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 in Yellowstone
Yellowstone bison exhibit behavior like their ancient ancestors.
Bighorn Sheep in Yellowstone
Most bighorn sheep in Yellowstone are migratory.
Elk in Yellowstone
Elk are the most abundant large mammal found in Yellowstone.
Moose in Yellowstone
Moose are the largest members of the deer family in Yellowstone.
Mountain Goats in Yellowstone
Mountain goats are considered a non-native species in Yellowstone National Park.
Mule Deer in Yellowstone
Also called blacktail deer, they are an exclusively western species.