Texas Deer Hunts

Table of Contents
I. Introduction, Background, and Definitions
II. The Studies
III. Other Related Facts, Results and Discussions:
IV. Applying These Studies to Real World Management Programs
V Other management concerns:
VI. Kerr Wildlife Management Area Penned Deer Studies,
Publications 1977-1999
VII. Appendices
A. Examples of gene interactions on phenotype and examples of changing gene
frequencies in populations
B. .Effects of Genetics and Nutrition on Antler Development and Body Size of
White-tailed Deer..
C. .Heritabilities for Antler Characteristics and Body Weight in Yearling White-Tailed
Deer.
D. .Antler Characteristics and Body Mass of Spike- and Fork-antlered Yearling
White-tailed Deer at Maturity.
E. Updated antler characteristic frequency charts for .Effects of Genetics and
Nutrition on Antler Development and Body Size of White-tailed Deer..
F. Updated antler characteristics and body weight by age and yearling status
comparison charts for the bulletin,.Effects of Genetics and Nutrition on
Antler Development and Body Size of White-tailed Deer..
G. Genetic/Environmental Interaction study . Antler characteristic and body
weight trend charts.

I. Introduction, Background, and Definitions
In the mid 1920s , a game law was passed in Texas which protected spike antlered deer.
The belief then was that spike antlered deer were young deer and would eventually grow
into big deer. By the mid 1950.s, biologists had learned how to age deer using a tooth
wear and replacement technique developed by Severinghaus (1949). It soon became
obvious that not all yearling deer were spikes and that not all spikes were yearlings.
About the same time, a review of nutritional studies (Verme and Ullrey,1972) was
published which strongly suggested that nutrition was a major determining factor in antler
size. Poor range conditions throughout Texas were assumed to be the reason for
spike-antlered deer. By the early 1970.s biologists had collected enough data from deer
grown on the same range and under similar conditions to suspect that more than nutrition
was influencing antler growth.
Deer that were grown under similar range conditions exhibited a wide range of yearling
antler characteristics. In 1974, a 16-acre research facility (now known as the Donnie E.
Harmel Deer Research Facility) was constructed on the Texas Parks and Wildlife
Department.s Kerr Wildlife Management Area. Biologists began a long-term research
program to understand why some deer produced big antlers and why some deer
produced smaller antlers. Research was approached from two viewpoints: one was
nutritional and one was genetic. The following is a review of over 26 years of research
conducted at these pens and its real world management implications.
What is a Spike
A spike is a male deer that is 1.5 years of age or older and whose antlers are
unbranched. It is not a fawn. Fawns may exhibit bumps on their foreheads that are
covered with skin. Older fawns may have a small amount of cartilage at the tip of the
protrusion. Only in very rare instances will a fawn have some hard bone tissue on their
head. Many people call a fawn that has lost its spots a yearling, biologists do not. When
biologists refer to yearlings, they are speaking of a deer that is between one to two
years of age.
Why a penned deer facility
In order to study and isolate nutritional effects and genetic effects, biologists need to
control diet and breeding and objectively analyze results. This can only be done with
penned deer. There are simply too many variables in the natural world to identify and
isolate biological causes. In 1973, biologists began gathering deer from throughout the
state of Texas and placing them in holding pens. Only Texas deer were used in the
research studies. The Pens were completed in August of 1974 and deer were moved from
holding facilities and placed in the research pens. In this penned facility, biologists placed
a single sire in each breeding pen in October. Most fawns were born in late June or early
July. Fawns were eartagged and tattooed with a unique number and matched to their
dams. If there was a question as to the proper dam, DNA tests confirmed parentage or
the fawn was not used in the study. Since 1974, no deer have been added. All deer used
in research have been born in the pens. Any deer born since 1974 has a pedigree record
dating back to 1974. Some basic deer biology.
Deer grow and lose their antlers yearly. Antler growth begins in March and is completed
by the middle of September. During this period, antlers consist of growing bone tissue
with a covering of skin commonly called velvet. In September, the velvet is shed leaving
only hard bone tissue. This velvet loss is partly due to the production of the male
hormone testosterone. The photoperiod or .length of daylight. triggers production of this
hormone. As far as body growth is concerned, approximately 60 percent of deer
growth takes place the first year of its life. Long bone growth in deer is essentially
complete after 3 years. This is when a deer completes his teenage years. For the first
three years of life, a great deal of nutrient resources are allocated to body growth. After
that time, more resources can be channeled into antler growth. Some Genetic Terms,
Principles, and Concepts used in this paper .
Gene...The ultimate unit of inheritance. Genes are attached to chromosomes and are in
the germ cells. They control the various trails of an individual. Two or more genes
controlling a trait may be capable of occupying the same position on a chromosome.
