It’s no secret that dogs possess powerful sniffers. In the same way humans perceive the world via vision, dogs see the world primarily through smell. Capable of catching scents at long distances or great depths, dogs have been put to work rescuing people and sniffing out drugs and explosives. Dogs have specialized noses that make that long-distance sniffing possible.
While breathing and smelling are the same action for humans, a dog’s nose is built to separate the two. Dogs have a fold of tissue inside their noses that separates air for inhaling and air for smelling. When a dog breathes, a portion of the air is directed a bony network called turbinates, dedicated to olfaction, while the rest of the air is diverted to the lungs. Dogs will take deeper, longer breaths for breathing, and use a short sniffing action to smell something. When a dog exhales, air is pushed out of slits in the sides of their noses, creating an airflow that draws new smells into their nose.
Dogs can detect tiny amounts of smell diluted in air, water or even underground. According to the Marbach Road Animal Hospital, dogs can pick up scents that are diluted to 1 or 2 parts per trillion; This allows them to smell things buried 40 feet underground. In one experiment, a dog was capable of sniffing out whale poop floating in Puget Sound from a mile away, according to Nova. The Whole Dog Journal states that dogs have scented people drowned in over 80 feet of water. Their ability to pick up on tiny traces of a particular scent is what allows them to follow trails that are a week old and even detect cancer cells.
Dogs have an organ that humans don’t possess: the Jacobson’s organ. It's an organ located in the bottom of the dog’s nasal passage that allows dogs to pick up on pheromones. These are important chemical cues all animals produce that signal things like when they’re ready to mate. The Jacobson’s organ is also important for dogs recognizing the scent of other dogs in their pack or puppies locating a nipple to nurse, If a dog is trying to get more scent to his Jacobson’s organ, he may pull back his upper lip and rear back his head, called the “flehmen” reaction.
Compared to Humans
A human’s sense of smell pales in comparison to a dogs. Depending on the breed, a dog's sense of smell is 10,000 to 100,000 times what a human is capable of, according to Nova. Humans only possess about 6 million smell receptors while our canines can have up to 300 million. The Marbach Road Animal Hospital says that the part of the brain dedicated to processing smells in 40 percent larger in a dog than in a human brain.
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