Properly aging deer key to herd health

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By Missy Hodgin
AgriLife Extension Agent

With archery season in full swing and the general white-tailed deer season just around the corner, it is definitely time to think about deer management.

One of the most important tools used in a white-tailed deer management program is keeping accurate deer harvest records.  These records can help land managers evaluate the effect of hunting pressure, set proper harvest rates, and determine the reproductive capability of their deer herd.  Combining harvest records with annual deer population survey data will help landowners determine if their management goals are being achieved.  Long term trends can then be analyzed and corrections made to existing management strategies.

The minimum data that should be collected from deer harvests are age, field-dressed weight, body condition and measurement of antler size.  The data should be grouped according to age categories and analyzed separately for bucks and does.  Other information that may provide insight about specific management goals includes date and time of harvest, location or pasture deer was harvested in and lactation rate of adult does (i.e.: The presence or lack of milk in her udder).

Deer harvest records serve a similar purpose as livestock records to ranchers in that they can be used to evaluate what is occurring in the deer herd and the success of previous deer management decisions.  Harvest records can provide valuable information to answer the following four major questions about deer herd management:

  • Is the level of nutrition adequate for my deer herd, or do I need to reduce deer numbers?
  • Am I harvesting too many bucks to maintain old enough deer in the herd to produce the quality I want?
  • Is my deer herd improving, remaining the same or declining?
  • If I have problems with deer quality, what are some of the likely causes?

Age    

Determining the age of white-tailed deer is the best source of information for determining the success of a deer management program and the accomplishment of long-term goals and objectives.  It provides insight into the health of a deer herd and the quality of individuals in the population.  Other data collected will have little meaning if not related to age.  To determine a deer’s age, jawbones must either be extracted from the harvested animal or visually examined by looking inside the opened mouth.  For those lacking experience in aging white-tailed deer, extracting the lower jawbone is the best way to preserve important data on each individual animal harvested.  Body or antler sizes are not necessarily good indicators of age.

Deer age is recorded in one-half year increments.  Fawns are normally born during late May and early June in most parts of Texas and if harvested are about 6 months of age.  In successive years, deer harvested during the fall will be 1 ½, 2 ½, 3 ½, etc.

It is important to adhere strictly to the aging technique and not let the physical appearance of the harvested animal influence judgment when assigning age.  Small body size may be the result of poor nutrition.  Spike bucks are primarily restricted to the 1 ½ or “yearling” age class, but age them anyway to be sure.  Determination of deer ages past 7 ½ years cannot be reliably determined by examination of jaw teeth.  Most errors are made between 1 ½ and 2 ½-year-old deer.  It is important to look at the very last cusp on tooth six if other characteristics are not clearly defined.

Weight

Field-dressed weights should be the weight of the deer with all internal organs removed including the heart, liver, lungs, etc.  Use a reliable scale and check it against a known weight each year to assure accuracy of your measurements.  Field-dressed weights of white-tailed deer reflect their nutritional status.  Average deer field dressed weights by age-class will indicate whether a manager is gaining or losing ground with a deer management program.  If field-dressed weights of deer harvested from a particular ranch fall consistently below age class averages, deer may not be receiving proper nutrition, which may indicate too many deer and/or heavy continuous grazing pressure exerted by livestock.

Antler Measurement

A standard for taking antler measurements is necessary to avoid errors in measurements obtained by different persons in a hunting camp.  Antler measurements should always consist of these measurements: 1) total number of points, 2) inside spread, 3) basal circumference, and 4) main beam length.  A point should be classified as a projection at least one inch long.  Spread is the inside spread between the main beams measured at right angles to the centerline of the skull at the widest point between the main beams.  Basal circumference is measured halfway between the burr and the first point (brow tines) on the main beam.  The main beam length is measured from the burr to the tip of the antler on the outside curve.

Nutrition is extremely important in antler development, particularly good quality forage during the months of April, May and June (when bucks are growing new antlers).  Antler measurements in the yearling age class can be a very good indicator of future antler growth.  A buck usually does not reach his maximum antler development until he is 5 ½ to 6 ½ years old.

Body Condition

Body condition can be divided into three categories 1) good – fat across the back and base of the tail, fat present on kidneys and in the body cavity, 2) fair – little or no excess fat, but bones not showing, 3) poor – ribs, backbone, and pelvic girdle showing under the skin.  During years of average or above average rainfall, few deer should be in poor body condition.  If over 10 percent of the deer harvested are judged to be in poor condition, then a lack of nutrition is indicated and reducing deer and/or livestock numbers will be necessary.

In conclusion, you can’t change what you don’t measure.  Proper deer harvest data collection is the cornerstone of any type of deer management plan.  Records are one of the few means available to determine deer herd health, nutrition levels, trends and adequacy of the harvest.  Enjoy the hunt! 

For more information on this subject, contact Missy at the extension office at (940) 538-5042 or 538-5052, or by email at mlhodgin@ag.tamu.edu.

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Pioneer Sentinel

The Pioneer Sentinel is an online newspaper designed to deliver the news of Clay County, Texas, in a concise and community-friendly format.

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