A dog’s sense of smell is powerful, and a key component of exploring his world.
Can you imagine living in a world dominated by odor? Anyone who has ever walked a dog down a leaf-strewn sidewalk or across any field can probably attest to just how powerful a dog’s nose is. The dog just can’t help himself as he sniffs along following only his nose and ignoring everything else around him.
A dog’s sense of smell is much more developed than ours and is one of the key ways he explores and interprets his world. Although the dog's brain is one tenth the size of a human's, the part of the dog’s brain that is devoted to analyzing smells is forty times greater! Given this simple fact, it’s no wonder why dogs are so focused when they're noses hit the ground. They know exactly where the squirrel squeezed through the fence or who was there before them. They have on average 220 million to a billion scent receptors in their noses compared to our rather paltry 6 million, making them exquisite gatherers of information just through smell alone.
The sniff
Look at your dog's nose and marvel at how incredible it is. His leather-like snout has wide open nostrils called nares, which gather the scent around him When he smells something in the air or on the ground, he disrupts his normal breathing to gather that scent, sniffing in and out (7 times a second) to collect and retain the scent for identification. Scent molecules stick and dissolve into the mucus inside his nose, and is pushed up through the nose by tiny hairs called cilia. The nostrils lead to a bony, shelf-like structure where scent is trapped and information is gathered by receptor cells. The odor is then sent to the olfactory bulbs and onto processing. Expiration forces air out the side of the nares so it doesn't disrupt the collection of odors that are still on the ground.
Layers of Odor
Your dog enters the room where you have been cooking chicken and vegetable soup. He's already smelled it from the other side of the house, and the odor only gets stronger as he moves to the source. Once he is in the kitchen, he is bombarded by layers of odor that give him a much wider range of information. While we just smell the soup, your dog smells the ingredients individually; the onions, the carrots, potatoes, peas and the chicken. This is known as odor layering and is why dogs can separate smells from each other, filtering out the ones that are less interesting and going towards the ones that they want to investigate more.
The Jacobson's Organ
Dogs have what is known as a vomeronasal or Jacabson's organ located above the hard palate of the mouth just behind the incisors, at the base of the nasal cavity. Information received through this organ goes straight to the limbic system, the part of the brain that regulates mood, drives emotions and regulates memory. This organ detects pheromones in the bodily secretions of other dogs and includes information about that dog's health, age, sex and emotional state.
The nose knows!
Humans are using the dog's incredible sense of smell to do a variety of jobs that it would take people or machines much longer to do. Odors play a vital role in relating information and this has been harnessed in a variety of ways.
- Dogs can find hidden explosives, locate illegal drugs, track missing people, and identify individuals, often through highly-diluted odors or just a few footprints.
- Dogs can be trained to detect the chemicals produced by human diseases, such as cancer and even Covid-19.
- There are some differences in how male and female dogs sniff each other when greeting. Male dogs tend to sniff the rump first because this area is vibrant with scent, while female dogs often go to the face first before moving toward the back end. This could be because the information they get from the head area is different to the info they get from the non-bitey end.
- Smelling odor might be how the dog tells time. When a dog sniffs at an odor on the ground, he is smelling the past - what used to be there. When he lifts his nose and smells odor on the air, he is smelling the future - what is to come.
A dog’s sense of smell: what this means for you
Knowing how potent and crucial a dog’s sense of smell is to him and his perception of the world is an important step in understanding your dog and providing him with opportunities for enrichment.
- Let your dog do some sniffing on the walk. Sniffing and following scent is a natural part of dog behavior and so your dog should be allowed to sniff things as you walk.
- If your dog isn’t responding to training in an area that is rich in smells, it might just be too hard for him to focus on you. Remember how powerful his nose is!
- Be understanding and patient when your dog greets or interacts with people in ways that look rude to us but are normal for dogs. Your dog might stick his nose anywhere he finds a smell! Remember, he doesn’t understand human conventions and sniffing people's crotches is a very useful way in obtaining all kinds of information about them. If you want to teach your dog to greet people in a different way, have him go get a toy and parade it around them instead. This way there can still be a greeting, but not in a way that is embarrassing!
- Many dogs love games and sports that involve using their nose and sense of smell. This can be as simple as letting your dog sniff out his kibble around the house or garden. You can also look into the sport of scent work, which teaches dogs to detect specific scents and is an enriching activity for dogs and handlers.
Related reading
References
Horowitz, A. (2010). Inside of a Dog: What Dogs See, Smell, and Know. Scribner.
Horowitz, A. (2016). Being a Dog. Simon and Schuster.
