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.



Example of a jawbone from a 0.5 year old (fawn) deer

Fawn

0.5 year old (fawn)

A. 3 or 4 fully erupted teeth on one side of the lower jaw.
B. P3 is a temporary 3–crested “milk” tooth.
C. M1 will be very white and unstained.

Fawns are the easiest group to age. The key to recognizing this group is the number of teeth, the presence of “milk” teeth, and a very short jawbone.



Example of a jawbone from a 1.5 year old (yearling) deer

Yearling

1.5 years old (yearling)

A. 6 teeth in lower jaw, although the 6th tooth (M3) may not be fully erupted if the deer was born late as a fawn or harvested very early in the hunting season.
B. In most cases, P3 will be a temporary “milk” tooth with 3 crests. However, if the animal was harvested very late in the season or if it was born very early as a fawn, it may have already replaced the temporary P3 with a permanent one. This situation is easily recognizable because the new P3 will have only 2 crests and it will be very white (unstained) and show almost no wear.

Note the permanent tooth erupting underneath the temporary one in the photograph. The key to identifying this group is the presence of 6 jaw teeth, but a three–cusped P3.



Example of a jawbone from a 2.5 year old deer

2.5 Year Old

2.5 years old

A. The presence of all 6 permanent teeth in the lower jaw. P3 is a permanent 2–crested tooth and M3 is fully erupted.
B. The dentine width on the lingual crests of M1 is less than 2 times as wide as one strip of the surrounding enamel.
C. Little or no dentine is showing on the lingual side of the second crest of M3. The back cusp may be worn level, but not slanting toward the buccal side or cupping.

This age group is identified by the presence of 6 fully erupted permanent teeth, the narrow dentine width on M1, and by the minimal wear on the last molar (M3), especially on the back cusp.



Example of a jawbone from a 3.5 year old deer

3.5 Year Old

3.5 years old

A. The dentine width on the lingual crests of M1 is approximately 2 times as wide as one strip of the surrounding enamel. The dentine width on M2 and M3 is less than 2 times as wide as the surrounding enamel.
B. Light to moderate wear is evident on P1, P2, and P3.
C. Dentine is showing slightly on the lingual side of the second crest of M3. The back cusp of M3 is beginning to show wear and often slanting to the buccal side.

The key to separating this group from the 2.5–year–olds is the width of the dentine on the first molar (M1), the presence of dentine on the second lingual crest of M3, and the presence of moderate wear on the back cusp of M3.



Example of a jawbone from a 4.5 year old deer

4.5 Year Old

4.5 years old

A. The dentine width on the lingual crests of M1 is more than 2 times as wide as one strip of the surrounding enamel while the dentine width on M2 is approximately 2 times as wide. The dentine width on M3 is substantially less than 2 times as wide as the surrounding enamel.
B. Wear is becoming pronounced on P1, P2, and P3. The lingual crests of P3 may be starting to erode away.
C. Dentine is very pronounced on both lingual crests of M3. The back cusp of M3 is showing pronounced wear and is slanting sharply to the buccal side or beginning to form a cup.

The best way to distinguish between a 3.5– and 4.5–year–old is by the dentine width on the lingual crests of M2 and by the level of wear on the back cusp of M3.



Example of a jawbone from a 5.5 year old deer

5.5 Year Old

5.5 years old

A. The dentine widths on the lingual crests of both M1 and M2 are more than 2 times as wide as the surrounding enamel while the dentine width on M3 is approximately 2 times as wide. M1 is showing pronounced wear but the infundibulum remains intact.
B. Wear is becoming heavy on P1, P2, and P3. The lingual crests of P2 and P3 are often worn nearly flat.
C. The back cusp of M3 is slanting heavily to the buccal side. In most cases, a noticeable cup is evident in the center of the back cusp.

Animals 4.5 and 5.5 years of age are often difficult to separate. The key to making this distinction is by paying close attention to the dentine width on the lingual crests of M3 and to the extent of wear on P3 and M1. The wear on the back cusp of M3 is also very important.



Example of a jawbone from a 6.5 year old deer

6.5 Year Old

6.5 years old

A. The dentine widths on the lingual crests of M1, M2, and M3 are all more than 2 times as wide as the surrounding enamel. M1 is heavily worn and the infundibulum is beginning to wear away.
B. Wear is very heavy on P1, P2, and P3. The lingual crests of P2, P3, and M1 are worn nearly flat.
C. The back cusp of M3 is heavily worn and deeply cupped.

The key to separating a 5.5–year–old from a 6.5–year–old is by the level of wear on M1 and M3 and by the erosion of the lingual crests on P3 and M1. Any deer showing more wear than described here for 6.5 year olds, should be classed as 6.5+ year olds.
With the above information and a little practice, you will soon become proficient at aging white–tailed deer. Being able to determine the age of your deer will definitely add to your hunting experience, the value of your trophy, and to your general knowledge of deer. So the next time you harvest a deer, remember to save the most important part—the lower jawbone—and give aging a try. For more information on aging white–tailed deer, including the necessary equipment and full–color aging charts, contact the QDMA at 800–209–3337 or click here to visit the QDMA Web Page

Brian Murphy is a wildlife biologist and has served as the Executive Director of the Quality Deer Management Association since 1997. For the past 15 years he has worked exclusively in deer research and management and has taught this aging technique for both white–tailed deer and fallow deer.