The Arabian Oryx – Oryx leucoryx
The Arabian Oryx – Oryx leucoryx
by Gerhard Damm
Arabian Oryx (Oryx leucoryx)
The scientific name of Oryx leucoryx was given by Pallas in 1777. After Lichtenstein had transferred the term leucoryx to the scimitar-horned oryx (now Oryx dammah) in 1826, the Arabian Oryx was named Oryx beatrix in 1857. In 1903, Oldfield Thomas renamed the scimitar-horned oryx 'Algazal' and the Arabian oryx received its original name Oryx leucoryx back. The name beatrix persisted for many years, but it is also known as asiatica, latipes, pallasii. The confusion between the scimitar-horned oryx and the Arabian oryx is reinforced by the fact that they both carried the name "white oryx". In Arabic Oryx leucoryx is called Maha, Wudhaihi, Baqar al Wash or Boosolah.
The smallest of the genus Oryx (female oryx weigh about 80kg and males about 90kg; occasionally males reach 100kg), the Arabian oryx is a muscular and compact antelope with a barrel-like body and spaced legs giving it a fast stable horse-like gait. Its reflective pelage is basically white with dark markings on face and there is often a dark stripe that runs under the neck to the forelegs. The lower limbs are a chocolate brown to black. The face and nose have dark patches which are lighter and often absent in summer. Dark markings also occur at the horn bases, median chest, front of legs and tail tip. The flank stripe is absent or only an indistinct smudge.
The large hooves are splayed and shovel-like, an adaptation for walking on loose sandy soils. The level of sexual dimorphism is very slight. Males and females present almost identical silhouettes although the males have a larger neck. Both sexes carry long horns about 0.530-0.810 m from anterior base to tip in adults, straight or slightly curved backwards, almost circular in section, and annulated proximally. Females' horns are usually thinner at the base than those of the males.
Arabian Oryx probably can reach a maximum age of about 20 years with good grazing, however under drought conditions this is greatly reduced. Male oryx are unlikely to start breeding until at least 3 years. Under good conditions, females older than 2 years give birth to a uniformly brown calf once a year after a gestation period of nine months. They usually move away from the herd for calving. During the calf’s month-long lying-out phase its activities are minimal. At this time the female is usually consorted by the dominant herd male. This consort behavior seems to be unique in the Arabian oryx. As soon as a lying calf rises to approach its mother, the male immediately takes up a position a few meters behind the calf and, with his head low to the ground he growls and directs it straight to its mother. When suckling is complete, the trio moves off, invariably with the female leading and the male again herding the calf after her. Often, the male apparently 'decides' when the calf should lie again, for he gently knocks it flat with the base of his horns. When the female turns and attempts to return to the sprawled calf, the male drives her away. Both may then stand 30 m away, watching while the calf rises and wanders off to a suitable lying place. Thus, both adults know the calf's lying-out site, and stare at intervals in its direction as they move away 1 km or more over the hours that the calf lies. The behavior of the male might not be as altruistic as it appears, since female oryx have a post-partum oestrus and thus can become pregnant within 10 days of giving birth.
The Arabian Oryx is perfectly adapted to withstand an inhospitable climate and barren landscape; its skin, coat texture and color and behavior are all finely tuned. Most of the adaptations are concerned with the conservation of body water.
Oryx eats mainly desert grasses; herbs, seedpods, fruit, fresh growth of trees, tubers and roots also form part of its diet. The feeding strategy of the oryx is flexible and depends on climatic conditions, plant availability and habitat. It has evolved the ability to survive for years without drinking and has the lowest mass-specific water turn-over rate (about four times lower than the camel). It can cover its daily water requirements with the preformed water of the ingested forage and early morning dew licking (86%) and the metabolic water produced (14%).
