“Boy, that buck looks like an oldtimer. I wonder how old he is?”

Many of us have asked that question over the years. For starters, we’re a curious lot, but recently the question has become more than one of passing fancy. Today, more than ever, it requires an answer. Age is a key ingredient, whether you’re managing the herd or trying to satisfy the curiosity of a fortunate hunter.

I found my own curiosity piqued earlier this year, after taking a buck that was clearly older than the norm. The big 8-pointer had well-worn, dark-stained teeth with a muzzle that was mostly gray, so I decided to have him aged. I also had the jawbone from a mature 10-pointer I’d shot in 2001, and I wanted to find out about him as well.

AGING METHODS
There are several ways to age whitetails. The most familiar technique, and the one most used by the public, is called the eruption-wear or wear-and-replacement method

We’ve all seen photos of deer jawbones with worn molars. This method is used to judge the amount of wear on the molar teeth of a whitetail by comparing it to the wear patterns of deer of known age.

Another technique, perhaps not as well known to whitetail hunters, is called the cementum-annuli method. The idea here is to process the incisor tooth of a whitetail through a series of scientific steps, then view it under a microscope. When properly prepared, the rings of growth can be counted to determine the age of a deer, much as we can age a tree by its rings.

Dr. Paul Friederich heads up a Michigan laboratory team that ages whitetails and other animals by the cementum-annuli method. Photo by Rick Adams.

To have my two deer aged, I traveled to the Rose Lake Research Laboratory, a Michigan Department of Natural Resources facility just northeast of Lansing. There, the cementum-annuli program is one of the areas of animal research administered by wildlife scientist Paul Friederich. In addition to aging whitetails, the lab also ages bears, otters, fishers, elk, bobcats, martins, badgers, foxes, coyotes and wolves for research and management purposes.

I was invited to join Paul and lab technicians Kristine Brown and Melinda Cosgrove as they guided me through the multiple steps required to age wild animals. The first of those steps, as you might guess, is the removal of the tooth.

“For whitetails, we need the central incisors, which are the teeth at the bottom front of a deer’s jaw,” Paul said. “The two in the middle work best.”

The incisors are easily removed while the deer is still fresh.

“Just take a knife and make a slice down either side of the tooth and at the bottom where the root lies, then gently remove it, being very careful not to break off the root tip,” Paul told me.

After the excess tissue is removed, the tooth is then placed in a small bag and delivered to the lab. There, the first step is to de-calcify (soften) the tooth by soaking it in a weak acid solution. As this is done, the tooth grows rubbery, like a pencil eraser.

The tooth is frozen for next ease of cutting and then placed in a cryostat. This is a machine that slices the tooth so thinly the resulting slices are measured in microns. The thin slices of tooth are, in turn, placed on a slide for viewing under a microscope.

Kristine arranged the wafer-thin tooth slices on a slide, and then added a solution containing methanol, glycerin and giesma stain to enhance them for viewing. A second glass slide was placed on top, and the slender tooth slices moved to a microscope.

Now the rings in most teeth will be clearly visible, and they can be counted in much the same fashion as rings in a tree. Each ring represents what scientists believe was a period of stress during the deer’s life. Maybe it’s the animal’s response in preparation for the hardship of oncoming winter or the stresses of breeding season. Researchers aren’t exactly sure why the rings form, but they do know that they form at very regular intervals, and that’s obviously the key to using them for aging specimens.

“Most teeth are very easy to read, but occasionally I will see some ‘noise’ in a tissue sample,” Paul noted. (“Noise” is a term for a line of a ring that isn’t distinct.) If there is enough noise in a tooth, it can create an error in aging. However, that doesn’t happen often with the cementum-annuli method. On whitetails, I would say our aging estimates are correct more than 85 percent of time.”