During December, the antlers of mule and white-tail deer, moose and stag caribou fall to the ground, making it common to see animals with just a single antler. Elk retain their antlers throughout the winter, only shedding them with the onset of spring. The antlers don't stay on the ground for long because the local rodent population makes short work of this high quality source of calcium.
While the antlers are impressive to look at, they are even more impressive on an evolutionary scale.Why Grow Antlers?
In every animal population, strategies have developed to help ensure the strongest individuals get the greatest opportunity to mate. While antler size has no bearing on the age of the individual, it IS a great indicator of the health of the animal. Antlers are renewed each year meaning the stags need to find a large source of calcium to supply the antler growth. With a diet of green vegetation, one might wonder where this secret source of calcium originates. The simple answer - from their own bones (primarily their rib cage). Since only the healthiest males will be able to afford such a large diversion of resources, an impressive set of antlers is also an impressive pedigree for parenthood.
During the autumn rut, the individuals with the largest antlers (generally matched with the toughest temperament) have an advantage when it comes to competing for mates. While a large pair of antlers means mating priority, it does have its disadvantages. The battle for supremacy can use up summer stores of energy, leaving them in poor condition at the onset of the long winter. Being the most successful stag may result in their perishing during the long mountain winter.
While only male deer, elk and moose grow antlers, caribou are unique in that both males and females go through the annual process of antler growth, just at different times of year. Male caribou grow antlers during the summer, use them to compete for mates, and then shed them. Once the rut ends, the females grow a short spike antler. This allows the females, who must divert resources to reproduction during the time of year when food is scarce, to outcompete the stags for limited winter food sources.
How Do Antlers Grow?
Antlers begin as bony growths covered with skin and hair (velvet). They grow at incredible rates, with the immense racks of deer, elk and moose growing in just 3 to 4 months. This makes them one of the fastest growing living tissues.
After the antlers have reached their maximum size, blood vessels at the base close down causing the skin to dry up and peel off. The owner assists this process by rubbing against trees. In many areas, you can see these rubbings as the thin bark of the aspen trees is rubbed off along with the velvet. As the velvet peels away, they eat the newly removed skin. Once the velvet is gone, only the hard bony core remains as a formidable weapon in the annual mating game.
In order to grow these huge racks, deer and elk must eat upwards of 50 kg of calcium each season. This is quite a feat when their diet is composed of plant material. Prehistoric elk had racks that measured upwards of 2 metres in size and would dwarf today's much smaller descendants.
Going, Going, Gone!
When the mating game ends, it would seem to make sense to shed them as soon as possible. For every kilogram of antler, the deer must consume enough food energy to support the weight. This is even more difficult during the harsh winter when food is not only of poorer quality, but also more limited in nature. Deer, moose and caribou usually shed their antlers by the end of December. Elk, on the other hand, are more social. They have found a secondary purpose in helping the stags compete for limited winter food supplies. This seems to outweigh the energy costs of carrying the antlers around. Elk only lose their antlers in April or early May, just in time to grow a new pair.
Prior to antler loss, the body begins to draw the calcium back into the body. This leaves the antlers more brittle, and somewhat more porous. A specialized layer of cells form near the base, adding to the brittle character, until finally, the antlers fall to the ground, usually one at a time, separated by a few hours or a few days. It is not uncommon at this time of year to see deer with only a single antler during the interim period.
Antlers vs. Horns
Visitors often comment on the impressive ‘horns’ of the elk stags wandering Jasper and Banff townsites. They are actually referring to antlers. Horns are very different. True horns, like those found on bighorn sheep, mountain goats, bison and pronghorn, grow continuously throughout an animals life, and cannot be replaced if damaged or broken off. The outer surface of horns is composed of keratin, a substance similar to finger nails, and they are nourished by blood vessels within the horn itself.
Antlers are essentially bones growing from the front of the skull of the deer. Antlers are usually longer than horns, and have many branches. No horned animal in the Rockies shows branching horns
The next time you marvel at the impressive antlers on a large elk or moose, remember, they took only 3 to 4 months to grow! They represent one of the great examples of adaptation and evolution in the deer family.