

14-02 S&H on bed crop

I fell asleep without washing up, so when I awoke, I was ready for a bath. As I arose, Sarah briefly opened her eyes; seeing that I wasn’t going anywhere of interest to her (that is, to the kitchen), she went back to sleep. Harley, who was losing his hearing and, therefore, sleeping through most normal sounds, didn’t wake at all.

I was reluctant to leave Harley on the bed because he got anxious whenever he woke up and didn’t see me. But, looking forward to taking a bath unaccompanied by canine critters, I convinced myself that he’d be fine. The bathtub was less than six feet from the bed, and I always leave the bathroom door open; so if Harley woke up while I was still in the tub, he should be able to find me easily, right? With our doggy “handicap ramp” alongside our bed, he could get on and off without injuring his arthritic back and legs. So I got up to take a bath.

However, a minute or so after I lowered myself into the luxury of a hot tub, I saw Harley scrambling down the doggy ramp. But instead of checking for me in the bathroom, he raced out the bedroom door. I could hear the familiar clack-clack, clack-clack of his footsteps as he frantically ran through the house, searching for me. With his increasing deafness, he couldn’t hear my efforts to call him. His vision was poor, too: He knew his way around the house, but his eye for detail, well, wasn’t.

As I started to get out of the tub to go find him, Harley charged into the bathroom. I expected him to greet me joyously. Instead, without a glance in my direction, he flew past me and the bathtub, straight toward the toilet. Evidently he’d caught sight (or scent) of my jeans, which were hanging off the toilet seat where I’d tossed them.

14-03 Jeans on toilet crop

Harley began prancing excitedly around the dangling legs of those jeans, sensuously rubbing his body against them while he happily wagged his coiled-up tail and wiggled his whole body in absolute ecstasy. It took me a moment to comprehend that he was doing this in the mistaken but definite belief that the empty legs of my jeans contained the actual legs of my body.

There I was, less than three feet away from him, but unseen and unheard by my beloved Harley. Smiling, with tears in my eyes, I didn’t know whether to laugh or cry, to be honored or insulted, as I saw the love and joy radiating from the clouded eyes of this dear, sweet old dog, my Velcro pug, as he looked up adoringly at what he was certain was his recently re-found mommy’s face: the bottle of toilet bowl cleaner on top of the tank….

14-04 Toilet cleaner crop.

The Banshee Shrieks

One day shortly after we adopted our pug Sarah, I was straightening the master bedroom, placing little knick-knacks on the bed so our once-a-month cleaning lady, Louise, could dust the dresser tops. Suddenly, the quiet was interrupted by the most ungodly screech I’ve ever heard: an incessant, continuous, guttural-sounding “Grgrgrgrgrrraaaauuuurrrrrghghghghghghghghchchchchchch!”

Louise, running to the bedroom from the other end of the house, breathlessly called, “Maija, are you all right? Should I call 911?” After I assured her that I was fine, she exclaimed, “Lord, I thought you were being murdered! What was that awful sound? It scared me half to death!”

That awful sound was just Sarah, being enthusiastically vocal about guarding our home. She was emitting what we’ve come to call her “banshee shriek.” Without consulting my husband Bill or me, Sarah decided early on that her most important job is to keep the home front safe from the menacing monsters that populate our neighborhood.

Ch8-01 Sarah on guard

Neither Bill nor I had known that monsters lurk in the guises of everyday mechanical conveyances, such as motor vehicles and lawn mowers. We learned that Sarah has a remarkable hatred of white vehicles, especially FedEx trucks; but she protects us from brown UPS trucks as well. She also despises yellow school buses. probably because she’s observed them swallowing children, whom she considers to be her best friends (even if she hasn’t met them yet).

These monsters apparently are dangerous only when they’re in motion or have just come to a stop. Parked vehicles don’t trouble her a bit, unless she observed them in motion before they stopped. Furthermore, she happily rides inside moving cars.

Nonetheless, Sarah does an excellent job of guarding us. She rushes to the window as soon as she suspects that a monster is in the area. She promptly sets about dispatching it out of the neighborhood before it can do any damage.

Indeed, we have not had a monster invade the house since Sarah joined our household.

Ch7-01 Sarah sit cropped no snout