How good is a dog’s sense of smell?

The Dog’s Sense of Smell

Before we discuss what makes a dog’s sense of smell special, we need to know how their sense of smell works and how scents are being received and processed by the brain.

Whenever a dog tries to smell an object or a surface, both the nose and the brain work together to interpret the signals and chemicals that their olfactory senses are picking up. These chemicals travel the nasal passages of a dog and stimulate the olfactory neurons located at the end of each nostril.

These olfactory neurons pick up and interpret the molecules from the scent and send neurological signals to the part of the brain responsible for interpreting olfactory signals, called an olfactory bulb. Aside from interpreting and making sense of what scents the dog is picking up, the olfactory bulb can also store memories, to a certain extent, which allows a dog to relate a particular smell to past experiences and knowledge.

This process of picking up, interpreting, and storing olfactory signals in the brain is pretty much similar across many species, including humans. However, the extent to how much they can detect varies greatly depending on the species. And dogs are one of the few animals that have a very advanced and sensitive sense of smell that allows them to detect and interpret scents more comprehensively than most animals.

What makes a dog’s sense of smell superior?

As mentioned, how a scent gets picked up, interpreted, and identified is pretty much similar across many species of animals. The difference lies in the number of receptors found on the olfactory surface of the nasal passages.

Humans have around 6 million olfactory receptors in their noses, which is sensitive enough for us to smell perfume or our food and decide if a certain scent is pleasant or possibly a threat to our health or safety. It’s even sensitive enough to detect scents from a few feet away if the signal is relatively strong.

Dogs, however, possess about 300 million of these receptors, about 50 times more than what we have. All these receptors work together to pick up and interpret even small concentrations of scent molecules floating in the air. In addition, their olfactory bulb, devoted to analyzing olfactory signals, is roughly around 40 times larger than those that are found in humans. This allows them to detect scents in concentrations significantly lower than our noses can pick up.

Lastly, though fundamentally similar, the way a dog smells is functionally different than how humans do it. For humans, the act of inhalation serves as both a way for us to breathe and to smell. Dogs, however, have folds in their nasal slits that help separate air needed for breathing and scent molecules. These slits prevent olfactory signals from escaping when a dog exhales and can stay inside the nasal passages for a couple of respiratory cycles.

All these physical properties amplify a dog’s sense of smell, making it highly sensitive to even the smallest and most subtle scent signals.

What can my dog smell?

The physical component of what makes a dog’s sense of smell has been described, but how does this translate to the sensitivity of their olfactory senses? How powerful is a dog’s sense?

It has been shown that a dog can detect a scent molecule at concentrations of one part per trillion. This means that a dog can smell a drop of liquid in 20 Olympic-sized swimming pools or can detect the smell of an object or a person as far as 20 kilometers away.

This degree of olfactory sensitivity has made dogs very invaluable for us humans. With proper training, they can detect and smell explosives and illegal drugs even if they’re tightly covered, packed, and hidden. Their ability to single out a certain scent, detect it from a distance, and locate it makes them very effective in tracking down missing persons.

A dog can even detect various human diseases such as bacterial infections like tuberculosis, malaria, diabetes, and even cancer cells. Their sense of smell is so sensitive that they can pick up hormones released by humans when they get stressed or anxious. This is the primary reason why dogs are often used as support animals for humans suffering from anxiety, stress, or trauma. They can also be trained to detect certain health conditions such as seizures even before they start to happen, and help protect humans with epilepsy from self-injury during a seizure episode.

Their loyal and gentle nature, coupled with their highly sensitive senses, make them one of the best animal companions for humans. This is a reason why dogs are considered a man’s best friend.

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