At an Israeli cave site dating back nearly 100,000
years, remains of a man were found clutching an
antler in his hands. Man has been interested in antlers since the beginning
of time and probably will be until the end of time. It is interesting
to ponder whether humans became so attached to antlers because of their
usefulness as tools or whether they became widely used as tools because we
were so fascinated by them. One cold February
morning in
Webb County, I found myself laying under my truck, pounding the starter
with the only tool available -- a big shed antler. Some things never
change. One of the things that makes antlers
so interesting is the infinite variety of
antler shapes, colours, textures, and unique characteristics. Discussion
and admiration of kickers, stickers, drop tines, cheaters, forks, double
brows, and triple beams consume many hours in deer camps and at gas
stations. It is the oddities and abnormalities that capture our interest
the most. If all bucks looked the same, they
would be about as interesting as does. Because of our interest in
non-typical antlers, much research has been directed at the causes of
antler abnormalities. There are many factors which can cause or affect the
expression of antler abnormalities: Genetics, Age, Nutrition, Injury,
Disease, Hormones, and magnetic/electronic forces.
Genetics
Many odd points and abnormalities are the result of
the animal’s genotype, or genetic blueprint. Antler characteristics are
inherited from the buck’s parents. A non-typical buck will frequently
produce a disproportionate number of offspring with non-typical points.
Also, does contribute half the genetic blueprint for antler qualities to
their offspring. As a result, does that had non-
typical
fathers may consistently produce buck fawns which grow up to be non-typicals
even though they had different fathers.
Genetically programmed antler abnormalities can be seen year after year in
an individual. A buck may have a small bump on the outside of his back tine
(G2) at 2.5 years old, then a 2-inch kicker in the same spot the next year
and a 4-inch kicker on each G2 at 4.5 years old. Palmated antlers, which
are webbed like a moose, are a good example of a characteristic which is
genetically inherited in whitetails. Biologists in Utah reported observing
14 mule deer bucks in the 1950s which had no antlers at all. They felt that
this was a genetic abnormality because all bucks came from one localized
drainage.
Age
We all know how age affects antler size; young
bucks are still allocating nutrient resources to body growth and not antler
development. Once the body becomes fully mature at about 2 years, a buck is
able to pass on nutrients to luxury items such as antlers. It follows then
that young bucks are not going to show many non-typical characteristics
which require robust antler growth. Bucks rarely start expressing kicker
points and drop tines before they are 3 years old.
Nutrition
In any given year, a buck only has enough energy
for growing large antlers if he satisfies his own body maintenance
requirements first. In poor years or on over-population ranges, deer do not
have the luxury of growing large cranial appendages because they barely
have enough nutrients to maintain their body condition. Good nutrition
means the buck has more energy to pass on to antler growth. More total
antler growth allows the buck to physically express his genetic traits.
Regardless of the cause of the abnormality, good nutrition is necessary to
provide the building materials. In Scotland, some red deer stags fail to
develop antlers until the age of 2 or 3 years. This lack of antlers is
thought to be caused by the poor level of nutrition. These antlerless
stags, called Hummels, are not physically able to cope with the rigors of
antler development until their body is fully grown. It has also been
reported that poor nutrition (specifically mineral deficiencies) can result
in whitetail antler tines which are “wavy”.
Injury
Physical injury or trauma to either the velvet
antlers or a major skeletal structure can result in antler abnormalities.
Injury probably accounts for most of the very freakish heads. Any injury to
the velvet antler may damage the mineralized cartilage structure of the
growing antler and affect the blood flow and hence the deposition of
calcium and phosphates. Nicks and cuts in the velvet antlers can produce
points and oddities. This has led some to suggest that the awe-inspiring
double drop tine might be caused by bucks trying to slip through a fence
and getting the underside of their main-beams caught (and nicked) on a
fence strand. This is an interesting observation, however, most people
agree that drop tines are mostly of a genetic origin. Bucks in velvet do a
pretty good job of protecting their antlers because they are sensitive
during that phase of the antler cycle. Game keepers in early Europe
reportedly would jump-shoot red deer with bird shot
when they were in velvet. The intent was not to kill the deer but to pepper
the growing antlers with lead pellets to cause non-typical points to
proliferate. Besides direct trauma to the growing antler, injuries to the
buck’s body can also cause antler abnormalities. Injury to a large skeletal
structure such as a broken leg bone often causes a misshapen rack the next
antler cycle. If it is a front leg that is injured, either side of the rack
may
be affected, however, if the rear leg is injured the opposite side of the
rack is frequently malformed. Some have written this off to coincidence,
however, there is a significant amount of evidence from several species of
deer showing this contralateral (opposite-side) effect is real. Studies by
Texas Parks & Wildlife Department in the late 1960s showed that amputation
of a rear leg stunted the opposite side of the rack in all 6 experimental
animals. Other researchers have also reported this phenomenon in mule deer,
whitetail, sambar deer, elk, and muntjacs (barking deer). The cause of this
contralateral effect is not known but many theories have been set forth.