These genes are said to be alleles. For example, a dominant gene along with its
recessive form are a pair of alleles. If there are four genes capable of occupying the same
position on a pair of chromosomes, with each gene producing a little different affect on a
trait, these are alleles Genes can be divided into two broad groups (1)Dominant genes --A
gene or phenotype that is expressed in either the homozygous or heterozygous state. It
is a gene that masks the expression of its allele or alleles (if more than two genes).
Example: C = black, c = white; CC and Cc produce black coats, cc produces a white
coat. Since black is a dominate gene, it takes precedence over white when both occur.
Recessive c cannot express itself alone. There are grades of dominance among genes
ranging from complete to incomplete to overdominance. (2)Recessive genes -- An allele
or phenotype that is expressed only in the homozygous state. It is a gene whose
expression is masked by a more dominant gene. When C is present, c cannot express
itself phenotypically. During reproduction individual genes are also referred to
asgametes.The .take home. message from this definition is that all genes or gene
combinations do not affect a character in the same way. As far as antler development is
concerned, researchers do not know the exact genes involved in antler development or
the relationship of these genes to each other. Researchers do know that various genes or
gene combinations are involved and that they can measure the effects of these genes by
studying the phenotypes of deer within a population.
Gene Frequency
The relative occurrence of a gene in a population. Gene
frequency may range from zero to 1, and may vary from population to population.
Chromosomes -- Carry the genes arranged in linear order. DNA molecules (strands)
containing genes are arranged in linear sequence. Phenotype - The appearance of an
individual as influenced by environmental and genetic factors. 6 Chromosomes in cells of
animals are normally in pairs. Backcross - A parent bred back to its offspring.
Backcrossing can lead into reasonably high levels of inbreeding if practiced for too many
generations.
Genotype - The genetic make up of an organism, in contrast to phenotype,
which refers to physical appearance. Phenotype - The appearance of an individual as
influenced by environmental and genetic factors. Heterozygosity, Heterozygous - Carrying
both the dominant and the recessive gene of a pair of alleles, or two different genes of a
series of multiple alleles. Example: T/ts, T/t, or ts/t, all are heterozygotes. If a T/ts mates
with another T/ts, the possible offspring would be TT, T/ts, T/ts, and ts/ts. A variety of
offspring would be produced. Homozygosity - Carrying two of either the dominant or
recessive genes of a pair of alleles, or carrying two identical genes of a series of multiple
alleles. Examples: T/T, ts/ts, or t/t, are all homozygous genotypes. If a T/T mates with a
T/T the possible offspring would be T/T, T/T, T/T, T/T. All the offspring would breed true.
Inbreeding -Mating between closely related individuals such as brothersister,
father-daughter, mother-son, and cousins. Intense inbreeding decreases heterozygosity,
exposes undesirable genes and their effects, and generally produces weaker individuals.
It must be practiced with caution. The Need for Studying Populations and Not Individuals
Because body characteristics of deer are the product of both genetic and = environmental
influences, it is difficult to look at an individual and assign the cause of the size and
shape of antlers to either genetics or environment. The cause of poor antler growth in an
individual deer may be that the deer was sick during the antler growing period. This would
be said to be an environmental cause. Or the cause may be that it simply does not
possess the genetic material for growing good antlers. This would be a genetic 7 result.
There are many reasons an individual deer looks the way it does. To overcome the
inability to directly measure the roles of genetics or environment, researchers must study
a large number of animals and apply the laws of statistical probability to determine
observed results as being either random or predictable. Results presented in this report
have been statistically tested by appropriate statistical methods. Sample sizes are listed
with the title of a study. More detailed discussions of research studies are presented in
the appendices. II. The Studies
Effects of Nutrition on Antler Development: 1974-1977 (33deer) In this study, a group of
male fawns were placed on controlled diets and their antler production monitored for four
years. There were four groups of deer used in the study. One group received a 16 % diet
(High Protein) throughout the study. One group
received an 8% diet (Low Protein) throughout the study. The diets of two other groups
were switched yearly between high to low or low to high. All deer were fed four pounds of
feed daily throughout the study with the exception of the 3rd year when all deer received
five pounds a day. As a group, those deer receiving a high protein diet produced more
antler mass than those deer that did not. The deer that remained on a high protein diet
during the four year study grew better than those that did not. It was determined from this
study that an animal's diet was an important component in antler development. The
results of this study are published in the 1989 Texas Parks and Wildlife bulletin, Effects
of Genetics and Nutrition on Antler Development and Body Size of White-tailed Deer.
Role of Genetics in Antler Development: 1974-1984 (534 records, 298 sets of antlers)
The primary purpose of this study was to determine if there was a genetic component to
antler development. Male deer that were spikes as yearlings (1.5 years of age) were
placed in an individual pen and bred to a group of does. These same spikes were then
bred back to their daughters in order to concentrate the gene pool of the sire.
