The antler cycle of the fallow deer

Antlers are grown by the males of all species of deer, although reindeer cows also grow them. They are used mainly as weapons, particularly during the rutting season when stags fight for control of a harem of does. Antlers are not the same as horns in that they are bony growths that drop off and are renewed every year, unlike the horns of other mammals that are permanent features. The cycle of growth, shedding and re-growth varies between deer species and their location; the cycle described here is that of fallow deer in Great Britain.

Fallow deer fawns are born around June, and in March of the following year male fawns develop stalks, known as pedicles, from which the antlers will later grow. Although antlers are cast and then re-grow, the pedicles are permanent features. The fawn’s first antlers start to appear at the tops of the pedicles in May.

The antlers, which are straight, slender spikes with branches appearing only rarely in the first year, grow rapidly and are complete by late July. The antlers are covered by a hairy skin called velvet which contains blood vessels that supply oxygen and food to the bone as it grows.

When the spikes have finished growing the velvet shrivels, being discarded by the buck as it rubs its head against tree trunks. By mid-August the antlers will be dead tissue, but they stay in place until the following spring.

The first antlers are cast in late May, usually one at a time with an interval of a few days between the castings. There will be some bleeding from the pedicles when the antlers break off, with scabs forming shortly afterwards.

New antlers start to grow within one or two weeks, and growth is rapid, as with the original pair. However, by early July the second pair will show signs of branching into two “tines” on each antler, one pointing forwards and the other backwards. The forward-facing tine will only grow a small amount, developing into a sharp point curving upwards, but the backward-facing tine, known as the main beam, will develop into a much more substantial structure.

Throughout July and August the main beam will grow and several more tines will then branch off it. The ends of the antlers will broaden out to form blades with spikes growing off them, looking not unlike holly leaves in general shape.

In late August, after the growth is complete, the velvet will be shed, as in the first year, with the animal using trees to help rub it off. However, because of the much greater amount of velvet involved, the result will look untidy for several days as bits of bloodstained velvet hang off the antlers. Observers may think that the young stag has been injured in a fight as blood drips off his antlers, but this is not usually the case.

By the end of August all the velvet will have gone and the antlers will be clean and hard, remaining in place throughout the winter until the process begins again in the following spring.

Each new pair of antlers will be larger and heavier than those of the previous year, with the blades becoming broader and the antlers curving upwards and outwards. A mature buck has antlers up to about 20 inches (50 centimetres) in length. This process continues into old age, so it is possible, up to a point, to judge the relative ages of stags within a herd. However, it is difficult to determining a mature stag’s age accurately from its antlers alone. There are also many variations in size and shape between the antlers of bucks of the same age.

© John Welford