The white-tailed deer’s cycle of antler growth, hardening, casting (dropping off), and regrowth is largely controlled by hormones. This cycle involves a complex interplay between the tiny pineal gland, the hypothalamus of the brain, the pituitary gland, and the testes, and is a response to seasonal changes in the amount of daylight. The cycle follows the seasonal, rhythmic rise and fall in blood levels of the male hormone testosterone, which is produced principally by the testes.
More so than the timing of other antler events, nutrition can have a strong influence on the timing of antler casting. In fact, within a given region of the country, the timing of a buck’s antler casting will provide a reasonably good indication of his general health status. Prolonged antler retention is indicative of good health, whereas physically exhausted, malnourished, injured, or diseased bucks tend to drop antlers early.
Antlers are cast when blood levels of the male hormone testosterone decline, which in turn are dependent upon the buck’s dominance rank and physical condition. Because antler casting is under hormonal control, a buck may drop both of his antlers on the same day, possibly only minutes apart, or, more rarely, carry one antler for a week or longer than the other. I observed one buck that had been injured while fighting drop its antlers a month apart.
On northern range, where harsh winters tend to start in early December, bucks generally drop antlers from mid-December to late January. Large old dominant bucks tend to drop their antlers earlier than do small young subordinates.
In the Midwest, where the weather is not so severe and nutrition is better, antler casting may extend from January to late March. Bucks with large antlers reportedly retain them longer than do bucks with small antlers.
By comparison, in the Deep South, where deer breeding seasons are prolonged, some bucks may retain their antlers until March or April, and large-antlered bucks there tend to carry antlers later than small-antlered ones.
It is important to note, though, that it is not latitude per se that causes the north-to-south difference in the timing of antler casting. A buck’s nutrition and general health status, as well as his dominance rank and length of the breeding season, interact to determine the time and order in which he casts his antlers.
We demonstrated, for example, that artificially raising the nutritional level of the Cusino Enclosure deer herd via supplemental feeding greatly delayed antler casting and caused many bucks, especially two and one-half year olds, to carry their antlers until March or, in some instances, even into April. Improved nutrition for our northern bucks, then, produced an antler casting schedule more closely resembling that of southern whitetails, even though the breeding schedule of enclosure does was not prolonged.
In a nutshell, antler retention is a good indicator of nutritional conditions for deer in northern areas. If you see many bucks without antlers during the extended archery season, in December, you’ll know range conditions are not the best in your general area. On the other hand, if bucks in your area carry their antlers until late February, or longer, it’s a good sign that they’re nutritionally well-off and likely to survive the winter season.