Bighorn sheep reproduce by mating in the fall, and after the males compete against one another for rights to the females, the ewes experience a gestation period of 150 to 180 days before giving birth. The rams engage in a fierce competition for females and run at one another at speeds up to 40 miles per hour to clash their curled horns together. Age, strength and horn size are all determining factors for the likelihood that rams will win their battles.
After the mating season, the ewes and the rams separate their herds, and the ewes deliver one lamb. The lambs are protected on high and steep mountainous ledges, and the lamb and ewe rejoin their herd once the lamb is about 1 week old.