Theoretically 25% of those offspring would receive the better characteristics of the sire,
25 percent the lesser characteristics and 50 percent would be somewhere in between.
This form of inbreeding helps geneticists to look at genetic limits. The original does
(those that were originally bred to the deer that were spikes as yearlings) were then bred
to a large-antlered male that had six points as a yearling. There was a significant
difference in progeny antler production between the three types of matings. The results of
these matings strongly indicated a genetic role in antler development. All deer throughout
this study were fed a free choice 16 percent protein diet. Nutrition was not a factor. This
study is also reported in the 1989 Texas Parks and Wildlife bulletin, .Effects of Genetics
and Nutrition on Antler Development and Body Size of Whitetailed Deer.

Spike vs. Fork-Antlered Yearlings: 1974-1984 (64 deer, 192 sets of antlers) As
researchers began to observe deer grown in the genetic determination study, it soon
became evident that forked antlered yearlings grew larger antlers at maturity than did
spike-antlered yearlings. By the end of the study, antler production records confirmed
these observations. Antlers produced by fork antlered yearlings and spike-antlered
yearlings were compared annually through 4.5 years of age. Fork-antlered deer produced
almost twice the antler mass each year as their spikeantlered counterpart. Results of this
study are also published in the 1989 Texas Parks and Wildlife bulletin .Effects of
Genetics and Nutrition on Antler Development and Body Size of White-tailed Deer.
From this analysis, it was determined that antler status at 1.5 years of age was a reliable
indicator of future antler production. From a research viewpoint, this ability to predict later
antler quality at 1.5 years of age would shorten the time necessary to turn over a
generation of deer from 4-5 years to 2 years. In other words, from this point on,
researchers could select brood bucks based on yearling antler characteristics. Another
related study compared antler production under field conditions of deer that were spike or
fork antlered as yearlings. This study was conducted in a 96 acre deer proof pasture over
a four year period. Deer were range grown without supplemental feed. Although small
sample size prevented the two groups of deer from being statistically different, trend data
indicated that antler production of fork antlered deer surpassed that of spikeantlered
Heritability Study: 1986-1990 (483 deer, 531 sets of antlers)
In 1986, a study was begun to determine the heritability of selected antler traits in
white-tailed deer. Only yearling deer were used as brood bucks. All deer were fed a free
choice 16% protein diet. All fawns were weaned in October. Selected sires were placed
in breeding pens in October. Antler measurements as well as body weights were taken
yearly for analysis. Heritability estimates were analyzed by three different statistical
methods. It was determined from this study that antler traits are highly heritable. In 1985,
data was reviewed from both the original spike vs. forked antlered deer study and the data
gained from the heritability study. The conclusion was that deer which began as fork
antlered yearlings produced almost twice the antler mass each year as deer which began
as spikeantlered yearlings. Antler production was compared annually until 4 years of age
This review resulted in a paper titled .Comparative Antler Characteristics of Spike- and
Fork Antlered Yearling White-tailed Deer in Texas at 4.5 Years. This paper was
presented at both the Texas Chapter of the Wildlife Society and the 1997 Southeast Deer
Study Group.
Spike Line Herd 1974- 2000 (67 males through 1999) (145 sets of antlers) Since 1974, a
breeding herd of deer was maintained separate from other studies. The deer in this herd
were selectively bred to produce small antlers. All deer in this study receive a free choice
16% protein diet. No formal report on the results of this study was published although
data on this herd was recorded in yearly Federal Aid Reports. The spike-line herd
illustrates how selection for poor antlers can influence antler production. Each year the
male producing the poorer antler characteristics is selected as a sire. This herd provides
a stark comparison to those deer being produced in the Genetic/Environmental
Interaction study in which only the best males are selected as sires. These deer
produced small antlers with few points. Body weights were also significantly less than
their forked antler cohorts. In Texas, spikes were protected from the mid 1920.s until the
early 80.s by general law although some counties under the Texas Parks and Wildlife
Department.s regulatory authority were allowed spike harvest beginning in the late 60.s.
Protecting these types of deer and allowing them to become the .brood bucks. can be
a contributing factor in reduction of antler size in a deer herd.
Antler Characteristics and Body Mass of Spike- and Fork-Antlered Yearling White-tailed
Deer at Maturity: 1994-1998(144 deer) This study compared antler characteristics and
body mass of 144 whitetailed deer at 4.5 years of age that were reared in the pens from
1973 to 1990. All yearling deer were classified as yearlings (spike, fork, 3-5 points and 6
or more points) and live body weight recorded. At 4.5 years of age the gross Boone and
Crockett score (GBC) was measured. The average GBC score of adult deer that were
fork-antlered yearlings was 127.8 while spike-antlered yearlings measured 89.9. Adults
that were fork-antlered yearlings also had greater tine lengths and beam circumferences
at each of the four GBC measurement positions. At 4.5 years of age, mean body
weight was also greater for the fork-antlered group (78.7 kg) than for the spike-antlered
group (66.7 kg). Average GBC scores of adults that had 6 or more points as yearlings
(134.0) exceeded that of adults that were spikeantlered as yearlings by 44 GBC points.
