The Bighorn sheep color ranges from gray-brown to ash-gray; the belly and rump are white. In rams, the large and beautiful horns are thick and coiled, while in ewes the horns are smaller and not coiled. While separated in the summer, rams and ewes come together in the fall where rams of equal size challenge each other for the ewes. Charging at up to 20 mph, the rams butt heads loudly; their impact cushioned by double-thick skulls with struts of bone. The sheep eat sedge, grass, sagebrush and alpine plants. A single lamb is born between May and June and remains with their herd. With a lifespan of 14 years, the Bighorn sheep is threatened by weather, disease, and a loss of habitat due to intrusion.