by Dr. Dave Samuel When Do Deer Drop Their Antlers? Last April a friend told me that he’d just seen an 8-point buck near his home. I was puzzled. After all, it was April, very late for a buck still to 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 8-pointer. Even though there is very little variation in the time of year that deer start to develop antlers (it happens in April or May all over the northern whitetail range), as typified by this example, shedding times can vary widely from one geographic 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 people think that bucks drop antlers early due to cold weather, while others insist that hot weather causes antlers to drop. Some claim that the older bucks lose their antlers first, while others suggest antler drop is impacted by injury, poor nutrition or dominance. The bottom line is that antlers will be dropping from mid-December (though that is early) to early April (though that is late). The Why & How One thing we do know is that after the rut, a buck’s testosterone levels begin to decrease, and when they drop to a certain level, antlers are 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 as they chase estrous does. Does will only come into estrus if they have not mated, so when you have large numbers of does, they do not all get bred in the first go-around. When that occurs, hot does will still be popping up later in winter, and rutting bucks will be chasing them. The more does that are not bred, the later the bucks’ antlers drop. And once most does are mated, the bucks’ testosterone levels drop and so do their 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 had they been healthier. Poor nutrition causes testosterone levels to drop and, as mentioned earlier, when testosterone drops, so do antlers. Other researchers have found that older bucks often shed earlier, and suggest that this is due to the physical toll on their bodies paid during the rut. Chasing does, fighting other bucks and being too busy to eat — all reduce bucks’ body condition. Thus, when the rut ends, if they are really run down, their testosterone levels drop faster than normal. 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 in the area will be poor. Since we know that testosterone levels drop when the bucks are undernourished, then poor habitat might also cause them to drop antlers earlier. In turn, I would suspect that deep early snows, which would limit food intake, also impact the time that antlers drop. In fact, studies show that farther 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 begin to drop antlers until mid-January or later. Even though these bucks rut hard and their overall body condition is down, their testosterone levels apparently aren’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 of them will be bred in 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 between good feed/habitat and 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 might be some later winter breeding, and this keeps testosterone levels higher for longer, leading to late shedding of antlers. However, usually when you have high doe numbers, you get overbrowsed habitat and poor nutrition. As just mentioned, this leads to early shedding. No wonder hunters banter this about every year. 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 that 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, other factors listed above 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 easy to answer, simply because there are so many things happening in the 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. It’s something to talk about the next time you and your hunting buddies get together.