The Corvallis Police K-9 Unit: Part II - It Makes Good Scents

Note: This is the second of several articles in a series that explores the value of police dogs to a community. Go to Archives to read Part I.

In Part I we learned that more and more communities all across the US are investing in police dogs for the reason that they have proven to be a valuable asset to community livability. Police dogs are greatly more efficient at finding objects, drugs, and people than officers, they enhance officer safety, they often cause criminals to surrender without a struggle, and they reduce a community's liability to law suits.

In this installment we will learn why police dogs are so good at what they do and we will also learn what makes a good K-9 handler.

A Great Nose for the Job

According to research at the Canine and Detection Research Institute at Auburn University's School of Veterinary Medicine, dogs can detect 1 to 100 parts per billion parts of air, perhaps even significantly less. To put this phenomenal ability into a more understandable perspective, this level of sensitivity is like being able to detect one grain of sand in a ten-meter patch. Or, another way to think of it is to consider that when we mow a lawn, the freshly mowed smell we enjoy from an entire lawn is the equivalent to one blade of grass for a dog.

So what biological features confer this amazing sense of smell? Whereas we humans have about five million olfactory sensors, the average dog has in excess of 200 million and working dogs, such as hounds, may have as many as 300 million sensors. When a dog smells, by making a deep, short intake of air, odor molecules in the air dissolve into the water vapor in the dog's nasal passage. The fluid on the dog's nasal membranes then absorbs the molecules and brings them into contact with the membranes. And once in contact with the membranes, odor molecules excite the olfactory nerves connected to the membranes. These nerves then send impulses to the olfactory center in the dog's brain for processing, a dog's olfactory center being some forty times larger than that of a human.

Other biological features favorable to keen smell are the shape and size of a dog's nose and the distribution of the olfactory sensors. In humans, the five million sensors are concentrated in a small area in the back of the nose. In dogs, however, the nasal membranes cover the turbinate bones that extend horizontally along the elongate nasal passage. These membranes have convoluted folds that add to the surface area and spread the sensors, allowing for the capture and detection of minute amounts of odor. Some research at Auburn suggests that dogs can detect down to a few parts per trillion.

With this wonderful sense of smell, police dogs are trained to distinguish and remember one smell from another. One way to think about this is that while a human will smell a pizza, a dog will smell dough, flour, tomato sauce, onions, mushrooms, olives, and pepperoni. Additionally, police dogs are trained to home in on one smell and ignore all others, hence their ability to track a sent or locate drugs. For example, drug dogs routinely find drugs that people try to hide by wrapping the drugs in perfumed cloth or even in dirty diapers. So while the drug dealer is smelling only perfume and diapers and feeling very clever, the drug dog simply eliminates the extraneous odors and quickly detects the drugs.

Did You See That?

Vision is another key sense that gives police dogs an advantage over their human handlers. Because dogs evolved as hunters active during the twilight hours of dusk and dawn, their eyesight is adapted to low-light conditions. Thus police dogs see much better than officers during the hours that criminals are the most active. And police dogs are also more effective in sighting a person hiding in a dark place. So what with most criminal activity taking place during darkness, and with criminals seeking dark places to hide, criminals play right into one of the strengths of police dogs.

With that said, however, it should be noted that dogs lack depth perception and neither see detail as well as humans nor see colors the same. But, dogs detect motion better than humans do. Why so? All of these differences in visual ability are due to anatomical differences between human and canine eyes.

Dogs can see better in low light because they have larger pupils and lenses (lets in more light) and, proportionally, more rods (primarily light sensory and motion detection cells). Humans see more detail because their eyes can focus light better and have, proportionally, more cones plus a fovea (cones primarily detect detail and color; a fovea is a retinal area of all cones). There is also a difference in the nerve connections between retina and brain. In dogs, several cones share one nerve whereas in humans each cone has its own nerve, allowing for the transmission of finer detail.

As for color vision, dogs are much like red-green colorblind humans. This is because humans have three types of cones and dogs, two. Each cone type has a photo pigment sensitive to a specific wavelength in the color spectrum. The result is that what humans see as red, dogs perceive as yellow and what humans see as green, dogs see as white or a shade of gray. But this difference in color vision in no way impedes a dog's police work. And neither does their inability to resolve fine detail. However, their lack of depth perception can lead to safety concerns that the handler needs to compensate for.

Do You Hear What I Hear?

Dogs also have an excellent sense of hearing, a sense that improves as they get older. They can detect sounds from 20 cycles per second to 35,000 cycles per second whereas the range for human hearing is 20cps to 20,000cps. Dogs also are very good at determining the direction from which sound comes. Both traits thus contribute to a dog's superiority over officers in searching for lost children and in finding criminals trying to hide. Not only do dogs hear what officers can't; they know exactly where the sound is coming from.

And so with these sensory advantages of superior smell (detect minute quantities, eliminate extraneous odors, track direction), sight (see in low light, detect motion), and hearing (1.3x broader range, detect direction), it is no wonder that police dogs far out-do officers in efficiency and effectiveness of finding objects and humans. We will learn in a future installment just how much more efficient and effective they are.

There are many traits that make some dogs suitable for one type of police work but not another. These traits include size (large for patrol, small to medium for drugs), temperament (aggressive for patrol, friendly for drugs), voice (deep bark for patrol, quiet for drugs), gender (alpha males for patrol, females for drugs), speed (for patrol) obedience, an instinct to hunt and protect, a strong drive to play, eagerness and vitality, loyalty, valor, intelligence, endurance, and an ability to be around all kinds of people individually and in crowds. A dog nervous around people will not make a good police dog for any use. We will read more about these traits in the future installment on selection and training.

Only the Best

And what makes a good handler? Police departments throughout the US consider only those officers who have outstanding records. Departments look for officers who are experienced in all aspects of police work, have a good record of arrests that are followed by convictions, interact well with their community's citizens, have good public presence, make good decisions, and are physically fit. Officers must be willing to put in long workweeks that often have call-outs for duty on off times. And there is always training. In addition, officers must be willing to commit to being a handler for the service life of their dog, which usually lasts about six years.

In the next installment we will learn more about handlers when we meet Corvallis' current K-9 Unit, Officer Jason Harvey and Xar, along with Officer Phil Howrey and Ike and Officer (now Detective) Mike Wells and Dag, who served our community before Jason and Xar.

References

Auburn University Veterinary Medicine Canine Detection Research Institute:
www.vetmed.auburn.edu/index.pl/cdri_publications

Coile, D. Caroline: Bringing Dog Vision Into Focus
www.workingdogs.com/vision_coile.htm

Corvallis Police: Detective Mike Wells, Officer Jason Harvey, Lt. Dave Henslee, Lt. Jon Martyr, Capt. Jon Sassaman

Davis, Jennifer: Color and Acuity Differences Between Dogs and Humans
www.uwsp.edu/psych/dog/LA/davis2.htm

How Stuff Works:
people.howstuffworks.com/police-dog1.htm