Horns versus Antlers

Close-up of a bighorn sheep ram with curled horns
Bighorn sheep, as the name implies, grown horns.


Antlers—found on members of the deer family—grow as an extension of the animal’s skull. They are true bone, are a single structure, and, generally, are found only on males.

Horns—found on pronghorn, bighorn sheep, and bison—are a two-part structure. An interior portion of bone (an extension of the skull) is covered by an exterior sheath grown by specialized hair follicles (similar to human fingernails). Horns are usually found on both males and (in a diminutive form) females.

Antlers are shed and regrown yearly while horns are never shed and continue to grow throughout an animal’s life. One exception is the pronghorn, which sheds and regrows its horn sheath each year.

Bison grazing in a grassy field next to a river.
Bison in Yellowstone

Yellowstone bison exhibit behavior like their ancient ancestors.

Close-up of a bighorn sheep's face.
Bighorn Sheep in Yellowstone

Most bighorn sheep in Yellowstone are migratory.

A male elk bugling on a cool autumn day.
Elk in Yellowstone

Elk are the most abundant large mammal found in Yellowstone.

A mother and child moose in a grassy field.
Moose in Yellowstone

Moose are the largest members of the deer family in Yellowstone.

Two mountain goats standing upon a rock pinnacle.
Mountain Goats in Yellowstone

Mountain goats are considered a non-native species in Yellowstone National Park.

A male mule deer walking through a forest.
Mule Deer in Yellowstone

Also called blacktail deer, they are an exclusively western species.

A pronghorn close-up
Pronghorn in Yellowstone

The surviving member of a group of animals that evolved in North America during the past 20 million years.

Two white-tailed deer forage amongst sagebrush.
White-tailed Deer in Yellowstone

A common deer on the East Coast, they are scarcely seen in Yellowstone.

Yellowstone National Park

Last updated: August 2, 2017