How far can dogs smell? And other ‘nosy’ questions answered

Dogs have a truly astonishing sense of smell that goes far beyond anything we could imagine. From picking up the scent of a potential mate miles away to uncovering an explosive, a dog's nose is always hard at work – particularly if it belongs to a scent hound – but exactly how far can dogs smell?

Over the last century, this special skill has been put to incredible use through specific training to help dogs detect everything from drugs to diabetes. In this article we'll take a look at the incredible world of canine olfaction, with the help from experienced vet Dr. Rebecca MacMillan.

A dog’s sense of smell

Research suggests that smell is a dog’s main sense and allows them to uncover current and historical information about their surroundings. Using the power of their nose, your dog can build a three-dimensional view of their environment which in the past would have helped them to discover food, avoid threat and find dogs to mate with.

“Dogs have an incredible sense of smell. They have many more smell receptors than humans and a greater surface area to pass more air through,” says Dr MacMillan. A receptor is a part of the nose responsible for recognising specific smell particles. The bigger surface area helps too, as it allows more air to pass through their nose giving them more opportunities to pick up smells.

Out on a walk, you likely notice your dog's preoccupation with sniffing. It can dominate the walk and sometimes get in the way of getting to where you want to go. But if you find yourself getting annoyed, you probably don’t realise just how impressive and important this super power is to your dog.

Dog sense of smell vs humans

And how could we begin to understand? Our sense of smell is, I’m sorry to say, rubbish in comparison! Depending on the breed, a dog's sense of smell is reported to be 10,000 to 100,000 times better than ours.

How far can a dog smell?

“According to some sources, dogs can smell objects or people up to 20km away under the right conditions,” says Dr MacMillan.

Some specific research into this question has found that dogs can detect the smell of a wild tortoise from up to 60m away, a rodent in the natural environment up to 50m away, decaying meat up to 200m and whale feces up to 1.93km away.

What affects how well a dog can smell?

“Factors that affect how far a dog can smell include wind conditions and the terrain. The age and type of scent will also influence how far it can be detected,” says Dr MacMillan. Outside of environmental and weather conditions, these factors can impact a dog's ability to smell:

• breed
• age
• physical health
• medication
• training

Which breeds of dog have the best sense of smell?

“Research findings are still mixed as to whether dogs with elongated noses can smell better than dogs with flatter faces. However, we know that bloodhounds, basset hounds, German Shepherds and pointers all have a great sense of smell,” says Dr MacMillan.

Certain breeds are bred specifically for their sense of smell, too – most of these dogs are hound breeds and they have a larger than average surface area in their nasal cavity.

Scent hounds, as the name suggests, have been bred specifically to use their sense of smell for tracking scents. They usually have long ears that help to collect scents out and about. They are also often low to the ground, enabling them to pick up more smells. Some of the most popular breeds with top notch sniffing abilities include beagles, basset hounds and bloodhounds.

What else can a dog detect with their nose?

“It has been shown that dogs can detect illnesses, such as diabetes or cancer in people, as well as smell explosives and drugs at trace levels,” says Dr MacMillan.

Because of their incredible sense of smell, dogs can be trained to track all manner of things from invasive species to missing people. Some of the best tracking dogs are police dogs who are trained to track suspects, find victims and recover evidence (including drugs, firearms and explosives).

While we might have dogs in the police force, they aren’t routinely used in medical settings, but that could change. Because a dog's sense of smell is so detailed, it can notice the subtlest change in human scent caused by disease. Add training to this natural skill, and we now have dogs that can detect all sorts of diseases.

One study found that trained dogs were able to detect breast cancer with 88% accuracy and lung cancer with 99% accuracy, across all four stages of the disease.

Another study showed dogs could correctly identify the scent of children infected with malaria parasites 70% of the time, just from the pair of socks they wore overnight. More research has found dogs can also help diagnose diabetes, Parkinson's disease and even detect a migraine attack up to 48 hours in advance.

How to make the most of your dog’s nose

Getting your dog one of the best snuffle mats for dogs will not only improve their scenting skills, but it will keep them stimulated and allow them to express their natural behaviour.

You can also use the power of scent to keep your dog happy next time you go on vacation – when you leave them with your pet sitter, give them a piece of your clothing too as the familiar scent can help them feel comforted in your absence.

Want to learn more about dogs? Here are our favorite interesting dog facts

Edited by Georgia Guerin.