The main beams may exceed four feet in length, and the tips of the two main beams may be as wide as three feet apart. Antlers are shed every year. Adult cows are about 25 percent smaller than bulls. Elk are polygamous and bulls begin to gather a harem of cows in early autumn. These harems may contain as many as 30 or more animals.
Bulls become very territorial during rutting season and often spar with other bulls.
These clashes, though dramatic, are seldom lethal. Elk generally mate in September and gestation is between eight and nine months. Calves are usually born in May or June. Rutting season is the only time bulls and cows herd together. The rest of the time cows and calves herd together, large bulls tend to be solitary and younger bulls live together in bachelor groups.