Can You Age By Antlers?
By: Dr. Mickey Hellickson
Have you ever wondered what characteristics are best for aging deer on the hoof? When I was growing up in the Midwest, I was mistakenly told that the number of antler points on a buck’s rack told you his age. If the buck was an 8-pointer, for example, he was eight years old. Unfortunately, before I knew anything about aging deer on the hoof, I mistakenly killed a 13-point buck in Iowa that still had his milk teeth — he was only 1 1/2 years old! Luckily, it didn’t take me long to figure out that the number of antler points had little to do with age.
After moving to south Texas, I was again told false information about aging deer on the hoof. This time I was told that you could not accurately age a buck by the overall size of his rack. Antler size, as you will soon learn, is a good characteristic for making initial age estimates on live bucks in the field, estimates which should then be confirmed with other characteristics.
More recently, I read an article in a popular hunting magazine that stated that you could age deer by the number of skin wrinkles in their ears. Even if this technique were accurate, it would not be very useful for aging deer on the hoof because of the difficulty in counting wrinkles from a distance. Obviously, a lot of bad information is floating around related to the best characteristics for aging deer on the hoof.
Why Do We Need To Age Deer On The Hoof?
The necessity for being able to accurately age deer on the hoof is becoming increasingly important as Quality Deer Management becomes more popular and more widespread across the United States. A cornerstone practice of QDM is avoiding the harvest of young bucks. Without being able to age deer on the hoof, how are you going to avoid harvesting the wrong buck?
Also, the ability to accurately age deer sighted during helicopter and spotlight surveys is important for biologists. The age ratios determined during these surveys are critical for setting harvest quotas, assessing herd population status, and providing information on deer productivity and mortality rates.
Dr. James Kroll, in his book on aging deer on the hoof, described characteristics that are useful in estimating ages of deer of both sexes. More recently, Dave Richards and Al Brothers summarized their guidelines for aging and scoring bucks on the hoof in their book, Observing and Evaluating Whitetails.
Only one scientific study has been published on how to age deer on the hoof. Charles DeYoung and his associates at Texas A&M University-Kingsville successfully classified 329 of 369 bucks sighted during 28 helicopter flights into two age groups — an 89 percent success rate. During earlier captures, they had previously marked the bucks with color-coded collars and ear tags and aged them based on tooth replacement and wear. During helicopter surveys, they placed the marked bucks they re-sighted into two age groups based on antler size and body musculature: 1 1/2 to 3 1/2 or 4 1/2-plus years old.
They considered antler spread well beyond the tips of the ears, “heavy” appearance of the antlers, long tines, “thick” necks and front shoulders, and a “blocky” appearance as indicative of an older-aged buck.
A Scientific Approach
Due to the growing need for information on how to age deer on the hoof, and the lack of scientific research, Stuart Stedman came up with the idea of measuring as many antler and body characteristics as possible from wild, free-ranging bucks that myself and other Texas A&M University-Kingsville students captured annually on his south Texas ranch. Since 1985, we had used a helicopter and a net gun to capture up to 100 different bucks each year on his ranch. Although these captures were conducted for other scientific studies through Texas A&M University-Kingsville and The University of Georgia, while we had each deer on the ground we also took measurements of various antler and body characteristics. Included in these measurements were chest girth or circumference, stomach girth, shoulder height, head length, forehead width and measures of each buck’s antlers in order to determine gross Boone & Crockett (B&C) score. In addition, we placed each buck into different categories based on how gray their muzzles were and the incidence of a Roman nose.
After capturing and measuring more than 700 wild, free-ranging bucks, I then used statistical methods to correlate these different measurements to the age of each buck as determined by tooth replacement and wear on the lower jaw. In addition, I also correlated the live and field-dressed weights of some of these bucks, which were measured when they were later harvested, to their age.
When Do Antler And Body Sizes Peak?
We captured a total of 766 bucks during the 13 years that we conducted deer captures. Surprisingly, antler size did not peak until bucks were 6 1/2 years old (refer to the chart on the opposite page). In addition, none of the individual antler measurements, such as main beam length and basal circumference, peaked until bucks reached this magical age — except one. The exception was inside antler spread, which peaked one year later when bucks were 7 1/2 years old. Most body measurements did not reach their peak until 7 1/2 years. Amazingly, in south Texas at least, a buck does not even reach his peak in antler or body growth until he is at least 6 1/2 years old! This may not be the case in many other parts of the country where some evidence indicates an earlier peak.
