Dogs and their Powerful Sense of Smell

With over 300 million receptors in their noses, dogs have a sense of smell one thousand times keener than humans.  This does not put them at the top of the heap. Bears, sharks, kiwi, snakes, and moths also posses superior senses of smell.  However, it is the mighty elephant which tops the sniff charts with the strongest sense of smell identified in a single species so far, a new study has found. “Published in the journal Genome Research, new data has revealed that African elephants possess the largest number of genes associated with smell documented to date, donning five times as many as humans and twice as many as dogs. To their surprise, they even beat the previous record holder, rats.” [source]

But since this is a blog about dogs, we will focus on our canine companions.

Research published in the Journal of Comparative Psychology find that dogs can make a mental representation of the objects they smell. The studies were done by experts from the Max Planck Institute for the Science of Human History and included 48 dogs, where 25 have been trained to work in search and rescue operations and 23 which were family dogs.

“One toy was used for the normal condition, where the dogs expected that the object would be there at the end of the trail. Another toy was used for the surprise condition, which was not the object the dogs expected to find at the end of the trail.

The normal condition showed predictable results, as most of the dogs were able to follow the trail and find their toy. In the surprise condition, however, many of the dogs interestingly showed hesitation for a toy they obviously knew because it was not the object used to lay down the trail of scent. The animals, whether working dogs or family dogs, appeared confused and continued to use their noses to search for the right toy.” [source]

Diagram of the test rooms

And which dogs have the best sense of smell? Here are 25 breeds from four different groups which top the lists (in no particular order). [source]

The Top 25 Canine Sniffers

– Scottish Terrier
– American Staffordshire Terrier
– Rat Terrier

– Basset Hound
– Beagle
– Black and Tan Coonhound
– Bloodhound
– Bluetick Coonhound
– Harrier
– Dachshund
– English Foxhound
– Redbone Coonhound
– Treeing Walker Coonhound
– Irish Water Spaniel

Sporting Dogs
– Irish Water Spaniel
– English Springer Spaniel
– German Shorthaired Pointer
– English Pointer
– Labrador Retriever
– Nova Scotia Duck Tolling Retriever
– Golden Retriever
– Chesapeake Bay Retriever

– German Shepherd
– Belgian Malinois
– Border Collie
– Collie (Rough and Smooth)


Here’s an excerpt from a video:

“As your dog catches the first hints of fresh air, her nose’s moist, spongy outside helps capture any scents the breeze carries. The ability to smell separately with each nostril, smelling in stereo, helps to determine the direction of the smell’s source so that within the first few moments of sniffing, the dog starts to become aware of not just what kind of things are out there but also where they’re located.

As air enters the nose, a small fold of tissue divides it into two separate folds, one for breathing and one just for smelling. This second airflow enters a region filled with highly specialized olfactory receptor cells, several hundred millions of them, compared to our five million.

And unlike our clumsy way of breathing in and out through the same passage, dogs exhale through slits at the side of their nose, creating swirls of air that help draw in new odor molecules and allow odor concentration to build up over multiple sniffs.

But all that impressive nasal architecture wouldn’t be much help without something to process the loads of information the nose scoops up. And it turns out that the olfactory system dedicated to processing smells takes up many times more relative brain area in dogs than in humans.

All of this allows dogs to distinguish and remember a staggering variety of specific scents at concentrations up to 100 million times less than what our noses can detect.”


According to Alexandra Horowitz,a dog-cognition researcher at Barnard College and author of Inside of a Dog: What Dogs See, Smell, and Know, dogs can detect some odors in parts per trillion. To put this in perspective, while humans “might notice if our coffee has had a teaspoon of sugar added to it, a dog could detect a teaspoon of sugar in a million gallons of water, or two Olympic-sized pools worth.” You might also think of the canine’s prowess as the ability to catch a whiff of one rotten apple in two million barrels. [source]

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