The Nose Knows

Stand on any busy corner of Manhattan and close your eyes. Inhale through your nose. Don’t exhale; let it linger. 

The acrid yellow-brown scent of street gunk hangs in the air, shot through with the fresh pinkish-green of newly blossoming flowers overhead. Get close to the ground and the cold tang of metal railings hovers a few inches from the sidewalk, the cool gray scent of concrete thrumming underneath. Pepto Bismol pink splashes in your face, entwined in the hair product of a passing stranger.

How many times have we heard trainers say, “Dogs see with their noses”? And how many times have we sat down to consider what that means?

When we think of our dogs, we imagine the color of their coats or the shape of their bodies. We crave eye contact with them, staring deep into their eyes and searching for connection. Without fail, we skip over the wet, black bump protruding from the end of their faces; we can’t even see our own noses without outside help, and the nose of a dog hardly seems worth the extra scrutiny.

Underneath the simple exterior is a complex organ that puts human noses to shame. Dogs possess up to 300 million receptors in their noses, compared to the paltry 6 million in ours. These receptors allow them to sniff out pheromones, receive status and health updates via urine, and even give some dogs the legendary ability to detect disease.

Dogs have the vomeronasal organ, also referred to as the Jacobsen’s organ. Located in the nasal cavity near the roof of their mouths, the vomeronasal organ specifically detects “undetectable” odors—adult dogs use it to determine whether another dog is receptive for breeding, while puppies use it to identify their mothers from unfamiliar dogs. The nerves in the vomeronasal organ do not respond to ordinary smells and lead directly to the brain.

Even the shape of their noses is designed to allow for continuous, uninterrupted sniffing. Air is exhaled through the slits on the sides of their noses so as to avoid pushing out a new scent. Unlike humans, who sneeze or exhale explosively to remove offensive odors!

The differences continue, as dogs’ nostrils can work independently of each other. Called stereo olfaction, the process of inhaling through one nostril and exhaling through the other allows dogs to analyze a scent and pinpoint which direction it’s coming from. Differences in the strength of the scent help determine the odor’s precise location. The nostrils work together to provide a rich tapestry of the surrounding area.

Dogs may also be able to use the cold, wet tips of their noses–the rhinarium–to detect the heat released by thermal radiation, aka living animals. While this trait is thought to be an adaptation allowing carnivorous predators to track down their prey, dogs share it with few other animals. Vampire bats, snakes, and some insect species have displayed similar abilities, but not many other mammals, making dogs just a bit more unique. 

And finally, more abstract but no less intriguing: Alexandra Horowitz, the author of Being a Dog, hypothesizes that dogs may experience the passage of time through scent. As the hours tick along, smells fade and change, giving the past its own perfume. Dogs know when a storm is hours away or someone is approaching. Thanks to constantly shifting air currents, canine nostrils analyze and experience the future before our human eyes see it. 

Dogs and humans have intertwined their lives together over thousands of years. We observe them at work, heads bent to the ground or lifted in the air, noses working frantically as they devote themselves to the all-important task of sniffing. Join AGDT's Dog Easter Egg Hunt for an opportunity to learn more and to experiment with your own dog's superpowers!