Science of the Senses - Level 2
Science of the Canine Senses
Learn all about the canine sense of smell, sound, sight, taste and touch.
By M. Christine Zink, D.V.M., Ph.D.
Have you ever wished that you could be a dog for a day? It would be fascinating to view the world through a dog’s senses. Within a few minutes of your human-to-dog transformation, it would be clear that the nose is as important to dogs as the eyes are to people.
Immediately after your transformation you would be struck by a wall of odors. You could identify hundreds of different odor molecules, from the cat food the neighbor put out on the back porch, to the “pee-mail” a wandering dog deposited on a nearby telephone pole, to the potato chip someone dropped on the floor of the pantry. Not only that, you could tell exactly when each of those events occurred because recent events have more molecules of scent.
If you were transformed into a hound, you would have additional scenting advantages: long, pendulous ears to waft scent around your face as you walk with your nose to the ground; drooly lips to keep the air around your nose moist and suspend scent molecules in the air long enough to be inhaled; and loose skin that droops over your eyes when you lower your head, eliminating your vision so more brain power can be used to identify and process scent.
Dogs’ eyes are quite different from ours. They have less visual acuity because they have not evolved to read or work with tools. Dogs are thought to have 20/75 vision, meaning they can see clearly at 20 feet what humans can see at 75 feet. As carnivores, dogs’ eyes are adapted for hunting, with superior night vision and an enhanced ability to detect movement. The retina (the area at the back of the eye where the light is read) has two types of light receptors. Rods are extremely sensitive to light and motion, but do not detect color. Cones detect red, green or blue, and produce extremely clear images. Not surprisingly, the canine retina has many more rods than cones. Although dogs do have some cones, and thus have some color vision, they have none of the cones that detect red. As a result, dogs can see yellow, green and blue, but red objects look yellow or green to dogs.
The sense of hearing is important to hunters, especially those that need to hear rodents running under the snow for survival in the winter. Dogs can hear sounds at the high frequencies small mammals make when they vocalize (anywhere from 47,000 to 65,000 hertz). In contrast, humans can only hear frequencies up to 20,000 hertz.
Dogs’ sense of taste is specially designed for the diet of a carnivore that lives with humans. Their most abundant taste buds detect sweet flavors, a useful adaptation considering the prominence of sweets in the human diet. But dogs also have large numbers of taste buds for acids, including amino acids, which are the building blocks of protein -- the major nutrient in meat.
Finely tuned touch
The sensitivity of the skin and whiskers of the face, the large number of nerve endings in the lips and tongue, and the sensitivity of the paw pads provide just the right sense of touch for a creature that is both a fleet-footed hunter and a canine cuddler.
A dog’s world
It’s clear that dogs and humans share the same five senses, but each species perceives the world in their own unique ways. Understanding how dogs perceive the world through their senses develops a better understanding of this unique species that has shared our homes and communities for tens of thousands of years.
M. Christine Zink, D.V.M., Ph.D., is a veterinarian and a consultant on canine sports medicine, evaluating canine structure and locomotion. She presents Coaching the Canine Athlete seminars worldwide.
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