What dogs’ noses know and how they work.
This essay was originally posted on Psychology Today
How dogs sense their world with their fascinating noses: Sniff first, ask questions later.
With 300 million receptors to our mere 5 million, a dog’s nose is estimated to be between 100,000 and 100 million times more sensitive than a human’s.
For decades I’ve been interested in “all things dog,” focusing on their cognitive, emotional, and moral lives, and how they sense their world. Anyone who’s spent even a short amount of time around dogs knows they love to snort and sniff just about everything, including odors that we find utterly repulsive. We all know dogs like to stick their noses everywhere, and they often snort when they’re doing it or shortly thereafter. Their supersensitive noses are legendary, so much so that their approach to life could be summed up as “sniff first, ask questions later.” When they can, dogs will spend upwards of 33% of their time with their noses pinned to the ground, and we also know they’ll freely put their noses into body parts, including groins and butts, that we think are disgusting and totally inappropriate. For example, in Canine Confidential: Why Dogs Do What They Do I write about various dogs including Bernie and Beatrice, “the butters,” and Gus and Greta “the groiners,” along with Sammy the schnozzola—whose noses know no bounds. These dogs can’t stop shamelessly running up nose first into everyone’s privates, which always ignites many questions about what dogs are smelling and why, since they clearly enjoy it. And now, Norwegian dog nose expert Dr. Frank Rosell, a professor in the Department of Environmental and Health Sciences at University College of Southeast Norway, tells us all there is to know about dogs’ noses and why they never seem to get enough of using this amazing organ in his new book called Secrets of the Snout: The Dog’s Incredible Nose.
I reached out to Rosell to see if he could take the time to answer a few questions about his book and also tell us more about how dogs’ noses work, and he said he could. Our interview went as follows.
“It is said that a dog that has lost its sense of smell is no longer a dog.”
Why did you write Secrets of the Snout: The Dog’s Incredible Nose?
When I was 12 years old, I got my first dog, a Shetland sheepdog named Tinka. That was the beginning of a lifelong fascination for dogs and their olfactory capabilities. When I was approaching the middle of my career, I wanted to begin incorporating dogs into my research. I tried to find a book that covered “everything” about the secrets of the dog’s snout, but I could not find one. Therefore, I decided to write the book myself. I also wanted to learn more about all the different disciplines this field encompasses, including agriculture, environmental studies, zoology, entomology, criminology, medicine, psychology, and wildlife biology. It was my hope that this book would contribute to bringing these disparate disciplines a little closer to one another and to open up new collaborative opportunities in the future. The dog still has a large, untapped potential as a working animal.
How does it follow up on your previous research?
My initial study focus was chemical engineering, but my fascination with the behavior of animals led me to chemical behavioral ecology as my field of expertise. I completed my doctorate in 2002 and became a full professor in this subject area five years later. For twenty years I have conducted research and taught on the odor-based communication of many different species of mammals, including the beaver, brown bear, yellow-bellied marmot, and European badger. I run a long-term research project on the Eurasian beaver at the University College of Southeast Norway. One of the main focuses has been olfaction in animal behavior; how animals use scent to communicate with one another. I have published more than 100 scientific papers on this and other related topics. My background research provided freezers full of scent samples from various mammals, which I used for my research on dogs.
What are some of your main messages?
Dogs have been domesticated for thousands of years but in the last 100 years, they have been trained to work in a variety of specialized fields. This is largely thanks to their noses. Dogs protect human life, both by serving to locate dangerous or missing people and detecting illegal substances and bombs. Dogs can also be used for medical purposes: detecting diabetes and the early stages of some cancer types and sniffing out invasive and rare animals and plants. The book also explains the importance of scent, including why dogs aim for the groin when meeting a stranger, and why felons who feel tempted to flee through the water should refrain from doing so. Dogs are fantastic, not only for their olfactory capabilities but also for the unique relationship we have with them!
Can you please tell readers about how dogs process odors and some surprises about dogs’ noses?
It is said that a dog who has lost its sense of smell is no longer a dog. When the dog’s nose is wet and cold it is easier for them to detect odors, due to glands that produce an oily fluid. How odorants enter the nostrils and the structure of the nose itself, with its olfactory recess located farthest back in the nostril, are both important for dogs’ keen sense of smell. When a dog sniffs, the air follows a side route and enters the olfactory recess, which contains genes for olfactory receptors, and olfactory receptor cells that absorb odorants. The olfactory mucous membrane is spread across a labyrinth of bone structures called nasal turbinates and is covered with millions of tiny olfactory hairs which capture odorants. When gaseous odorants come into contact with the olfactory membrane, they are dissolved in the layer of mucus. Odorants that are easily dissolved are released in the front part of the olfactory recess, while moderately soluble and insoluble odorants are distributed more evenly across the entire olfactory recess. How the odorants are deposited therefore plays a role in compound recognition. After the odorants have passed the olfactory receptors, they are transformed into an electrical signal that travels via the olfactory nerve to the olfactory center of the brain where the information is interpreted.
There are many surprises about the dog’s nose. Many of us have heard that the dog has a much better sense of smell than human beings. In general, the dog’s nose is 100,000 to 1 million times more sensitive than the human’s, while the bloodhound has a nose that is 10 to 100 million times more sensitive than ours. The section of a dog’s brain related to processing smells is almost seven times larger than ours. In addition, the dog’s fantastic sense of smell can be explained by the fact that dogs don’t exhale when sniffing a faint scent. This enables the dog to sniff faint odors without disturbing or destroying them. Dogs have a wing-like flap in each nostril that determines the direction of the airstream in and out of the nose. When the dog inhales, an opening above and beside this flap allows air to pass through. When the dog exhales, this opening closes and the air comes out below and beside this flap through another opening, enabling the dog to increase its collection of odors. As a result, the warm air that is exhaled flows backward and away from the odor being sniffed, preventing them from mixing. Dogs also use their nostrils differently according to the nature of the scent. During behavioral trials, when dogs sniffed at unfamiliar smells that were not dangerous, first they used the right nostril and then switched to the left nostril to sniff at the odors again. Once they had become familiar with the smell, the left side of the brain took over. When they sniffed sweat odors from veterinarians who worked at a kennel, they used only the right nostril. In short, the left and right sides of the brain take in different kinds of information. The right side of the brain is associated with intense feelings, such as aggression, flight behavior, and fear. For most dogs, a veterinarian is a frightening person.
