In the same way as in other
domestic animals, the age of dogs can be
ascertained mainly on the basis of an examination of the teeth. For
various reasons this method is not as reliable in dogs as in other
domestic animals, and therefore the determination of age in this manner
in dogs must be considered at best only an approximation.
Ordinarily, the adult dog has forty-two teeth—twenty in the upper jaw
and twenty-two in the lower—which are designated as incisors, canines,
premolars, and molars. The incisors number six in each jaw, and are
respectively called pincers, intermediates, and corners. In the upper
jaw the corner incisor is shaped somewhat like a canine tooth. The
temporary incisors are small, have three cusps on their free extremity,
and are very white. The newly erupted permanent incisors are white and
glistening and their surfaces are distinctly divided into three cusps
resembling a clover leaf. The canines or fangs are cone-shaped,
elongated, and slightly curved. Age determination is based mainly on
the characteristics of the incisors and the canines.
At birth the dog is blind and deaf. Its eyes and auditory canals are
closed. Save in very rare exceptions, the jaws are devoid of teeth.
Between the tenth and twelfth day the eyes open and the ears become
The temporary incisors and canines erupt in both jaws during the third
week. Up to two months of age the teeth touch each other.
Gradually they lose contact and progressively space themselves until
they are replaced by the permanent
teeth. Generally they get pretty well worn down in the course of three
These temporary incisors and canines are replaced during the fourth or
fifth month. This occurs a little sooner in large dogs and a little
later in the smaller breeds. The permanent teeth are almost always
erupted at six months of age.
At one year the teeth are fresh, white, and whole.
At fifteen months the cusps of the lower pincers start to show some
Between eighteen months and two years the cusps on the lower pincers
Between two and a half and three years the cusps on the lower
intermediates disappear, and the cusps on the upper pincers show some
At four years the cusps on the upper pincers disappear and the
intermediates start to flatten out. The teeth begin to get yellow, and
tartar deposits are often observed at the base of the canines.
At five years the incisors are markedly worn. The wearing of the teeth
might, however, be advanced or retarded in proportion to the care and
nourishment the dog has received.
Henceforth, the age can still be determined by the degree of wear of
the teeth, the accentuation of their darker color, their gradual loss
or removal, and several other signs furnished by the hair and the
skin. In young animals, the fangs are white, shining, and pointed. With
age they gradually become yellow and worn. Toward the sixth year the
canines get greenish and mossy.
In most dark-haired dogs, gray hairs appear under the lips and around
the nose. Also the muzzle becomes enlarged. In old age the hair
becomes quite gray in the region of the eyes and extending to the
forehead. The ends of the digits become enlarged and rounded, the claws
become elongated and very curved; and in animals that have a chronic
eczema, the skin of the back and loins shows partial loss of hair, a
general thickening, and wartiness.
Old age sets in from the eighth to the tenth year, depending on the
individual dog. Longevity varies notably from one breed to another.
Certain "deluxe" dogs, such as small Spaniels and English Terriers,
live from sixteen to eighteen years. Some privileged few reach, or even
live beyond, their twentieth year.
Since age determination in dogs mainly by way of the teeth has often
proven unreliable, another method has occasionally been suggested.
This is based on an examination of the pupils of the eyes. In young
dogs, the pupil appears to have a dark, clear, blue color. As the
animal gets older, the pupil becomes lighter and whiter in color until
in the aged dog the pupil of the normal eye will be quite white. Only
by the examination of large numbers of eyes can the age be determined
in this manner with any degree of accuracy. It is apparent that this
method also can yield at best only approximate results, since it
depends too much on the observation of the individual observer and
also since older dogs often develop disease conditions that may
substantially interfere with an adequate interpretation of the color of
TEETH AT VARIOUS AGES