Pronghorn Shed and Regrow Their Horn Sheaths Every Year

Antlers fall off every year, horns usually do not. The pronghorn breaks that rule. The U.S. National Park Service explains that pronghorn have true horns, made of modified, fused hair growing over permanent bony cores, but they differ from those of other horned animals in two major ways: the sheaths are shed and grown every year, and they are pronged. Some other horned mammals occasionally shed their horns, the Park Service notes, but not annually. The timing is regular. Males usually shed the sheaths in November or December and begin growing the next year’s set in February or March, reaching maximum development in August or September. Adult males typically have horns 10 to 16 inches long. About 70 percent of females also have horns, but they average only 1 to 2 inches and are not pronged.