Hot air balloon Dubai calm sky ride

Arabian Desert ٱلصَّحْرَاء ٱلْعَرَبِيَّة
Desert near Sharjah, United Arab Emirates
Map of the Arabian Desert ecoregion
Ecology
Realm	Palearctic
Biome	deserts and xeric shrublands
Borders	List Gulf of Oman desert and semi-desert Mesopotamian shrub desert Middle East steppe North Saharan steppe and woodlands Persian Gulf desert and semi-desert Red Sea Nubo-Sindian tropical desert and semi-desert Tigris-Euphrates alluvial salt marsh
Geography
Area	1,855,470[1] km2 (716,400 mi2)
Countries	List Saudi Arabia Iraq Jordan Kuwait Oman Qatar United Arab Emirates Iran (khuzestan) Yemen Egypt (Sinai)
Conservation
Conservation status	critical/endangered[2]
Protected	4.368%[1]

The Arabian Desert (Arabic: ٱلصَّحْرَاء ٱلْعَرَبِيَّة) is a vast desert wilderness in West Asia that occupies almost the entire Arabian Peninsula with an area of 2,330,000 square kilometers (900,000 sq mi).^[3] It stretches from Yemen to the Persian Gulf and Oman to Jordan and Iraq. It is the fourth largest desert in the world and the largest in Asia. At its center is Ar-Rub' al-Khali (The Empty Quarter), one of the largest continuous bodies of sand in the world. It is an extension of the Sahara Desert.^[4]

Gazelles, oryx, sand cats, and spiny-tailed lizards are just some of the desert-adapted species that survive in this extreme environment, which features everything from red dunes to deadly quicksand. The climate is mostly dry (the major part receives around 100 mm (3.9 in) of rain per year, but some very rare places receive as little as 50 mm), and temperatures oscillate between very high heat and seasonal night time freezes. It is part of the deserts and xeric shrublands biome and lie in biogeographical realms of the Palearctic (northern part) and Afrotropical (southern part).

The Arabian Desert ecoregion has little biodiversity, although a few endemic plants grow here. Many species, such as the striped hyena, jackal and honey badger, have died out as a result of hunting, habitat destruction, overgrazing by livestock, off-road driving, and human encroachment on their habitat. Other species, such as the Arabian sand gazelle, have been successfully re-introduced and are protected at reserves.

The desert lies mostly in Saudi Arabia and covers most of the country. It extends into neighboring southern Iraq, southern Jordan, central Qatar, most of the Abu Dhabi emirate in the United Arab Emirates, western Oman, and northeastern Yemen. The ecoregion also includes most of the Sinai Peninsula in Egypt and the adjacent Negev desert in southern Israel.^[1]

The Rub' al-Khali desert is a sedimentary basin stretching along a south-west to north-east axis across the Arabian Shelf.^[5] At an altitude of 1,000 metres (3,300 ft), rock landscapes yield to the Rub' al-Khali, a vast stretch of sand whose extreme southern point crosses the center of Yemen. The sand overlies gravel or gypsum plains and the dunes reach maximum heights of up to 250 m (820 ft). The sands are predominantly silicates, composed of 80 to 90% quartz and the remainder feldspar, whose iron oxide-coated grains color the sands orange, purple, and red.

A corridor of sandy terrain known as the Ad-Dahna desert connects the An-Nafud desert (65,000 km² or 40,389 square miles) in the north of Saudi Arabia to the Rub' al-Khali in the south-east.^{[citation needed]} The Tuwaiq escarpment is an 800 km (500 mi) arc that includes limestone cliffs, plateaus, and canyons.^{[citation needed]} There are brackish salt flats, including the quicksands of Umm al Samim.^[2] The Sharqiya Sands, formerly known as Wahiba Sands of Oman are an isolated sand sea bordering the east coast.^[6][7]

The Arabian Desert has a subtropical, hot desert climate, similar to the climate of the Sahara Desert (the world's largest hot desert). The Arabian Desert is actually an extension of the Sahara Desert over the Arabian peninsula.

