You may think you know your dog’s nose. After all, you see it in action every day! Everybody knows dogs are superior smellers, but those noses can do a lot more than sniff out treats in your pocket.
In her book Being a Dog, founder Alexandra Horowitz of the Dog Cognition Lab at Barnard College explores the mechanics of how, what, and why dogs smell so well. Dogs are incredible olfactory detectives, able to tell time, predict weather, identify dangerous substances, and even detect cancer with their noses.
Read on to learn about the secret history (and amazing abilities) of your dog’s nose!
How dogs smell from the outside
If your dog is nearby, examine her nose from the outside. Go on, give it a touch. It might feel kind of squishy, cold, and wet. That moist, spongy exterior helps your dog’s nose capture scents on the air.
Next, take a look at her nostrils. Dog noses are stereoscopic, meaning their two nostrils can operate independently of one another, essentially “smelling in stereo.” That two-pronged smelling ability lets dogs determine where smells come from, so they aren’t just identifying the smell of a discarded piece of pizza, but locating it in the world.
Dogs’ stereoscopic nostrils mean they “smell in stereo.”
Now, notice the slits at the side of your dog’s nose. I always thought that was just an interesting cosmetic quirk, but it turns out, those slits are where your dog exhales. Dogs inhale through their nostrils and exhale through slits at the side of the nose, creating a circulation of air and scent molecules that lets them smell far more than we can even imagine.
Finally, notice your dog’s snout (its length varies). The long, spacious snouts many dogs have help to humidify and filter the air, and move it rapidly towards their scent receptors.
How smell works inside your dog’s nose
Once scents have entered your dog’s nasal cavity, they’re filtered and evaluated.
- First, air entering the nose is divided into two separate folds: one for breathing, and one for determining scent
- Next, the air being evaluated for scent hits your dog’s 300 million olfactory receptor cells. By comparison, humans only have just 5 million olfactory receptor cells, making your dog’s sense of smell 60 times more powerful than your own!
- Finally, the brain works its magic, evaluating and distinguishing scent information in concentrations up to 100 million times less than what humans are able to detect.
Your dog’s olfactory system is three times as big as your own, and they have a lot more relative brain area devoted only to smell.
Smelling the invisible
In addition to being able to smell substances in their environment, dogs have a second scent receptor in their nose called the vomeronasal organ that’s dedicated solely to sniffing out pheromones. The vomeronasal organ makes it possible for your dog to:
- Identify potential mates
- Discern between friendly animals and potential predators or enemies
- Recognize their human companions’ emotional states
- Notice when someone is pregnant
- Notice when someone is getting sick (some dogs can even sniff out cancer)
You know how your dog spends so much time sniffing fire hydrants and trees? Dr. Horowitz refers to these doggy landmarks as “aromatic bulletin boards, carrying messages of who’s been by, what they’ve been eating, and how they’re feeling.”
Your dog’s ability to identify hormones and pheromones also explains how she knows to be extra-attentive when you’re feeling sad or sick.
How dogs can tell time with their noses
Dr. Horowitz theorizes that dogs can track time throughout the day by the odors circulating in their environment. Think of it this way: as a human, you can tell what time of day it is with visual and sensory cues from the sun. If you sit in the same room all day, you’ll notice the light changing as the hours go on, and feel the change of temperature on your skin. Dogs notice similar changes, but with scent.
“Dogs smell time.”
As Horowitz explains, “Smells in a room change as the day goes on. Hot air rises, and it usually rises in currents along the walls and will rise to the ceiling and go kind of to the center of the room and drop.” That movement of odor throughout the day is discernible to dogs.
Dogs can also tell how long a smell has been around. Scents lose power over time, so a stronger odor is probably more recent, and a weaker one is from farther in the past. Horowitz explains that when they detect a scent, dogs can tell not just what it is, but how long ago it was left. In other words, “Dogs smell time.”
Why does your dog smell your crotch?
It can be embarrassing to be on the receiving end of a nose nudge in the crotch, but it’s not unusual. Think about it: it’s one of the most scent-heavy parts of your body,
Dogs with strong noses are drawn to particularly odorous places, including:
- Other dogs’ rear ends
- The litter box
- Your shoes
- Your neighbor’s trash can
If you’re troubled by a nose in a delicate area, Dr. Horowitz recommends offering an alternative smell to distract them.
Why you should let your dog sniff the world
It’s tempting to hurry your dog along when he’s lingering over a particularly odorous patch of sidewalk, but according to Dr. Horowitz, pulling dogs away from smell-rich environments can cause their sense of smell to diminish.
If you pressure your dog to live in “our visual world,” she says, “they start attending to our pointing and our gestures and our facial expressions more, and less to smells.”
Of course, it’s nice when your dog pays attention to your expression, but you don’t want them to lose their true superpower: their incredible sense of smell!