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When a Dog "Nose" Best: Scent Science

Dogs have an amazing sense of smell, an olfactory system that is far more sophisticated than our own. With scent training, some breeds of dogs learn to perform specialized tasks, including helping monitor people with Type 1 Diabetes. These service dogs put their noses to work every day to save lives!

When a Dog Nose Best: Scent Science - Jedi, a diabetic alert dog after alerting to a low blood sugar
Above: Jedi, diabetic alert dog for 7-year-old Luke, after alerting a caregiver to a low blood glucose, which was confirmed using a blood glucose meter. Photo used with permission of Luke and Jedi's family. To learn more about Luke and Jedi, see Luke and Jedi: A boy and his dog fight type 1 diabetes together.

If you have ever taken care of a dog, you have probably noticed how important smell is in how a dog interacts with its environment. If you have ever walked a dog on a leash, you may have seen the dog sniff the ground and everything you walked by with incredible intensity. You may even have a dog that will stop at one bush, fire hydrant, streetlight post, or brick in a wall and sniff and sniff and sniff, oblivious to your attempts to shepherd it along. For a dog, every surface holds a potential roadmap and time capsule of scents that it can detect, differentiate, and track as it moves through its environment. This roadmap, invisible to humans, helps a dog understand its surroundings and keep track of its location. With training, a dog's strong sense of smell can be used to help detect, locate, and monitor very specific smells, scents that are imperceptible to humans.


A Powerful Sense of Smell

While most dogs seem to lead with their noses, how attuned your dog is to smell has a lot to do with the breed of the dog. Some dogs are better "sniffers" than others, but dogs, in general, have a much stronger sense of smell than humans. Scientists estimate that dogs smell 10,000 to 100,000 times better than we do and can detect some odors in parts per trillion!

Beyond the fact that dogs have many, many times the number of olfactory receptors that humans do (in the range of 300 million compared to our six million), the physiology involved in a dog's system of smell is quite different from a human's. According to a NOVA scienceNOW article on dogs and their sense of smell, the part of a dog's brain devoted to interpreting smell is 40 times larger than the part of the human brain that serves the same role. Dogs also have not just one but two olfactory systems and an extra smell-related organ, the vomeronasal (or Jacobson's) organ!

Dogs have a much more sophisticated sense of smell than humans, so much more smell power that it can be hard to really understand the magnitude of their ability to detect, differentiate, and follow scents. Think about the smell of bacon cooking or muffins baking. Think about the smell of a skunk that passes by your house at night. Even with our puny human sense of smell, a skunk in the night can be pungent. What would it smell like if intensified by a factor of 10,000? We may not be able to fathom the depths of what our own sense of smell times 10,000 might be like, but we know what it looks like. We see it in television shows and movies (like Max (2015)). We see it in stories about dogs in the military. We see it on the news when a dog helps investigators track down evidence that solves a case or finds a missing person. We see it in science news stories about dogs that can detect cancer by smell. We can even see it in action with our own household canine companions.


The Family Dog

On a routine walk, my own dog often sniffs the concrete with such focus and determination that it sometimes seems she will suck the concrete up as she hones in on a single spot in the pavement, nose almost touching the ground. Her obsession with the smells around us often means we walk at a snail's pace, covering very little ground when we go out. At times, her focus is a bit higher than the cement, and she will stand, very still, head up, her nostrils wrinkling as she sniffs something she smells in the wind. (Dogs can also wriggle each nostril independently, something humans can't do.) Depending on what my dog smells, she may refuse to go any farther in a certain direction, or she may start weaving up and down the sidewalk following an invisible trail. She's got quite a nose, but she isn't trained to do anything with it.

Turning a dog's sense of smell into a specialized tool requires training, lots and lots of training.

Above: "How do dogs 'see' with their noses?" a TedED presentation by Alexandra Horowitz about dogs and the sense of smell.


Working Dogs

The powerful sense of smell dogs possess enables service and working dogs to be specially trained to detect and respond to certain kinds of substances or smells. K-9 unit dogs that are trained to sniff out illegal drugs or explosives, for instance, are often an important part of law enforcement departments. Search and rescue teams often rely on assistance from dogs that can lock onto a scent and track it for miles, ignoring all other distracting smells along the way. Military units, too, often employ working dogs that are scent-trained.

