Arrangement of harvest data by ages is very important to interpretation. For example, knowing the age of a deer aids in determinging why the deer may have small antlers or be light in weight. A sample worksheet is icluded in this publication for use in orgainizing and calculating harvest data.
Field Dressed Weights
The figures given are for the Edwards Plateau only an dare used as an example. Specific weights will be different in other areas; however, the principle is the same.
Ramsey (1981) notes that yearling deer are the most sensitive indicator of herd welfare among deer harvested during a hunting season. The yearling deer have greater nutrition requirements than older deer and therefore reflect deficiencies.
Weights of field dressed deer should be separated on the basis of bucks and oes. then, both buck and doe recorded weights are grouped by ages. For example, all 1 1/2-year-old bucks are grouped together, all 1 1/2-year-old does, all 2 1/2-year-old bucks, and so forth. Average weights for each group are calculated and these average weights serve as an indicator of herd nutrition levels and health. Harmel and Litton (01981) list the following field dressed weights as minimal for whitetail (Odocoileus virginianus) bucks within each age class during years with normal or above normal rainfall in the Edwards Plateau of Texas:
Buck fawns…………………………35 pounds
Buck 1.5 years old………………….60 pounds
Bucks 2.5 years old…………………75 pounds
Bucks 3.5 years old…………………85 pounds
Bucks 4.5+ years old……………….105 pounds
If average field dressed weights of whitetail deer consistently fall below the minimums listed on an Edwards Plateau ranc, this indicates that the herd needs improved management. The cause is usually lack of proper nutrition and lowering deer and/or livestock numbers is necessary.
Body condition can be divided into three categories (good, fair and poor). Subjective criteria for placing animals in these three categories have been given previouly with listings of data to include in harvest records. Arranging this information by sex and age groups gives an overall view of herd health. During years of average or above average rainfall, few deer should be inpoor body condition. If over 10 percent of your deer harvested are listed in poor condition, then a lack of nutrition is indicated and reducing deer and/or livestock numbers may be necessary.
Nutrition is extremely important in antler development. A lack of adequate nutrition first may become evident in smaller antler development. Continured lack of nutrition is characterized by yearly development of small antlers and small body siz (weights) of deer.
Antler development of white-tailed deer is influenced by three factors: food quality and availability, age of the deer and genetics. The deer manager can increase the size and number of “trophy” bucks in a herd by proper management of these three factors. To aid in interpreting the reasons for antler sizes in the harvest, all bucks’ antler measurements are grouped by age classes.
The prime age of a deer is 5 1/2 to 6 1/2 years old. A buck’s annual set of antlers should be near their largest during this period of his life. By analyzing average spread, beam length and other antler measurements of bucks in these age classes, one can determine if quality of bucks being produced is consistent with goals, or if steps need to be taken to improve management.
Spike bucks are defined as bucks with hard antlers that have no branches or points. The percent of spike bucks in each age class is an indictor of the quality of bucks produced. Spike antler formation may be the result of lack of nutrition inhibiting antler development or it may be due to genetic influences, or both factors combined. If a high percent of spike bucks (“spikes”) is found in the harvest, interpretation of causes will depend partly on reviewing body weights (low body weights support lack of nutrition as the main cause of poor antler development). If whitetail deer body weights are equal to aor abve the minumum listed, then genetic inffluence may be suspicioned as the major factor causing poor antler development. Emphasis on harvesting “spikes” is one method of attempting to redue this genetic influence in Texas whitetails. Minimum quality to look for regarding “spike” whitetail deer in the harvest is indicated by Harmel and Litton (1981) for the Edwards Plateau of Texas.
During years of normal or above average rainfall, at least 50 percent of the yearling bucks harvested should be fork-antlered or larger. Also, spike bucks should be found onl in the yearling age class of animals.
Note: This statement assumes a harvest of bucks where hunters shoot the first legal buck they see. Obvioulsly, if hunters are stressing shooting “spikes” or if they pass up small deer to shoot only trophy size bucks, a bias in the hunter selection will have to be taken into account when analyzing buck harvests.
Percent of Harvest Listed by Age Classes
Harvest data should be separated between bucks and does for thes calculations. Numbers of buck deer harvested are summed for each age category (likewise for the does). The sum total of all bucks harvested is calculated (as well as the sum total of all does harvested). For each age category, the number of bucks (does> of that age is divided by the total harvest of bucks (does) harvest is composed of that aged class. Table 1 shows an example of calculations:
|Age Class||No. of Bucks Harvested||Calculation||Percent of Buck Harvest|
|1 1/2 years||5||5/20=0.25||25%|
|2 1/2 years||8||8/20=0.40||40%|
|3 1/2 years||4||4/20=0.20||20%|
|4 1/2 years||3||3/20=0.15||15%|
|20||Total Buck Harvest 100%|
Table 1. Deer Harvest Calculations.
The information of interest is in the “percent of harvest” column. This information gives an idea of the basic age structure of the buck (or doe) segmant of a deer herd (factors of hunter selection must be taken into account when making this analysis). For example, suppose profucting trophy bucks is a management goal, and there is a lack of large trophy bucks int he harvest. One reason may be that bucks are being too heavily harvested and they are not having an opportunity to gain enough age (5 or 6 years) necessary to produce larger antlers. To determine if this is indeed the cause of lack of trophies, an analysis of the percent of the buck harvest listed by age class is needed. If less than half the bucks are in the 4 1/2 year or older age class, then an overharvest of bucks is indicated and reducing the number of bucks in the harvest will be necessary so more bucks will have an opportunity to mature to the older age classes.
The percent of harest shown by age class also can be graphed as in the following example. This method of displaying data can be easily interpreted by looking at the age classes where the curve peaks. Calculations and graphs can be made for the doe segment of the deer herd as well as the bucks. Analyzing this information for does compared to bucks will help determine if equal hunting pressure is being exerted on both sexes. By analyzing age composition of the doe harvest, a determination can be made of the intensity of doe harvest. For example, if the majority of does harvested are in the 1 1/2 and 2 1/2 year age classes, indications are that a large percent of the doe population is harvested annually. If a high harvest of the doe population is desired, this is an indication that the goal is being achieved.