The climate is mainly dry. Most areas get around 100 mm (3.9 in) of rain per year. Unlike the Sahara Desert—more than half of which is hyperarid (having rainfall of less than 50 mm (2.0 in) per year)—the Arabian Desert has only a few hyperarid areas. These rare driest areas may get only 30 to 40 mm (1.6 in) of rain per year.

The Arabian Desert’s sunshine duration index is very high by global standards: between 2,900 hours (66.2% of daylight hours) and 3,600 hours (82.1% of daylight hours), but typically around 3,400 hours (77.6% of daylight hours). Thus clear-sky conditions with plenty of sunshine prevail over the region throughout the year, and cloudy periods are infrequent. Visibility at ground level is relatively low, despite the brightness of the sun and moon, because of dust and humidity.

Temperatures remain high year round. In the summer, in low-lying areas, average high temperatures are generally over 40 °C (104 °F). In extremely low-lying areas, especially along the Persian Gulf (near sea level), summer temperatures can reach 48 °C (118 °F). Average low temperatures in summer are typically over 20 °C (68 °F) and in the south can sometimes exceed 30 °C (86 °F). Record high temperatures above 50 °C (122 °F) have been reached in many areas of the desert, partly because its overall elevation is relatively low. ^{[citation needed]}

The Arabian Desert ecoregion has about 900 species of plants.^[8] The Rub'al-Khali has very limited floristic diversity. There are only 37 plant species, 20 recorded in the main body of the sands and 17 around the outer margins. Of these 37 species, one or two are endemic. Vegetation is very diffuse but fairly evenly distributed, with some interruptions of near sterile dunes.^[2] Some typical plants are Calligonum crinitum on dune slopes, Cornulaca arabica (saltbush), Salsola stocksii (saltbush), and Cyperus conglomeratus. Other widespread species are Dipterygium glaucum, Limeum arabicum, and Zygophyllum mandavillei. Very few trees are found except at the outer margin (typically Acacia ehrenbergiana and Prosopis cineraria). Other species are a woody perennial Calligonum comosum, and annual herbs such as Danthonia forskallii.^[2]

There are 102 native species of mammals.^[8] Native mammals include the Arabian oryx (Oryx leucoryx), sand gazelle (Gazella marica), mountain gazelle (G. gazella), Nubian ibex (Capra nubiana), Arabian wolf (Canis lupus arabs), striped hyaena (Hyaena hyaena), caracal (Caracal caracal), sand cat (Felis margarita), red fox (Vulpes vulpes), and Cape hare (Lepus capensis).^[2] The Asiatic cheetah^[9] and Asiatic lion^[10] used to live in the Arabian Desert. The ecoregion is home to 310 bird species.^[8]

The area is home to several different cultures, languages, and peoples, with Islam as the predominant faith. The major ethnic group in the region is the Arabs, whose primary language is Arabic.

In the center of the desert lies Riyadh, the capital of Saudi Arabia, with more than 7 million inhabitants.^[11] Other large cities, such as Dubai, Abu Dhabi, or Kuwait City, lie on the coast of the Persian Gulf.

Natural resources available in the Arabian Desert include oil, natural gas, phosphates, and sulfur.^{[citation needed]}

Threats to the ecoregion include overgrazing by livestock and feral camels and goats, wildlife poaching, and damage to vegetation by off-road driving.^[2]

The conservation status of the desert is critical/endangered. In the UAE, the sand gazelle and Arabian oryx are threatened, and honey badgers, jackals, and striped hyaenas already extirpated.^[2]

4.37% of the ecoregion is in protected areas.^[1]

Saudi Arabia has established a system of reserves overseen by the National Commission for Wildlife Conservation and Development (NCWCD).^[2]

