Using The Technique

Charles W. Ramsey, Donny W. Steinbach and David W. Rideout*

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 ue 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.

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*Extension wildlife specialist and Extension program leader for wildlife and fisheries sciences, The Texas A&M University System; and Texas Parks and Wildlife Department technical guidance biologist.

Using the technique
Figure 1. The jawbreaker-extractor can be used to remove a deer’s jawbone. This makes it much easier to age the deer by examining the teeth.

Using the technique
Position the head so that you can see the teeth in the lower jaw. If the deer has been dead for several hour, you may need to use a jawbreaker to open the jaws before proceeding further. Insert the small end of the tool in front of the cheek teeth and rotate the handle to 90 degrees. Rinse the teeth with water if necessary.

Examine both sides of the lower jaws and select the one which looks normal (no broken teeth or deformed jaw). Use a flashlight to see the teeth clearly for aging.

It is much easier to examine the teeth with the lower jaw detached from the carcass, so if the deer’s head is not to be mounted, but open the cheek and remove a lower jaw with a knife or lopping shears. Be sure to tag the extracted jaw so that it can be matched with the other recorded measurements of the carcass.

If you plan to have the head mounted, do not cut the cheeks or any part of the neck above the shoulders. You may remove a jaw without cutting the cape by using a jawbreaker-extractor and lopping shears. Turn the deer’s head upright. As you straddle the neck, insert the jawbreaker between the cheek and gum and push downward to separate the muscle tissue from the skin.

Next, insert the lopping shears so that the blade is over the tongue and the cutting bar is to the outside of the lower jaw to be cut. Cut through the lower jaw where it curves upward and try to make the cut parallel to the roof of the mouth. Press downward on the shears as you cut through the bone completely.

After severing the bone, insert the jawbreaker-extractor horizontally and hook the loop over the cut end of the lower jaw (see Figure 1). Place one hand underneath the jaw to help guide it over the lip of the puller. Once secured, stand on the neck of the animal and pull up to extract the jaw. Continue to pull until the puller reaches the front of the jaw, then rotate the puller about 90 degrees to break the jaws apart in front. The jaw is then free and can be pulled out.