Nose smart – how [your dog’s] nose knows
Your dog’s sense of smell is nothing short of a superpower. The following book excerpt offers fascinating details on how canine olfaction works and why our dogs’ odor-detecting abilities are so amazingly sharp.
If you pay close attention to your dog’s nose when he’s intent on a scent, you’ll see it do that cute little wiggle and hear the staccato beats of its work. As a tool, a dog’s nose is a triumph of natural selection: a complex set of cogs and wheels we rarely think about.
When a dog inhales, the air can follow two possible routes — one for plain old breathing, and the other for olfaction. During intense exploration or tracking, the rapid sniff, sniff, sniff — up to around 200 times a minute compared with about 30 times a minute for a dog on a stroll – takes in extra air and rushes volatile particles into the system. The action creates tiny wind currents on exhales to help the inhales along. Then, within the nasal tissue, a maze of receptor sites awaits, tooled with tiny hairs that snag and hold scent molecules as they whistle by.
Our two nostrils always work in tandem, but a dog’s can work independently, further boosting his access to scents. Nostril mobility helps the pup know where a smell is coming from, and a wet nose, dampened by a thin layer of secreted mucus plus saliva, picks up scent better than a dry one. And though human nostrils have to manage both inhalations and exhalations through the same door, a dog taking in new air can, with a twitch of muscles, push old air down deep or release it through slits in the sides of the nose: an elegant solution to the “too many smells” problem.
Not only do dogs have hundreds of millions more odor-detecting neurons than we, do, but their olfactory epithelium – the sheet of tissue that converts odor molecules into neural signals that brains interpret as smells – is also a complex labyrinth of turns, folds, and bumps compared to our single flat sheet. Dogs also have a working vomeronasal organ (VNO), a sac packed with additional receptors that sits atop the roof of the mouth and picks up chemical cues called pheromones from incoming air and when the dogs licks its nose. When a dog sniffs something message-laden like urine of a female in heat, he seems to “eat” the scent – a behavior that draws more odor molecules to the VNO. What lands there is thought to affect social and reproductive behavior.
Olfactory performance is sensitive to humidity and barometric pressure, inflammation, nasal dehydration, excess mucus, exposure to toxins and pharmaceuticals – and of course, the effects of diet, aging, and disease. A dog can experience olfactory fatigue or “nose blindness,” like us, finding herself temporarily unable to distinguish a particular odor after smelling it too much. Thresholds vary across individual dogs. This desensitization occurs to free up the nervous system to respond to new smells that might be important: a smart move for a nose thinker. The gut microbiome may even affect sensitivity to scene. So do training methods; how and how often a dog is exposed to an odor of (our) interest can change his ability to distinguish it from others.
So dogs’ nose intelligence depends on a great many factors, many of which are in the handlers’ control. And in supporting our dogs’ natural olfactory talents, we can boost the superpower that arguably has the greatest value to both species.
Reprinted with permission from www.animalwellnessmagazine.com
