The Sniff

The dog nose, in most breeds, is anything but subtle.

Dogs do not act on the world by handling objects or by eyeballing them, as people might, or by pointing and asking others to act on the object; instead they bravely stride right up to a new, unknown object, stretch their magnificent snouts within millimeters of it, and take a nice deep sniff.

As we see the world, the dog smells it. The dog's universe is a stratum of complex odors. The world of scents is at least as rich as the world of sight.

Few have looked closely at exactly what happens in a sniff. But recently some researchers have used a specialized photographic method that shows air flow in order to detect when, and how, dogs are sniffing.

The sniff begins with muscles in the nostrils straining to draw a current of air into them - this allows a large amount of any air-based odorant to enter the nose. At the same time, the air already in the nose has to be displaced. Again, the nostrils quiver slightly to push the present air deeper into the nose, or off through slits in the side of the nose and backward, out the nose and out of the way. In this way inhaled odors do not need to jostle with the air already in the nose for access to the lining of the nose. The photography also reveals that the slight wind generated by the exhale in fact helps to pull more of the new scent in, by creating a current of air over it.

Dogs naturally create tiny wind currents in exhalations that hurry the inhalations in. So for dogs, the sniff includes an exhaled component that helps the sniffer smell. Watch for a small put of dust rising up from the ground next time your dog investigates with his nose.