Bruce White, age 13, of Fredericton, New Brunswick, Canada, for his question:
CAN DOGS SEE ONLY IN BLACK AND WHITE?
One hundred and twenty one breeds and varieties of purebred dogs are recognized by the American Kennel Club, the chief organization of dog breeders in North America. They range in size from the foot long Chihuahua to the 200¬pound Saint Bernard and the three foot high Irish wolfhound. Purebred dogs are those whose parents belong to the same breed.
No one can dispute the old saying that the dog is man's best friend. For thousands of years the friendly animal has played an important role as a faithful companion to man.
It is interesting to discover that the dog's body functions differ only slightly from a human's. A dog, for example, has a normal body temperature of 101 degrees Fahrenheit, which is only a little higher than a human's normal temperature of 98.6 degrees. The dog's heart beats normally between 70 and 120 times per minute, while the human heart comes in with a count between 70 and 80.
When it comes to a dog's eyes, however, there is a marked difference from man's. First of all, a dog cannot see as well as men. They also have difficulty telling colors apart.
Tests taken of the eyes of dogs have established that they can indeed see color and are not just restricted to black and white vision. Dogs can determine the degree of brightness of colors, but the experts consider them to be colorblind. A dog will first see an object by its movement. It will then see it by its brightness and finally by its shape.
When it comes to hearing, the dog takes all honors over man. A person cannot hear most sounds that originate beyond 25 yards, but a dog can hear sounds from as far as 250 yards away. The human ear can detect sound waves that vibrate at frequencies up to 20,000 times per second, while his best friend, the dog, can hear sound waves that vibrate at frequencies of more than 30,000 times per second.
On the outside of a dog's ears are flaps of skin called leathers. These protect the dog's ears and can also be moved to help catch and locate sounds. Most small dogs have better hearing than large dogs.
Dogs can also hear very high pitched sounds. Some people call their pets by blowing on high pitched whistles that cannot be heard by humans.
While the dog scores low on his vision tests, he has an excellent sense of smell. A dog will detect the scent of an object much as man recognizes things by sight. Moisture helps a dog detect odors, and most dogs have moist noses. A dog will often lick his nose to keep it moist. Many healthy dogs, however, can have dry, warm noses.