• Harrat al-Harrah Reserve (12,150 km²), established in 1987, is on the border with Jordan and Iraq, and protects a portion of the stony basaltic Harrat al-Sham desert. The reserve includes rough terrain of black basaltic boulders and extinct volcanic cones from the middle Miocene. It provides habitat to over 250 species of plants, 50 species of birds, and 22 mammal species.^[2]
• 'Uruq Bani Ma'arid Reserve (12,000 km²) is on the western edge of the Rub’ al-Khali. Arabian oryx and sand gazelle were reintroduced to the reserve in 1995.
• Ibex Reserve (200 km²) is south of Riyadh. It protects Nubian ibex and a reintroduced population of mountain gazelle.^[2]
• Al-Tabayq Special Nature Reserve is in northern Saudi Arabia, and protects a population of Nubian ibex.^[2]

Protected areas in the United Arab Emirates include Al Houbara Protected Area (2492.0 km²), Al Ghadha Protected Area (1087.51 km²), Arabian Oryx Protected Area (5974.47 km²), Ramlah Protected Area (544.44 km²), and Al Beda'a Protected Area (417.0 km²).^[12]

• ʿĀd
• Iram of the Pillars

Wikimedia Commons has media related to Arabian Desert.

• "Arabian Desert". Terrestrial Ecoregions. World Wildlife Fund.
• Arabian Desert (DOPA)
• [2]^{[permanent dead link]}

Camel Temporal range: Pliocene–Recent[1] PreꞒ Ꞓ O S D C P T J K Pg N   ↓
Dromedary (Camelus dromedarius)
Bactrian camel (Camelus bactrianus)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Family:	Camelidae
Tribe:	Camelini
Genus:	Camelus Linnaeus, 1758
Type species
Camelus dromedarius [6] Linnaeus, 1758
Species
Camelus bactrianus Camelus dromedarius Camelus ferus †Camelus grattardi (fossil)[2] †Camelus knoblochi (fossil)[3] †Syrian camel (fossil) †Camelus sivalensis (fossil)[4] †Camelus thomasi (fossil)[5]
Distribution of camels worldwide
Synonyms
List Camellus Molina, 1782 Dromedarius Gloger, 1841

A camel (from Latin: camelus and Ancient Greek: κάμηλος (kamēlos) from Ancient Semitic: gāmāl^[7][8]) is an even-toed ungulate in the genus Camelus that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provide food (camel milk and meat) and textiles (fiber and felt from camel hair). Camels are working animals especially suited to their desert habitat and are a vital means of transport for passengers and cargo. There are three surviving species of camel. The one-humped dromedary makes up 94% of the world's camel population, and the two-humped Bactrian camel makes up 6%. The wild Bactrian camel is a distinct species that is not ancestral to the domestic Bactrian camel, and is now critically endangered, with fewer than 1,000 individuals.

The word camel is also used informally in a wider sense, where the more correct term is "camelid", to include all seven species of the family Camelidae: the true camels (the above three species), along with the "New World" camelids: the llama, the alpaca, the guanaco, and the vicuña, which belong to the separate tribe Lamini.^[9] Camelids originated in North America during the Eocene, with the ancestor of modern camels, Paracamelus, migrating across the Bering land bridge into Asia during the late Miocene, around 6 million years ago.

Three species are extant:^[10][11]

Genus Camelus – Linnaeus, 1758 – nine species

Common name	Scientific name and subspecies	Range	Size and ecology	IUCN status and estimated population
Bactrian camel	Camelus bactrianus Linnaeus, 1758	Domesticated; Central Asia, including the historical region of Bactria and Turkey.	Size: Habitat: Diet:	NE  Unknown
Dromedary / Arabian camel	Camelus dromedarius Linnaeus, 1758	Domesticated; the Middle East, Sahara Desert, and South Asia; introduced to Australia	Size: Habitat: Diet:	NE  Unknown
Wild Bactrian camel	Camelus ferus Przewalski, 1878	Remote areas of northwest China and Mongolia	Size: Habitat: Diet:	EN  Unknown

