Texas Parks & Wildlife Magazine   


The Secret Lives of Big Bucks

Think you know a few things about whitetails? Ready to learn a few more?

By Larry D. Hodge

Few things hold more fascination for hunters than white-tailed deer, especially big bucks. Yet despite all the attention they receive in print, video and deer-hunters' dreams, we actually know very little about many aspects of bucks' lives.

The mystery is part of the fascination these phantoms of the forest hold for hunters. On some level, I think we understand that the hunter who brings home a buck is taking part in a saga that spans aeons and yet reaches its denouement in seconds. Holding an antler, we clutch the physical manifestation of a natural process the understanding of which eludes our grasp. In the final analysis, a hunt for a buck offers perhaps the most intense and personal connection to the little-understood ways of nature most of us are ever likely to have.

Why deer have antlers at all is a mystery, says Bob Brown, chair of the department of wildlife and fisheries sciences at Texas A&M University. "Why are antlers necessary? Why do deer expend so many resources on growing antlers? We'll probably never really understand that - that's why they are so fascinating." While we don't know much about why deer grow antlers - and only members of the deer family, including elk, moose, and caribou, do - we know quite a bit about how they do it. Here again, though, some mystery - and perhaps a bit of magic - remains.

The yearly beginning of antler growth in white-tailed deer is related to the fact that the earth is tilted on its axis. As the earth travels around the sun and begins to point its north pole at the sun, days in the Northern Hemisphere grow longer. The lengthening photoperiod stimulates a buck's pituitary gland to begin producing hormones that control skeletal growth, and the first bone begins to grow from the pedicels, or bases, atop the deer's head. The process begins a few months after the old set of antlers is dropped; in Texas, sheds begin to hit the ground anywhere from late December to late March.

Deer native to equatorial regions, such as axis deer, grow and lose their antlers at different times of the year and have a year-round breeding system. White-tailed deer in the Southern Hemisphere follow a similar pattern to their northern kin, although the seasons are reversed and they drop their antlers just as bucks in the Northern Hemisphere are coming into the breeding season.

Why are lengthening days the stimulus for the most important event in a white-tailed buck's year?

Bill Armstrong, a Texas Parks and Wildlife biologist on the Kerr Wildlife Management Area, speculates that natural selection may be the answer. Over extremely long periods of time, bucks outside the equatorial region that passed on their genes were those that bred at the time of year that resulted in fawns being born in early summer, when food was plentiful and fawn survival was higher. Near the equator, seasons are less pronounced, and the availability of food does not fluctuate as much. Therefore, the timing of births is not as critical to survival of the offspring. "Different animals interpret the photoperiod differently," Armstrong says. "You have a genetically controlled photoperiod, but you also have environmental influences that sometimes override that photoperiod."

The entire story of a buck's life is, in fact, a constant balancing act between hormonally induced changes in its body and the struggle for physical survival. These two opposing forces clash most dramatically during the time bucks are growing antlers. Ironically, this is the Dark Age of bucks' lives, a time little studied or understood, since most people find bucks far more interesting after they already have racks. But the changes that take place in the buck's body - and atop his head - from April through September determine whether he becomes just another deer or a bad case of antler avarice come hunting season.

"About the first of March, the lengthening photoperiod says, 'Antlers fall off,'" says Armstrong. "Then the buck begins to rebuild his body from the stress of the rut." (Bucks eat little during the breeding season and may lose 25 to 30 percent of their body weight.) Testosterone production almost ceases when antlers are shed, and bucks become more docile and social. They go from being combative loners ready to take on all comers to just one of the guys in a bachelor group. "It makes sense when you put it all together," says Donnie Frels, manager of the Kerr WMA. "Your antlers fall off, and you become a lot nicer, because it wouldn't be good to be aggressive around other bucks that still have their antlers."

Dramatic physical changes take place. Bucks begin losing their winter hair and start growing a summer coat lighter in both color and thickness. Hair is mostly protein, so a diet high in protein is required. Spring forbs and browse supply the protein, but antlers are bone tissue, and there is no readily available source of calcium and phosphorus in the quantities needed.

"Some of the bigger deer will grow more than 170 inches of antlers between March and the end of August," Armstrong says. "That's like you cutting off both your legs and growing them back in three months." Since the deer can't get all the raw material they need for this rapid growth of antlers from their food, they borrow it from within their bodies. In a process similar to osteoporosis in humans, minerals are taken from ribs, sternum and skull and redeposited in the antlers. Bone density may decrease as much as 30 percent.

