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Several years ago a friend had taken a good eight-point buck during Michigan's gun season. As often happens the question of age came up. Guesses from fellow hunters were all over the board. Now even more curious about the animal's age my friend removed its jawbone for possible future aging. Well, the following year he brought the jaw to a hunting awards banquet. At one of the tables sat five wildlife biologists. During the course of the afternoon he had asked each of the five how old the buck was. The results? The five came back with four different answers ranging from 3½ to 6½ years of age. Confusing? Yes. So what can a hunter do if he or she truly wants to know how old a whitetail is?
Tooth-Wear Method Most hunters have seen photos of deer jaws in hunting articles or tooth aging charts showing different amounts of tooth wear and dentine exposure. This comparative analysis is called eruption-wear or the tooth-wear method. The idea is to compare photos of teeth of known age animals to the teeth of the deer that you're trying to age. This was the method used by the biologists at the table when aging my friend's buck. Cementum-Aging Method Another technique, less known but much more accurate is cementum-aging. This method requires more work than tooth-wear, but the results are well worth the effort for many hunters. Cementum-aging is a method that processes a deer's tooth in a laboratory. It's accomplished in such a way that the rings of growth occurring in a deer's tooth may be viewed. The rings reveal a whitetails age. Scientists aren't exactly sure why the rings occur. It's probably yearly stress, perhaps brought on by the onset of the rut or the adaptations required for each coming winter. But whatever the reason, they form with annual regularity, and are visible to a technician with aid of a microscope. The rings are then counted to determine the animal's age, much like counting the rings of a tree. Cementum-Aging At Work The cementum-aging process requires the two front incisors of the deer's lower jaw. They should be carefully removed so that the root tips or bottom part of the teeth are undamaged. This is where the cementum-annuli are located. The teeth are then cleaned (tissue removed), placed in a paper envelope and sent-off to a lab for processing. A lab-technician places the teeth in a light acid solution to decalcify the teeth. With decalcification, the hardness is removed and the teeth become as flexible and rubbery as an eraser on a pencil. The rubbery teeth are then frozen (for ease of cutting) and placed into a machine called a cryostat. The cryostat's job is to slice micron-thin samples of the root tip. The sliver-thin slices are placed on a glass slide where a special dye is added to enhance viewing. Another slide is placed over the tissue and the sample is then viewed with a high-powered microscope, where a technician may study the cross-sectioned tooth and count the rings. How Does Cementum-Aging compare to Tooth-Wear Aging? Tooth-wear aging, is used by most wildlife biologists for managing state deer populations. It's cost effective, which is great for state budgets, and generally suits their purpose for management studies. Generally, the purpose of these state studies is to place deer into one of three categories: fawns, immature animals (1½ years of age), and mature animals (2½ years and older). However for a curious hunter with an older animal, or a deer camp that is monitoring the age of its whitetail harvest, an educated guess may not be close enough. A study was done comparing the effectiveness of the tooth-wear method to that of cementum-aging. The research was completed and published in the Wildlife Journal 2000 by Hamlin, Pac, Sime, DeSimone, and Dusek. The research study was set-up this way: Six wildlife biologists experienced in eruption-wear were asked to view a number of known-age whitetails, elk and mule deer to determine their age. In a separate study, the teeth of known-age animals were submitted to a lab for cementum-aging. The results were recorded for both studies, but for the purpose of this article we will only look at the findings for whitetail deer. The results were telling. The six biologists experienced in tooth-wear aging were correct on 42.9 % of whitetail deer aged from fawns to nine year olds. The accuracy dropped even more for older deer. The six wildlife biologists were successful only 36 percent of the time for animals older than 2½ years, with some estimates off by 3 and even 4 years. These biologists had aged thousands upon thousands of teeth, imagine the results for the average hunter that looks at a chart or reads an article and attempts to age a whitetail. Believe me it isn't their fault. Deer inhabiting different areas feed on browse that grows in varying soil types (sandy and gritty) creating different tooth-wear patterns. In addition deer have unique tooth genetics that probably cause teeth to wear at different rates. And whitetails, like many humans, prefer chewing on one side of the mouth in favor of the other which would create more wear on the favored side. These factors all come into play when aging deer using the tooth-wear method. How Successful Is Cementum-Aging? Well then, how did the cementum-aging method fare? The research results that came from the lab were outstanding. Cementum aging was right on the money for 85.1 % of the whitetail study group. And almost as impressively the small percentage that missed the target were off by only 1 year, not 3 or 4 years. New Deer Hunting Philosophy is Taking Hold Over the past several deer hunting seasons the philosophy for harvesting bucks and does alike has gone through change. It wasn't so very long ago that most hunters would take any yearling buck with legal (3 inch) antlers while placing does in a sacred no-hunt category. But that thinking has changed for many hunters. It's a direct result of becoming better educated. Hunters are learning about the advantages of having a more closely balanced buck to doe ratio. And just as importantly the new philosophy emphasizes the importance of letting younger males walk and grow old. They are also starting to realize the value of managing deer populations to available habitat. These new hunting strategies allow more bucks to live longer. What The Expert Say about Cementum-Aging John Ozoga, retired wildlife biologist and research editor for Deer and Deer Hunting magazine, said, "Eruption-aging is not a very accurate technique for deer 2 ½ years old and older". Jerry Weinrich, retired D.N.R. wildlife biologist, commenting on Cementum aging said, "It doesn't lie. It's much more accurate than eruption-wear, especially for older deer". "Cementum-aging takes guessing and arguments out of the picture", said Ed Spinazzola, National Director for Quality Deer Management Association (QDMA). "For deer 2½ years and older cementum-aging is more accurate than eruption-wear and when a deer gets older it's even more accurate", said Paul Friederich, D.N.R. wildlife scientist responsible for aging many Michigan, animals including whitetails, bear, elk , etc. Where to Find More About Cementum-Aging Many hunters find that aging a deer is a unique way to add to the hunting experience. To learn that a buck or doe is a mature trophy and has defied the percentages to travel the path to adulthood can be very exciting. And for other hunters, aging a deer to insure that they are getting the most from their land and deer management practices is highly recommended. It's truly the only way to learn if the methods you are employing are working. To know that the bucks they are taking aren't barely mature 2 ½ or 3 ½ year olds, but bucks that are 4½ to 6½ years of age, animals that are truly in their prime years. Deer hunting continues to evolve. Aging deer will continue to play a important role in American whitetail hunting. It's as important to the manager as it is exciting to the hunter to learn the true age of the deer they harvest. There is a web site now dedicated to cementum-aging. The site www.whitetaildeer-bullseye.com offers hunters the opportunity to have deer aged and certified using the cementum-aging method. It also contains features about aging deer as well as stories of older trophy bucks. |
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