Dog Manual

How To Determine Age

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 functional.

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 months.

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 wear.

Between eighteen months and two years the cusps on the lower pincers finally disappear.

Between two and a half and three years the cusps on the lower intermediates disappear, and the cusps on the upper pincers show some wear.

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 the pupil.


2 months

4 months

1 year

1 1/2 years

2 1/2 years

Over 3 years

Aged Dog