Growing antlers and hair at the same time puts tremendous demands on the buck's body, and eating dominates the agenda. Deer raised in the Kerr WMA's experimental pens begin eating heavily in April, and by late August are eating about seven pounds of food a day. Early on, much of the food is converted to hair and replacement bone. "Antler growth is really slow at first and stays slow until about the third week in June," says Gene Fuchs, a biologist on the Kerr. "Then some deer will put on four to five inches in three weeks, as much as half an inch a day on each point. As a rule, deer 2-½ years old or older will have all their points showing by the middle of July." Antler formation is said to be the most rapid growth known in the animal kingdom. (As impressive as white-tailed antler growth is, it is tiny compared to that of elk and moose.)

During the growing period, antlers are covered and nourished by a thin layer of skin known as velvet. (Happily for the deer, the blood-rich velvet serves as a sort of radiator, helping cool the deer's body during the summer.) The antlers appear to be sensitive and are easily damaged, so bucks tend to protect them. This may be one reason for their lack of aggression during this time. If bucks do fight during this period, they flail at each other with their forefeet, much as does do. If an antler base (or pedicel) is damaged while in velvet, somehow the deformity that results becomes "remembered" by the nervous system and will be replicated in future years.

Social standing within a group of bucks becomes established as the antlers develop. Conventional wisdom holds that the deer with the biggest antlers will dominate the others. But there may be a surprise lurking here, too, says Bob Brown. "Even when deer don't have their antlers, there are still dominant animals. One European study shows that large antlers may be the result of being the dominant buck, not the cause," he says. Possible explanations are that dominant animals may get more to eat and that antler-growing hormones are both the cause and result of social dominance.

While humans tend to recognize particular bucks by their antlers, the deer themselves recognize each other with or without antlers. However, their interactions with each other depend partly on which has the bigger headgear. Bucks in the research pens at the Kerr have their antlers sawed off each October before the rut begins, to keep the deer from hurting each other. Dramatic changes in behavior sometimes result. "We have 2-year-old deer that will fight 5-year-old deer after we saw their antlers off," says Gene Fuchs. "When they fight without antlers - which doesn't start until about a month after the antlers are sawed off - little bucks don't back away from the older deer."

Attitude may play a part, says Bill Armstrong. "I think there are some deer that just think they are bad. They are like the 5-foot 1-inch guy who goes into a bar and walks up to a 7-footer and gets whipped."

By about the first of September, antler growth is complete. Suddenly bucks undergo a transformation. A sharp rise in testosterone level triggers a shutdown of the blood supply to the velvet. The velvet dies and sloughs off with amazing speed. "Velvet is shed and antlers are completely polished [by rubbing on brush or weeds] within 24 hours," says Fuchs. "Some velvet comes off just like a rotten banana peel without any rubbing. I've seen deer at 10 a.m. one day with no sign of shedding velvet that had completely polished antlers at 9 a.m. the next day."

The growth of antlers in white-tailed deer is closely linked to the ability to breed. Not until growth of the antlers is complete is a buck capable of producing sperm. Loss of the velvet signals that a buck is capable of breeding. Bucks lose interest in eating, reducing their food intake by half to three-quarters. Now reproduction is the name of the game. By this time all the bucks in a given territory know each other and the rank of each within the hierarchy, so real fights between them are few. All-out battles generally occur only between bucks that are strangers to each other and meet when one invades another's territory while searching for does. "Bucks probably use the time they spend in bachelor groups to figure out who is boss," says Bill Armstrong.

The objective of being the boss probably is related to the drive to reproduce. Dominant bucks - whether they have the biggest antlers or not - are believed to do most of the breeding. (Confirmation may come from a recent TPW study. See sidebar "Does Size Matter?") But there is no doubt what a buck's role in life is. "A buck's job is to breed does," says Armstrong. "The rest of the year they are just mountain lion food."

That assessment, while biologically apt, fails to convey the wonder of an animal whose whole life - and success therein - revolves around how many inches of bone it can sprout from its skull during a five-month period each year. This daunting task is made more difficult by the fact that the process begins in winter and peaks in late summer, the two times of the year when the quantity and quality of food available are at their lowest. Production of a massive set of antlers under such adverse conditions truly is the mark of a creature superior to others of its kind. Perhaps that, more than anything else, explains why antlers fascinate and excite human observers.