Some have stated that it is related to the fact that the right side of the
brain controls the left side of the body, and vice versa. Others have
postulated that while still in velvet, the buck frequently turns to lick
the injured leg thereby repeatedly injuring the opposite side of the rack
on nearby brush. This seems unlikely because of the care bucks take to
protect their growing antlers and the fact that the opposite antler is
usually under-developed not just deformed from repeated trauma. The most
widely accepted explanation is that the uneven rack counter-balances the
injured leg and allows the animal to move around more comfortably. This
would be difficult to prove in any conclusive manner but it makes more
sense than most other explanations. It is interesting that after amputation
of a rear leg, this contralateral effect occurs annually with each set of
antlers for the rest of the deer’s life. Injury to the pedicle (base)
itself nearly always causes abnormalities. Extensive trauma to the pedicle
before growth begins or soon after is the source for many large freakish
racks. Bucks with 2 main-beams on one side are usually the result of this
type of injury. If one pedicle is injured severely, that side or both sides
will be malformed during the next antler cycle. In addition, the nerves may
remember the injury and reproduce non-typical antlers for several years.
This atrophical memory only occurs when the injury is substantial and
occurs in the early stages of antler growth when there is a high density of
nerve connections in the growing antler tissue. We can add this incredible
phenomenon to our list of antler mysteries we don’t fully understand. Acorn
points are a common oddity we frequently see each fall. This is a swelling
in the hardened antler tine that looks like a ball of water running through
a cartoon hose. Acorn points are caused when the
buck bumps the growing tip of the tine on something hard. The velvet on the
tip is injured and in the process of repairing itself, deposits more
calcium and phosphates at that location. If an antler tine breaks
completely while still in the velvet phase it may stay attached to the rack
and re-fuse with it leaving a pendulous, or hanging, tine that frequently
has a large rounded tip. Researchers working with sika, roe, fallow, and
red deer, have also succeeded in making antlers grow out of abnormal places
on the buck’s skull. By grafting cells from a buck’s pedicle (base) to
another place on the frontal bone (forehead), researchers have been able to
produce deer with a third antler growing out of their head between their
eyes. All 3 antlers undergo the normal sequence of growth, velvet shedding,
and casting (drop off). One experiment involved grafting pedicle cells on
to the leg of a European roe buck. Incredibly, a small antler grew on the
leg, lost its velvet and was later cast normally! Few people would argue
that this buck would belong in the non-typical category of Boone & Crockett
(Do I get the greatest inside spread?). Trauma to the frontal bone of the
skull can even induce antler growth in does. In 1894, W. Blasius reported
that a female European roe deer grew a 4-inch antler after a piece of
window glass was accidentally driven into her scalp. Researchers have also
reproduced this response under controlled circumstances.
Hormones
The proper production of a variety of hormones is
necessary to produce antlers. Seasonal fluctuations of male hormones
(androgens) occur because the pituitary gland at the base of the brain
records changes in day length via information from the optic nerve running
from the eyes to the brain. As the days get longer in the spring or shorter
in the fall, the pituitary gland responds by regulating different levels of
some hormones differently. Not long after birth, a buck fawn experiences a
rise in the level of testosterone which induces the development of the
pedicles. Not much else occurs in the area of antler development for these
little guys until the next spring when another small but important rise in
testosterone initiates antler growth. After a full summer of growth, a
substantial increase on this male hormone associated with the onset of rut
causes the velvet’s blood vessels to dry up and the velvet is stripped off
in a short period of time. The hardened antlers then remain firmly attached
to the pedicles throughout rut until falling testosterone levels weakens
their attachment and they drop free. The antler cycle is incredibly
complicated and involves an intricate coordination between several
androgens (not just testosterone) and compounds which act as an
antler-growth stimulus regulated by the pituitary gland (via day length).
