Mountain goat

The mountain goat (Oreamnos americanus), also known as the Rocky Mountain goat, is a hoofed mammal endemic to North America. A subalpine to alpine species, it is a sure-footed climber commonly seen on cliffs and ice. Despite its vernacular name, it 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. 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. Notably, the takins of the Himalayan region, while not a sister lineage of the mountain goat, are nonetheless very closely related and almost coeval; they and the mountain goat are a case of parallel evolution from an ancestral goat. Other members of this group are the Pseudois 'blue sheep', the true goats and the Himalayan tahr. The chamois and true sheep lineages are 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. 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. Unfortunately, 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. 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 billy (male) and nanny (female) mountain goats have beards, short tails, and long black horns, 15–28 cm (5.9–11.0 in) in length, which contain yearly growth rings. They are protected from the elements by their woolly 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 −50 °F (−46 °C) and winds of up to 160 kilometres per hour (99 mph). A billy stands about 1 m (3.3 ft) at the shoulder to the waist and can weigh considerably more than the nanny (around 30% more in some cases). Male goats also have longer horns and longer beards than females. Mountain goats can weigh between 45 and 140 kg (99 and 309 lb), and billies will often weigh less than 82 kg (181 lb). The head-and-body length can range from 120–179 cm (47–70 in), with a small tail adding 10–20 cm (3.9–7.9 in). The mountain goat's feet are well-suited for climbing steep, rocky slopes with pitches exceeding 60°, with inner pads that provide traction and cloven hooves that can spread apart. The tips of their feet have sharp dewclaws that keep them from slipping. They have powerful shoulder and neck muscles that help propel them up steep slopes.