东非直角长角羚种

东非直角长角羚肩高1米，重约175公斤。它们的毛皮呈灰色，腹部白色，白色与灰色间有一道黑色斑纹分界，头部与颈部之间、沿鼻子、由眼睛至口及在前额也有黑色斑纹。它们有一束细小的栗色鬃毛。角幼而直，雄羚及雌羚都有，一般长75-80厘米。

东非直角长角羚栖息在半沙漠及沙地，主要吃草、叶子及芽。它们可以储存水分来提升体温。群落约有5-40个成员，一般雌羚在前头，较大的雄羚在后头保护。一些年老的雄羚是独居的。无线电追踪发现独居的雄羚有时会与发情期的雌羚一起生活一段短时间，从而增加繁殖的机会。

The East African oryx (Oryx beisa), also known as the beisa, is a species of medium-sized antelope from East Africa. It has two subspecies: the common beisa oryx (Oryx beisa beisa) found in steppe and semidesert throughout the Horn of Africa Somalia and north of the Tana River, and the fringe-eared oryx (Oryx beisa callotis) south of the Tana River in southern Kenya Somalia and parts of Tanzania. The species is listed as Endangered by the IUCN.

In the past, some taxonomists considered it a subspecies of the gemsbok (Oryx gazella), but they are genetically distinct; the diploid chromosome count is 56 for the beisa and 58 for the gemsbok.

Description

The East African oryx stands between 0.79 and 1.25 m (2.6 and 4.1 ft) tall at the shoulder and typically weighs between 220 and 460 lb (100 and 209 kg). It has a grey coat with a white underside, separated from the grey by a stripe of black, with black stripes where the head attaches to the neck, along the nose, and from the eye to the mouth and on the forehead. The mane is small and chestnut-coloured; the ringed horns are thin and straight. They are found on both sexes and typically measure 75–80 cm (30–31 in). Comparably, the gemsbok has an entirely black tail, a black patch at the base of the tail, and more black on the legs (including a patch on the hindlegs) and lower flanks. The smaller Arabian oryx is overall whiter with largely dark legs.

Behaviour

East African oryx live in semidesert and steppes, where they eat grasses, leaves, fruit and buds. During periods of dehydration, they limit water losses by allowing their body temperatures to increase (so as to avoid perspiration). They gather in herds of five to 40 animals, often with females moving at the front and a large male guarding from the rear. Some older males are solitary. Radio tracking studies show the solitary males are often accompanied for brief periods by breeding-condition females, so it is probable they are executing a strategy to maximise their chances of reproduction.