Antlers are fascinating. Elk, deer and moose have them, and their antlers are shed in the spring, and then they start growing back almost immediately until they become that regal headgear prized by hunters.
Antlers differ from horns because antlers are shed and regrown every year. Horns stay with most animals and they slowly grow over time like fingernails.
The antlers from a trophy-sized elk can weigh upward of 40 pounds, and an elk can grow them from nubs within about four months.
The fact elk can grow antlers is amazing enough, but Idaho Fish and Game's Toby Boudreau says how large they get depends a great deal on nutrition.
There is a limit to antler size, and to dispel a common myth, an elk's antlers will not get larger every year until the animal dies.
As a general guideline, yearlings grow lengthy spikes, while 4-year-olds can easily grow antlers with five points or more and as long as five feet.
At peak maturity at 7 or 8 years old, elk can grow some amazingly large antlers, among the biggest in the world.
But there comes a certain point when the antlers will start to regress in size as the animal gets older and less healthy.
There's some interesting biology that occurs with antler growth. Surprisingly, it all starts with the amount of sunlight in a day.
Bull elk have a photo receptor in their eyes that triggers hormone changes that send a signal to drop the old antlers and new ones to sprout.
Big bulls are usually the first to lose their antlers, due to sheer weight. They drop their headgear somewhere near the last week of March to mid-April.
Boudreau said most antlers get eaten by mice, squirrels, porcupines and other small critters. Antlers are one of nature's best sources of calcium, a mineral that is stored in animals' (and humans') bones and teeth.
Antlers are also prized by collectors.
Every spring at the National Elk Refuge in Jackson, Wyo., Boy Scouts collect shed elk antlers.
According to the U.S. Fish and Wildlife Service, which manages the refuge, 8,507 pounds of antlers were gathered and sold at the auction for $131,400 this spring. Bidders paid an average of $15.43 per pound for antlers.
No sooner do shed antlers hit the ground than elk start producing the next pair.
Within three to four weeks, a new pair will start to show, and usually the antlers are full-grown by mid-August. But they won't be the gleaming set of brown antlers with ivory tips that you see in the fall.
Antlers are grown from a fuzzy tissue commonly known as velvet.
Once the bull feels the need to remove the outer skin, or velvet, it will start to rub its antlers on trees, shrubs, bushes and anything else it can find, which creates color variations in antlers.
Boudreau said that antlers are white under the velvet. They get color from whatever vegetation the elk rub their antlers on.
So an elk from a high plains region could have antlers a different shade than one from a forest.
Growing antlers requires elk to consume large amounts of nutrients, and the quality of forage available, along with genetics and other factors, can ultimately determine how large their antlers get.
One reason you rarely see bulls and cows together during spring and summer is that females concentrate on foods that provide nutrients for lactating and feeding their calves, while bulls feed on plants that benefit antler growth.
Their nutrition requirements are totally independent of one another, so they are usually away from each other.
Mark Krepps is a freelance writer, author and blogger.