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Whitetail

How To Age Deer Accurately

by C. J. Winand   |  December 4th, 2017 0

Knowing the age of a buck is important to most deer hunters. Years ago, I was registering a doe at a deer check station when a hunter brought in a gray-colored, 10-point buck that would most likely score in the 140s. The hunter asked the state biologist working at the check station if he could age his buck. The biologist looked in the deer’s mouth, and then told the hunter his buck was 6½ years old.

Later, I looked at the deer’s lower jaw and determined the buck was only 31⁄2 years old. I was so confident that I told the hunter I’d be willing to bet both my bows on my assessment. The proud hunter was very inquisitive on our differing age calculations. Upon further discussion with the hunter, I explained how biologists use a technique based on tooth replacement and wear.

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The cementum annuli method is the most accurate way to age a deer. Wildlife Analytical Laboratory can age your deer this way for only $25. This forensic picture shows the number of rings (or annuli) in determining a deer’s specific age. This free-ranging New York doe made it until 18 years of age before being harvested. If this isn’t a trophy, I don’t know what is! (Photo courtesy of Henry Chidgey)

Back in 1949, a New York deer researcher by the name of C.W. Severinghaus studied known-age deer. Within this classic study, Severinghaus focused on the lower jaw bones of harvested deer he had tagged as fawns. As you can imagine, older deer exhibited more wear on the back molars. But, depending on what deer eat and the amount of sandy soils in an area, this deer-aging technique can be subjective across the deer world.

Because of the discrepancies between biologists in aging deer using the Severinghaus method, a study was conducted in the late 1980s using the upper (not lower) molars as a new way to determine a deer’s age. The conclusions were clear: This “new” technique was no better than the standard Severinghaus method.

In the early 2000s, another tooth study looked at using digital photographs on the wear of the back molars. Again, their conclusions were no better than the Severinghaus method. As of today, whether you kill a deer in the North or South, this 68-year-old study is still the standard for aging harvested deer.

As in the case with my check-station experience, the difference in age determination between biologists can be significant. Obviously, one’s experience and learned skill in this technique can cause many discrepancies. Although I mean no disrespect to fellow biologists, I’ve met some hunters who are clearly better at aging deer by this method than some professionals. For more information on aging deer using the tooth replacement wear method, click here.

Another increasingly popular technique for aging deer is on the hoof. Compared to younger deer, older deer have differing physical proportions such as the size of the hindquarters, sag in the stomach, mass of the chest, and the extent of its neck and legs.

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This microtome is a precision cutting tool used to finely slice a tooth longitudinally to determine an animal’s exact age using the cementum or annual growth rings. Multiple cuts/slides are taken to make sure the root is completely cross-sectioned at the precise angle, after which it is dyed for viewing under a microscope to determine an accurate age. (Photo courtesy of Henry Chidgey)

Many outfitters are mandating that you not harvest any bucks under a certain age class. For me, once I identify a buck, my mind/eyes focus on the three B’s: back, belly, and butt. I find most deer can be aged somewhat accurately (at least I think so). But, just like using the tooth replacement wear method, aging deer on the hoof is also very subjective. More information on aging deer on the hoof can be found on the QDMA’s website.

So, what is the check-station hunter to do with his buck? He was told the amount of gray hairs around the deer’s muzzle area would give him an indication on age. This, of course, is dead wrong. For example, think of how many men in their 20s are already gray and/or going bald. Big antlers and body weight are also a very poor indicator for determining a deer’s age. Again, just like people, there are some really big-antlered, fat young bucks out there.

All antlers within a specific age class fall somewhere in a bell-shaped curve. For example, some 5½-year-old bucks will only sport 100 inches of antler, while bucks in this age class at the other end of the scale will measure over 170 inches. The majority of bucks will end up scoring somewhere in between. Each specific age class of bucks will exhibit the same distribution of antler scores within the bell-shaped curve.

The most accurate method to age deer is called the cementum annuli technique. This is where you remove the two bottom front teeth (called the incisors) with a pocket knife and send them to a lab to count the rings — just like you would the annual growth rings on a tree. The teeth are then placed in a mild hydrochloric acid for up 18 hours to decalcify them. The acid changes the tooth to the consistency of a hard pencil eraser.

Then the examiner can cut the enamel part of the tooth with a sharp knife, retaining the root for more processing. The root is cast into a paraffin block, so that very thin longitudinal slices (10 microns thick) can be taken with a machine called a microtome and placed on a microscope slide and stained with a colored dye. A cover slip is then applied, and when viewed through a microscope at 160X, the technician is able to observe the cementum layers. Just like a tree’s growth rings, a cementum layer is added to a deer’s tooth every year the deer is alive.

So, why don’t all state wildlife agencies use this methodology if it’s so accurate? In short, because they simply don’t have the funds to accurately age all harvested deer using the cementum annuli method. Furthermore, because many state wildlife departments use population-reconstruction models to estimate deer herds, they mostly use three age classes: fawn, yearling, and adult.

Remember the check-station hunter whose buck I aged at 3½ years old? After sending the lower front tooth to Wildlife Analytical Laboratory, the cementum annuli reading was 4½ years old. Can you say humble pie? Luckily for me, I got to keep my bows.

C.J.’s Summary: Knowing how to age deer is a key ingredient in determining the age structure of your deer herd. My all-time favorite buck only scored 145 inches, but it was 9½ years old. If you would like to have your deer or other game species accurately aged using the cementum annuli method, contact the Wildlife Analytical Laboratory at (512) 756-1989, or visit them online at deerage.com. The lab also provides a really neat framed certificate of aging, which is proudly displayed by many of my mounts. Other aging tools using the tooth replacement and wear method can be purchased at QDMA.com.

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