Larry D. Hodge is wildlife editor of Texas Parks & Wildlife magazine and executive editor of Texas Parks and Wildlife Press.

Does Size Matter?

To humans fixated on large antlers, it seems reasonable that the buck with the biggest rack will dominate bucks with smaller antlers when it comes to breeding. However, this will remain speculation until results are received from a research project carried out on Mason Mountain WMA during the 1999 - 2000 breeding season.

Bucks of known age and antler size were released into two separate high-fenced pastures along with does. All deer not part of the study were removed. Bucks released were evenly distributed among four groups: yearlings with low antler quality, yearlings with high antler quality, bucks five years old or older with antlers scoring less than 100 points Boone and Crockett, and bucks five or older scoring more than 120. All bucks were DNA-typed prior to release.

Following the breeding season, does were removed from the pastures and DNA extracted from their embryos. The DNA is in the process of being typed to determine paternity. If more than 25 percent of the fawns were sired by older bucks with large antlers, it can be inferred that age or size do indeed matter.

Why Do Antlers Attract?

I suspect the attraction of antlers is embedded in human genes. Cave art depicts shamans with headdresses of deer antlers, which were clearly symbols of power or magic. It seems reasonable to me that hunters who killed bucks were judged superior to those who did not. They were therefore more likely to be able to provide for a family and were thus privileged - as were bucks with larger antlers - to pass on their genes.

If my theory is correct, natural selection over millennia produced in us today an inexplicable preference for shooting anything with "horns" as opposed to antlerless animals. Somewhere in the spiral helix of our DNA may be encoded the belief that he who bags big buck wins fair maid. Am I crazy? Think of yourself with the choice of shooting a doe or a buck. Most of you in that situation will, I believe, shoot the buck. Why? Because you want those "horns."

It's worth noting here that horns and antlers are not the same. Horns are made of keratin, the same substance in fingernails and hooves, and, with the exception only of the pronghorn antelope, are permanent. Antlers are bone and are shed and regrown annually. Cows, goats and sheep have horns. Deer, elk, caribou and moose have antlers, but many people refer to them as horns.

Food for Thought

Year-round supplemental feeding of deer in hopes of helping bucks grow bigger antlers is a common practice, especially on high-fenced properties. Pelletized feeds with a minimum protein content of 16 percent are the norm.

However, much of the money spent on such feeds may be wasted, says Texas A&M University's Bob Brown. "Bucks have a voluntary decrease in food consumption when their testosterone level goes up in the fall," he says. "They don't get their appetite back until around April. They can survive on next to nothing for some time. If they are not growing antlers, they don't care about eating. If people want to supplemental feed during the winter, I recommend they use a low-protein, low-cost feed like a 10 percent protein oat/corn/molasses mix."

By the same token, good nutrition, preferably from the natural habitat or maybe food plots, will produce the greatest benefits during the spring and summer for both bucks and does - and buck fawns that are born healthy and fed well tend to produce better quality antlers not only in their first but also in succeeding years. "During the winter months, does are in the second trimester of pregnancy, the fetus is only the size of your thumb, and extra nutrition is not that important," says Brown. "The critical period for does is April through June."

Studies also show that as much as half the feed put out for deer during the winter is consumed by other animals, primarily raccoons. Feeding expensive high-protein rations from October through March makes sense only if you are ranching raccoons.

The Shape of Things to Come

No matter how big or how small they are, all white-tailed deer antlers come in three basic configurations: basket, wide, and high.

Basket-shaped antlers are arguably some of the most attractive. The main beams curve toward each other, and the tips may almost touch. The tines also angle inward, making for a very pleasing rack.

Wide antlers are just that. The main beams grow outward from the head at a slight upward angle before curving forward and paralleling each other, making a rack that gapes open when seen head-on.

A high rack has main beams that grow up past the tips of the deer's ears at about a 45-degree angle before curving forward while maintaining an upward trend.

A deer's first set of antlers is a good predictor of antler potential, although it will probably add points and mass each year until development peaks. Individual bucks can be recognized from year to year by their antlers, and the characteristics of their racks are passed on to their offspring. However, does also contribute at least half the genes that control antler growth.

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