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Dog
The body of a dog
Sporting dogs
Working dogs
Herding dogs
Working dogs
Herding dogs
Terriers dog
Toy dogs
Nonsporting dogs
Life of a dog
Choosing a dog
Dog feeding
Dog-Shelter
Dog-Grooming
Dog-Exercise and play
Dog-Medical care
Parrot
Kinds of parrots
Animal
Camel
Elephant
African elephants
Indian elephants
The life of an
elephant
The body of a dog
Dogs vary greatly
in size. The smallest breed is the Chihuahua. On average, Chihuahuas weigh only
about 2 kilograms and stand about 13 centimetres high at the shoulders. The
tallest breed is the Irish wolfhound, which may grow up to 86 centimetres in
height. The St. Bernard ranks as the heaviest dog. It weighs as much as 90
kilograms.
The size, shape, and other characteristics of a dog's body vary widely from
breed to breed. But in spite of their differences, all dogs share certain basic
physical features. Except for limitations in size, all breeds can mate with one
another and produce offspring.
Coat. Most dogs have two coats--an outer coat of long guard hairs and an
undercoat of shorter, fluffy hair. The guard hairs protect the dog against rain
and snow, and the undercoat keeps the dog warm. Most dogs shed the undercoat in
late spring and grow it back in autumn. Dogs also have long, stiff whiskers
about the muzzle. The whiskers are highly sensitive touch organs.
The texture, length, and colour of the coat differ greatly among the various
breeds. The hair may be curly, as on the poodle, or straight, as on the German
shepherd. The collie's coat feels rough, and the Kerry blue terrier's coat is
soft. Such breeds as the Afghan hound and the Pekingese have a long, silky coat.
The boxer and the whippet have an extremely short coat. The colour of the coat
may vary even within a breed. For example, a Labrador retriever's coat may be
black, yellow, or chocolate-brown.
Body structure is determined mainly by a dog's skeleton. Dogs have an average of
320 bones. The exact number of bones varies, depending on the length of the
dog's tail. Male dogs have one additional bone, located in the penis. It is
called the os penis. Although all breeds have the same number of bones, the size
and shape of the bones differ greatly from breed to breed. For example, the
basset hound has very short, thick leg bones. In contrast, the greyhound has
unusually long leg bones. The Chinese crested dog has unique elongation of the
joints, especially of the forefeet, making it appear to have an extra joint.
Dogs have four toes on each foot plus an extra thumblike toe called a dewclaw on
each front foot. Some dogs also have a dewclaw on each hind foot. Dewclaws do
not reach the ground. Feet vary in shape considerably. Some dogs, such as the
Newfoundland, have webbed feet. Others have feet like cats or hares. Each of a
dog's toes has a blunt toenail, or claw. But unlike cats, dogs cannot pull their
claws back. The bottoms of a dog's paws have cushiony pads covered with tough
skin.
The shape of the skull determines whether a dog has a long, slender face like
that of a collie or a short, broad face like that of the bulldog, pug, and
Pekingese. Long-faced dogs have eyes that are nearer the sides of their heads,
giving them a wide field of vision. Dogs with broad skulls have eyes that look
forward like those of human beings, letting them judge distances better.
Puppies have about 28 temporary teeth, which they begin to lose when they are
about 5 months old. Adult dogs have about 42 teeth. Dogs with short faces have
fewer teeth. A dog uses its 12 small front teeth, called incisors, to pick up
food and groom itself. The dog tears meat with its 4 large, pointed canine
teeth. It uses the 26 other teeth, its premolars and molars, to grind and crush
food.
Many breeds of dogs have pointed, prick ears that stand straight up. Other
breeds have pendulous ears, which hang down. Many people have the ears of
certain pendulous-eared breeds cropped (cut) to make them stand up. Such breeds
include Doberman pinschers and miniature schnauzers. Cropping is done at an age
when puppies are highly sensitive to pain. Australia, New Zealand and the
Scandinavian countries have outlawed cropping as a cruel practice. On terriers
and some other breeds, the tail is also docked (cut short). Docking is done a
few days after birth and so is much less painful than ear cropping. However,
docking a dog's tail does not benefit the dog at all and is only done to satisfy
an owner's preference for a short tail.
Body functions of a dog differ only slightly from those of a human being. For
example, a dog's heart beats 70 to 120 times per minute. The human heart, on
average, beats 70 to 80 times per minute. A dog's normal body temperature is
38.6 °C, only a little higher than a person's normal temperature of 37 °C. But
unlike human beings, dogs do not cool the body by sweating. Instead, a dog
sticks out its tongue and pants. As the dog pants, evaporation of water from the
mouth cools its body. Dogs do have sweat glands on the pads of the feet, but
they play only a small role in reducing the body temperature.
Senses. A dog's most highly developed sense is its sense of smell. Dogs
recognize objects chiefly by smell, much as people recognize them by sight. Dogs
can detect some odours that are millions of times too faint for people to
detect. By sniffing a group of objects, a dog can pick out the ones that a
particular person touched. Fluid from a gland inside the nose keeps the tip of a
dog's nose moist. The moisture helps a dog detect odours. A dog also licks its
nose to help keep it moist. In addition, a dog's whiskers may sense the wind
direction and so help the dog determine the direction from which an odour is
coming. Some dogs, such as bloodhounds, can follow scent trails more than four
days old under certain conditions.
Dogs also have a much better sense of hearing than people have. Dogs can hear
high-pitched sounds far above the limit of human hearing. They can also hear
sounds at much greater distances than people can. In addition, dogs have a
highly developed ability to recognize different complicated sounds. For example,
many dogs can recognize the sound of their owner's car and so tell it apart from
other cars. Dogs cannot see as well as people. Dogs detect movement well, which
helps make them good hunters. But they see patterns and forms much more poorly
than people do. A dog's colour vision is mainly limited to shades of grey and
perhaps blue. Dogs therefore cannot tell certain colours apart. They see green,
yellow, orange, and red as the same shade. |
