Why Do Dogs Sniff?

Every dog owner knows that sniffing is a huge part of a dog’s life. Many dogs seem to spend every second seeking out new smells to investigate, even ones we humans would rather avoid! Their sense of smell is the best way for them to get new information about the world around them–the scent environment is sort of like a dog’s morning newspaper! 

Dogs have a sense of smell that is much stronger than humans. The average dog has about 220 million olfactory receptors, but some specialized breeds–such as bloodhounds–have up to 300 million. In comparison, human noses only have about 6 million receptors. Dogs’ brains are also specialized to be able to interpret all of the extra data. Their olfactory bulb (the part of the brain involved with the sense of smell) is 40% larger than ours, relative to brain size. All that extra processing power lets dogs get loads of information from smells that we barely notice. 

Tracking down the source of a smell is way easier for dogs than it is for humans. They can distinguish tiny differences in the strength of smells as they fade over short periods of time. You can imagine that as someone walks, each step leaves a smell “footprint”. In the second between one step and the next, the smell of the previous “prints” gets a little fainter. This lets dogs know what direction an animal was going, and gives them a clue about how long it has been since they walked by. 

Dogs can even smell directionally, in 3-D because they smell independently from each nostril. The same way we use our two eyes to get depth perception, dogs can tell the direction and approximate location of something smelly. Their noses have a special structure called an alar fold, which pushes the air out of the sides of the nostrils when they exhale. This creates suction and brings different air into their nose when they sniff in, meaning they get a fresh new batch of smell particles to enjoy. In addition, dogs split up the air they breathe, with most of it going to the lungs, but about 12% going directly to the nasal turbinates–the complicated, scroll shaped structures inside the nose which increase the surface area for smell receptors.

Dogs even have a whole extra organ for smelling which humans lack. The vomeronasal organ, or Jacobson’s organ, is located between the nose and the roof of the mouth. It allows dogs to sense and interpret pheromones through smell or taste. This gives dogs an extra way to learn how other dogs, animals, and humans are feeling, since specific pheromones are produced when someone is excited, scared, or angry. Dogs can also use this sense to distinguish the age, sex, and overall health of everyone they meet. 

The smells of the world are rich and exciting for dogs. Sniffing out a new smell might be like reading a book, or looking at a beautiful painting–they can learn new things about the world, as well as engaging their brains. Giving your dog a chance to stop and smell the flowers (and all the other weird stuff they want to smell) is important to keeping them happy, alert, and engaged with the world around them. Some dogs might enjoy special “scent work” training, learning to identify and locate smells on command. Others might do well with smell-based puzzle toys that let them solve problems with their nose. Long walks where dogs can sniff up tons of new smells from strange people and animals are a great way to keep your dog sharp. Want to give your pup a little extra time to enjoy their sniffer? Consider hiring a dog walker!