How Long Do Dogs Remember Your Scent?

By John Martin - May 12, 2021

Closeup of dog nose

In Homer’s epic ‘Odyssey’, Odysseus, who has been given up for lost, returns home after 10 years. He enters his city disguised as a beggar to surprise his wife and son. On the way to his house, he sees his pet dog Argos lying on a heap of waste.

Argos is in the last stages of his life, but on seeing Odysseus, he wags his tail joyfully and tries to raise himself up. Being frail, he is unable to do so and lies back again to rest forever, as if he has accomplished the only task that remained before he breathed his last.

Written almost 28 centuries ago at the end of 8th Century BC, this seems to very strongly suggest that your dog never forgets you. Considering the dog was across the street and too weak, and that Odysseus was in disguise, the only thing that could have alerted Argos to his master’s presence is his scent.

Research Supports

Gregory S Berns, Andrew M Brooks and Mark Spivak studied how the canine brain responds to familiar and unfamiliar human and dog scents. According to the results published in Science Direct, it was found that olfaction is the dogs’ most powerful and perhaps important sense.

A cohort of 12 dogs was presented with five scents: that of the dog itself, of a familiar human, a stranger, a familiar dog and a strange dog. It was found that the olfactory bulb/peduncle was stimulated by all the scents but the caudate was activated the most when it smelt a familiar human even though only the handler was present.

This not only shows how powerful the dog’s sense of smell is, but also how strong the memories attached to it are and how important humans in their lives are for them.

Related: Why Do Dogs Chase Squirrels?

Dogs’ Eyes Are Its Nose

It is interesting how dogs seem to perceive the world through their nose rather than their eyes. A study shows that dogs were unable to recognize themselves in the mirror, but that’s because they don’t rely so much on their eyes as much as their nose. A study by Alexandra Horowitz shows that dogs can differentiate between different odors and spend more time when they smell another odor mixed with their urine, no doubt puzzling about what makes it different.

When compared to a human’s sense of smell, a dog’s is 10,000 times more acute and accurate. Can you believe that a dog has up to 300 million olfactory receptors in its nose as against six million in humans? And that it has a part of the brain devoted to analyzing smells that is 40 times greater than ours!

This is one of the reasons why dogs are also used to sniff out missing people, marijuana, bombs and so on. They can even differentiate smells in parts per million, meaning, identify a teaspoon of sugar in a million gallons of water!

Feats Using Scent

This is one of the reasons why dogs are great sniffers and used in crime investigations and searches. They can process scents and segregate the ones that matter from those that don’t. This is especially useful in crime investigations.

Some examples of situations where a dog’s sense of smell has aided people:

  • At crossroads, they can determine the direction a person has taken from as few as the first five steps even after an hour of that person walking that way!
  • They can track and trace missing persons after sniffing on an object belonging to that person.
  • A drug-sniffing dog could detect 35 pounds of marijuana packed inside a plastic container and submerged in gasoline in a gas tank.
  • A cancer-sniffing dog spotted melanoma in a spot of the skin of a patient whom the doctors had declared cancer-free. Biopsy revealed the cancerous growth in a small fraction of the cells.

Anatomy of a Dog’s Nose

The secret of dogs’ ability to have a nuanced sense of smell lies in the construction of their nose. Humans breathe and smell through the same airways in the nose. When a dog inhales, on the other hand, the two functions are separated by a fold of tissue that splits the airflow into two different paths. One takes care of respiration and the other, olfaction.

Whatever is smelt enters and exits through the same passage in humans. The human sense of smell is confined to a small region on the roof of the nasal cavity. While exhaling through our nose, we eliminate the odors along with the air.

In dogs, 88% of the inspired air enters the pharynx and makes its way to the lungs. The remaining 12% heads towards a dedicated area in the nose through turbinates, a labyrinth of scroll-like bony structures containing odor-laden air filters for olfaction. The odor molecules are sieved by the turbinates based on different chemical properties. The tissue lining along the turbinates contains olfactory receptors within which it can identify the odor molecules by their shape and direct the electrical signals to the brain for analysis.

Dogs exhale through the side slits in air swirls that attract new odors into the dog’s nose. As a result, the dogs can sniff almost continuously without pausing to breathe.

Their olfactory system is so evolved that they can smell pheromones, the chemicals advertising mating readiness and other sex-related details, separately. This is called the vomeronasal or Jacobson’s organ and can be found at the bottom of the dog’s nasal passage.

With so much work going into detecting and segregating smells, do you think a dog is likely to forget the smell of its most loved parent, that is, you?

Without a doubt, a dog’s smelling capability is strong. You may well ask, do they retain the memory of the scent for long.

Related: Why Are Dogs Afraid of Vacuums?

Episodic Memory

Of course, till some time ago it was believed that animals generally do not have memories, and definitely not long term memories. To find out if they retain scent memories, studies would require the parents to be separated from their pets for a long period of time, which is not easy for either and therefore not feasible.

Recently, however, the episodic memory of dogs has been studied and they reveal that a dog has as complex a memory as humans. It has been seen that dogs not only remember what they have been trained to do but can even imitate actions irrelevant to them that they have not even paid attention to. This suggests that their memories are more complex than earlier thought to be.

For this scientists tested dogs to repeat actions after a ‘do as I do’ training. The dogs were found to be able to recall and imitate actions even after an hour. Called ‘episodic memory’, the dogs are able to remember even those actions that they are not expected to learn and don’t expect to be asked to perform. This context-rich encoding opens up new doors to understanding how dogs store memories and interact with humans.

It also shows that dogs do have memories. Putting two and two together, we can see that dogs do remember scents, can distinguish between smells and are capable of remembering things and people.

Touching Reunions

A dog gets familiar with people by studying their smells rather than memorizing faces. Whenever they are curious about anyone or anything, it is their noses that reach out first, no doubt, to assimilate the smell of that person or thing and store it for future reference.

This reference comes into play when they meet someone after a gap. These days, we can see evidence of dogs remembering their parents even after a gap in the many videos available on social media.

When you own a pet, it is a bond of a lifetime. Children leave homes for higher studies and pursue careers. Their visits back home become rarer with longer gaps between each. But every time they visit, along with the parents, it will be the canine pets who will greet them with great enthusiasm and unbridled affection.

Whether it is the scent or a loved face may be a topic of debate. But their olfactory system works overtime and has a complex system that can process multiple smells at the same time. Therefore, it is most likely that it is the memory of the scent that triggers the joyful reaction first.

Whatever else about you may change, if your smell remains the same, you can be sure that your pet will remember you till his lifetime.