南非剑羚种

生理型态

身体

体长约150到200公分，肩高约110到130公分。体重约100到200公斤，是剑羚属中最大型的种类。身体上覆盖的毛是灰褐色，但脸部、腹部及四肢下部的体毛是白色。脸部中央、眼睛到嘴巴四周、咽部、前肢与后肢之间的体侧、四肢的胫部及尾巴都有黑色的毛分布。

不论是雄性或是雌性都有长而直的角，其中以雄性的角较大，最长可以达到约120公分。

散热机制

为了在沙漠中生存，南非剑羚可调节脑部温度以减少水分蒸发。炎热时，它的鼻腔黏液会在吸入空气时冷却血液，随后血液将流向海绵窦。气温低时，通往大脑血管的瓣膜会关闭以暂停冷却过程。

生态

栖息于沙漠之中，以一只强大的雄性为中心，形成约10到40匹的群体共同生活。年迈的雄性会离开群体独自生活。南非剑羚为草食性动物，吃草或树叶等。繁殖的形式是胎生，一次可以产下一匹幼体。繁殖期时，雄性之间会互相以角搏斗，以竞争与某只雌性繁殖的机会。

The gemsbok (Oryx gazella) is a large antelope in the genus Oryx. It is endemic to the dry and barren regions of Botswana, Namibia, South Africa and (parts of) Zimbabwe, mainly inhabiting the Kalahari and Namib Deserts, areas in which it is supremely adapted for survival. Previously, some sources classified the related East African oryx, or beisa oryx (Oryx beisa), as a subspecies.

Name

The name gemsbok is from Afrikaans, which itself is from the Dutch word of the same spelling, meaning "male chamois", composed of gems ("chamois") + bok ("buck, male goat"). The Dutch gems is further from German Gämse ("chamois"). Although some superficial similarities in appearance (especially in the facial pattern) are noticed, the chamois and the oryx are not closely related. The usual pronunciation in English is.

Description

Gemsbok are light taupe to tan in color, with lighter patches toward the bottom rear of the rump. Their tails are long and black in color. A blackish stripe extends from the chin down the lower edge of the neck, through the juncture of the shoulder and leg along the lower flank of each side to the blackish section of the rear leg. They have muscular necks and shoulders, and their legs have white 'socks' with a black patch on the front of both the front legs, and both sexes have long, straight horns. Comparably, the East African oryx lacks a dark patch at the base of the tail, has less black on the legs (none on the hindlegs), and less black on the lower flanks.

Genomics

A near chromosome-scale genome assembly of Oryx gazella was published in 2019. The genome size is approximately 2.9 Gb, with 47 predicted chromosome fragments assembled. The assembly contained 93.8% of expected genes according to BUSCO analysis, and 23,125 protein-coding genes were annotated. This was reported as the first high-quality chromosome-scale genome assembly for the gemsbok.

Horns

Gemsbok are widely hunted for their spectacular horns that average 85 cm (33 in) in length. From a distance, the only outward difference between males and females is their horns, and many hunters mistake females for males each year. In males, horns tend to be thicker with larger bases; females have slightly longer, thinner horns.

Distribution and habitat

Gemsbok are found in arid and semi-arid bushlands in southwestern Africa, especially around the Namib and Kalahari deserts, in Botswana, Zimbabwe, Namibia, South Africa and formerly Angola (where they are considered extirpated).

A sizeable introduced population of several thousand is also present in the Chihuahuan Desert in Southern New Mexico at the White Sands Missile Range where they are problematic for the local ecosystem.

Ecology and biology

Gemsbok live in herds of about 10–40 animals, which consist of a dominant male, a few nondominant males, and females. They are mainly desert-dwelling and do not depend on drinking water to supply their physiological needs. They can reach running speeds of up to 60 km/h (37 mph). Gemsbok are mostly crepuscular in nature, since temperatures are tolerable and predator detection rates are highest during these times.

Diet

The gemsbok is generally a grazer but changes to browsing during the dry season or when grass is sparse.

Introduction to North America

In 1969, the New Mexico State Department of Game and Fish decided to introduce gemsbok to the Tularosa Basin, New Mexico, in the United States. Ninety-three were released from 1969 to 1977, with the current population estimated to be around 3,000 individuals. Gradually expanding their range from Tularosa Basin towards the west and northwest, an unknown number of animals are now also established in the San Andres National Wildlife Refuge, the Fra Cristobal Range, and the Jornada Biosphere Reserve as well as the endorheic drainage basins east of Caballo Mountains, especially where these are traversed by the Jornada del Muerto trail north of Upham.

Significance to humans

The gemsbok is depicted on the coat of arms of Namibia, where the current population of the species is estimated at 373,000 individuals. In the town of Oranjemund, resident gemsbok wander freely around the streets, taking advantage of the vegetation in the town, such as the grass in parks, road medians, and browsing on low branches of the many trees.