Depending on the breed, dogs are said to smell between 10,000 and 100,000 times better than humans. They have up to 60 times more olfactory receptors and can smell up to 20 kilometers away in good conditions. The nose is also the primary sensory organ of dogs.
In humans, however, vision is the primary sensory perception. While we explore the world with our eyes, dogs sniff their surroundings.
Poor eyesight is therefore much more noticeable in dogs than in people. In addition, dogs' hearing is also much better.
This also explains why sniffer dogs are used by both the police and emergency services for a wide variety of jobs.
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How much better do dogs smell than people?
Dogs are said to hear between 10,000 and 100,000 times better than humans. At least that is the general consensus. [1, 2]
However, information between 1 thousand and 100 million can also be found on the Internet. In any case, your sense of smell is much better. [3, 4]
These numbers are hard to imagine for us. So let's go through an example together:
People with a healthy sense of smell are able to smell a sugar cube in a cup of tea (200 ml).
A dog that smells 10,000 times better can therefore smell a sugar cube in 12 full bathtubs. With a factor of 100,000, there are a whopping 120 full bathtubs.
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This also explains the following fascinating examples:
- A sniffer dog was able to sniff out marijuana that was vacuum packed inside a gasoline tank and completely covered in gasoline. [5]
- Trained sniffer dogs are said to be able to smell a corpse even through 5 meters of concrete.
- Dogs can smell up to 12 meters underground. [6]
By now you also know why the four-legged friends are used as rescue, avalanche and drug detection dogs.
Compared to humans, dogs smell between 10,000 and 100,000 times better. It allows you to detect a variety of smells that even the best human nose cannot smell.
Why do dogs smell better than people?
Dogs are nasal animals – so-called “macrosmatics”. Their sense of smell is therefore the primary sensory perception they use to perceive their environment.
Humans are said to be able to distinguish 1 trillion smells, but dogs far exceed this. [7] The following 5 factors explain why:
#1 More olfactory receptors
Olfactory receptors act as a kind of “docking site” for scent molecules. After docking, they trigger an electrical impulse that is then processed in the brain.
The more olfactory receptors a living being has, the more clearly and precisely it can perceive smells.
An average person has a total of around 5 million olfactory receptors and around 400 different types of them.
Dogs, on the other hand, have between 125 and 300 million olfactory receptors, depending on the species, and a whopping 800 different types of them. [8, 9]
Specifically, this means that compared to humans, dogs have up to 60 times more olfactory receptors and around twice as many different types.
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If elephants were cheaper to keep and a little easier to train, then we would probably have “sniffer elephants” everywhere at the borders and at customs.
#2 Different inhalation and exhalation
When people breathe in through their nose, the air goes through the nasal passage to the lungs. We then perceive the smell on the short path through our nose.
In dogs, on the other hand, only 88% of the air goes to the lungs when they inhale. The remaining 12%, however, flows through a labyrinth of olfactory receptors. [11]
Specifically, this means that dogs use part of the air specifically to be able to perceive all the odor particles it contains.
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But exhaling in dogs is also designed in such a way that, unlike humans, they do not have a “smell break”.
When we exhale, we blow all the air out of our nose, which transports all odor particles outside. The opposite is true with dogs.
When dogs breathe out, they let the air out through the side slit of their nose. This simultaneously creates a suction that draws odor particles into the nose. [12]
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This means that dogs smell consistently – both when inhaling and exhaling. They only have a “smell break” when they hold their breath.
#3 Second olfactory system
Unlike humans, dogs have a second olfactory system – the so-called “Jacobsonian organ”.
In humans, this also forms as a fetus, but it completely regresses by birth. [13]
This means dogs are able to absorb pheromones, hormones and other chemicals. All things that cannot be smelled by humans.
These give them conclusions about the species, gender and willingness to mate.
A puppy can therefore easily identify its birth mother in a crowd full of dog mothers. Human babies are incapable of this.
#4 Better signal processing
Although smells are absorbed with the nose, the processing takes place in the brain. And here too, dogs are superior.
