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Earth Notes: How to Age an Elk

With the arrival of spring across Arizona’s high country, lengthening daylight triggers hormonal changes in elk bulls. In March they lose their old antlers, and by April they’re growing new ones. The antlers are one clue to the animal’s age, but teeth are even better.

Antler development depends on food supply. The prolonged drought from fall 2017 through spring 2018 affected Arizona’s bull elk. Many produced shorter tines—those sharp points off the main beam—compared to longer tines produced in wetter years.

Antler growth can suggest a bull elk’s age. Yearlings normally have a pair of single spikes, while bulls with three or four times on each side of their antlers are typically two years old. Five-to-7-year-old animals have the largest headgear.

But for an accurate age–whether a bull or cow elk—Arizona Game and Fish biologists look at the teeth, especially the amount of wear. A three-cusp premolar is a sure sign of a yearling. But teeth worn down to two cusps indicate the elk is likely two years or older. And after six years of munching hard forage, all the molars will be ground into a tell-tale cup shape. For a more precise age, biologists pull the front incisor from a dead animal. In the lab an extremely thin slice of tooth is sawn, and it’s stained and examined under a microscope. The number of rings corresponds to the elk’s age in years—much like getting the date on a tree from growth rings.

In Arizona, elk may live 14 to 17 years—the oldest known so far reached the grand old age of 25.

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