readily distinguished by the presence of horns and by black stripes on the legs, both of which the females lack. The coat is pale fawn to reddish-brown, with a whitish belly, and is particularly thick and woolly. The face is almost black in colour, with prominent nasal swellings that have a paler colour in males. In general, the colouration of males becomes more intense during the annual rut, with the coat becoming much paler, almost white, contrasting with the darker patterns on the face and legs. The males have long, curved-back horns that typically measure in length. The horns are slender, with ring-like ridges on their lower portions and smooth, pointed, tips. Although the horns are relatively uniform in length, there is some variation in their exact shape, so the distance between the tips can be quite variable, ranging from . Unlike caprines, the horns do not grow throughout life. The ears are short and pointed, and the tail is also relatively short, at around in length. The fur of Tibetan antelopes is distinctive, and consists of long guard hairs and a silky undercoat of shorter fibres. The individual guard hairs are thicker than those of other goats, with unusually thin walls, and have a unique pattern of cuticular scales, said to resemble the shape of a benzene ring. Distribution and habitat Endemic to the Tibetan Plateau, the Tibetan antelope inhabits open alpine and cold steppe environments between elevation. They prefer flat, open terrain, with sparse vegetation cover. They are found almost entirely in China, where they inhabit Tibet, southern Xinjiang, and western Qinghai; a few are also found across the border in Ladakh, India. The westernmost population of Tibetan antelope is in Depsang Plains, where they are found at altitudes of up to 5500 m. Today, the majority are found within the Chang Tang Nature Reserve of northern Tibet. The first specimens to be described, in 1826, were from Nepal; the species has apparently since been extirpated from the region. No subspecies are recognised. Zhuonai Lake (卓乃湖) in Hoh Xil is known as a calving ground for the Tibetan antelope. A special adaptation of the species to its high altitude habitat is the retention of the fetal version of hemoglobin even in adult animals, which provides higher oxygen affinity. The Tibetan antelope is the only species of mammal where this adaptation has been documented. Behaviour Tibetan antelope feed on