Since rainfall is largely unpredictable, both in terms of time (when it will fall) and space (where it may fall) the oryx must be able to move to those areas where rain has fallen in order to take advantage of the best possible grazing. Herds are usually led to new grazing by the dominant female. The territorial male may not move, but prefer to hold his own territory and await females that pass through his area. Typically about 70% of all oryx will find fresh grazing within 28 days of rainfall. The species is adapted for walking great distances and incidents where animals covered around 100km in 24 hours have been reported. This endurance when walking enables oryx to move between widely spaced pastures. The Arabian oryx ruminates when on the move across barren areas, rather than delaying this activity to rest periods. Periods of rumination and walking alternate rapidly with taking a few mouthfuls of isolated grass clumps.
The small nomadic herds contain all age groups and both sexes probably stay together for a considerable time. Ranges in excess of 2,000 km² have been recorded in Oman and of 1,700 km² in Saudi Arabia. This may decrease to less than 300 km² after rainfall or in the heat of summer. Oryx migrating towards rainfall might congregate to herds of 30 or more, but in drought it is rare to see a herd of more than five oryx. Oryx are very compatible with one another - the low frequency of aggressive inter- actions allows animals to share scattered shade trees under which they may spend 8 of the daylight hours in the summer heat.
In the 4 hottest months of the year daytime temperatures usually exceed the body temperature of the oryx, which is usually about 39o C, leading to potential heat stress. However, the oryx have evolved a range of strategies to maintain heat balance and conserve water. The summer coat of the oryx is short, sparse and very white – reflecting solar radiation. They spend the day mostly completely inactive in the shade of desert trees thereby avoiding direct sunlight and conducting body heat into the ground to reduce water loss from evaporation. To rest it digs shallow depressions in soft ground under trees and shrubs. If a cloud shadow passes over a shading herd, all may start grazing in the open almost immediately. Normally, they forage at night and select water-rich food species. Conversely in the cold winter months the oryx shelter from the cold night winds and feed by day. Then the hair of the oryx may pilo-erect allowing the warm solar radiation to reach the black skin under the white fur.
Against the sun, the oryx can be invisible at 100m because of glare and lack of reflection. When an oryx moves into shade, particularly if dappled, it is also very hard to see. The 'white' light due to prevailing atmospheric dust and heat shimmer reduces visibility and definition. Yet with the sun behind an observer and with the animal in the open, the white coat makes it clearly visible to the unaided human eye up to 3 km. Oryx take advantage of this conspicuousness when searching for a herd by standing motionless on prominent ridges to advertise themselves.
Shading oryx are most reluctant to leave shade. This reluctance is probably a response to potentially fatal problems of thermoregulation if an oryx has to run in the sun. Its flight when chased is slow and cumbersome and in open country the oryx can be chased by vehicle and caught surprisingly quickly. Running plays no part in normal social life and interactions, and the oryx cannot change quickly from walking to running, neither does it display much stamina.
In centuries past, images of the oryx probably gave rise to its more famous mythical counterpart -- the unicorn. A side view of the oryx, seen from a distance, would seem to strengthen this legend, as the two finely curved horns then seem to merge into one. For the hunters of old, the oryx proved difficult to track in the vast, empty desert landscape. Oryx meat was particularly prized, as it was believed to possess medicinal properties, but every part of the animal, including horns, fat, skin and blood, served a useful purpose.
Around 1800 the Arabian oryx was thought to have occurred over most of the Arabian Peninsula. It inhabited sandy areas and the gravel plains surrounding them, but did not occur in the mountains. The cores of its distribution seem to have been the Great Nafud desert in the North and the southern Rub' al-Khali. In the north, oryx may have ranged as far as the Euphrates River and the Syrian Desert. It is unlikely that the oryx ever occurred east of the Euphrates. In the south, the oryx inhabited the vast Rub' al-Khali (aka Empty Quarter) sand sea and gravel plains in Saudi Arabia and extended into the UAE, Yemen, Oman. Both ranges were connected by the ad-Dahna, the narrow sand desert stretching from the Nafud to the Rub' al-Khali.
