The Basics of Canine Senses
A dog’s nervous and sensory systems are essential to his health and well-being. Perceptions and reactions to his environment are dependent on his senses; movement is controlled through the central nervous system (the brain and spinal cord); and the endocrine system (the hormone-producing glands) controls his patterns of behaviour.
Canine vision is inferior to human during the day, but is superior at night. Dogs do see colours, but not as distinctly as humans (in pastel as opposed to strong colours), and their peripheral vision is better than ours. In addition to the upper and lower eyelids, there is a third eyelid – the nictitating membrane (haw), which is comprised of a thin sheet of pale tissue tucked away in the corner of the eye. Its function is to help remove dust and dirt from the surface of the eye (cornea) by moving across it during any inward movement, and also to help keep the eyeball moist and lubricated.
A dog’s hearing is vastly superior to that of a human and he is, therefore, more sensitive to sounds than we are – especially those at high frequencies which we cannot hear (hence the use of ‘silent’ dog whistles). A dog’s mobile ears help to pinpoint the source of a sound, since they can be directed towards it.
A dog’s primary sense is his sense of smell, as it is essential in relation to his sex life and hunting for food and water. The area in a dog’s nose for detecting scent is nearly 37 times larger than that in humans, and is approximately 100 times more powerful than a human’s. The parts of the brain that process signals coming in from the nose are far greater in size and complexity in a dog than are the corresponding parts of the human brain.