When Do Deer Drop Their Antlers?

Reprinted from my Jan 2008 Know Whitetails column in Whitetail Journal

Last April my phone rang and a friend told me that he’d just seen an eight-point buck near his home. I was puzzled. After all, it was April, very late for a buck to still be carrying antlers. Then he added one more tidbit of information. The buck was in velvet. I immediately told him that it was either a doe with antlers, or a buck whose testes had not descended. Both conditions lead to late shedding and velvet-covered antlers. Four months later the mystery was solved when another friend who lives in the same area told me that he had photos of a "buck" with twin fawns eating apples in his back yard. He was a she and it appeared that "she" again would develop into an eight pointer.

Even though there is very little variation in the time that antlers start to develop (it happens in April-May all over the northern whitetail range), as typified by this example, shedding times can be extremely variable from one area to the next. The variation in shedding times (also known as "casting") leads to all kinds of hunter speculation on why bucks shed. Some feel they drop them early due to cold weather. Others say that hot weather causes antlers to drop. Hmmm. Some say the older bucks lose their antlers first. Others say that injured bucks lose their antlers first. Some say that bucks that have poor nutrition drop antlers first. Others say the most dominant big bucks do. The bottom line is that antlers can be found dropping from mid December (though that is early) to early April (though that is late).

One thing we do know is that after the rut, the hormone testosterone begins to decrease and when it drops to a certain level, antlers will shed. Since antlers shed at different times in certain areas and in certain years, something causes the testosterone levels to vary from area to area and winter to winter. Thus, the real question is, what causes the testosterone levels to drop to the required level?

We know that testosterone and mating are related, so high numbers of does could lead to late shedding of antlers. Here is how that works. Testosterone in bucks stays high when they chase estrus does. Does will only come into estrus if they have not mated, so when you have large numbers of does, all do not get bred in November. When that occurs, we’ll have hot does popping up in mid December, and rutting bucks will be chasing. The more does not bred, the later antlers drop and once most does are mated, the buck’s testosterone levels drop and so does his antlers.

 

One researcher working with captive deer suggested that bucks in poor nutritional condition, or those that are diseased, shed their antlers earlier than they would if they were on good nutrition (i.e. healthier). Poor nutrition causes testosterone to drop, and as mentioned earlier, when testosterone drops, so do antlers.

Other researchers have found that big and/or older bucks often shed earlier, and suggest that this is due to the fact that their high social rank during the rut takes a physical toll on their body. Chasing does, not eating, fighting other bucks, all reduces their body condition, and thus when the rut ends, if they are really run down, their testosterone levels drop faster than normal, and this leads to casting of antlers. One New York study showed that 62 percent of bucks 3½-years old and older dropped their antlers by mid December, while only 23 percent of younger bucks did.

Tied to this poor nutrition theory is habitat. If habitat is over browsed, then the body condition of bucks will be poor. Since we know that testosterone levels drop when the bucks are under nourished, then a poor habitat may also cause them to drop antlers earlier. I would suspect then, that deep early snows, which would limit food intake, would also impact the time that antlers drop. In fact, studies show that further North, where snows are heavier, antlers begin to drop from mid December to late January.

If poor nutrition leads to early shedding then good nutrition should lead to late drops. Right? In fact, studies show that bucks from the Midwest farm country (where nutrition is very good) don’t seem to begin to drop antlers until mid January or later. Even though they rut hard, and their overall body condition is down, it apparently isn’t affected as much as deer from poorer habitats. Thus, they keep their antlers longer.

Good nutrition leads to one other factor that causes bucks to keep their antlers later in winter. When doe fawns have good feed, many get bred their first year. A study done in Iowa showed that almost 75 percent of doe fawns were bred, most during December, again leading to bucks keeping their antlers later than in other parts of the country. This correlation of good feed and good habitat to antler shedding has led several researchers to conclude that antler retention is a good measure of the habitat. If the antlers drop later, those bucks live in good habitat. If bucks tend to drop earlier, such as mid December to mid January, those bucks live in poor habitat.

Earlier I mentioned that when you have lots of does, there may be some later winter breeding, and this keeps testosterone levels higher, longer, leading to late shedding of antlers. However, usually when you have high doe numbers you get over browsed habitat, and poor nutrition. As just mentioned this leads to early shedding. Hmmm. No wonder hunters banter this about every years. So many variables can impact the time when antlers shed.

One researcher in Mississippi looked at the casting dates for individual bucks in captivity and found that as long as the environment was the same, individual bucks dropped their antlers about the same date every year. These captive bucks got the same diet all the time, thus their body condition probably stayed the same after the rut, year after year. The fact they dropped their antlers on the same date each year suggests some kind of innate program within each buck that causes them to drop their antlers. That’s fine for captive bucks, but in the wild the factors listed above would come into play, causing the great variation we see in the timing of antler drop.

The question of why some bucks drop early or late is not an easy to answer simply because there are so many things happening in deer woods that impact antler casting. Will knowing all this impact your hunting success? Of course not, but I hope that I’ve "shed" some light on why there is so much variation in the timing antlers are cast.

Return To List

All Contents © Copyright 2005
Dr. David Samuel