What Can a Dog Smell?

My daughter has an imaginary friend, as many 5 year olds do.  This imaginary friend happens to be a talking dog.  They chat about things like mermaids and unicorns and such.  Though a bit far-fetched, it got me imagining what a real conversation with a dog might be like. It may go something like this:

Dog:  “Dude, you smell that?”

Human:  “Smell what? I don’t smell anything.”

Dog:  “Really??? I can practically taste it.”

Aside from this canine’s exaggerated sense of vocabulary, the content of the conversation is not off base at all.  It is no secret a dog’s sense of smell is far superior to its human companions….but how much?

The Science Behind a Dog’s Nose

It is estimated to be between 1,000 and 10,000 times greater.  Most dogs have more than 220 million olfactory (scent) receptors in their nose.  Humans have 5 million.  Though
their brain is 1/10 the size of a humans, the part dedicated to the sense of smell is 40 times larger.  They have a chamber within their nasal system which collects scent particles.  The particles stay there even when the dog exhales.  This enables the particles to build up there until there is a high enough concentration for them to identify the odor.  Oh, and the whole tasting thing- not a farce.  There is this neat thing they have which is termed Jacobson’s organ.  Its function is basically a fusion of taste and smell.

What Can a Dog Smell?

So what kinds of things can dogs smell?  They can smell fear (due to a release of  pheromones), they can smell scent articles up to 40 feet underground, they can smell insects within the ground or in woodwork, they can smell disease in humans (sometimes referred to as the sick sense), and they can smell human fingerprints that are a week old.  The list goes on and on.  I suppose a more challenging question would be “what can’t they smell?”  The benefits to the human world are paramount.  The more obvious roles include detection of drugs and explosives, cadaver detection and search &  rescue.  Some dogs olfactory optimus is used to ascertain termite infestations, diagnose early signs of cancer or oncoming epileptic attacks, detect rodents and snakes in overseas shipping arenas and determining the best time for farmers to breed their livestock.

I read somewhere that a dog’s sense of smell compares to ours like our ability to reason compares to theirs.  It is so far beyond human ability it is difficult to comprehend.  I do know this: the next time you are walking with your canine companion and he turns to you
and says “something smells fishy”- get your rod and cast a line!


Do you have a question about how a dog’s nose works?  Leave it for us in the comments section below, and we’ll be happy to respond.

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