Like dogs can be trained to detect and alert for the presence of an explosive or drug, dogs can be trained to smell and respond to changes in human biochemistry. One application of this ability is scent training for a diabetic alert dog (DAD). A diabetic alert dog is a special type of service dog trained to detect high or low blood glucose, or rising and falling blood glucose, and alert a person with diabetes or a caregiver. These dogs are often able to detect changes in blood glucose in advance of other tools, helping people with diabetes (and caregivers) address potentially dangerous periods of high or low blood glucose as soon as possible.

Some people with Type 1 diabetes are not able to tell when their blood glucose is low. The inability to recognize or "feel" low blood glucose is called Hypoglycemia Unawareness and can be especially dangerous for a person with Type 1 diabetes. Blood glucose that drops below a safe level and continues to drop without immediate treatment can be life threatening. Even people with Type 1 diabetes who typically notice the signs of low blood glucose, however, may not detect low blood glucose when they are asleep. The fact that low blood glucose levels do not always wake a person with diabetes can create a frightening situation for individuals and their caregivers. Many caregivers check blood glucose levels every few hours during the night to help ensure blood glucose levels remain within a safe range. Many people with diabetes also wear a continuous glucose monitor that helps provide blood glucose level information and, depending on the system, can alarm if a problem arises. A trained diabetic alert dog may help detect and alert to the signs of a blood glucose problem at any hour of the day, including in the middle of the night when everyone else is asleep.

For someone with Type 1 Diabetes, a diabetic alert dog may be one of many alert and monitoring tools, but a diabetic alert dog performs a potentially life-saving act every time it alerts to a dangerous blood glucose level.


Intense Training

With a person with Type 1 Diabetes in my house, periods of high and low blood glucose are common. As I have interacted with different foster dogs in recent years, I have watched, closely, to see if any of the dogs we have brought into the house have shown any interest in (or awareness of) shifting blood glucose levels. People with Type 1 diabetes test their blood glucose frequently, and their blood glucose levels change throughout the day. There have been plenty of opportunities for dogs in my house to notice the specific scents related to high and low blood glucose, but despite keen interest in other smells, none have shown any awareness of scents related to changes in blood glucose. But with extensive training, many breeds of dogs can be trained to detect and respond to blood glucose. Some breeds commonly trained as diabetic alert dogs are Golden retrievers, Labrador retrievers, and poodles.

Many people with a family member with Type 1 Diabetes have an untrained dog (or even another pet) that at times seems to demonstrate an awareness of changes in blood glucose. These pets may even enact some form of alert (getting a caregiver's attention) or protective behavior. A true working service dog, however, is one that has been formally scent trained. In many cases, scent training begins when a dog is young. This is a process that takes many months, repeated and ongoing training, and consistent work and reinforcement. Organizations that train diabetic alert dogs (and then work with dog owners to continue scent training) often charge thousands of dollars for this specialized service dog training.


Student Science Connections

Is your dog an excellent sniffer? Is your dog a breed commonly associated with hunting or tracking? Is your dog easy to train? While you may not be able to turn your household pet into a diabetic alert dog, you can use your science project to learn more about dogs and their powerful sense of smell and/or explore approaches to dog training that might be similar to those used during scent training.

Students interested in dogs and dog training may find the following science projects of particular interest:

None of the above projects are specifically about diabetes or training dogs to detect and alert for blood glucose events. These student science projects do, however, provide a foundation for exploring a dog's sense of smell, better understanding dog behavior, and experimenting with methods of dog training. Both the Dog Scents and Tricks for Treats projects could easily be adapted for a more specific diabetes-focused project or science investigation.


Further Reading

To learn more about service dogs, diabetic alert dogs, scent training, and dog training (in general), see the following resources:


The following videos and articles showcase stories about individual children with Type 1 Diabetes and their diabetic alert dogs:

A Career in STEM

Students interested in animal behavior and training, animal biology, or diabetes can find out more about related career paths in the following science career profiles:

Diabetes and Student Science Projects

For students with a personal interest in science topics related to diabetes, there are many ways to re-focus and customize science projects to explore aspects of diabetes health, treatment, and related technology. See our Diabetes Science Project Ideas special collection for ideas to get you started. See also: Increasing Awareness about Diabetes with Student STEM Projects.


Science Buddies Project Ideas that support student exploration of diabetes and other global health issues are sponsored by Novo Nordisk.



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