The indigenous pronghorn antelope (Antilocapra americana), evolving from ancestral forms originating in North America 25 million years ago, is the only surviving species of the Family Antilocapridae. It became a major ungulate on the Great Plains from central Mexico to southern Alberta and Saskatchewan. Estimates suggest that 30–40 million existed prior to European settlement. Pronghorns are smaller than most horned and antlered North American mammals; mature males and females can attain body weights of 70 kg and 56 kg respectively. The horns of males are bony extensions of the skull, covered by a blackish sheath that develops a forward-projecting prong; these sheaths are usually cast off in early November. Females are hornless. Large eyes set in protruding bone-rimmed sockets provide keen eyesight. This, and the pronghorn’s ability to attain a running speed of 100 kilometres per hour, serves the animals well in open, treeless habitats. Their reddish-tan coat with white and dark coloration blends with the brown prairie vegetation. The long white erectile hairs of the rump patch, raised by muscles into an expanded rosette when a pronghorn is alarmed, trigger the rump glands to secrete pheromones, providing both a visual and olfactory communication between herd members. Canadian pronghorns inhabit and feed on mixed prairie regions supporting shrubs, forbs, and grasses. Rutting-season males gather and control female harems in September. A gestation period of approximately 250 days usually produces twin kids. Pronghorn mortality factors include predation by coyotes and bobcats, heavy snowfall increasing the difficulties of obtaining food, and accidental traffic deaths on highways and railroads.