By the 1900's, the distribution of oryx had already severely contracted and was largely restricted to the remote and inaccessible places like Nafud, ad-Dahna and Rub' al-Khali. In the 1930s, the northern and southern populations were no longer linked. Oryx were also probably eliminated from the northwestern and northeastern edges of the Empty Quarter by then. Around 1950, the northern population became extinct, as did the population of the western end of the Rub' al-Khali. Thereafter oryx remained only around the southern and south-eastern margins of the Rub' al-Khali from Yemen to Oman, but reduction in their range continued from both ends. By the early 1960s, no oryx survived west of 51ºE, remaining only on the Eastern Aden Protectorate-Oman border; in Dhofar, especially in the foothills of Jabal Qara; and in the Jiddat al-Harrasis, where the last wild oryx are believed to have been killed in 1972. With the flow of oil revenue to Saudi Arabia in the second half of the 20th century, pressures on oryx populations had increased dramatically and hunters with automatic weapons and using motorized fleets heavily persecuted them for trophies and meat. The Arabian oryx probably disappeared from Saudi Arabia in the 1960-70s
Lee Talbot reported in 1960 in his book 'A Look at Threatened Species' that Arabian Oryx appeared to be extinct in all parts of its former range along the southern edge of the Rub' alKhali. He believed that the few hundred animals that might still exist would be exterminated within the next few years and recommended that a captive breeding program be initiated. In the Eastern Aden Protectorate the 'Operation Oryx' caught three males and one female in 1962 (a male died after capture) and the animals were quarantined in Kenya. In 1963 these three animals together with two females (from the Zoological Society of London and the ruler of Kuwait respectively) were brought to Phoenix Zoo in Arizona, followed in 1964 by two pairs given by HRH King Saud to form a 'World Herd'. The herd grew steadily to reach around 100 by 1977. Form then onwards some Arabian oryx were returned to the Middle East; 10 went to Jordan between 1978 and 1990, 12 to Israel between 1978 and 1992, 35 to Oman between 1980 and 1995, 55 to Saudi Arabia between 1982 and 1992 and 18 to the UAE between 1983 and 1987 (16 to Abu Dhabi and 2 to Dubai).
In June 1982 the first 10 oryx were released to the wild in the Jiddat al-Harasis in Oman. A second release followed in 1984. The population grew steadily and by October 1995 there were about 280 oryx in the wild. However in 1996 oryx were poached or captured and smuggled out of Oman for sale to middle east private collectors. Despite that, the population continued to increase and by October 1996 was estimated to be just over 400. As poaching intensified in 1997 and 1998, the wild population collapsed to 138 animals and a captive herd was formed. In 2003 the wild population in Oman stood at 106, albeit seriously biased with 100 males and 6 females In 1995 Saudi Arabia established a second free-ranging population in the 5,500 km2 Uruq Bani Ma'arid protected area. Together with the 500 oryx in 2,900 km Mahazat as-Sayd PA, the Saudi oryx population is probably the only viable wild population. In that year Bahrain counted 15 and Israel 65 wild Arabian Oryx. The market for wild caught oryx, particularly females, is nowhere near saturated and the problems of illegal capture, smuggling and sale have not been solved, so a 20% decline over the next five years is a conservative estimate justifying the EN C1 listing.
IUCN Red List Status: EN C1 - CITES Appendix 1
The present wild populations of Arabian Oryx are strictly protected – it may not be hunted in the wild, although hunting opportunities exist on introduced Arabian Oryx on game ranches in North America and South Africa.
Rowland Ward Records of Big Game list nine specimens; the longest horn on record measures 27 ¼ inch with a 4 ¼ inch base diameter. This specimen dates from 1913 from Tebuk in Saudi Arabia. The latest specimens registered in RW date from 1934 – all entries originate from Arabia, although the exact locations are mostly unspecified. RW does not have a category for introduced Arabian Oryx.
The Record Book of Safari Club International (SCI) lists only animals from introduced captive populations outside the original range and has two categories – one for “North American Introduced” and one for “African Introduced”.