The elk, or wapiti (Cervus canadensis), is one of the largest species of deer in the world and one of the largest mammals in North America and eastern Asia. In the deer family (Cervidae), only the moose, Alces alces (called an "elk" in Europe), is larger, and Cervus unicolor (the "Sambar" deer) can rival the elk in size. Wapiti are almost identical to red deer found in Europe, of which they were long believed to be a subspecies; however, mitochondrial DNA evidence from 2004 strongly suggests they are a distinct species. Elk range in forest and forest-edge habitat, feeding on grasses, plants, leaves, and bark. Although native to North America and eastern Asia, they have adapted well to countries where they have been introduced, including New Zealand and Argentina. Their high level of adaptability poses a threat to endemic species and ecosystems where they have been introduced. Male elk have large antlers which are shed each year. Males engage in ritualized mating behaviors during the rut, including posturing, antler wrestling, and bugling, a loud series of screams which establishes dominance over other males and attracts females. The bugle call is one of the most distinctive calls in nature. Elk are susceptible to a number of infectious diseases, some of which can be transmitted to livestock. Efforts to eliminate infectious diseases from elk populations, largely through vaccination, have had mixed success. Some cultures revere the elk as a spiritual force. In parts of Asia, antlers and their velvet are used in traditional medicines. Elk are hunted as a game species; the meat is leaner and higher in protein than beef or chicken.