Super Smellers and Their Anosmic Humans
Clarissa Cutrell
Every morning my dogs are anxious to get outside and read the pee-mail. That’s what I call it. Their daily ritual of exploring the world with that ever-quivering nose. This tree, that bush, and always the fence at the corner, which I always imagine as a doggy community bulletin board, spilling over with notices tacked one on top of the other. Except the notices they read are all scents.
Imagine understanding the world as a cacophany of smells! It’s hard to do with our tiny, unevolved snouts. Most people rely more heavily on vision and sound to gather the information they need to make sense of their surroundings, and consider the sense of smell a bonus sensation. It offers pleasure or displeasure, but really isn’t essential for gathering anything but peripheral information (except of course, when we’re trying to see if the milk’s gone bad). But if our noses were as efficient and complex as that of a dog, would we feel differently?
Human noses feature about six million sensory receptor sites. Impressive, right? Well yes, until you compare it to a sheepdog nose, which has over 200 million of those receptor sites. Or better still, consider the beagle nose, which sports a whopping 300 million receptors! Not only do dogs have more receptor sites for detecting scents, but they have more brain space and more cells dedicated to decoding those scents. So not only can dogs smell things much too faint for the human nose, but they can detect scents the human nose wouldn’t begin to know how to interpret.
In addition to keen noses, dogs also have another weapon in their olfactory arsenal–the vomeronasal organ. The vomeronasal organ isn’t actually unique to dogs. It was first found in reptiles and then discovered in many other animals. The organ is a special sac that sits in the nose or above the roof of the mouth (as in dogs), and allows the animal to detect pheromones. Yes, pheromones, the stuff of legends that indicate changing hormone levels, and announce one’s readiness for sex, or their anger or fear. There is a whole world of information drifting under our noses, literally, that human beings are largely oblivious too. But dogs aren’t.
Urine is rich with pheromones. This is probably why dogs are so eager to smell it. And each other’s butts, of course. The anal gland is virtually (sometimes literally) spilling over with scent information! They can also pick up this information with the mouth, which is why your dog loves to disgust you by licking pee and eating poop. It’s so informative! It’s thought that dogs may have wet noses to assist in getting pheromone information as well, as moisture helps move molecules to the vomeronasal organ.
There’s a Glade commercial I remember seeing advertising a product that alternates between two scents so your nose doesn’t become inured to one, making you unable to smell it at all. It happens all the time. Maybe the trash is stinky, but you’ve been sitting in the house for hours, and aren’t even aware of the stench until someone comes in from the outside and starts gagging. Dogs don’t have this problem (if you can call being unable to smell the stinky trash a “problem”). In addition to adding an extra layer of information to the already impressive dog snout, it’s thought that the vomeronasal organ may switch roles with the dog nose to keep the scent alive. This is an invaluable trait for dogs trained to track scents, often for hours, and often with little scent information to go on.
To a trained dog, a scent trail couldn’t be more obvious.
Dogs can smell a dizzying array of scents, but that doesn’t mean they understand them all. They can, however, be trained to identify certain smells, which is why canines are so great at tracking suspects in criminal manhunts, and finding people lost in the rubble of fallen buildings after earthquakes. They are also being used more and more in healthcare. Some researchers, for example, have taught dogs to identify the chemical odor produced by cancerous tissue.
There’s a lot more to the canine snoz than one meager post can cover. But suffice it to say that your dog’s morning pee-mail ritual is every bit as complex as my Sunday New York Times Crossword ritual. Probably more so, as they can’t cheat.
Quiver on, you miraculous nose! I’ll just be the one at the end of the leash, blindly enjoying the vague fresh scent of the morning.