Scimitar Horned Oryx

The scimitar oryx (''Oryx dammah''), also known as the scimitar-horned oryx and the Sahara oryx, is a ''Oryx'' species that was once widespread across North Africa. In 2000, it was declared extinct in the wild on the IUCN Red List.

A captive bred group was released into an acclimation enclosure within the Ouadi Rimé-Ouadi Achim Faunal Reserve in 2016, then reintroduced into the wild. An additional 21 individuals were released into the acclimation enclosure in 2017. The first ones to be relocated were released into the wild in 2016 and have adapted well to their surroundings. In 2017, another herd of 75 scimitar-horned oryxes arrived in an operation led by Chad's Ministry of Environment and Fisheries and the Sahara Conservation Fund. In 2021, 60 new calves were born, bringing the number in the wild to about 400. This particular oryx can survive for months or even years without drinking water. A grazing animal, it derives most of its daily moisture intake from plants.

The scimitar oryx has a long taxonomic history since its scientific description in 1816 by Lorenz Oken, who named it ''Oryx algazel''. This antelope stands a little more than at the shoulder. The males weigh and the females weigh . The coat is white with a red-brown chest and black markings on the forehead and down the length of the nose. The calves are born with a yellow coat without distinguishing marks; their coats change to adult coloration at 3–12 months old.

The scimitar oryx formed herds of mixed sexes of up to 70 members, usually guided by the bulls. They inhabited semideserts and deserts and were adapted to live in extreme heat, with their efficient cooling mechanism and very low requirement of water. Scimitar oryx feed on foliage, grasses, succulent plants, and plant parts during the night or early morning. Births peak between March and October. After a gestation of 8-9 months, one calf is born. Soon after, the female has a postpartum estrus.

The decline of the scimitar oryx population began as a result of climate change during the Neolithic period, and later it was hunted extensively for its horns. Today, it is bred in captivity in special reserves in Tunisia, Morocco, and Senegal, and on private exotic animal ranches in the Texas Hill Country. In 2016, a reintroduction program was launched and currently a small herd has been successfully reintroduced in Chad.

The scimitar oryx was domesticated in Ancient Egypt and is believed to have been used as food and sacrificed as offerings to gods. Wealthy people in Ancient Rome also bred them. The use of their valuable hides began in the Middle Ages. The unicorn myth may have originated from sightings of a scimitar oryx with a broken horn.

The scimitar oryx was the emblem of the ancient Egyptian Oryx nome and today is the animal symbol of the Sahara Conservation Fund.

Taxonomy and naming

The scimitar oryx is a member of the genus ''Oryx'' and the family Bovidae. German naturalist Lorenz Oken first described it in 1816, naming it ''Oryx algazel''. The nomenclature has undergone various changes since then, with the introduction of names such as ''Oryx tao'', ''O. leucoryx'', ''O. damma'', ''O. dammah'', ''O. bezoarticus'', and ''O. ensicornis''. In 1826, Philipp Jakob Cretzschmar used the name ''Oryx ammah'' for the species. A year later, the name ''Oryx leucoryx'' came into use, but as this was a synonym of the Arabian oryx (then called ''Oryx beatrix''), it was abandoned, and ''Oryx algazel'' was accepted once more. Over 100 years later in 1951, Sir John Ellerman and Terence Morrison-Scott found that the name ''Oryx algazel'' was also ineligible for use. Finally, in January 1956, the International Trust for Zoological Nomenclature accepted ''Oryx dammah'' as the scientific name. No more changes have been made since then, though many papers published after 1956 created confusion by using names such as ''O. gazella tao''.

Its scientific name, ''Oryx dammah'', is derived from: Ancient Greek ('), meaning a gazelle or antelope (originally a pickaxe); Latin ' (fallow deer or antelope); and Arabic ' (sheep). The scimitar oryx is named for its horns, which resemble scimitars. Its common name in English is "scimitar-horned oryx", or simply "scimitar oryx".

Genetics and evolution

The scimitar oryx has 58 chromosomes - one pair of large submetacentric autosomes and 27 acrocentric autosomal pairs. The X and Y chromosomes are the largest and smallest acrocentrics. The first molecular study of this species (published in 2007) observed genetic diversity among European, North American, and some other captive groups. Divergence was found within the mitochondrial DNA haplotypes, and was estimated to have taken place between 2.1 and 2.7 million years ago. Population increases occurred about 1.2 and 0.5 million years ago.

In another study, intended to note genetic differences between ''Oryx'' species, karyotypes of ''Oryx'' species and subspecies – namely '' O. gazella'', '' O. b. beisa'', '' O. b. callotis'', ''O. dammah'', and '' O. leucoryx'' – were compared with the standard karyotype of ''Bos taurus''. The number of autosomes in all karyotypes was 58. The X and Y chromosomes were conserved in all five species.

Physical description

The scimitar oryx is a straight-horned antelope that stands just over at the shoulder. The males weigh and the females . The body measures from the head to the base of the tail. The tail is long and ends with a tuft. They are sexually dimorphic with males being larger than females.

