Last updated: August 2, 2017
Article
Horns versus Antlers
![Bighorn sheep ram Close-up of a bighorn sheep ram with curled horns](/articles/images/18026d_bighornram_1.jpg?maxwidth=1300&maxheight=1300&autorotate=false)
NPS
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.](/common/uploads/grid_builder/articles/crop16_9/6775CDB0-1DD8-B71B-0B621126173E0ABF.jpg?width=1300&quality=90&mode=crop)
Yellowstone bison exhibit behavior like their ancient ancestors.
![Close-up of a bighorn sheep's face.](/common/uploads/grid_builder/articles/crop16_9/6715A61E-1DD8-B71B-0B65D44672233FA8.jpg?width=640&quality=90&mode=crop)
Most bighorn sheep in Yellowstone are migratory.
![A male elk bugling on a cool autumn day.](/common/uploads/grid_builder/articles/crop16_9/66F020E1-1DD8-B71B-0B9023FCC4601BF8.jpg?width=640&quality=90&mode=crop)
Elk are the most abundant large mammal found in Yellowstone.
![A mother and child moose in a grassy field.](/common/uploads/grid_builder/articles/crop16_9/66DC3F00-1DD8-B71B-0BD689A2A957D988.jpg?width=640&quality=90&mode=crop)
Moose are the largest members of the deer family in Yellowstone.
![Two mountain goats standing upon a rock pinnacle.](/common/uploads/grid_builder/articles/crop16_9/663A4640-1DD8-B71B-0BDA2E8566C9E50A.jpg?width=640&quality=90&mode=crop)
Mountain goats are considered a non-native species in Yellowstone National Park.
![A male mule deer walking through a forest.](/common/uploads/grid_builder/articles/crop16_9/66715A20-1DD8-B71B-0B54BC406E16457B.jpg?width=640&quality=90&mode=crop)
Also called blacktail deer, they are an exclusively western species.
![A pronghorn close-up](/common/uploads/grid_builder/articles/crop16_9/664850D4-1DD8-B71B-0B3252329897B0FA.jpg?width=640&quality=90&mode=crop)
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.](/common/uploads/grid_builder/articles/crop16_9/665A21D0-1DD8-B71B-0B9E15CBBF82A33B.jpg?width=640&quality=90&mode=crop)
A common deer on the East Coast, they are scarcely seen in Yellowstone.