A Guide To the Dog's Olfactory Super-power


It's not hard to see why our ancient ancestors recruited dogs to their domestic staff.

As well as being extremely intelligent, dogs are blessed with senses much more powerful than those of humans. In particular, their sense of smell is extraordinarily well-developed.

Dogs are capable of sniffing everything from drugs to electricity, underground gas pipelines to ovulating animals.

Recent studies suggest that dogs may even be capable of using their super-sensitive snouts to detect human illnesses from epileptic fits to cancers.

 How Dogs Smell

Smell is the dog’s dominant sense, so much so that a huge part of its brain is devoted to analysing odours. Dogs have two giant olfactory bulbs attached to the brain which decode every smell they encounter. The bulbs weigh around 60 grams, four times as much as human olfactory bulbs. Given that a canine brain is one tenth of the size of a human one, that means the canine brain has forty times as much of its brain devoted to smell as we do.
Little wonder then that a  dog’s sense of smell is reckoned to be 100,000 times better than a humans. In tests dogs have been able to pick up chemical solutions that form one or two parts in a trillion. That is the equivalent of smelling one bad apple in two billion barrels.

The source of the dog’s exceptional ability to smell is its wet snout. The moist leathery surface of the snout acts like velcro catching even the tiniest molecules of smells, then dissolving them so that the dog’s internal, smell receptor cells can analyse them properly. To keep his nose wet a dog must produce a constant supply of mucus through its nasal cavities. Scientists reckon the average dog produces a pint of this mucus every day.

What Dogs Can Smell

Dogs really can smell fear. If a dog goes into a room where a frightened dog has just left, he will appear anxious and agitated. This isn’t, as many would claim, some kind of
ESP type response. It’s caused by a scent, an alarm pheromone, which is produced by the anal glands of frightened dogs.

Dogs can detect odours that are up to 40 feet underground. They have been used to detect leaky gas pipes. They can also smell insects embedded in the ground or in woodwork. In the
United States dogs are used to sniff out termite infestations. Dogs can also pick up the faintest whiff of other creatures.
Guam, the US Department of Agriculture’s Wildlife Services use specially trained Jack Russells to sniff out brown tree snakes in the loading bays of aeroplanes.

Dogs can smell human fingerprints that are a week old.

Dogs’ noses are so sensitive that they can even smell electricity. While conducting an experiment, a researcher found that a dog could smell which of two compartments contained an electric current. He concluded this was because the charge resulted in the release of tiny amounts of ozone which the dog could detect.

Dogs can tell from the smell of a cow’s urine whether it is in oestrus, or heat. Farmers train them to do this so they know the best time to introduce a bull for breeding.

Dogs react in different ways to different smells. In tests, for example, it has been found that dogs relax when the aroma of lavender is fed into their environment. Camomile also makes dogs calmer.
 Rosemary and peppermint, on the other hand, makes dogs more excited.

As far as dogs are concerned, all humans have a unique smell. They can pick people out according to body and other odours they project. Scientists think the only way a dog wouldn’t be able to tell two people apart would be if they were identical twins on identical diets. The twins would also have to remain silent.

As a result of this, dogs can track human smells over long distances. Scientists think they can pick up on the difference in odours from different footprints to work out which direction their prey is headed. They can do this twenty minutes after a person has passed by even though the footprints are made a single second apart.
Scientists who tested four German Shepherds discovered they track footprints by dividing the job into three phases. During the first, search phase they move quickly, sniffing 10-20 times each breath. Once they have detected the smell they enter the deciding phase where they sniff at between two and five specific footprints. They do this for a longer period, slowing down as they do so. Finally, once the direction has been established, the tracking phase begin with the dog once more moving quickly.

 Sick Sense: How Dogs Smell Illness

Dogs can detect cancer in humans.
Scientists think that simply by sniffing samples of human’s breath, dogs can detect lung, breast and other cancers with an accuracy rate of between 88 and 97 percent. The accuracy rate of a multi-million-pound hospital scanner is between 85 and 90 per cent.
Dogs can also be trained to alert people with heart conditions they are about to suffer a seizure.

Dogs can also anticipate in advance when a person is going to have an epileptic fit.
A Canadian study found that dogs who lived with children prone to epileptic episodes behaved unusually in advance of the attacks.
Some dogs would lick the child’s face or act protectively. One dog even guided a young girl away from a set of stairs shortly before she had an attack. The dogs’ warnings came as early as five hours before the first symptoms of the epileptic episode were visible.
A separate study involving six dogs found that they could be trained to accurately warn owners who were about to suffer fits.
Health authorities around the world are now training “seizure alert” or “seizure response” dogs, some of which can predict fits, and all of which will respond in an appropriate way when an owner does have a fit. Some will be trained to stay with and guard the owner, and some even to press a button on a phone which dials the emergency services.

It remains a mystery how they are able to pick up on epilepsy in this way. Some think they pick up on tiny behavioural or scent cues. Others are convinced it is a reaction to electrical activity in the body. But the fact that dogs also respond to psychological seizures, which are non-epileptic and don’t display abnormal electrical activity, casts doubt on this.