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Leaves of Bone

Leaves of Bone

This story is featured in Montana Outdoors March–April 2014 issue

Did you hear that? It was the sound of an elk antler dropping on a windblown, grassy hillside.

Bull elk are shedding their antlers this time of year, much to the delight of that human subspecies, the inaptly named “horn” hunter.

A mature bull elk’s mammoth headgear, weighing as much as 40 pounds, takes about five months to grow. That means within a week or two after an elk drops its old antlers, the two bumps (pedicels) atop its head start to bulge, then begin to grow into what hunters drool over six months later.

Antlers are fascinating feats of nature, the only mammalian appendages capable of complete regeneration. Some amphibians can regrow a severed tail or limb. Not so mammals, except in the case of antlers.

For members of the deer family, antlers are both weapons and status symbols (think male supremacy). For humans, antlers are sources of fascination and trophies. In spring, antler afficionados hunt for “sheds” in winter range where elk congregate until greenup. State wildlife management areas generally open for “horn hunts” in mid-May.

Biologically, antlers are much different from horns. Antlers grow only on male members of the deer family, with the exception of female caribou, which grow them, too. Horns, carried by bison, mountain goats, and bighorn sheep, are found on both sexes.

Antlers, made of solid dead bone and often branched, are shed annually (like deciduous tree leaves). Horns come from layers of converted skin (epidermal) cells and are permanent (like evergreen needles).

So often the exception, pronghorns—male and female—shed and re-grow a sheathlike covering each year. Though called horns, the pronghorns’ headgear isn’t the same as those on Montana’s other horned critters.

What causes some but not all deer or elk to grow enormous antlers? Though genetics and nutrition play a role, the biggest factor is age.

The older the buck or bull—up to a certain age—the larger the headgear. Bull elk usually grow their first set of antlers, called spikes, when they are a year and a half old. A two-year-old may have three to six points on each antler, and a mature bull age seven and older will often have six points or more.
From age three and up, the antlers often become thicker and heavier rather than grow longer or add more points. And if a bull reaches old age—say eight or older—his antlers actually decline in size and mass from previous years.

No matter what the size, antler growth happens in spring and summer. Triggered by increasing daylight hours, antler development begins when sex hormones such as testosterone are at their lowest levels. The growing bone is covered by blood vessels, nerves, and fine, velvet-like hair appropriately known as velvet. The rise of the animal’s testosterone levels near summer’s end causes the antler bone to die and shed the velvet covering. The antlers are then ready to use for fighting and attracting females, coinciding with the peak of breeding: mid-September for elk, mid- to late November for deer. When cold weather arrives, testosterone levels decline, eventually causing the headgear to fall off by winter’s end. Within weeks or even days, the process begins anew.

That miracle of regenerating enormous headgear on a male moose, elk, or deer is starting right about now.Bear bullet

Bruce Auchly manages the regional Information and Education Program in Great Falls.

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