The average life expectancy of a camel is 40 to 50 years.^[12] A full-grown adult dromedary camel stands 1.85 m (6 ft 1 in) at the shoulder and 2.15 m (7 ft 1 in) at the hump.^[13] Bactrian camels can be a foot taller. Camels can run at up to 65 km/h (40 mph) in short bursts and sustain speeds of up to 40 km/h (25 mph).^[14] Bactrian camels weigh 300 to 1,000 kg (660 to 2,200 lb) and dromedaries 300 to 600 kg (660 to 1,320 lb). The widening toes on a camel's hoof provide supplemental grip for varying soil sediments.^[15]

The male dromedary camel has an organ called a dulla in his throat, a large, inflatable sac that he extrudes from his mouth when in rut to assert dominance and attract females. It resembles a long, swollen, pink tongue hanging out of the side of the camel's mouth.^[16] Camels mate by having both male and female sitting on the ground, with the male mounting from behind.^[17] The male usually ejaculates three or four times within a single mating session.^[18] Camelids are the only ungulates to mate in a sitting position.^[19]

It is a common myth that a camel stores water in its hump,^[20] but the humps in fact are reservoirs of fatty tissue, which can be used as a reserve source of calories, not water. When this tissue is metabolized, it yields a greater mass of water than that of the fat processed. This fat metabolization, while releasing energy, causes water to evaporate from the lungs during respiration (as oxygen is required for the metabolic process): overall, there is a net decrease in water.^[21][22]

Camels have a series of physiological adaptations that allow them to withstand long periods of time without any external source of water.^[24] The dromedary camel can drink as seldom as once every 10 days even under very hot conditions, and can lose up to 30% of its body mass due to dehydration.^[25] They can drink as much as 30 imperial gallons (140 litres) at a time^[26] but this is stored in the animal's bloodstream, not, as popularly believed, in its humps.^[20]

Unlike other mammals, camels' red blood cells are oval rather than circular in shape. This facilitates the flow of red blood cells during dehydration^[27] and makes them better at withstanding high osmotic variation without rupturing when drinking large amounts of water.^[28][29]

Camels are able to withstand changes in body temperature and water consumption that would kill most other mammals. Their temperature ranges from 34 °C (93 °F) at dawn and steadily increases to 40 °C (104 °F) by sunset, before they cool off at night again.^[24] In general, to compare between camels and the other livestock, camels lose only 1.3 liters of fluid intake every day while the other livestock lose 20 to 40 liters per day.^[30] Maintaining the brain temperature within certain limits is critical for animals; to assist this, camels have a rete mirabile, a complex of arteries and veins lying very close to each other which utilizes countercurrent blood flow to cool blood flowing to the brain.^[31] Camels rarely sweat, even when ambient temperatures reach 49 °C (120 °F).^[32] Any sweat that does occur evaporates at the skin level rather than at the surface of their coat; the heat of vaporization therefore comes from body heat rather than ambient heat. Camels can withstand losing 25% of their body weight in water, whereas most other mammals can withstand only about 12–14% dehydration before cardiac failure results from circulatory disturbance.^[29]

When the camel exhales, water vapor becomes trapped in their nostrils and is reabsorbed into the body as a means to conserve water.^[33] Camels eating green herbage can ingest sufficient moisture in milder conditions to maintain their bodies' hydrated state without the need for drinking.^[34]

Camels have three-chambered stomachs and perform rumination as part of their digestive process, even though they are not part of the ruminant sub-order.^[35]

The camel's thick coat insulates it from the intense heat radiated from desert sand; a shorn camel must sweat 50% more to avoid overheating.^[36] During the summer the coat becomes lighter in color, reflecting light as well as helping avoid sunburn.^[29] The camel's long legs help by keeping its body farther from the ground, which can heat up to 70 °C (158 °F).^[37][38] Dromedaries have a pad of thick tissue over the sternum called the pedestal. When the animal lies down in a sternal recumbent position, the pedestal raises the body from the hot surface and allows cooling air to pass under the body.^[31]

Camels' mouths have a thick leathery lining, allowing them to chew thorny desert plants. Long eyelashes and ear hairs, together with nostrils that can close, form a barrier against sand. If sand gets lodged in their eyes, they can dislodge it using their translucent third eyelid (also known as the nictitating membrane). The camels' gait and widened feet help them move without sinking into the sand.^[37][39]

