The Difference Between Horns & Antlers

Cattle and goats have horns. Deer and elk have antlers. What are the differences between the two?

Horns are:
• Made of bony core covered by a thin layer of keratin, the same material as your fingernails;
• Slow growing and permanent; they are not shed each year;
• More like daggers than branches;
• Usually grown by both sexes; and
• Usually grow in yearly "rings" that mark the animal's age.

Antlers are:
• Fast-growing bone that is shed each year
• Usually grown only by males (both sexes of caribou grow antlers); and
• Often branched (but the number of points does not signify age).

About Antlers
Each spring, male deer and elk begin growing antlers from bony bumps on their skulls called pedicles. Increasing daylight elevates the level of the hormone testosterone in the animal's blood, which triggers the growth of antlers. Antlers begin as layer upon layer of cartilage that slowly mineralizes into bone. They are light and easily damaged until they completely mineralize in late summer. A soft covering called velvet helps protect the antlers and carries blood to the growing bone tissue.

If you look closely at a deer or elk antler, you'll see grooves and ridges on it. These mark the paths of veins that carried blood throughout the growing antlers. The blood stops flowing to the antlers in August, the antlers finish hardening, and the velvet falls off or is rubbed off. The hardened antlers are composed of calcium, phosphorous and as much as 50 percent water.

An antler grows faster than any other kind of bone. It can grow up to 1 inch (2.5 cm) a day during the summer. Biologists are studying antlers in the hopes of learning the secrets of rampant cell growth, secrets that may unlock cures to various forms of cancer.
In his second year, a bull elk usually grows slim, unbranched antlers called spikes that are 10-20 inches (25-50 cm) long. By the third year, antlers begin developing tines that branch from the main beam. By the seventh summer, a bull's antlers may have six tines each, weigh as much as 40 pounds (18 kg), and grow to a length and spread of more than four feet (1.2 m). Why would an animal need to carry around a rack of antlers that weighs so much? A large rack identifies a bull that is successful in finding food, lots of food.
A bull must consume huge amounts of nutrients to obtain the energy and minerals needed to grow antlers as well as the energy to carry them around. Large antlers also identify a bull that is able to defend himself against other bulls and against predators. This information is of great interest to female elk (cows) because they will mate with the strongest, most successful males -- usually the bulls with the biggest antlers.

They Fall in the Spring
Bull elk "cast" or shed their antlers every spring. Testosterone is the hormone in the bull's body controlling the "cement" that holds the antlers secure. In the spring, the testosterone level drops like a rock, and so do the antlers.
On top of every bull's head are two pedicles -- bones shaped like cups and covered with skin. Antlers grow out of these pedicles. Once testosterone hardens the bond, the antlers are locked into the pedicles so tightly that a bull could wear 10 bowling balls from each antler and the antlers wouldn't budge.

Testosterone is also the hormone that rages through a bull in September. He bugles, fights with other bulls, and tries to mate with the cows. But by October, the amount of testosterone slowly begins dropping, and will continue to fall until early spring when the antlers snap off and startle the bull. The pedicles bleed a little right after the antlers fall off, but they soon heal. And the cycle begins again as a new set of antlers sprouts from the pedicles.

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