Researchers have successfully produced 2 complete sets of antlers in one
year by duplicating the day length sequence of two annual cycles in a
12-month period. They have also conditioned deer to grow antlers throughout
the winter and shed them in the spring when most deer are just starting
their annual development. Young fawns that are castrated shortly after
birth, do not develop pedicles because they never produce necessary
testosterone required for this first step in antler development. A buck
that is castrated while in velvet will never polish or shed his antlers
because he lacks the necessary rise in testosterone to trigger the drying
of the velvet. The buck then continues to grow more antler material in the
next antler cycle but never sheds its antlers until he finally carries a
grotesque mass of velvet antlers. These bucks are often referred to as
cactus bucks. Antler growth is still possible because low levels of male
hormones are produced by other structures besides the testicles (the
adrenal cortex). These low levels are enough to grow antler material but
not enough to complete velvet drying and antler shedding, which require a
substantial increase in the testosterone level. Bucks which are castrated
while in the hardened antler stage will drop their antlers within a few
weeks because of the sharply falling (no pun intended) testosterone level.
Bucks castrated after they drop their hardened antlers, will grow new
antlers the next year but they will never be polished or shed because of
the lack of sufficient hormone levels. In the 1840s, early naturalist John
J. Audubon described 2 castrated whitetail bucks he observed: “Their horns
continued to grow for several years; the antlers were of enormous length
and very irregularly branched, but the velvet was retained on them....they
had become very large and when first seen at a distance we supposed them to
be elk” (if we could all be as lucky this fall). Caribou have evolved
alternative (other than the testicles) sources of male hormones to regulate
antler growth since it is the only member of the deer family in which the
females also grow antlers. Interestingly, when a male caribou is castrated,
the antlers remain in velvet but mineralize completely and are dropped
normally. They still continue to carry out a normal antler cycle except the
velvet is retained on the surface of the hardened antlers. Tumors have been
known to affect the hormonal environment and thereby produce antler
abnormalities such as antlered does or cactus bucks. Viruses such as
Epizootic Hemorrhagic Disease (EHD) can also cause hemorrhaging in the
testicles or other effects which disrupt the proper production and
circulation of male hormones which regulate antler growth.
Disease
Besides disease-caused hormonal imbalances, various
parasites and viruses can play a minor role in the occurrence of antler
abnormalities by directly affecting the growing antlers. Some viruses such
as EHD can result in incomplete hardening of the antler tips because of
damage to the velvet’s blood vessels before antler growth is complete. The
disease commonly strikes deer in late July-August which corresponds to the
last stages of antler growth. In elk, the brainworm (Elaeophora schneideri)
clogs the carotid artery which supplies blood to the head and results in
gnarly and malformed antlers. Ticks are common on velvet antlers, although
in some cases, even blood sucking parasites can cause malformed antlers if
they disturb the velvet and disrupt the flow of minerals to the growing
antler.
Magnetic fields, Electric currents, Geo-Physical
effects, and other hocus pocus.
It has been observed that bizarre antler shapes can
be produced by applying a strong magnetic field to developing antlers. This
is more of an interesting side-light than anything of practical value to
the deer manager (unless criss-crossing the ranch with high voltage lines
is an option). The application of a constant, low-level DC current to the
growing antler tips can drastically alter the shape and direction the
antlers grow. Electric current generally reduces the length of the tines
but increases the number of odd points and other abnormalities. Caribou
racks are characterized by 2 similar antlers with usually only one bearing
a large shovel-shaped brow-tine. Caribou in the northern hemisphere usually
develop this shovel on the left, but caribou that have been introduced on
to a few islands in the southern hemisphere carry the shovel primarily on
the right side. This mirror-image occurrence has lead one researcher to
conclude that this was the result of differing Geo-Physical forces between
the 2 hemispheres. There are many possible causes of antler abnormalities,
but injuries and genetics account for a vast majority of those observed in
the field. Oddities and freaks are normally not tolerated by nature;
natural selection quickly removes them from the gene pool. However, an
enormous non-typical freak is certainly not at a disadvantage when it comes
to battling for dominance. Early in the spring antler growing season when
dominance hierarchies are worked out, other members of the bachelor group
would give a large, freaky buck wide berth. The process of natural
selection has worked remarkably well throughout evolution but I’m sure glad
for this exception. Antlers, especially non-typical ones, will always
capture our attention. After 100,000 years, many of us would still consider
ourselves lucky to be clutching an antler when our time is up.
-Jim Heffelfinger
Editors note:
Jim Heffelfinger completed his Masters Degree in
wildlife at Texas A&M-Kingsville researching the effects of coyote
predation on post-rut trophy whitetails. He has also conducted a state-wide
buck mortality study for Mississippi State University and worked as the
Manager of Wildlife Operations for the Rio Paisano Ranch in South Texas. He
now works for the Arizona Game & Fish Department as the Regional Game
Specialist for southeastern Arizona.