The dog's sense of smell is very advanced and hard for us simple humans to understand. It is probably the dog's most spectacular and crucial of all the senses. The sensory receptor cells in a dog's nose are highly evolved. The brain picks up messages from the nerves in the nose and processes and stores up this information.
They can utilize each nostril independently and are adept at differentiating one odour from another and remembering it.
Dogs use scents for various functions including marking territory, recognising other animals, and communicating with other dogs.
Dogs are able to bond with humans through their senses. Although they do see you and hear you, the dog most identifies with your smell. They can determine your mood and emotional state from your body language and by the scent you are giving off.
We can't compare to our dog's sense of smell and It's been said by some scientists that a dog's sense of smell is 100,000 times more efficient than a human's.
Dogs can apply their sense of smell for such tasks as tracking missing persons, rescuing people underground, helping to find survivors after disasters such as earthquakes and tracing gases, that humans may be incapable of smelling. A dog's sense of smell can detect drugs, explosives, and the scents of their masters.
Some dog breeds, such as the German shepherd and the bloodhound, have a much more keenly developed sense of smell than other breeds and can be used as specialists in their particular fields with police forces and customs officers.
Dogs have a good sense of smell when they are born. When a dog gives birth to puppies, she will immediately lick the pups and her teats so they can find their way back to her, using their sense of smell, to feed and bond with the mother.
Without this highly developed sense of smell the bonding process could never begin.