Northern Prairie Wildlife Research Center
Pronghorn in North Dakota are primarily born between late May and early July. Therefore, when most animals are harvested in October they are considered either four months, 1 1/3 years, 2 1/3 years, 3 1/3 years, etc., in age. For consistency across species, however, we generally age big game animals in half-year intervals (i.e., 1 ½, 2½, etc.). The overall age structure of a hunted pronghorn population is younger than many people think.
Horn and body size can give some indication of a buck's age, but physical characteristics are often misleading and provide little help in aging does. Horn size in bucks and physical development in both genders is greatly affected by diet, which may account for differences between animals of the same age taken from different locations.
Like humans, pronghorn replace their "baby teeth" with permanent teeth at a relatively set rate. As surely as a 6-year-old child will soon get her two front teeth, a 16-month-old buck will be in the process of gaining its central two incisors.
By the time an antelope is 3½ years old, all permanent teeth are in. At this stage, estimating age is based largely on rate of tooth wear. Diet and soil types may accelerate tooth wear, but generally, estimating adult pronghorn age is straight-forward until they reach 5½. Beyond that, estimating age by tooth wear is less reliable.