Estimating Buck Age in the Field

In recent years, there has been an explosion in interest among hunters and land managers in how they can manage their properties and deer herds to increase the number and size of bucks available for harvest. Once relatively uncommon, today Quality Deer Management, or QDM, is arguably the most popular deer hunting and management approach.

In its simplest form, QDM strives to balance deer herds with their habitats while improving the adult sex ratio and number of older bucks in the population. This approach generally involves four important cornerstones: 1) herd management, 2) habitat management, 3) hunter management and 4) herd monitoring. Of these, herd management is among the most important. Hunters must determine the number of does they should harvest as well as the best way to protect young bucks to enable them to reach an older age.

Age is the Key

Selecting the appropriate buck harvest restriction requires a basic understanding of antler development. While most hunters realize that age, nutrition and genetics are the “big three” when it comes to the size of a buck’s antlers, there is still much confusion regarding their order of importance. Without question, age is the most important. This is because regardless of a buck’s genetic potential or how much high quality nutrition it consumes, it will still have relatively small antlers if harvested as a yearling (1.5 years old). Nutrition also plays a key role and is second in importance in most QDM programs. The importance of genetics, however, is often exaggerated by hunters, especially in free-ranging deer herds. In fact, recent studies have shown that impacting genetics in wild deer herds is about as likely as altering the salinity of the ocean by adding a cup of fresh water. So, hunters needn’t concern themselves with genetics, but rather focus on the factors they can control and which have repeatedly been shown to positively impact buck antler quality – age and nutrition.

Thankfully, buck age structure is the easiest, cheapest, and quickest of the “big three” to improve. Simply by protecting yearling bucks and allowing them to live another year or two before harvest provides the greatest return on investment from an antler growth standpoint. For example, research has shown that the average yearling buck expresses only 15-25 percent of its antler growth potential. However, this increases to 40-50 percent at age 2.5, 70-75 percent at age 3.5, and up to 90 percent at age 4.5. From this it is easy to understand why age is so important.

Selecting the Appropriate Buck Harvest Restriction

What is the best way to protect young bucks? While there are many approaches, and none is perfect, most fall into three broad categories: 1) restricting hunter opportunity or harvest, 2) implementing an antler restriction, or 3) harvesting by buck age. Restricting hunter opportunity can be achieved by restricting the number of hunters, the number of bucks harvested, or the type of weapons that can be used. While these approaches can be effective, they are generally unpopular with hunters for obvious reasons.

The most common way to protect bucks is through an antler restriction. Examples of antler restrictions include a minimum number of antler points, a minimum inside spread, or a minimum gross Boone and Crockett score. While antler restrictions are popular and can be effective in many areas, they are rarely the best approach. This is because they inevitably protect some mature bucks that don’t meet the restriction while allowing some high-quality younger bucks to be harvested. Consequently, the best approach is to harvest by age. This allows the greatest precision with respect to protecting young bucks without protecting older bucks that don’t meet a certain antler restriction. Bottom line, harvesting by age is the most biologically sound approach.

Many hunters are quick to argue that aging bucks in the field is an impossible task. I typically respond by asking if they can assign humans to broad, 10-year age groups, to which most admit is fairly simple. The only difference between aging deer and humans is experience. As humans, we recognize subtle differences in body size and shape, musculature, facial features, behavior and other factors that allow us to determine the approximate age of another person. With experience, the same approach can be used to determine the age of deer. While not an exact science, it’s amazing how accurate you can become with practice.

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The key to aging bucks in the field is to learn the body characteristics that change most over their life and to refine these characteristics using deer in your area. While body and antler size vary considerably across the whitetail’s range, body characteristics remain very similar. As a result, once you learn how to age bucks in your area, you can use these same skills to age deer in other areas. Below are the key distinguishing features of bucks from 1.5 to 6.5 years of age.

1.5 years old

• Looks like a doe with antlers (slim body, thin neck)
• Distinct line of separation between neck and shoulder
• Legs appear too long in proportion to the body
• Wide variation in number of antler points
• Antlers thin and spread generally narrower than width of ears
• Small tarsal glands featuring little or no staining

2.5 years old

• Thin waist and shoulders
• Legs still not in proportion to body (gangly appearance)
• Minimal neck swelling during rut
• Back and belly lines are straight
• Medium sized tarsal glands with light staining

3.5 years old

• Noticeably enlarged neck during rut, but there is still clear separation between the neck and shoulders.
• Chest/shoulder area beginning to look heavier than hindquarters
• Neck width wider than face width during rut
• Has the “racehorse” look of a prime athlete
• Large tarsal glands featuring moderate staining

4.5 years old

• Fully muscled neck and shoulders blend together seamlessly
• No longer appear lanky or lean, legs in proportion to the body
• Slight belly sag may be apparent, especially prior to rut
• Large, heavily stained tarsal glands, often with staining extending well down the rear legs

5.5 years old

• Characteristic “buffalo” shape with enlarged neck and shoulders appearing as one large mass
• Legs beginning to appear too short for the body
• Belly sag common prior to rut
• Forehead region often dark due to increased gland activity
• Large, heavily stained tarsal glands, with staining extending well down legs

6.5+ years old

• Heavy, muscled body,
• Sagging belly and back
• Legs appear too short for the body
• Neck and chest appear as one continuous muscle
• Skin around face and neck often loose and rippled
• A flap of loose skin often evident at jawline

Practice Makes Perfect

Like any new skill, learning to age bucks in the field requires practice and experience. However, most hunters don’t have enough older bucks in their area on which to practice and refine their skills. As a result, I encourage you to use all available resources. One of the best ways is through the use of game camera photos from your property. Using body characteristics, group all buck photos by age from 1.5 to at least 5.5. Then, anytime one of your photographed bucks is harvested, have a wildlife biologist age it based on tooth wear to check your field age. In a short time, you will be surprised how accurate your field-aging skills will become.

Other great resources include DVDs and posters like the one offered by the Quality Deer Management Association (www.QDMA.com). Harvesting bucks by age is not only the best way to protect young bucks, it also adds a new and rewarding dimension to your deer-hunting experience. It’s just another way we use Whitetail Science to improve our understanding and management of North America’s premiere game species.

Brian Murphy is a wildlife biologist and CEO of the Quality Deer Management Association (www.QDMA.com). He also has been an avid bowhunter for the past 30 years.