Untertitel: WDR mediagroup digital GmbH im Auftrag des WDR
A terrible stench to some, a lovely fragrance to others.
The perception of scent varies tremendously
as do natures "smelling devices".
There are countless variations in the appearance of noses.
But what really matters lies beyond the nostrils.
Many animals rely on smell as their primary sense.
Even in our own everyday lives odours play a bigger role
than we commonly think.
Pure, uncorrupted air seems to waft through the village.
Up close it's a different story.
Scents in every corner, which sniffer dog Kelly
has a much higher appreciation for than her owner Angelika.
The drug detecting duo get ready for their shift at customs,
while their landlords downstairs prepare a midday feast.
Fried sausage aroma permeates the house.
Molecules of water vapour, grease and meat create a potpourri,
that we register as "Bratwurst".
The fact that we perceive some odours as pleasant
and others as repulsive benefits our health.
Our nose helps us to distinguish between edible and spoiled foods...
...and it warns us to keep away from potentially hazardous feces.
How we interpret a scent
depends on the concentration of the substance.
Musk, when highly diluted, gives a perfume that special something.
The smell of pure musk, however, rivals that of a full diaper.
Odorants are inhaled with every breath.
A portion of foreign substances like dust or bacteria
are stopped by the mucous within the nasal passages
and are eliminated in tried and tested fashion.
Our perception of the aroma depends upon the number
and the kind of volatile molecules
that find their way to the olfactory region.
More than 10 million receptor cells
project from the roof of the nasal cavity.
Each of these cells carries microscopic hairs.
Certain odorants bind to certain receptors.
When a molecule hits a compatible hair,
it adheres and thus stimulates the cell.
The signals sent out by the stimulated cells come together
in the olfactory bulb.
When a number of signals arrive simultaneously,
the message is transmitted from the olfactory bulb
to other regions of the brain.
Only then do we consciously recognise
and interpret the current scents around us.
The brain often links certain smells to very specific memories.
When a dog encounters a certain aroma,
perhaps even they start reminiscing about their very first sausage.
Back in the present: German shepherd Kelly on her way to the airport.
Dogs like Kelly
are invaluable assistants in providing flight security.
Their sensitive noses help customs officers
detect illicit drugs or explosives.
A human wouldn't be a suitable sniffer at all.
Our 10 million receptors pale
in comparison to the 200 million inside a dogs nose.
Their sheer multitude enables a dog
to sense every nuance of even the faintest odour.
Score: security 1, criminals nil.
Without their canine partners
customs officers would hardly stand a chance of finding the needle
in the haystack of countless bags and suitcases.
A training session for Kelly:
Her task is to find a suitcase in which her trainers hid marijuana.
Her favourite toy, a plastic tube, contains some of the herb.
But she doesn't know
inside which suitcase this tube is hidden today.
She remembers the smell and knows that when she detects it,
she gets to play with her plastic toy.
Motivation enough to hunt for the faintest traces of scents
of which we don't have even the slightest perception.
For canine supernoses there are other employment opportunities
besides drug detection.
Some dogs are flown into regions of conflict
to help discover bodies or land mines.
Its vision wouldn't get this "flying nose" very far.
Mosquitoes carry scent receptors on their antennas that can detect a gas
thats completely odorless to us: carbon dioxide.
Because their victims constantly exhale CO2,
the bloodsuckers thus have an easy time locating their victims.
Sweat and body heat are clues that lead them to the red elixir.
Most insects employ smell to discover food sources.
Ants take it one step further, they communicate via scent.
A scout ant marked the way to the sweet banquet with her scent gland.
The scent marks act as beacons to guide her comrades to the feast.
Much to the dismay of the human sweet tooth...
...who retaliates with rather drastic measures.
Beyond the pipes, a place permanently dark and damp.
This is where possessing sensitive nostrils really pays off.
Eyes are practically useless around here,
but fragrances travel far in moist air.
The average person can smell
a doughnut from a distance of several meters.
A rat can perceive
the tempting flavour from several hundred meters away.
This is the home of the ultimate "supernose".
A champion who doesn't even boast a massive conk: the eel.
His olfactory receptors
lie in two tubes that can be moved independently.
Just like we see in three dimensions an eel can smell three-dimensionally
and thus sniff out its preys exact position.
Odorants waft through the water just like they do in the air.
The eels nose is so sensitive
that it would be able to detect the aroma of the dead fish.
Even if it were diluted with the volume of the lake of Constance:
billions of liters of water.
A horses sense of smell is also highly developed.
For the ungulates, scent is an important means of communication.
They recognise each other based on their individual body odour.
An intense aura pervades the stables.
Those who spend an extended period of time within,
will soon no longer smell the stench.
Their receptors become temporarily "immune" to the present odorants
and no longer send signals to the brain.
A new arrival has an entirely different perception.
The human nose is much less sensitive than that of a horse.
Still, we also use scent for communication:
We try to seduce with perfume or tempt
the adored with the smell of roses.
There are others who also enjoy the fragrance of flowers:
Butterflies are attracted from distances of several kilometers
by the smell of nectar.
For some of the males among them,
there is an even more irresistible smell in the air.
Females, ready to mate, exude pheromones
fragrances specifically geared towards the males of their species.
This volatile message lures potential partners from afar
to the object of desire.
The human body also gives off pheromones.
However, we don't perceive them on a conscious level.
Still, they do play a role in whether we succumb
to someone's aura or smell a rat.
Our olfactory sense is by no means a "supernose",
compared to most of our fellow creatures.
Yet it's an important part in our arsenal of senses
that help us interpret the world around us.
A world in which tastes vary tremendously.
Copyright WDR 2012