Age Determination

The only way to truly tell the age of a deer, is to examine the teeth. Deer are born with four teeth on their lower jaw. These four front teeth are called incisors. After a few weeks, sixteen more teeth grow in, giving it eight front incisors, six premolars on the bottom jaw, and six premolars on the upper jaw.
When the deer is one year old, six more molars erupt on both the upper and lower jaws. This gives the deer a full set of 32 teeth. The darker material in the tooth is called the dentine. As the hard enamel is worn away, more dentine is visible.The amount of visible dentine is an important factor in determining the age. The tooth wear and replacement method is not 100% accurate however, due to the differences in habitat. Tooth wear on a farmland deer may not be as fast as that of a deep woods buck.
The most accurate way to tell a deer's age is by removing a tooth, cutting a cross section of it, and counting the rings under a microscope, (much like aging a tree). Each winter, when a deer's blood-serum protein and phosphate levels are low, a layer of cementum is formed on the tooth. Therefore the tooth has one layer for each winter the deer has lived through.
Whitetails.com- Whitetail Deer Age Determination by Teeth

Six Months:
The nose or muzzle of the deer appears short or stubby, when compared to older deer. The central two incisors may still be erupting. Incisors may appear twisted as they emerge through the gum. Generally, there are only four cheek teeth showing. The third premolar has three cusps. The black lines on the teeth below indicates where the gum line was.

Whitetails.com- Whitetail Deer Age Determination by Teeth
Whitetails.com- Whitetail Deer Age Determination by Teeth

1-1/2; Years:
All permanent front teeth are in. Six cheek teeth are visible in the lower jaw. The third premolar may still have three cusps, or the permanent third premolar may now be in (two cusps). Third molar may still be erupting through the gum. Lingual crest of molars have sharp points. Inset: Extremely worn third premolar may fool people into thinking deer is older. Actually, this tooth is lost after 1-1/2; years and replaced with a permanent two-cusped premolar.

Whitetails.com- Whitetail Deer Age Determination by Teeth
2-1/2; Years:
All permanent premolars and molars are in place. Look closely at the fourth cheek tooth (first molar). The cusps are sharp and show little or no wear. Enamel (white portion) of the lingual crest shows well above the dentine (brown portion). The enamel portion of the cusp is wider than the dentine. Some wear on third cusp of sixth cheek tooth (third molar).
Whitetails.com- Whitetail Deer Age Determination by Teeth

3-1/2; Years:
Lingual crests of cheek teeth show some wear and cusps are starting to become blunt. Dentine now thicker than enamel on cusp of fourth cheek tooth (first molar). Dentine of fifth cheek tooth (second molar) usually not as wide as enamel. Last cusp of sixth cheek tooth is flattened.

Whitetails.com- Whitetail Deer Age Determination by Teeth

4-1/2; Years:
Lingual crest of fourth cheek tooth (first molar) is gone. Crest of cusps on fifth and sixth cheek teeth (second and third molar) are blunt. Dentine of fourth cheek tooth now twice as wide as enamel. Dentine of fifth cheek tooth wider than enamel.

Whitetails.com- Whitetail Deer Age Determination by Teeth

5-1/2; Years and older:
In most hunted deer populations, less than two percent of the animals are more than five years of age. Accurately aging these deer by tooth wear is usually more of a guessing game than a science. In general, deer close to 5-1/2; years of age will show considerable wear on the premolars, and the first cusp of the fourth cheek tooth (first molar) will be dished out or show signs of "cupping."

5-1/2, 6-1/2 and 7-1/2 Years :
If you are interested in aging mature deer click on the above link. This information is provided by the Texas Agricultural Extension Service. It takes several minutes to load this page.
Whitetails.com- Whitetail Deer Age Determination by Teeth
9-1/2; Years:
By 9-1/2; years, all cheek teeth are cupped and worn nearly to the gum line