The Mountain Goat (Oreamnos americanus), also known as the Rocky Mountain goat, is a hoofed mammal endemic to mountainous areas of western North America. A subalpine to alpine species, it is a sure-footed climber commonly seen on cliffs and ice.
Despite its vernacular name and both genera being in the same subfamily (Caprinae), the mountain goat is not a member of Capra, the genus that includes all other goats, such as the wild goat (Capra aegagrus), from which the domestic goat is derived. Instead, it is more closely allied with the takins (Budorcas) and chamois (Rupicapra).
The mountain goat is an even-toed ungulate of the order Artiodactyla and the family Bovidae that includes antelopes, gazelles, and cattle. It belongs to the subfamily Caprinae, along with true goats, wild sheep, the chamois, the muskox and other species. The takins of the Himalayan region, while not a sister lineage of the mountain goat, are nonetheless very closely related and almost coeval to the mountain goat; they evolved in parallel from an ancestral goat. Other members of this group are the bharal, the true goats, and the Himalayan tahr. The sheep lineage is also very closely related, while the muskox lineage is somewhat more distant. The mountain goats probably diverged from their relatives in the late Tortonian, some 7.5 to 8 million years ago.[citation needed]
Given that all major caprine lineages emerged in the Late Miocene and contain at least one but usually several species from the eastern Himalayan region, their most likely place of origin is between today's Tibet and Mongolia or nearby. The mountain goat's ancestors thus probably crossed the Bering Strait after they split from their relatives, presumably before the Wisconsinian glaciation. No Pliocene mountain goats have been identified yet; the known fossil record is fairly recent, entirely from North America, and barely differs from the living animals. In the Pleistocene, the small prehistoric mountain goat Oreamnos harringtoni lived in the southern Rocky Mountains. Ancient DNA studies suggest that this was the sister species of the living mountain goat, not its ancestor; consequently, the living species would also date back to the Pleistocene at least.[2][3]
The mountain goat is the only living species in the genus Oreamnos. The name Oreamnos is derived from the Greek term oros (stem ore-) "mountain" (or, alternatively, oreas "mountain nymph") and the word amnos "lamb".
Both male and female mountain goats have beards, short tails, and long black horns, 15–28 cm (5.9–11 in) in length, which contain yearly growth rings. They are protected from the elements by their woolly grayish white double coats. The fine, dense wool of their undercoats is covered by an outer layer of longer, hollow hairs. Mountain goats molt in spring by rubbing against rocks and trees, with the adult billies shedding their extra wool first and the pregnant nannies shedding last. Their coats help them to withstand winter temperatures as low as −46 °C (−51 °F) and winds of up to 160 kilometres per hour (99 mph).
