Knowing how to tell the age of an animal has been an important skill for managers and users of animals for hundreds of years. Selecting an animal the right age for a particular use was a mark of an experienced herdsman.
Cattle Producers use well established criteria based on the replacement of front teeth for determining the age of their livestock. Horsemen also use the pattern of eruption of permanent teeth to age their animals. However, since horses live many years after growing permanent teeth, horsemen also use the degree of wear on the teeth as indicators of age.
Wildlife biologists applied these techniques to aging deer. They found that deer shed and replace all front teeth (incisiform milk teeth) by 7 months of age. Thus, they could not determine the age of an adult deer solely by examining the replacement of front teeth.
The teeth of all mammals wear as an animal chews its food. Soft parts of the cheek teeth wear more than hard parts. Biologists found that in large herbivores such as deer, elk and antelope, the ridges on the top of the cheek teeth (crests) wore in a predictable manner. As the hard, white outer coat (enamel) wore away an increasing amount of the softer, dark inner core of each tooth (dentine) was exposed.
By examining animals of known age, biologists found that the tooth ridges next to the tongue (lingual crests) were best for comparisons. They developed criteria for identifying age classes based on the width of exposed dentine compared to the adjacent enamel in particular teeth.
Texas wildlife biologists and technicians tested the technique with white-tailed deer of known ages. ?They found a small percentage of animals whose teeth did not fit the criteria for their corresponding age class, but these were only a single year off. The most common error was overestimation the age of mature animals (4+ years of age) by 1 year.
The biologists learned that it was best to use multiple criteria to describe deer age classes, because accident, deformity or individual differences can cause unusual wear on any single tooth. They found that using multiple characteristics tended to be self-correcting and allowed them to age a deer even with a missing tooth.