Spike Line Study In a companion study, spike antlered males were bred to does from spike antlered sires. This study demonstrated the effects of not harvesting spikes on future antler quality. All deer in this study were fed a high-protein diet, and 78% were spikes as yearlings. Results of Selection Each board displays 4 generations of deer. All antlers are from 3 year-old deer. From top to bottom are the great grandfather, grandfather, father, and son. The antlers on the left are from deer that were forked antlered as yearlings and whose dams were from fork antlered sires. The antlers on the right were from bucks that were spike antlered as yearlings. Their dams were also sired by spike antlered bucks. Through selection, antlers of succeeding generations were either made larger or smaller.

Age of Doe No Kerr WMA studies were specifically designed to determine the effect of dam age on antler production. However, a review of data from the Kerr deer-pen studies indicated that age of the doe had no effect. When age of doe was analyzed by study, no relationship of age to spike production was found. The analysis did show that large numbers of spikes for all age classes were produced by spike-antlered sires.

Summary of Results

There are 3 equally important factors that control antler development in white-tailed deer: nutrition, genetics, and age. Antler development is genetically based, environmentally influenced, and reaches its peak at maturity. The key to quality deer management is to remove those bucks which have the least desirable antler characteristics at an early age. Kerr WMA studies show that yearling antlers predict a buck's antler quality at maturity. Kerr genetic studies indicate bucks with the best antlers will produce more progeny with exceptional antlers than will poorer bucks. The does influence antler production as well. Harvest of older does is important to insure younger does are products of better bucks. Habitat should be managed so that deer can achieve their greatest antler potential. There are no methods to "jump-start" a quality deer program.

The breeding study involved the examination of 2,436 does, the largest number of deer ever utilized in a Texas breeding study. The date of conception can be determined by looking at fetus length. An average of 200 days from conception was used to determine fawning dates. Biologists got as much information as they could from the does collected. They looked at the timing of the rut and at breeding success on 16 study areas throughout Texas for three years.

All years were combined to produce the graphs that show the rut timing. In most areas the rut varied very little from year to year. You can use the map and graphs to determine the timing of the rut in your area of interest. Will the information help with the planning of your hunt? You be the judge.

Breeding Success and Fawn Survival

In some Texas circles, you still hear people talk about the "old barren doe" that lives in a certain pasture. This train of thought blames poor fawn production on the idea that many older does do not get pregnant. In reality, if the doe isn't bred during the first estrous period, she will be receptive again in 28 days. This explains the high breeding success in white-tailed deer even when bucks are scarce. We found that on the average, 92 of every 100 does sampled in the state were pregnant. The western part of the state was in a drought during much of the study. In the Trans-Pecos the number of bred does was the lowest. There the breeding rate dropped to only 81 percent (81 of 100).

White-tailed deer are known for producing twins. Statewide, over half of the does examined had twins. Triplets were not common, and the occurrence of triplets was less than two percent. Quadruplets didn't show up in the study. There were more male fetuses than female fetuses. Males represented 56 percent of the unborn fawns over the three years of the study.

An average sample of ten does had 15 fawns, or 1.5 fetuses per doe. In some parts of the state, though, deer numbers build up slowly. Failure to breed is not a problem, so where do the fawns go? Life is full of dangers for a fawn, and food and cover (the fawning habitat) is the difference in living and dying for fawns. In many parts of the state, predation is severe unless there is adequate hiding cover for young fawns. Imported fire-ants are a problem for fawns in heavily infested areas, but their impact can often mask the real problem. Adequate nutrition is often limiting, and if fawns make it past fire-ants and predators to weaning, they still face the challenge of finding food and cover.

Fawn survival depends primarily on habitat quality. Malnutrition and associated problems are probably responsible for poor fawn survival in much of the state. Dry conditions aggravate the problem of inadequate food. "Empty belly disease" is the most limiting factor on whitetails in Texas. Delayed breeding could cause fawns to be born late, which would be a disadvantage on ranges where food is scarce.

The Early and Late Ruts

What about the early and late ruts? Hunters and outdoor writers often talk about the rut being early or late. In Texas, at least, the breeding season for white-tailed deer is fairly predictable from year to year. Within a specific area, habitat conditions not only affect fawn survival, but can affect thetiming of breeding. A doe in poor condition or a young doe may not breed until late in the season. A doe may be attractive to bucks for about five days, but may be willing to breed for a period of only 24 hours. If the doe is not bred during her first cycle, she will generally come into heat again about 28 days later.

In areas where there are few bucks, a doe may not encounter a buck when she is first receptive and may not be bred until one of her later cycles. A hunter, landowner or biologist who sees the late breeding activity may be convinced that there was a late rut. On the other hand, those who see does attended by bucks in the early part of the season believe there was an early rut. This helps explain the wide variety of opinions on the timing of the rut during a particular year.

"Hunter chronology" has a lot to do with the perceived timing of the rut. Traditionally, hunters are more likely to be afield during cool weather. They will usually be out in force with the onset of the first weekend norther during the deer season. When there are many observers spending time in the field it is more likely that breeding activity will be noticed.

Bucks, like hunters, have a tendency to move around during cool weather. Bucks with hardened antlers are ready to breed and are looking for a willing doe. More movement means more opportunity to encounter a receptive doe. This increased movement helps give rise to the idea that cold weather causes the rut. However, this theory is disproved by white-tailed deer breeding in tropical climates.

We once thought that late fawning could be a problem in areas where survival was low and antlers were poorly developed. Newly weaned fawns on the range in late fall would have a harder time surviving. A lack of adequate nutrition at this time could affect future body and antler production. The study showed that very few fawns are born late in Texas. South Texas has the latest breeding period. Even there, fawns are born before August and are weaned by October.