ASK THE EXPERTS

This article was originally printed in the December 2001 / January 2002 issue of Deer Tracking
This article is copyrighted and may not be reproduced in any form without permission.

Question: I realize there is science behind aging deer by toothwear. But in reality, is this absolutely accurate to the year?

Answers:

*Aging whitetails and mule deer by tooth replacement and wear is nearly 100% accurate for 0.5, 1.5, 2.5, and 3.5+ because of changes in tooth eruption and wear of a few definite cusps. After 3 years, wear rather than eruption of new teeth are used for aging and things get a little less reliable.

Research shows that "Field Aging" (tooth replacement and wear) is more accurate than cementum annuli for deer 3.5 and younger. For deer older than that cementum annuli gave better results. There can be variability between observers on the same deer, but for management purposes, field aging is a very useful tool. In Arizona we place deer into 6 age classes, grouping some of the older ones because it is not reliable (nor necessary) to differentiate between a 6.5 year old and a 7.5 year old when managing a wild population.

Our age categories are 0.5, 1.5, 2.5, 3.5 to 5.5, 6.5 to 8.5, and 9+. We feel reasonably confident we can place most in these categories accurately and these classes are useful for management purposes. The half ages are because the fawns are born in summer and we normally age them during the fall hunting season so they are always at half ages.

If you are interested in more, our department sells a $3 age guide that shows how to age deer, elk, and most other big game species. The guide is called "Age criteria for Arizona game animals", but the aging methods are applicable to these species throughout their range. You can order (by mail, not on-line) the age guide by following this link: www.azqfd.com/frames/whatsnew/idf_pub.htm

Jim Heffelfinger
Regional Game Specialist
Arizona Game and Fish Department
and Adjunct Professor, University of Arizona

*Aging white-tailed deer by tooth eruption is quite reliable through about 3.5 years of age, relatively good for 4.5 to 5.5 years of age and just a guess beyond 6.5 years of age (other than to say "It's old."). The procedure depends on the presence and replacement of deciduous premolars ("baby teeth") and the eruption of the last molar. For older animals, the wear of the permanent teeth is used. This procedure is easier in hunter-killed animals where you can either cut the cheek skin or pull the lower jaw. It is more difficult in live animals as visualization of that last molar can be tricky. As with any procedure, it is not 100% accurate, but it is good for estimating age structures within populations.

Ken Waldrup , DVM, PhD
Texas Animal Health Commission

*No. It works well for the first 3 years and then starts to get progressively more error prone. You could still separate old deer from young deer without hesitation, but you could not identify an 8-year-old or even a 5-year-old with confidence. As deer get older, individual differences start to dominate the general wear pattern that comes with age. It's just like people - most of us start out with good teeth but by middle age there are huge differences between individuals, some who still have good teeth and others who have terrible teeth. You could start a reference collection of your own by saving lower jaws of known-age animals that die or are slaughtered from your farm.

Dave Hirth
Wildlife Biology Program University of Vermont

*Ken Gee with the Noble Foundation in southern Oklahoma evaluated the tooth-wear and eruption method for aging deer; his results were less definitive than those that Heffelfinger reported for AZ. The abstract from a talk that Gee gave at a deer symposium a couple of years ago reads:

"Abstract: Aging white-tailed deer using the tooth replacement and wear aging technique is widely used and accepted. We established a reference collection of known-age free-ranging deer from south-central Oklahoma to evaluate the accuracy of the technique. Results from that study indicate that the technique allows us to confidently place deer into 3 age-classes only, i.e. fawn, yearling, and adult. Attempts to place adult deer into specific year age-classes using traditional methods were very inaccurate. Management or research programs requiring accurate and precise age determination of adult white-tailed deer should carefully review and critique the method." More details at: http://texnat.tamu.edu/symposia/genetics/p18.htm

I know that Dr. Charles DeYoung of (then) Texas A&I University in Kingsville compared ages as estimated by tooth wear vs. cementum annuli, but I cannot recall his exact findings (these are likely the results that Heffelfinger is alluding to). Perhaps someone else on the list has those data or conclusions in electronic form?

Dale Rollins
Professor and Extension Wildlife Specialist
Texas Cooperative Extension
San Angelo

*We studied this a bit with deer from NE Illinois. For adults (2.5 +), experienced agers were quite variable relative to cementum age. Agers tended to overestimate the ages of 2.5 yr olds (more so for male deer). For 3.5 yr olds, agers were somewhat underestimating the ages of females but were about right for males (errors of over estimation = errors of under estimation). For deer older than 3.5, agers tended to under estimate deer ages for both sexes.

In all cases, agers tended to over estimate the age of male deer relative to females of the same cementum year class. This made sense because measurements of visible dentine of the occlusal surface were larger for male deer - even when we corrected for small differences in tooth size. I know from experience that I make most of my errors in trying to separate 2.5 and 3.5 yr olds.

Cite: Van Deelen et al. 2000. Sex affects age determination and wear of molarifom teeth in white-tailed deer. J. Wildl. Manage. 64:1076-1083.

Tim Van Deelen
Research Scientist
Wisconsin Department of Natural Resources

Question: One more question... Consider aging farmed deer (by pulling teeth or deaths), given the different browsing choices available to them and more grains, peas, pellets, etc., would you expect them to wear differently than wild deer? Less wear? More wear? And would this same method be accurate in determining age of deer on farm and from farm to farm?

Answer:

*It's been my experience (with WT deer only) that when I use the tooth wear technique on known age, adult deer, born and raised in confinement, I almost always underage them by a year and in most cases two. In all the cases the deer had been fed in troughs. If they had been fed on the ground, heaven forbid, where they would likely ingest a lot of soil, I don't believe the above situation would necessarily be true.

Larry Varner
Wildlife Nutritionist
Purina Mills, Inc.
Seguin, TX

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