Caleb McLaughlan, of Balclutha Primary School, asks :-

Why are dogs better at smelling than people?

David Thomas, an animal nutritionist at Massey University's Institute of Veterinary, Animal and Biomedical Sciences, responded.

Dogs are better at smelling because they have bigger noses and use more of their brains to distinguish the different smells. More specifically, they have a much larger lining to their nose where the smells are detected. In both dogs and people, this region has folds which increase the area of nose lining; however in dogs this area is between 18 and 150 square centimetres (depending on the breed/size of the dog), compared to only 3 to 4 square centimetres in people.

The dog also uses other methods to maximise its ability to smell, such as sniffing. A sniff is not a normal breath, but a quick series of small inhalations and exhalations, with the sniffed air trapped in the nose and held next to the smell receptors. People can’t sniff like dogs can. When people sniff, they breathe in and out through the same holes (nostrils) and only smell the air briefly as it passes through the nose on its way to and from the lungs. In dogs, each nostril is smaller than the distance between them. This means that dogs inhale air from two distinct regions of space, allowing them to work out the direction of a smell.

The sniff also funnels stale air out through the sides of the nostrils, and pulls new air into the nose. Once inside a dog’s nose the air is exposed to up to 300 million smell receptors, compared with a person 6 million. Nerves run from these receptors and relay signals to the brain. The area of the dog’s brain that processes the smell information, takes up 12.5% of their total brain mass, while in people it accounts for less than 1%. All this makes a dog’s sense of smell a thousand times more sensitive than that of people.