Who is your intended audience?
The book is written for dog enthusiasts, dog researchers, and people who wish to broaden their knowledge about dogs in general. I especially hope that it will benefit all people who wish to make dog training, especially in specific fields, aware of what has been done and what can be done. I also hope it will make a good “starting point” for dog trainers, handlers, and researchers to do the same or come up with new ideas. If the reader wants to get deeper into this topic they have a very good “starting point” with this book due to the references cited. I hope dog trainers, SAR people, customs, the military, and the police will use the book as their course syllabus. Other groups interested in the book may be dog school trainers, hunters, and of course people interested in the relatively new sport “Nose work”.
Here are some specific examples:
- The pet dog owner who wants to understand how the dog’s nose works, what humans use the dog’s nose for or use their own dog(s) for nose work;
- Dog trainers who want to help their clients to become successful in all types of detection dog work;
- Veterinarians who want to understand how the dog’s nose works;
- Lawyers and expert witnesses who use canine-based olfaction evidence in court;
- Administrators of hospitals and health care facilities who want to understand the success of dogs in detecting cancers and other diseases;
- Scientists at all levels who want to study dog olfaction.
What are some practical applications for people who live with dogs?
I think the topic of canine olfaction is a timely one because of the diverse uses of the dog’s sense of smell ranging from life-saving (cancer detection) to fun (nose work). Dogs love to sniff here and there and it’s essential to allow them to do so. I hope that more dogs will have the chance to enrich their lives as working dogs, whereby they will be given a range of tasks for the use of their noses, for their own pleasure, and ours. Giving a dog the chance to perform work tasks and to make decisions is important for its well-being. I have given my own dogs, three Border collies, these opportunities. I really hope that after reading this book you will arrive at plenty of new ideas to get your dog(s) into sniffing activities that will enrich their lives as well. Our amazing “best friend” deserves that!
What are some of your current and future projects?
At the moment I have several students (BSc, MSc, and PhD) working on dog-related questions. We are working on the following projects:
- Can dogs tell us if beaver scents code for sex?
- Can dogs be used as a model species, by attaching tri-axial accelerometers on their back, to figure out how other canines scent mark their territories?
- Can dogs scent-match individual beavers by sniffing out their anal gland secretion?
- Can dogs recognize the scats of rock ptarmigan and distinguish this species from the willow ptarmigan?
- Do dogs have an innate ability to recognize predator scents?
- Can dogs tell the sex of another dog by sniffing scent from their feet or footprints in the snow?
We just submitted a scientific paper called “Dogs as scent mark sniffers: discrimination of native Eurasian beavers and invasive North American beavers.” I hope that one day dogs can be used as an efficient non-invasive tool to manage the invasive North American beaver in Europe. We will also soon start to train dogs to sniff out invasive beetles from Asia.
Is there anything else you’d like to tell readers?
As visual creatures, the sense of smell is difficult for us humans to understand and therefore to appreciate in the dog. We can’t see odors. However, the dog’s nose is the organ most people are curious about because it’s so much more sensitive than our own, and dogs use it most of the time, often in ways we wish they didn’t. On many occasions, we simply don’t understand why they’re doing what they’re doing as their nose leads the way. I hope dog owners will understand more about this fascinating topic after reading the book. Look closely at how your dog uses its nose when you are out on your daily walk, or when doing some training. Take a look at their tails as well; is it wagging to the right or the left? Many will be surprised how important the snout is for them and many scent tasks make them happy. However, there’s still a lot we don’t know, and I want to help with that. Students that are interested in dog olfaction are welcome to contact me at the University College of Southeast Norway. And please feel free to check out my Facebook page with the same name as the title of this book.
Let dogs sniff to their nose’s content
Thank you, Frank, for a very informative and detailed interview. I hope your groundbreaking book will read an international audience. Knowing more about dogs’ noses and how and why they snort and sniff will surely make living with a dog and watching them interact with one another, with humans, and with their environs more interesting. There are some very good reasons why dogs need to sniff and it’s important for them to be allowed to use their senses and not suffer from sensory deprivation. As you note, there also are some important practical applications about knowing more about how dogs sniff their world. It’s essential to know as much as we can about the behavior of dogs so we can give them the best lives possible.
All in all, a dog’s nose is a work of art, an exquisite adaptation, evolution at its best. And all without a plan or goal. When people tell me they wish they had a dog’s nose, I hasten to add they should be careful what they wish for. I’m happy to know about this most remarkable adaptation, but even I don’t have any desire to experience all of the many odors dogs take in and clearly savor.
When it comes to smells, we should let dogs be dogs and not hold them to human standards of propriety. This means we should let them sniff one another to their nose’s content and, for example, we must let their walks be their walks, not ours, as frustrating and challenging as this might be. Dogs’ sense organs, like their muscles, heart, and lungs, need to be exercised, and we need to make time for them to do so.
Bekoff, Marc. Canine Confidential: Why Dogs Do What They Do. Chicago: University of Chicago Press, 2018.
Rosell, Frank. Secrets of the Snout: The Dog’s Incredible Nose. Chicago: University of Chicago Press, 2018.