Its coat is white with a red-brown chest and black markings on the forehead and down the length of the nose. The coat reflects the sun's rays, while the black portions and the tip of the tongue provide protection against sunburn. The white coat helps to reflect the heat of the desert. Calves are born with yellow coats and lack distinguishing marks, which appear later in life. Their pelage changes to adult coloration at 3–12 months old.

Both male and female oryxes have horns, with the females' being more slender. The horns are long, thin, and symmetrical, and curve backward (a distinctive feature of this species); they can reach in both sexes. The hollow walls of the horns are so thin that they can easily break. The female's udder has four teats. The large, spreading hooves are well adapted to allow these antelopes to walk on the sand of their dry habitats. A scimitar oryx can live as long as 20 years. At Smithsonian National Zoo, a female oryx died at 21, an exceptional age since females generally have a lifespan of about 15 years.

Diseases and parasites

The scimitar oryx can be infected with cryptosporidiosis, a parasitic disease caused by protozoan parasites of the genus ''Cryptosporidium'' in the phylum Apicomplexa. A study in 2004 revealed that '' C. parvum'' or similar organisms infected 155 mammal species, including the scimitar oryx. An analysis in 2005 found ''Cryptosporidium'' parasites in stool samples from 100 mammals, including the scimitar oryx. Oocysts of a new parasite, ''Eimeria oryxae'', have been discovered in the feces of a scimitar oryx from Zoo Garden in Riyadh. In France, '' Streptococcus uberis'' was isolated for the first time in an oryx. It had caused vegetative endocarditis in the animal, leading to fatal congestive heart failure.

Ecology and behavior

The scimitar oryx was a very sociable animal and traveled in herds of two to 40 individuals, generally, led by a dominant bull. This species once gathered in groups of several thousand for migration. During the wet season, they migrated north into the Sahara. Scimitar oryx are diurnal. In the cool early mornings and evenings, they rest under trees and shrubs, or if neither is available, they dig depressions in the soil with their hooves and rest there. Males fight often, but not for long and not violently. Predators, such as lions, leopards, hyenas, cheetahs, golden jackals, vultures, and Cape hunting dogs, mostly kill weak and young oryx.

Adaptations

With a metabolism that functions at the high temperatures prevalent in their habitats, scimitar oryxes need less water for evaporation to help conduct heat away from the body, enabling them to go for long periods without water. They can allow their body temperatures to rise to almost before beginning to perspire. In times of ample supply, oryx can use fluid loss through urination and feces to lower their body temperatures to below at night, giving more time before reaching maximum body temperature the following day. They can tolerate high temperatures that would be lethal to most mammals. They have a network of fine blood vessels that carries blood from the heart to the brain, passing close to the nasal passage, thus allowing the blood to cool by up to before reaching the brain, which is one of the more heat-sensitive organs of the body.

Diet

The habitat of the scimitar oryx in the wild was steppe and desert, where they ate foliage, grass, herbs, shrubs, succulent plants, legumes, juicy roots, buds, and fruit. They can survive without water for 9-10 months because their kidneys prevent water loss from urination – an adaptation to desert habitats. They can get water from water-rich plants such as the wild melon (''Citrullus colocynthis'') and ''Indigofera oblongifolia'' and from the leafless twigs of ''Capparis decidua''. In the night or early morning, they often search for plants such as ''Indigofera colutea'', which produce a hygroscopic secretion that fulfills water requirements. They eat tuft grasses such as ''Cymbopogon schoenanthus'' after rains, but they normally prefer more palatable grasses, such as '' Cenchrus biflorus'', ''Panicum laetum'', and '' Dactyloctenium aegyptium''. When the dry season begins, they feed on the seedpods of ''Acacia raddiana'', and during the dry season, they rely on perennial grasses of genera such as ''Panicum'' (especially ''Panicum turgidum'') and ''Aristida'', and browse plants such as '' Leptadenia'' species, ''Cassia italica'', and ''Cornulaca monacantha''.

Reproduction

Both males and females reach sexual maturity at 18-24 months of age. Births peak between March and October. Mating frequency is greater when environmental conditions are favorable. In zoos, males are sexually most active in autumn. The estrous cycle lasts roughly 24 days, and females experience an anovulatory period in spring. Periods between births are less than 332 days, showing that the scimitar oryx is polyestrous.

Courting is done by means of a mating circle; the male and female stand parallel to one another, facing in opposite directions, and then circle around each other until the female allows the male to mount from behind. If the female is not ready to mate, she runs away and circles in the reverse direction. Pregnant females leave the herd for a week, give birth to the calf, and mate again during their postpartum estrus; thus, they can produce one calf a year. Gestation lasts about nine months, after which a single calf is born, weighing . Twin births are very rare - only 0.7% of the births observed in one study. Both mother and calf return to the main herd within hours of the birth. The female separates herself from the herd for a few hours while she nurses the calf. Weaning starts at 3.5 months, and the young become fully independent around 14 weeks old.

Habitat and distribution

The scimitar oryx once inhabited grassy steppes, semideserts and deserts in a narrow strip of central north Africa (Niger

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