It is possible to tell the age of deer using several techniques, including visual observations and looking at teeth. In their first year of life, bucks and does may be visually indistinguishable from a distance, as they have thin necks, lack muscle definition and males may not have antlers. They exhibit pronounced physical differences with each successive year, however, and even have different tooth growth patterns, which makes aging them easier.
Regardless of gender, looking at teeth is a good way to age deer. At 6 months, fawns have between five and six teeth, regardless of gender. A seventh tooth appears at 7 months. At about 18 months, deer have a high gumline in the back of their mouths. At 30 months, deer have all their molars, which are fully formed and sharp. A year later, back cusps will show wear. Between the ages of 4 and 5, tooth wear continues, particularly along the back cusps and lingual crowns.
At the year to 18-month mark, young bucks may have small antlers. They still appear lean and leggy, and have slim necks and bodies. At age 2, they may have thicker necks and stained tarsals. At age 3 1/2, bucks have prominent muscles; their chests and rears should be roughly the same size, and they have defined necks and shoulders. A year later, their antlers and muscles are fully grown. At age 5 1/2 onward, muscle fades and backs and stomachs begin sagging. 7- to 8-year-old bucks have lean, light faces, too.