Elk (Cervus elapses), also called the "Wapiti". Once common across North America, elk now occur naturally only in the Rocky Mountains, western United States and Canada. They eat large quantities of grasses, leaves and other woody plants. During rutting season, they make a high-pitched whistling sound. Second in size to the moose, the male can stand over 5 feet and weigh up to 990 pounds (450 kg). Their towering branched antlers usually bear five times. Fun Fact: Elk can run 35 mph and are strong swimmers.