You may have heard the popular phrase "let them sniff" but just how important of a role does scent play in our dog's lives?

Remarkably, with training, dogs can sniff out bombs, drugs, pursue suspects, and find dead bodies. And more and more, they’re being used experimentally to detect human diseases; cancer, diabetes, tuberculosis, and now, malaria all just from the smell alone. But just how powerful is a dogs nose? And why is it so important for their overall health and well-being?

Well, compared to humans, a dog's olfactory cortex contains more than 250,000,000 more olfactory receptors. Your dog's nose is so powerful, it can detect a scent at remarkable concentrations.

The olfactory cortex is the structure in the front of the brain that sends information to the other areas of the body's central command for processing and it is at least 3 x larger than ours despite the size of their brain is much smaller overall. The vomeronasal organ is used separately, to detect pheromones - the chemicals produced by other dogs and animals to signal messages.

*Schematic structure of the olfactory system in dogs and humans*

A Nose For Emotions

The olfactory cortex is also the part of the brain which is responsible for emotions, memory and behaviour and so a dog's sense of smell is likely more important to them than any of the other senses. Their olfactory cortex being completely indispensable to them - it can both inform and forworn them.

By simply smelling, and interpreting the amines and acids emitted by other dogs, a dog can determine if a new friend is male or female, happy or aggressive, healthy or ill. Dogs can gain a general understanding of one another by a loose sniff however, to be able to get more intricate information - they must get more personal, this is what is happening when we see dogs sniff one another's private parts!

A simple scent can have a host of complex meanings, memories and emotional ties for our dogs as the scent is directly linked to both memory and emotion via the limbic system. Smell memories are thought to last for their entire lifetime! and can be used to elicit a positive emotion to assist in cases of fear and phobia.

These scent memories allow dogs to easily identify other dogs they haven't seen for years. Even more interestingly - dogs that are in the same family which have been separated for some time can pick up on the changes in odours which can translate to where the dog went, what they fed on etc. - all of this just by using their sense of smell!

Using Smell to Perceive The World;

When a dog sniffs - the air flows into the nostrils and enters the nasal passage which is lined by nasal membranes - if these nasal membranes were laid out flat they would have a larger surface area than the area of the dog's entire body. This nasal membrane is on average around 7 square meters!

This process is completely different to when a dog breathes in air normally - in which case the air floods in through the nasal passage and continues down to the lungs. Dogs' noses also function quite differently than our own. When we inhale, we smell and breathe through the same airways within our noses. When dogs inhale, a fold of tissue just inside their nostril helps to separate these two functions.

It is well theorized by Vallortigara et al. that dogs use each side of their nose for different types of scents. On the left side, normal odours are picked up and filtered through the olfactory epithelium and on the right -The vomeronasal organ filters non-volatile odorants such as pheromones - chemical signals that stimulate behavioural and/or physiological changes.

*This schematic shows the traditional structure of the chemical substances detection system.*

Whilst we humans rely mostly on our sight sense, for dogs it's all in the nose - “What the dog sees and knows comes through his nose,” affirms Barnard College professor Alexandra Horowitz in her book Being a Dog: Following the Dog Into a World of Smell. “The information that every dog — the tracking dog, of course, but also the dog lying next to you, snoring, on the couch — has about the world based on smell is unthinkably rich.”

Allowing our dogs freedom to sniff - especially whilst out of the household environment is crucial to your dog's happiness and wellbeing. After all, A mentally stimulated dog is a happy dog. There are a variety of things you can do to enrich your dog’s life and stave off boredom. Just 15 minutes of sniffing consumes the same amount of calories as an hour's walk.

Here are some benefits of just letting your dog sniff on a walk;

lowers pulse and creates a feeling of calm
lowers cortisol levels, therefore, reducing stress - which can aid in the management of behavioural issues.
A slow walk whereby the dog is given plenty of opportunities to stop and sniff uses up more energy and calories than they would on a fast-paced walk such as a walk to heel. This is a great way to tire out puppies or adult dogs who frequently display destructive or mischievous behaviours in the home.
Provides mental stimulation - a mentally stimulated dog is a happy dog.

A new study by Charlotte Duranton and Alexandra Horowitz investigated how much dogs sniff based on the length of their walk and the length of their lead.

In conclusion, it found that off-lead dogs spent 3 x the average sniffing time of dogs on short leads and that dogs on longer leads spent almost the same amount of time as the off-lead dogs and again 3 x the average sniffing time of the dogs kept on short leads.

This study also found that sniffing resulted in lowered pulse rates, and the more intensely they sniffed, the more their pulse rates lowered. Pulse rate was also lowered when dogs “shook off” during walks on all leash lengths. The “shake off” behaviour was often seen when the dog’s pulse rate was particularly high.

There are lots of things we can do both at home and out and about to offer enrichment for our dogs and provide ample sniffing opportunities.

If it's safe to do so - use a longer lead to walk and in controlled environments, let your dog off-lead so they can freely explore.

Slow walks down - contrary to popular belief, dog walks don't have to be lengthy. Studies show that shorter walks whereby the dog is given ample opportunity to stop and sniff uses up much more energy.

Letting your dog choose the walk by allowing them to freely follow their noses can be a much more beneficial experience for both dog and owner. Paying attention to the things your dog likes to sniff the most will help you learn more about your dogs too.

Foraging - scattering pieces of healthy food across the floor (indoors or out) can encourage your dog to use their noses.

hide and seek - if toys are your dog's thing try hiding them around the house in unusual places and let your dog sniff them out.

puzzles - there are so many different pet puzzles available on the market - the Nina Ottoson brand is a favourite of ours. They allow you to hide your dog's favourite treats and your dog has to use their nose to seek them out. Each puzzle game increases in difficulty so you can be sure that there will always be a new challenge for your dog to go after.
kongs - snuffle mats - treat balls are also great nose work toys that can be purchased inexpensively