Of all five senses that man and dog have in common, smell/scent (or olfaction) is, in my opinion, the one that differs the most between both species.
Human smell – Different smells are captured by the olfactory nerve, which receptors are found within the lining of our nasal cavities. This nerve ends in the area immediately below the brain’s frontal lobes, which makes it very short. Smell may influence our behaviour – for example, a newborn baby moves his mouth towards the source of the odour of his mother’s milk, ignoring other odours. At this age our brain functions don’t differ much from the brain functions of other animals, so we may assume that smell is as important to a newborn baby as it is to a two week old puppy. However, as the infant grows his sense of smell becomes less important whereas other senses, especially sight, become more important. With dogs, things evolve quite differently.
Dog’s smell – scent is, by far, more developed in dogs than in humans. A dog’s nostrils can be used independently from each other. Dogs have much larger olfactory bulbs and possess around 220 million scent receptors in their nose as opposed to man, who only has 5 million. Dogs have a much larger area of nasal membrane than us. Through scent, they gather a tremendous amount of information from the environment, other dogs, people, places, other animals. . . and can learn to detect drugs such as cocaine and cannabis, detect explosives and cancerous cells. They can even detect a seizure in a human before it occurs, and detect a variety of substances at concentrations one thousand to one million times lower than we can.
How does the dog’s nose function? The dog can smell and he can sniff.
A dog resorts to sniffing not only to communicate with other dogs and gather information from pheromones released by them, but to also identify weaker smells such as diluted or hidden substances. The septal organ is the most sensitive part of the dog’s nose and it is responsible for initiating sniffing behaviour, which is different from regular breathing patterns.
The dog’s moist nose is typical of animals with an acute sense of smell as opposed to humans, who have dry noses. According to Dr. Caroline Coyle, moist noses may attract odour molecules and keep them in the vicinity of the nasal openings.
Another organ which plays a very important role in the dog’s excellent sense of smell is the vomeronasal (or Jacobson’s) organ. Due to its location, smells can reach it via the nose or mouth. They are channelled to this organ by a slow opening and closing motion of the mouth, which allows for a more accurate analysis of smells.
So amazing is the dog’s sense of smell, that it is more accurate than a lot of odour detecting devices on the market!
Taste is the sense that we’ll be comparing in the next article.
Canine behaviour consultant, trainer and author of Dog Care Books