Mule deer are one of the most fascinating animals on the planet. I've felt that way since I was about 10 years old when my father started taking me hunting. His stories about big mule deer bucks really hooked me; stories of giant bucks lying prone as a hunter walked by only a stone's throw away, the days spent searching for a certain big buck, or just the glimpse of a big and wide 4-point as he ducked into the cover forever.

Part of this fascination has lead me to learn all I can about my chosen quarry. I want to know everything that can help me become a better hunter. While reading books from expert hunters, studying published research, and spending time listening to other successful mule deer hunters are all good and necessary, I want to know more about the bucks that I've killed. Accurately knowing the age of a big mule deer buck has taught me a bookful about big mule deer behavior.

The Importance of Deer Age

Age is one of the three most important factors in predicting how big a buck will grow, along with genetics and nutrition. As much as age is talked about, it's the one factor that is hardest to determine. That is because there is only one practical method to accurately determine age and few people have access to it. You cannot just look at the antlers, teeth, or body in order to figure out the birth month and year of a buck no matter what you've been told at the check station, bar, or forum. Only by cementum-age analysis can you accurately determine the age of a buck.

What Is Cementum-age Analysis?

Cememtum-age analysis is a process done by a qualified lab that looks at the cementum growth of a tooth. Cementum is the outer layer of a tooth that is regenerated yearly.

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A lab technician can age a mammal by counting the rings in a tooth sample just like counting tree rings to age a tree. It is considered the gold-standard in aging mammals.

Cementum slide of a tooth showing growth rings. Photo courtesy of Matson's Laboratory

Why Learn the Age of a Buck?

By aging my own mule deer, it has helped me refine my hunting skills as I really do know the true age of bucks I've taken. This one piece of information allows me to differentiate behavior between older mature bucks and younger less-experienced bucks (which, by the way, can still have big antlers).

As I write in my book, Hunting Big Mule Deer, older bucks are a subset of the mule deer species. I say this because they behave differently than the rest of the herd. Where they live, where they bed, when they feed, and how they react to hunting pressure are only a few of the differences I've noted. Knowing how old bucks were when I killed them is just one more piece of the puzzle in figuring out how to tag my next one.

In addition, lab aging allows me to see patterns in peak antler growth in different states and units. For example, some of the best Idaho and Wyoming bucks that I've killed have been only five years old, yet my better Colorado bucks have been six years old. By aging, I can also get a feel for how different management strategies are affecting the bucks. Aging also brings another level of satisfaction to your mule deer hunting experiences.

If you’re interested in lab aging your mule deer, whitetail, elk, moose, or antelope, you need to save the lower jaw bone. Even jawbones that are years old can be tested. You can either ship the lower jawbone, cut it off behind the front row of teeth, or remove the front two teeth (see picture below). Removing the front two teeth is only recommended if the jawbone is fresh or you’re very patient.

Photo credit: Matson's Laboratory

You can learn more about the lab aging process, information on shipping and associated costs here.

Also, you can find out more great hunting information by visiting Rokslide.com.