The kidneys and intestines of a camel are very efficient at reabsorbing water. Camels' kidneys have a 1:4 cortex to medulla ratio.^[40] Thus, the medullary part of a camel's kidney occupies twice as much area as a cow's kidney. Secondly, renal corpuscles have a smaller diameter, which reduces surface area for filtration. These two major anatomical characteristics enable camels to conserve water and limit the volume of urine in extreme desert conditions.^[41] Camel urine comes out as a thick syrup, and camel faeces are so dry that they do not require drying when used to fuel fires.^{[42][43][44][45]}

The camel immune system differs from those of other mammals. Normally, the Y-shaped antibody molecules consist of two heavy (or long) chains along the length of the Y, and two light (or short) chains at each tip of the Y.^[46] Camels, in addition to these, also have antibodies made of only two heavy chains, a trait that makes them smaller and more durable.^[46] These "heavy-chain-only" antibodies, discovered in 1993, are thought to have developed 50 million years ago, after camelids split from ruminants and pigs.^[46]

The parasite Trypanosoma evansi causes the disease surra in camels.^[47]: 2

The karyotypes of different camelid species have been studied earlier by many groups,^{[48][49][50][51][52][53]} but no agreement on chromosome nomenclature of camelids has been reached. A 2007 study flow sorted camel chromosomes, building on the fact that camels have 37 pairs of chromosomes (2n=74), and found that the karyotype consisted of one metacentric, three submetacentric, and 32 acrocentric autosomes. The Y is a small metacentric chromosome, while the X is a large metacentric chromosome.^[54]

The hybrid camel, a hybrid between Bactrian and dromedary camels, has one hump, though it has an indentation 4–12 cm (1.6–4.7 in) deep that divides the front from the back. The hybrid is 2.15 m (7 ft 1 in) at the shoulder and 2.32 m (7 ft 7 in) tall at the hump. It weighs an average of 650 kg (1,430 lb) and can carry around 400 to 450 kg (880 to 990 lb), which is more than either the dromedary or Bactrian can.^[55]

According to molecular data, the wild Bactrian camel (C. ferus) separated from the domestic Bactrian camel (C. bactrianus) about 1 million years ago.^[56][57] New World and Old World camelids diverged about 11 million years ago.^[58] In spite of this, these species can hybridize and produce viable offspring.^[59] The cama is a camel-llama hybrid bred by scientists to see how closely related the parent species are.^[60] Scientists collected semen from a camel via an artificial vagina and inseminated a llama after stimulating ovulation with gonadotrophin injections.^[61] The cama is halfway in size between a camel and a llama and lacks a hump. It has ears intermediate between those of camels and llamas, longer legs than the llama, and partially cloven hooves.^[62][63] Like the mule, camas are sterile, despite both parents having the same number of chromosomes.^[61]

The earliest known camel, called Protylopus, lived in North America 40 to 50 million years ago (during the Eocene).^[18] It was about the size of a rabbit and lived in the open woodlands of what is now South Dakota.^[64][65] By 35 million years ago, the Poebrotherium was the size of a goat and had many more traits similar to camels and llamas.^[66][67] The hoofed Stenomylus, which walked on the tips of its toes, also existed around this time, and the long-necked Aepycamelus evolved in the Miocene.^[68] The split between the tribes Camelini, which contains modern camels and Lamini, modern llamas, alpacas, vicuñas, and guanacos, is estimated to have occurred over 16 million years ago.^[69]

The ancestor of modern camels, Paracamelus, migrated into Eurasia from North America via Beringia during the late Miocene, between 7.5 and 6.5 million years ago.^[70][71][72] During the Pleistocene, around 3 to 1 million years ago, the North American Camelidae spread to South America as part of the Great American Interchange via the newly formed Isthmus of Panama, where they gave rise to guanacos and related animals.^[18][64][65] Populations of Paracamelus continued to exist in the North American Arctic into the Early Pleistocene.^[71][73] This creature is estimated to have stood around nine feet (2.7 metres) tall. The Bactrian camel diverged from the dromedary about 1 million years ago, according to the fossil record.^[74]

