How dogs smell

A whole separate olfactory system, called the vomeronasal organ, above the roof of the mouth, detects the hormones all animals, Including humans, naturally release.

It lets dogs identify potential mates, or distinguish between friendly and hostile animals. It alerts them to our various emotional states, and it can even tell them when someone is pregnant or sick. Because olfaction is more primal than other senses, bypassing the thalamus to connect directly to the brain structures involving emotion and instinct, we might even say a dog's perception is more immediate and visceral than ours.

But the most amazing thing about your dog's nose is that it can traverse time. The past appears in tracks left by passersby, and by the warmth of a recently parked car where the residue of where you've been and what you've done recently. Landmarks like fire hydrants and trees are aromatic bulletin boards carrying messages of who's been by, what they've been eating, and how they're feeling.

And the future is in the breeze, alerting them to something or someone approaching long before you see them. Where we see and hear something at a single moment, a dog smells an entire story from start to finish.

In some of the best examples of canine-human collaboration, dogs help us by sharing and reacting to those stories. They can respond with kindness to people in distress, or with aggression to threats because stress and anger manifest as a cloud of hormones recognizable to the dog's nose.

A dog's nose works differently from a person's, with these differences being crucial to a heightened sense of smell. First, a dog's nostrils are independent from each other. This allows a dog to quickly determine from what direction a scent has come. This area is used exclusively to break down the chemical makeup of odors in the air, which is forced through bony structures called turbinates.

Olfactory receptors in the lining of the turbinates recognize the chemicals' molecular shapes and transmit that information to the dog's brain for analysis.

The olfactory lobe in a dog is, proportionately, 40 times larger than a person's, and some estimates suggest it may occupy up to a third of the brain's work.

Additionally, a dog also has a unique olfactory organ: the vomeronasal or Jacobson's organ. Think about how dogs greet each other. Information is transmitted via noses rather than barks or paw shakes.

In fact, dogs obtain more detailed information from scent than we can even imagine. First, their noses are far more powerful than ours. Humans have only 5—6 million scent receptors in our noses. Depending on the breed, dogs have up million or more scent receptors in their noses. And those terrific trackers we know as Bloodhounds have million! Dogs can detect some smells in parts per trillion.

You might smell chocolate chip cookies, but your dog can smell the chocolate chips, flour, eggs, and other ingredients. And when dogs sniff another dog, they smell more than doggy odor. Dogs also have a special scent organ called the vomeronasal organ, located between the roof of the mouth and the bottom of the nasal passage. Indeed, the smelling section of a dog brain is 40 times larger than ours. Preventing your dog from experiencing the world through scent is like putting a blindfold on a human.

The chance to smell provides your dog with important information and essential mental stimulation.