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Antlers

Velvet-covered Antlers Growing

Male White-tailed Deer grow a new pair of antlers every year starting when they are one year old.  The size of the antlers depends on the age of the deer, genetics, and diet. Before antlers actually appear, structures called pedicles that connect the antlers to the skull develop.  Growth of the actual antlers begins in March or April and as more nutritious food becomes more available during May and June antlers grow more rapidly.

Antlers are one of the fastest growing bones that exist; growth is regulated by hormones which are controlled by the photoperiod, or length of day . Yearling antlers can grow about 1/8-inch a day during the summer, and adults as much as 1/4th of an inch.  While they are growing, antlers are covered with a layer of tissue called “velvet” which is dense with blood vessels that carry nutrients to the antlers. In August the supply of blood to the velvet diminishes and the antlers begin to harden. By September the velvet has dried and is falling off.  Antlers are used as weapons during rut, or the mating season, after which they fall to the ground, providing a valuable source of calcium and phosphorus for rodents. (Photo by Erin Donahue)

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White-tailed Bucks Shedding Antlers

White-tailed Deer bucks grow and shed a pair of antlers annually.  The main purpose of these bony growths is to serve as weapons against rival bucks during rut, or mating season.  During this time in the fall, prior to their 24-hour receptive period, does release chemicals to signal their readiness to bucks.  These chemicals keep the bucks’ testosterone level high, which in turn keeps antlers firmly attached to their heads.  Once rut is over, does stop emitting these chemicals, and as a consequence, the bucks’ testosterone level drops significantly.

When a buck’s testosterone level drops, it triggers cells called osteoclasts to become more active in the buck’s pedicles, the permanent bony bases which anchor the antlers to the buck’s skull. As a result, calcium is extracted from the pedicles which weakens the antlers’ connection to the buck’s skull, and eventually the antlers drop off.

It is rare that both antlers drop at the same time – usually there are four to eight days between the loss of the first and the second antler. I assumed that bucks needed to knock their antlers against something hard, such as the trunk of a tree, in order to get them to fall off.  However, years ago I witnessed a buck shedding an antler simply by dropping his head and then quickly flicking it upwards, sending an antler flying through the air. (Note pedicle where antler used to be attached. Photo by Alfred Balch)

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White-tailed Bucks Shedding Antlers

1-2-16-antler-049a2440Antlers, the fastest growing mammal tissue on earth, are grown by male White-tailed Deer (and very occasionally females) every year and shed every year. They begin growing in the spring, usually April, and complete their growth in August or September. During this period they are covered with “velvet,” a soft skin containing blood vessels and nervous tissue that supply oxygen and nutrients to the antler. Once growth ceases, the velvet dries up and falls off or is inadvertently rubbed off. The mating season of White-tailed Deer, or rut, during which time their antlers are instrumental in establishing hierarchy and securing a mate, peaks in mid-November. Once mating is over, the disadvantages of antlers (cumbersome shape for traveling through woods, and the energy required to carry them) promote the shedding of these bony structures. Specialized cells (osteoclasts) destroy the bone tissue between the antlers and the skull and antlers are shed sometime between the end of December and the beginning of February.

Most sources state that antlers just fall off or that the buck knocks them off by striking them against a tree. My personal observation of a buck in captivity clarified the way antlers are dropped, at least in this one instance. The buck put his head down, quickly jerked it up and to one side, and the antler went flying.

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Moose Antlers Growing

moose antlers 795Antlers grow faster than any other mammal bone — a big bull moose can grow an 80-pound rack in a summer, adding a pound of bone a day. While genetics has an influence on antler growth and size, nutrition is by far the most important factor, and males in high quality habitats grow much larger antlers.

In the early stage of growth, antlers are covered with a fuzzy skin called velvet, which contains a tremendous concentration of nerves and as well as a supply of blood. The velvet nourishes the growing antler for about five months, during which time the antlers are extremely sensitive to touch, and if injured, may be permanently misshapen. Eventually, when the bone stops growing, the velvet is shed. Bull moose then use their antlers to attract and fight for mates, as well as to root plants from the pond floor. A month or two after they have served their purpose of securing a mate, antlers are shed.

In moose, antlers may act as large hearing aids. Moose with antlers have far more sensitive hearing than moose without, and a study of antlers (with an artificial ear) confirmed that the antler behaves like a parabolic reflector.

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