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How Dogs Smell

Posted by Chieko Clark on

Dogs’ noses are tens of thousands of times more sensitive to odours than humans, but how exactly do these super sniffers’ noses work? And why are man’s best friend so much better at smelling out stuff than we are?

Dogs can detect some odours in parts per trillion. Dog cognition researchers have reported that, while we might notice if our cuppa 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. They are adept at detecting even the most minute odour discriminations. How do they achieve such sniffing feats? 

Champion Whiffers – How Dogs’ Noses Work

Dogs’ super noses work quite differently to our horribly ineffective hooters. When a dog breathes in, the air separates into two distinct paths, one flowing into the olfactory area and the other passing through the pharynx to the lung; when we inhale, we smell and breathe through the same airways within our nose.

Dogs possess up to 300 million olfactory receptors in their noses, compared to about six million in humans. Moreover, the part of a dog's brain that is devoted to analysing smells is, proportionally speaking, 40 times greater than ours. Like a giant sieve, the back of the dog’s nose sifts through odour molecules and the receptors ‘recognise’ these molecules and dispatch electrical signals to the brain for analysis.

Breathe in, Breathe out

When humans exhale through our noses, we send the used air out the way it came in, forcing out any incoming odors. When dogs exhale, the spent air exits through the slits in the sides of their noses, helping to usher in new smells into the dog's nose at the same time. More importantly, this also allows dogs to sniff more or less continuously.

Sadly, we can't wiggle our nostrils independently. Dogs can. This, along with the fact that the so-called aerodynamic reach of each of their nostrils is smaller than the distance between the nostrils, helps them to determine which nostril a particular whiff arrived in. This aids them in locating the source of smells—we've all seen dogs on an interesting scent weave back and forth across its invisible trail.

Olfactory Awesomeness

In addition, dogs have a second olfactory capability that we don't have, made possible by an organ we don't even possess: the vomeronasal organ, also known as Jacobson's organ. Located in the bottom of a dog's nasal passage, Jacobson's organ picks up pheromones, the chemicals unique to each animal species that advertise mating readiness and other sex-related details.

The pheromone molecules that the organ detects—and their analysis by the brain—do not get mixed up with odour molecules or their analysis, because the organ has its own nerves leading to a part of the brain devoted entirely to interpreting its signals. It's as if Jacobson's organ has its very own dedicated computer server.

Tracking Experts

Dogs’ basic smelling skills are pretty amazing, but what they manage to achieve with those skills is truly astounding.

Take tracking, for example. Scent-tracking dogs take such tracking to the extreme, routinely accomplishing remarkable feats in unfamiliar environments and on the trail of unfamiliar people such as missing persons. It is not really understood how dogs accomplish their tracking accomplishments – they are able to come to a branch point and decipher which direction someone took despite variables like changing wind and humidity and despite other powerful odours that might be in the air. And we still don’t fully understand how!

Other helping factors

There are some breeds of dog who also have a helping hand with their sniffing capacity from – of all things – their ears As a bloodhound moves along the ground, its giant, flappy ears help fan up odours to its nose, one reason the breed is the superstar of scent-tracking.

Dogs' sense of smell overpowers our own by orders of magnitude—it's 10,000 to 100,000 times as acute, scientists say. If you equate that to vision, what us humans could see at a third of a mile, a dog could see more than 3,000 miles away and still see as well.  They really are super sniffers.

 


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