How do dogs smell so much better than we do?
A dog brain is built around smell the way ours is built around sight. A bloodhound can follow a trail that is several days old.
βΆ Start the storyDogs smell better than we do because far more of their body and brain is devoted to it. The human brain is dominated by a large visual cortex, while the dog brain is dominated by a large . Dogs have roughly forty times more smell-sensitive receptors than humans, from about 125 million to nearly 300 million in some breeds, such as bloodhounds. Compared with humans, dogs have a superior sense of smell and hearing, but less acute vision.
The hardware shows up in the nose. Humans have about 10 square centimetres of , the lining that holds the receptors, where some dogs have 170. A dog's epithelium is also more densely innervated, with a hundred times more receptors per square centimetre. The that receives the signals is roughly 40 times bigger in dogs than in humans, relative to total brain size. The bloodhound is the champion: the breed is known for its ability to discern human scent over large distances and extended periods of time, and it can follow a scent trail left several days in the past.
Human
- About 10 square centimetres of
- Visual cortex dominates the brain
Dog
- Up to 170 square centimetres in some dogs
- Receptors: about 125 to nearly 300 million
- dominates the brain
People put this to work. are trained to find explosives, illegal drugs, currency and other things, and the sense they use most is smell. They can track bed bugs in every phase of their life cycle, and a US Department of Agriculture study found that sniffer dogs identified citrus trees infected with citrus greening disease with 99% accuracy, as early as two weeks after onset. But a better nose is not a perfect detective: a 2006 review in New South Wales found that prohibited drugs turned up in only 26% of searches following an indication by a drug sniffer dog.
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Recap
More receptors and a bigger smell brain make dogs better sniffers, though their alerts are not always right.
π‘ A trick to remember it Β· A dog sees the world through its nose the way we see it through our eyes: its smell brain is the big screen.
Surprising fact Β· Dogs have roughly forty times more smell receptors than humans, up to nearly 300 million in bloodhounds.
Sources (5)
No source, no claim. Every fact in this lesson (13 claims) cites at least one of these.