Arabian oryx (oryx leucoryx).jpg

The Arabian oryx (''Oryx leucoryx'') or white oryx is a medium-sized antelope with a distinct shoulder bump, long, straight horns, and a tufted tail. It is a bovid, and the smallest member of the genus ''Oryx'', native to desert and steppe areas of the Arabian Peninsula. The Arabian oryx was extinct in the wild by the early 1970s, but was saved in zoos and private reserves, and was reintroduced into the wild starting in 1980.

In 1986, the Arabian oryx was classified as endangered on the IUCN Red List, and in 2011, it was the first animal to revert to vulnerable status after previously being listed as extinct in the wild. It is listed in CITES Appendix I. In 2016, populations were estimated at 1,220 individuals in the wild, including 850 mature individuals, and 6,000–7,000 in captivity worldwide.

Etymology

The taxonomic name ''Oryx leucoryx'' is from the Greek ' (gazelle or antelope) and ' (white). The Arabian oryx is also called the white oryx in English, ' in Hebrew, and is known as ', and ' in Arabic.

Prussian zoologist Peter Simon Pallas introduced "oryx" into scientific literature in 1767, applying the name to the common eland as ''Antilope oryx'' (Pallas, 1767). In 1777, he transferred the name to the Cape gemsbok. At the same time, he also described what is now called the Arabian oryx as ''Oryx leucoryx'', giving its range as "Arabia, and perhaps Libya". In 1816, Henri Marie Ducrotay de Blainville subdivided the antelope group, adopted ''Oryx'' as a genus name, and changed the ''Antilope oryx'' of Pallas to ''Oryx gazella'' (de Blainville, 1818). In 1826, Martin Lichtenstein confused matters by transferring the name ''Oryx leucoryx'' to the scimitar oryx (now ''Oryx dammah'') which was found in the Sudan by the German naturalists Wilhelm Friedrich Hemprich and Christian Gottfried Ehrenberg (Lichtenstein, 1826). The Arabian oryx was then nameless until the first living specimens in Europe were donated to the Zoological Society of London in 1857. Not realizing this might be the ''Oryx leucoryx'' of previous authors, Dr. John Edward Gray proposed calling it ''Oryx beatrix'' after HRH the Princess Beatrice of the United Kingdom (Gray, 1857). Though this name was to persist for many years, Oldfield Thomas renamed the scimitar oryx as ''Oryx algazal'' in 1903 (it has since been renamed ''Oryx dammah''), and gave the Arabian oryx back its original name. The confusion between the two species has been exacerbated because both have been called the white oryx in English.

Anatomy and morphology

An Arabian oryx stands about high at the shoulder and weighs around . Its coat is an almost luminous white, the undersides and legs are brown, and black stripes occur where the head meet the neck, on the forehead, on the nose, and going from the horn down across the eye to the mouth. Both sexes have long, straight or slightly curved, ringed horns which are long.

Arabian oryxes rest during the heat of the day. They can detect rainfall and move towards it, meaning they have huge ranges; a herd in Oman can range over . Herds are of mixed sex and usually contain between two and 15 animals, though herds up to 100 have been reported. Arabian oryxes are generally not aggressive toward one another, which allows herds to exist peacefully for some time.

Other than humans, wolves are the Arabian oryx's only predator. In captivity and safe conditions in the wild, Arabian oryxes have a lifespan of up to 20 years. In periods of drought, though, their life expectancy may be significantly reduced by malnutrition and dehydration. Other causes of death include fights between males, snakebites, disease, and drowning during floods.

Distribution and habitat

Historically, the Arabian oryx probably ranged throughout most of the Middle East. In the early 1800s, they could still be found in the Sinai, Palestine, the Transjordan, much of Iraq, and most of the Arabian Peninsula. During the 19th and early 20th centuries, their range was pushed back towards Saudi Arabia, and by 1914, only a few survived outside that country. A few were reported in Jordan into the 1930s, but by the mid-1930s, the only remaining populations were in the Nafud Desert in northwestern Saudi Arabia and the Rub' al Khali in the south.

In the 1930s, Arabian princes and oil company clerks started hunting Arabian oryxes with automobiles and rifles. Hunts grew in size, and some were reported to employ as many as 300 vehicles. By the middle of the 20th century, the northern population was effectively extinct. The last Arabian oryx in the wild prior to reintroduction were reported in 1972.

Arabian oryxes prefer to range in gravel desert or hard sand, where their speed and endurance will protect them from most predators, as well as most hunters on foot. In the sand deserts in Saudi Arabia, they used to be found in the hard sand areas of the flats between the softer dunes and ridges.

Arabian oryxes have been reintroduced to Oman, Saudi Arabia, Israel, the United Arab Emirates, Syria, and Jordan. A small population was introduced on Hawar Island, Bahrain, and large semi-managed populations at several sites in Qatar and the UAE. The total reintroduced population is now estimated to be around 1,000. This puts the Arabian oryx well over the threshold of 250 mature individuals needed to qualify for endangered status. However, the majority of the population is concentrated in Saudi Arabia.

Ecology

Feeding

The diets of the Arabian oryx consist mainly of grasses, but they eat a large variety of vegetation, including buds, herbs, fruit, tubers and roots. Herds of Arabian oryxes follow infrequent rains to eat the new plants that grow afterward. They can go several weeks without water. Research in Oman has found grasses of the genus ''Stipagrostis'' are primarily taken; flowers from ''Stipagrostis'' plants appeared highest in crude protein and water, while leaves seemed a better food source with other vegetation.

Behavior

When the Arabian oryx is not wandering its habitat or eating, it digs shallow depressions in soft ground under shrubs or trees for resting. They are able to detect rainfall from a distance and follow in the direction of fresh plant growth. The number of individuals in a herd can vary greatly (up to 100 have been reported occasionally), but the average is 10 or fewer individuals. Bachelor herds do not occur, and single territorial males are rare. Herds establish a straightforward hierarchy that involves all females and males above the age of about seven months. Arabian oryxes tend to maintain visual contact with other herd members, with subordinate males taking positions between the main body of the herd and the outlying females. If separated, males will search areas where the herd last visited, settling into a solitary existence until the herd's return. Where water and grazing conditions permit, male Arabian oryxes establish territories. Bachelor males are solitary. A dominance hierarchy is created within the herd by posturing displays, which avoid the danger of serious injury their long, sharp horns could potentially inflict. Males and females use their horns to defend the sparse territorial resources against interlopers.

Adaptations for desert environments

The Arabian oryx changes its physiology and behavior at different times of the year to increase survival during times when food and water are in limited supply. During the summer, when droughts are common in the desert environments where it lives, the Arabian oryx will drastically reduce its minimal fasting metabolic rate by lying completely inactive beneath shade trees during the day and ranging over smaller areas at night to forage. By letting its body temperature rise during the heat of the day, it uses less evaporative cooling and retains more body water, and at night, the cool night air lowers its temperature back to the normal range. The oryx’s arterial blood temperature is partly lowered by a network of small arterial vessels with a large surface area called the rete mirabile, which branches from the two carotid arteries

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