These results show that classifying yearlings as spike- or fork-antlered is useful in
predicting antler characteristics and body mass at maturity. This project was an
extension of the original Ott study completed in 1990. It was conducted by Dr. Jim Ott,
Dr. John Baccus and Scott Roberts of Southwest Texas State University.
A further analysis of Boone and Crockett scores comparing antler points at 1.5 years to
B&C scores at 4.5 was made by Eugene Fuchs. At 4.5 years of age , deer that were
forked as yearlings produced 3 feet more B&C score than deer that were spikes as
yearlings.
Genetic/Environmental Interaction: 1992-2000 (41 sires, 137 dams, 217 yearling antler
sets) Since 1983, wildlife biologists of the Texas Parks and Wildlife Department have
been collecting white-tailed deer age, weight, and antler data from hunter harvested deer
throughout the Edwards Plateau. Analysis of this data has demonstrated that in years
with good nutritional range conditions, fewer spikes were in the harvest. It also indicated
those years in which range conditions were poor, there were more spikes in the harvest.
Range nutrition was affecting antler production. However, this same data also indicated
that even under poor range conditions, there were some deer that produced good
antlers. It also demonstrated that under good range conditions, there were always some
spike-antlered deer. From these data biologists concluded that there were three types of
yearling deer on the range (1) deer that always produce fork antlers even under adverse
conditions, (2) deer that always produced poor antler even under good conditions and (3)
deer that in good years produced forked-antlers and in poor years produce spike-antlers.
Biologists named this third group of deer, .swing deer.. From a management point of
view, swing deer slow management gains because poor genetic traits are masked in
good years. Researchers reasoned that if there was a genetic basis for these deer, then
the frequency of .swing deer. in a population could be reduced through a selection
program and more rapid antler improvement would result. A study titled, �Genetic/
Environmental Interaction in White-tailed Deer� was initiated to see if swing deer could be
reduced or eliminated from a population. In this study, fawns were weaned in October and
were placed on an 8% protein ration in which daily intake was also highly restricted
(approximately � normal intake) to duplicate drought effects. The deer were raised on
this limited ration until they completed their antler growth the following October. They
were then placed on a 16% ad lib ration and their antler production will be monitored until
they are four years old (this portion of the study is not complete). Only yearling data is
presented here. The five
yearlings that exhibited the best antler growth each year on this limited diet were used as
brood bucks and bred to unrelated does. Only yearling bucks were used as brood bucks.
Their offspring were weaned in October and placed on the limited ration. This process
was repeated yearly in order to make more rapid genetic gain. Doe Management within
the Study:
Does contribute 50 percent of the genetic potential for antler production. With some
exceptions, yearling females sired by stressed males were added to the breeding pens
each year. This had the effect of concentrating selected for genes in the doe segment of
the study. If a yearling buck was a spike, the records of the dam were checked to see if
the dam had produced another spike from another buck. If she had, both the dam and
sisters would be removed from the breeding herd. (In other words, two spikes and you.re
out). If the dam did not produce another spike, she was allowed to remain. This had the
effect of ensuring that swing deer genes were not maintained in the herd and more rapid
gain could be made. There were 137 females used during the study for a total of 410
matings. Only 5 females were culled because they produced 2 or more spikes. Seven 1.5
year old does were also culled because they were sisters to these spikes. A total of 12
does were removed due to this criteria. The deer pens can only hold a limited number of
deer. An additional, 27 does were removed for numbers control. Criteria for this removal
was based on age, past fawn production and survival, state of health, and genetic (antler)
potential of the offspring. In yearling does, antler potential was determined from family
history. As the study progressed, there were fewer spikes and more 6 and 8 point
yearlings with larger antler mass being produced. This allowed for a higher degree of
selection each year for numbers control. By the end of the study, does with histories of
producing less than 6 point yearlings were some of those deer selected for removal. Data
from this study indicate a genetic/nutritional interaction that governs swing deer. It also
suggests the best time to harvest spikes and make genetic gain is during droughts or
other periods of nutritional stress. One of the best times to harvest swing deer is when
starting a habitat management program on unmanaged ranches when deer numbers may
be excessive and herd reduction is needed to improve habitat. Removing poorly
performing stressed deer at this time will not only help accelerate genetic gains but will
also remove deer for habitat improvement.

Complete Research Study Link...

http://www.tpwd.state.tx.us/publications/pwdpubs/media/pwd_rp_w7000_0827.pdf