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. On average, overall antler size is the best method for aging live bucks. This antler characteristic, which is a combination of different antler measurements, is also one of the easiest to judge in the field. In fact, a lot of hunters are already very adept at estimating gross B&C score because they routinely do so before harvesting a buck.
Statistically, the next best antler characteristics for estimating age were basal circumference 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 1/2 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 together for aging live bucks were gross B&C score and stomach girth.
An underlying assumption in our analyses was that estimated ages using the tooth replacement and wear technique were accurate, because few deer were of known age, and this technique can be inaccurate in the older age classes. However, at present no other technique available for aging live southern deer is more accurate than the technique we used. In addition, harvested deer are aged almost exclusively using this method. Therefore, relating antler and body measures to the age as determined by tooth wear provided results much more useful to managers and hunters, who “verify” deer ages “in hand” using the tooth wear technique.
Unlike most studies involving free-ranging deer, the age structure of the buck segment of the deer herd in our study was well distributed through all age classes, with more than 42 percent of bucks being 5 1/2 years old or older. This allowed us to obtain unusually large sample sizes in the older age classes.
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. Statistically, antler characteristics provided the least overlap among age classes, were the 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. General body shape and appearance, although not easily quantifiable, when taken as a whole may also be useful.
The best available option is to use the combination of both antler and body characteristics, emphasizing 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. 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.
Of course, to make use of my recommendations, you must establish parameters that are typical or normal for your region of the country. A lot of factors affect antler growth besides age. Where a 135-class, gross-score south Texas buck is likely to be mature, that buck is probably only “middle aged” in the Midwest. In order to set your own gauge for your deer herd, you must consider the bucks harvested in your area, measure and record their gross antler score, have them aged, and begin to compile averages for the information you collect. This is important, because there are always exceptions — any individual buck could score higher or lower than the average buck of the same age in that region. This is why I suggest that, after your initial field estimate based on gross antler score, you always verify this estimate by studying other characteristics.
Additional characteristics, which we did not examine in our study, may also be useful in estimating age on the hoof. Behavioral characteristics 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.
Obviously, aging deer on the hoof is not an exact science; therefore, mistakes will occur. You may encounter a buck with the antlers of an immature deer but a body and behavioral characteristics that clearly indicate that the deer is mature. Whether you harvest this animal depends on your skill level at determining age on the hoof, local or state antler restrictions that might be in play, the rules that apply on the particular property, whether the QDM effort on this property is well advanced, and other factors — in short, that’s an article for another day. You may also encounter a buck with antlers that suggest maturity but with a body and behaviors that point to immaturity. This is where verification based on characteristics other than antlers can pay off — in most QDM programs, this is a buck that should not be harvested.
A good example of this happened to me several years ago. I was guiding a 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 1/2 years old or older were eligible for harvest. In addition, the cost of the hunt also hinged on the gross B&C score of the rack. If the buck’s score broke the 150-inch mark, then the hunter had to pay an additional fee.
During the course of the afternoon hunt, we looked over 22 different bucks. During the last hour of the hunt, two big-racked bucks entered the field. Both easily gross-scored more than 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. 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, because bucks can lose up to 30 percent of their body weight during the rut. By the time the rut ends, it becomes very difficult to separate middle-aged bucks from mature bucks based on body characteristics.
Finally, after we watched both bucks for 30 to 40 minutes, they came close enough to each other that a dominance interaction occurred. The result of this interaction made it 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 buck 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 the tooth wear on the buck’s lower jaw indicated that he was only 4 1/2 years old.
Field judging the live age of deer is especially difficult for bucks 4 1/2 to 6 1/2 years old. And, even with years of practice, mistakes will occasionally happen. But by studying and learning your deer, both harvested and on the hoof, you will soon be making the calls that count — a skill that brings enjoyment and rewards to the hunt.
About the Author: Dr. Mickey Hellickson is the chief wildlife biologist for the 825,000-acre King Ranch in south Texas. He is also a private wildlife consultant, managing over one million acres in south Texas, and he is a regular contributor to Quality Whitetails.