More specifically, dogs’ odor “processing center” is around 40 times larger than that of humans. [14]
So you can not only absorb many times more smells, but you can also interpret them many times better.
In addition, their nostrils can work completely independently of each other and analyze smells separately. This helps them especially when it comes to locating smells.
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Dogs' olfactory memory is also superior. They can therefore recognize animals that they have only smelled once several years ago.
#5 Additional tools
Dogs don't let anything go wrong when it comes to their sense of smell. They therefore also have other special weapons that help them smell:
As paradoxical as it may sound, many sniffer dogs use their floppy ears to smell. Because when you run, your ears wag odor particles towards your nose.
- Additional nasal mucosa
Have you ever wondered why dogs always have wet noses? Well, this is a mucous membrane that picks up additional odor particles.
Dogs are naturally much more curious than humans. They therefore not only perceive smells passively, but also actively go on a “sniffing hunt”.
Have you ever noticed that many sniffer dogs have deep wrinkles on their faces? These not only capture odors, but also store them for later analysis.
Dogs smell better than humans because they have a second olfactory system and up to 60 times more olfactory receptors. They also perceive smells even when they exhale, can process them better and also use other aids to smell.
How far do dogs smell?
Under perfect conditions, dogs are said to be able to smell up to 20 kilometers away. [15] However, the actual range depends heavily on the following factors:
- Wind direction and speed
Smelling against a strong wind is much more difficult than with the wind. The same also applies to hearing.
It makes a big difference whether there is a meadow or a 10 meter thick concrete wall between the object and the sniffer nose.
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- Type and intensity of the smell
Like humans, dogs are more sensitive to some smells than others. They can therefore smell more penetrating odors from further distances.
There is a reason why police sniffer dogs go through at least a 6-month intensive training camp. This primarily trains their attention to smell.
The most impressive proof of the reach of dogs came from “Bobby the Wonder Dog.” He was lost about 2,500 miles from home during a family trip.
Within 6 months he found his way home independently. Completely dirty, with less weight and completely worn out toenails. [16]
Under ideal conditions, dogs should be able to smell around 20 kilometers away. However, this is massively influenced by the wind direction, wind speed and obstacles. The intensity of the smell and training also play a role.
What dogs can and cannot smell
Dogs explore the world through their noses. Compared to humans, they can therefore sniff out a variety of things that we cannot even smell in dreams:
CategoryCan dogs smell it?FearYes. When people are stressed and anxious, they release the hormone “adrenaline”. This is partially transported to the outside via the skin and can be smelled by dogs. [17]Covid-19Yes. The latest studies have shown that sniffer dogs can detect people infected with the coronavirus with an accuracy of around 94%. [18]DiabetesYesNo. Dogs can't smell diabetes itself, but with a little training they can smell high and low sugar levels. However, the success rate should only be around 40%. [19]BombsYes. Through special training, sniffer dogs can detect bombs and fuel that cannot be detected by even the most sophisticated devices. [20]CancerYes. According to studies, with special training, dogs have a 97% chance of being able to smell tumors. It is still unclear whether this applies to all types of cancer. [21]DrugsYes. Sniffer dogs can sniff out any drug they have been trained to detect. They also smell the drugs that were consumed by the owner. [22]PregnancyYes. During pregnancy, a woman's hormones change dramatically. Although dogs can smell this change, they do not associate it with the birth of a child. [23]Bed bugsYes. Specially trained dogs can sniff out bed bugs even behind walls. They are therefore used more often by exterminators. [24]Vacuum packedYes. Dogs can smell through vacuum-sealed plastic packaging, but not through airtight glass and steel containers. [25]MourningYes. Very trusting dogs can smell sadness from the hormonal changes. In addition, they can also recognize depressive behavior by their posture. [26]MenstruationYes. Dogs can smell a woman's period from both blood and hormonal changes. Their muzzle therefore goes between their legs more often. [27]CashYes. Specially trained dogs can not only sniff out cash, but can also sound the alarm when it comes to gold and silver. [28]
Basically, the wider and longer a dog's snout is, the better their sense of smell is. And vice versa.
The best dogs for this job are…