Deer Data Collection—Part III: Aging Whitetailed Deer

Photo by Brian P. Murphy


Article and Photos by Brian P. Murphy


I could sense the excitement in the air as I approached the group of deer hunters that cool December morning. They were huddled around the back of a pickup admiring a beautiful 10–point buck that had just been taken by a member of their party. I was immediately informed that this was THE buck—the monarch of the property they had been chasing for the last five years. Several hunters began detailing their sightings of the buck during previous seasons and two even reported missing shots at the buck.

Surely an animal of this quality that had eluded hunters and poachers for countless seasons would have be at least 6.5 or 7.5 years old. After a few minutes admiring the buck, I asked the lucky hunter if I could remove one of the buck’s lower jawbones to determine its age. Once convinced that I would not damage his cape, he granted me permission. I returned to my truck and retrieved my jawbone extractor and a pair of pruning shears and quickly removed one of the buck’s lower jawbones.

After studying the jawbone for a few moments, I determined its age. You could have heard a pin drop when I announced that the buck was not 6.5 or 7.5 years old he was only 3.5 years old. Clearly, this was not the old monarch of the property because it wasn’t even born when it was reportedly seen for the first time.

I have experienced this scenario many times and it demonstrates the need for hunters to be able to determine the age of deer. Without knowing the age of harvested deer, comparisons between antler measurements, body weights, and other physical parameters are largely invalid.

Getting Started

Before outlining the aging process, it is necessary to review the basic parts of a deer jawbone and the terminology used (Figures 1 and 2). It is highly recommended that you obtain a deer jawbone for reference during the remainder of this article.

Figure 2

Premolars. The first three small jaw teeth. These are used for cutting the food. These are labeled P1, P2, and P3 in the diagram.
Molars. The last three large jaw teeth. These are used for grinding the food. These are labeled M1, M2, and M3 in the diagram.
Milk teeth. Temporary premolars that are later replaced by permanent ones.
Enamel. The hard, white outer coat of the tooth.
Dentine. The soft, darker inner core of a tooth.
Lingual crests. The sharp, taller tooth ridges running front to back on the tongue side of the jawbone.
Buccal crests. The shorter tooth ridges running front to back on the cheek side of the jawbone.
Infundibulum. The dark central depression between the buccal and lingual crests of the teeth.
Back cusp. The shelf–like surface on the very back of the last molar (M3).
Incisors. The four tiny cutting teeth at the front of the lower jaw. They will not be used for aging in this article.

Aging Techniques

It should first be stated that no aging technique is 100 percent accurate. Individual animal variation, date of birth, and available food sources all can affect age determination. Fortunately, aging accuracy of around 70 percent (to the exact year) is adequate for most management purposes. There are two techniques commonly used to age deer—the cementum annuli technique and the tooth eruption and wear technique.

Cementum Annuli Technique

This technique is based on the principle that cementum (bony material on the root surface of teeth) layers are deposited continuously on the external root surface of teeth. This process is similar to the addition of new growth rings in trees. As with trees, these growth rings are deposited each year in a relatively constant manner but can be affected by severe seasonal or physiological stress. The main disadvantages of this technique are that it requires specialized equipment, takes considerable time, and is fairly expensive. However, this technique is generally considered more accurate than the tooth eruption and wear technique, especially for older animals. Since most whitetails are harvested at young ages (especially bucks), the tooth eruption and wear technique is adequate and is the method used by most biologists. The major advantages of this technique are that it requires no specialized equipment, is relatively easy, costs nothing, and can be performed in the field or hunting camp. The remainder of this article will focus on this technique.

Tooth Eruption and Wear Technique

This technique is actually based on two processes that occur on a deer’s jawbone—tooth eruption and tooth wear. Tooth eruption is used to age deer under 2.5 years of age and tooth wear is used to age animals 2.5 years of age and older.

Tooth Eruption

Tooth eruption criteria are based on the fact that white–tailed deer, like humans, gain additional teeth as they get older and replace some of their temporary teeth with permanent ones. At birth, whitetail fawns have three temporary premolars (called “milk” teeth). All three “milk” teeth are replaced with permanent teeth when they are approximately 18 months old.
White–tailed deer also gain three additional permanent molars from birth until they are 18 months old. This knowledge allows us to quickly separate deer into three basic age groups—fawns, yearlings, and adults (Figure 3). This is done by simply examining the number and type of teeth (temporary or permanent) on one side of a deer’s lower jawbone. Fawns (0.5 year old) will have 3 or 4 teeth, yearlings (1.5 years old) will have 6 teeth, but the first three will be temporary “milk” teeth, and adults (2.5 years old and older) will have 6 teeth and permanent premolars.
Distinguishing between the different teeth may be slightly difficult at first but can be picked up with minimal practice. The easiest way to determine where the different teeth begin and end is to look at where they enter the jawbone. All adult white–tailed deer (2.5+ years old) should have 6 permanent teeth on each side of their lower jaw including 3 premolars and 3 molars.

Tooth Wear

Tooth wear criteria are based on the level of wear on a deer’s teeth as they wear down over time. During this process, the width of the dentine increases in relation to the width of the surrounding enamel. This process can be best described as a sharp mountain peak being slowly eroded by weather until the peak disappears. The outer shell of the mountain is the enamel and the material underneath is the dentine. As the peak of the mountain disappears, more of the inner portion of the mountain (dentine) is exposed. As a result, the dentine appears as if it is getting wider with increasing wear. It is very important to understand this concept because it is the basis of this technique.

Aging Criteria for White–tailed Deer

The following tooth eruption and wear criteria should be used as a general guide only because deer in your area may have slightly different wear patterns. The key to being successful at aging deer is to use all the available clues rather than just one or two. The use of multiple characteristics will substantially increase your accuracy and consistency.

Click here for a complete tour with photographs on aging your deer.

 

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