Antlers grow annually from the pedicle of the frontal bone of male deer. They are male secondary sexual characteristics, hence are only grown by stags, although in the wider Cervidae family, they also grow in female reindeer (also known as 'caribou' in North America). Antlers are quite unlike the horns of cattle, which do not regrow if removed correctly. Antlers also develop and mature in a manner different to horns and broadly two stages of antler development are recognised: velvet antler and hard antler.Velvet antler is defined as growing antler which contains an abundant blood and nerve supply and which has a fully intact skin with a covering of soft fine hair. Hard antler is the antler when growth has ceased, calcification has occurred, and the skin, nerve and blood supply are no longer functional.
Function of antlers
The functions of antlers are to:
Establish and maintain the social order, by being a visible expression of dominance
Attract hinds in oestrus
Defend the stag or a harem of deer from attack
In respect of dominance, the stag with the largest antlers tends to be dominant. This is evident by the temporary exhibition of dominance by a younger stag when the elder, dominant stag casts his antlers. (Older stags cast antlers first). The older stag resumes dominance upon the younger stag casting his antlers, despite neither of them having antlers at that stage. Occasionally dominance is attained by a stag that exhibits the most intimidating social behaviours.
Whilst hinds in oestrus preferentially seek the stag with the largest antlers, the lack of antlers does not impair a stag's ability to successfully mate a hind.
The male deer of most species develop a pair of antlers every year from bony outgrowths called pedicles at the top of the skull. In New Zealand, velvet antler is removed from red deer stags, wapiti (elk) stags and red/wapiti hybrid stags.
Velvet antler growth
The annual growth cycle of antlers starts in spring with the rapid development of a soft cartilaginous core from each of the two pedicles. This core is covered with a layer of connective tissue, then skin with a dense covering of fine hair, and the whole antler is well supplied with blood vessels and nerves. Velvet antler is very sensitive during this growth phase, and the male deer are protective of it and non-aggressive. Velvet antlers grow very rapidly, at a rate of up to 2 cm a day. As growth occurs, cartilage is gradually replaced by bone by a process of calcification. When growth is complete, the antler ‘hardens’ or calcifies completely, the blood vessels at the junction between the pedicle and the antler close off, and the skin, nerves and connective tissue dry, shrivel and flake off. The bony cores remain as hard antler ready for the ‘rutting’ season in autumn, when the stags are aggressive and combative as they compete for hinds. At the end of the rutting season, in early spring, the pedicle-antler junction weakens and the antlers are cast naturally.
Deer velvet is a unique structure, because it is the only organised mammalian tissue that regrows completely, and it does so every year. Moreover it grows extraordinarily rapidly, and the rapid growth is likely to be regulated by pharmacodynamic substances that are either unique or that can be found in other tissues but are at particularly high concentrations in deer velvet. In Asia, the unique nature of deer velvet has no doubt contributed to its reputation as a powerful remedy.