Tuesday, January 1, 2013

Whitetail Deer: Shedding Antlers

At the start of the New Year, the saying, “Out with the old…” may seem quite appropriate to male white-tailed deer residing in wilderness regions of the Adirondacks. As the calendar year comes to an end, bucks traditionally lose their antlers, making it nearly impossible to distinguish between the sexes when a small herd is noticed standing along the side of a road, or in a forest clearing. Some bucks may be observed supporting their characteristic boney headwear well into January or February, which reflects an abnormal ratio of bucks to does in that general area.

The primary purpose of a set of antlers is to serve as a weapon when confronting a rival buck prior to and during the rutting, or mating, season. Initially, a month or more before the first doe comes into heat, bucks half-heartedly spar with one another in an attempt to establish dominance. The testosterone level in the bucks increases with the shortening length of daylight and more frequent detection of female pheromones, which alerts the bucks to the does awakening reproductive state. This causes the level and intensity of the fighting between males to increase.

Within a day or two of a doe coming into her estrous or heat period, a buck begins to spend most, if not all, of his time with the soon-to-be receptive doe and vigorously challenges any other buck that comes into the immediate area. The female’s heat period lasts only 24 hours. After that time the buck leaves her and goes in search of another doe that is nearing, or having her day long estrous period. Because all of the does in one general area tend to come into heat within a span of 7 to 10 days, a single buck is often physically unable to service the needs of all of the does in that general vicinity during this interval of time. The peak of this primary rut generally occurs in the Adirondacks in early to mid November.

If a doe was unsuccessful in attracting a buck, and failed to breed during her initial heat period, her reproductive system will produce another estrous period 28 days later. Just as in her first heat cycle, she emits various chemicals to the surroundings prior to the time when she is receptive, alerting any bucks in the area to her condition. Detecting female hormones keeps the buck’s testosterone level high, which allows the animal to retain its antlers.

Females in the Adirondacks that did not successfully breed in November come into their next estrous period in early to mid December, producing a secondary rutting season. As a general rule, all does eventually are serviced during this occasion.

Afterwards, there is a rapid decline of female scents designed to stimulate a buck’s sexual drive, causing the male’s testosterone level to drop sharply. As this occurs, it triggers the release of chemicals in the pedicle section of the skull, which securely anchors the antlers to the head. A special ring of cells at the very base of the antlers engage in an osteoclast reaction, or one that allows the break down of the bone tissue in this immediate area by extracting calcium from this harden tissue.

As this ring dissolves minerals from the antlers, it greatly weakens the connection to the skull. Eventually, the antlers drop off, although rarely do both fall off simultaneously. In most instances, there is a 4 to 8 day period between the loss of one and then the other.

In some areas in the Adirondacks, where hunting pressure is high, the number of bucks may drop to a low enough level that not all of the does can locate breeding partners during their second estrous period. These animals continue to produce reproductive pheromones that excite the bucks and allow them to maintain a high enough level of testosterone to keep their antlers well into the start of the New Year. Bucks supporting a set of antlers have been reported as late as mid February, which would be caused by a fourth estrous period for an older doe. (A young doe during its first breeding season often comes into heat later than the older females of the area.)

In remote, wilderness regions of the Park, where hunting pressure is minimal, the ratio of bucks to does is high enough to allow most, if not all, the does to successfully breed by the end of the secondary rutting season in mid December. (Carrying these structures around in an excited state requires a higher caloric expenditure.) By the end of the year, nature allows the bucks to shed their antlers and expend less energy. It is possible to assess the status of a deer herd these first few weeks of the New Year, as the sight of a buck with a pair of circular scabs on top of its head is a good sign that the herd in that general area is well balanced.

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Tom Kalinowski

Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

2 Responses

  1. Mary C Randall says:

    Thank you for clarifing that, very interesting. Happy New Year.

  2. TiSentinel65 says:

    There is no greater evidence of a bucks ability to persevere from the pursuit of hunters than a shed. It is always exciting to find one. One can only surmise where this buck was during the hunting season and question how he was so sly to make it through such carefully crafted plans. If a person knows where deer have hearded up for the winter, he or she may seacrch that area in the spring after the snow has melted away, but before new vegetation begins sprouting, and be rewarded with a shed. Usually areas with a southern exposure or areas the have low lying trees like cedar swamps are a good spot to look. If deer find a good source of food they usually will exploit it until spring thaw, thus increasing the odds that a buck will shed his horns in that area. I have heard stories of bucks returning year after year to the same area to cast his horns, but I am not sure this the rule of thumb.

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