Aging White-Tailed Deer on the Hoof - Part II

Last week we discussed the scientific approach of aging of deer on the hoof. This week we focus on characteristics that will help you age deer in the field.

The Best Characteristics For Aging Deer On The Hoof Are...
Results of statistical tests indicated that the single best antler characteristic to use for aging bucks on the hoof was gross B&C score. Overall antler size is the best method for aging live bucks, contrary to what I was mistakenly told when I first moved to Texas. Accurate field judgment of gross B&C score can become nearly instantaneous with practice. In fact, a lot of south Texas hunters are already very adept at estimating antler size because they routinely estimate this before harvesting a buck anyway.

The next best antler characteristics for estimating age were basal circumference (i.e., mass) and inside antler spread. The best body characteristic for estimating age was stomach girth. However, none of the body characteristics were significantly different for bucks 2.5 years old or older. This means that either the characteristic does not change much as a buck grows older; or, a large amount of variation occurs in these measurements within age classes to the point that there is a lot of overlap among different age classes.

I then used additional statistical tests to tell me which combination of characteristics would work together the best for aging deer on the hoof. These tests indicated that the two best characteristics to be used in combination for aging live bucks were gross B&C score and stomach girth.

How You Can Age Deer On-The-Hoof
Our study suggests that gross B&C score, basal circumference, inside antler spread, main beam length, and stomach girth could all be useful for estimating buck ages on the hoof. Antler characteristics provided the least overlap among age classes, were most correlated with age, and are easier to visually estimate from a distance than body characteristics because ear length and tip-to-tip ear spread can be used as yardsticks. In addition, antler size is fixed within years, so this measure is obviously not affected by the seasonal changes that can dramatically affect body size.

The best available option is to use the combination of both gross B&C score and stomach girth. In fact, I recommend that hunters first look at a buck’s rack to field-judge his age. If antler size indicates that the buck is mature, the hunter should next “verify” this by carefully examining the buck’s stomach girth before he ever thinks about squeezing the trigger – hunters should never shoot a buck based only on antler size. The guideline I recommend for judging stomach girth is as follows: if the bottom line of the stomach sags noticeably lower than the bottom line of the brisket, the buck is likely mature. If both antler size and stomach girth agree, the hunter should shoot because he has done about all he can from a visual standpoint to properly field-judge that buck.

Post Rut Aging Characteristics
The above criteria work very well during the pre-rut period when buck body size reaches its annual peak, but during the rut, bucks lose an average of 27 percent of their body weight. Obviously, stomach girth is not a useful characteristic after the rut has occurred. So what can hunters use in addition to antler size to age bucks during the post-rut period?

Fortunately, additional characteristics are also useful in combination with antler size for estimating age on the hoof. Saggy, lose skin around the jaw and brisket and darkly stained tarsal glands are two characteristics I focus on during the post rut. Behavioral characteristics also often provide clues to a deer’s age, especially if you have an opportunity to observe the deer in question interacting with other deer. Generally speaking, the dominant buck in the group is often the oldest. If you witness subordinate bucks backing down from a dominant buck when he lays his ears back, tips his rack downward in a threatening manner, or when he “puffs” his body hair out; you can bet he is the oldest buck of the bunch. The same holds true for aging does. Another good method for aging does on-the-hoof, is to compare head or muzzle lengths. Typically, adult does have long, “bottle-nosed” faces, compared to fawns and yearlings that have shorter muzzles.

A Lesson Learned…
Obviously, aging deer on the hoof is not an exact science; therefore, mistakes will occur. A good example of this happened to me several years ago. I was guiding a package hunter during mid-January in south Texas on a private ranch where I consulted. The hunter and I were perched in a box blind overlooking a food plot of oats.

On this particular ranch only mature bucks that were 6.5 years old or older were eligible for harvest. The age restriction meant that we had to carefully age each buck that entered the oat field. During the course of the afternoon, we looked over a total of 22 different bucks. The majority of these bucks were either too young, or they did not possess the type of rack that the hunter was looking for. Finally, during the last hour of the hunt, two big-racked bucks entered the field. Both bucks easily gross-scored over 150 B&C.

Our next question was, do either of the bucks meet the age restriction? We very carefully examined all of the characteristics that indicate age on each buck. Both bucks were “blocky” and muscular, but neither buck stood out as being obviously mature. The fact that we were field judging these bucks after the rut peak made things even more difficult.

Finally, after watching both bucks for 30-40 minutes, they came close enough to each other that a dominance interaction occurred. The result of their confrontation made clear to us which of the two bucks was most dominant. I then gave the O.K. to my hunter to shoot the most dominant of the two big bucks.

The hunter made an excellent shot, but when we climbed down to examine the buck up close, I was surprised to see that tooth wear indicated he was only 4.5 years old. Although the buck could easily have been 5.5 years old, he was still younger than what the ranch owner wanted hunters to harvest. To make matters worse, the buck had indications of a drop tine on one main beam. This knob may have developed into a full-blown drop tine by next fall if we had let the buck walk.

Unfortunately, the buck’s young age put a damper on the hunt for both the hunter and myself. However, field judging the live age of deer is especially difficult for bucks 4.5 to 6.5 years old. And, even with years of practice, mistakes will happen. However, don’t let the occasional mistake discourage you from making every attempt to properly field judge a buck’s age on the hoof because the success of your management program depends on it. In fact, you can do everything else right, from supplemental feeding to growing food plots, and all of those management efforts will be for naught if you do not allow bucks to express their full potential for antler growth before harvest.

Join me next week for the first of a three-part series of one of my favorite hunting techniques to use during the rut, that brings the big bucks a running.

Photo By Hardy Jackson

Posted by Dr. Mickey W. Hellickson

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