The last camel native to North America was Camelops hesternus, which vanished along with horses, short-faced bears, mammoths and mastodons, ground sloths, sabertooth cats, and many other megafauna as part of the Quaternary extinction event, coinciding with the migration of humans from Asia at the end of the Pleistocene, around 13–11,000 years ago.^[75][76]

An extinct giant camel species, Camelus knoblochi roamed Asia during the Late Pleistocene, before becoming extinct around 20,000 years ago.^[77]

• 
  Stenomylus illustration
• 
  Stenomylus skeleton
• 
  Poebrotherium skeleton
• 
  Procamelus skull
• 
  Camelops hesternus, the last true camel native to North America

Like horses, camels originated in North America and eventually spread across Beringia to Asia. They survived in the Old World, and eventually humans domesticated them and spread them globally. Along with many other megafauna in North America, the original wild camels were wiped out during the spread of the first indigenous peoples of the Americas from Asia into North America, 10 to 12,000 years ago; although fossils have never been associated with definitive evidence of hunting.^[75][76]

Most camels surviving today are domesticated.^[45][78] Although feral populations exist in Australia, India and Kazakhstan, wild camels survive only in the wild Bactrian camel population of the Gobi Desert.^[12]

When humans first domesticated camels is disputed. Dromedaries may have first been domesticated by humans in Somalia or South Arabia sometime during the 3rd millennium BC, the Bactrian in central Asia around 2,500 BC,^{[18][79][80][81]} as at Shar-i Sokhta (also known as the Burnt City), Iran.^[82] A study from 2016, which genotyped and used world-wide sequencing of modern and ancient mitochondrial DNA (mtDNA), suggested that they were initially domesticated in the southeast Arabian Peninsula,^[83] with the Bactrian type later being domesticated around Central Asia.^[84]

Martin Heide's 2010 work on the domestication of the camel tentatively concludes that humans had domesticated the Bactrian camel by at least the middle of the third millennium somewhere east of the Zagros Mountains, with the practice then moving into Mesopotamia. Heide suggests that mentions of camels "in the patriarchal narratives may refer, at least in some places, to the Bactrian camel", while noting that the camel is not mentioned in relationship to Canaan.^[85] Heide and Joris Peters reasserted that conclusion in their 2021 study on the subject.^[86]

In 2009–2013, excavations in the Timna Valley by Lidar Sapir-Hen and Erez Ben-Yosef discovered what may be the earliest domestic camel bones yet found in Israel or even outside the Arabian Peninsula, dating to around 930 BC. This garnered considerable media coverage, as it is strong evidence that the stories of Abraham, Jacob, Esau, and Joseph were written after this time.^[87][88]

The existence of camels in Mesopotamia and Arabia but not in Syria is not a new idea. The historian Richard Bulliet thought that although camels were occasionally mentioned in the Bible, this didn't mean that the domestic camels were common in the Holy Land at that time.^[89] The archaeologist William F. Albright, writing even earlier, saw camels in the Bible as an anachronism.^[90]

The official report by Sapir-Hen and Ben-Joseph says:

The introduction of the dromedary camel (Camelus dromedarius) as a pack animal to the southern Levant ... substantially facilitated trade across the vast deserts of Arabia, promoting both economic and social change (e.g., Kohler 1984; Borowski 1998: 112–116; Jasmin 2005). This ... has generated extensive discussion regarding the date of the earliest domestic camel in the southern Levant (and beyond) (e.g., Albright 1949: 207; Epstein 1971: 558–584; Bulliet 1975; Zarins 1989; Köhler-Rollefson 1993; Uerpmann and Uerpmann 2002; Jasmin 2005; 2006; Heide 2010; Rosen and Saidel 2010; Grigson 2012). Most scholars today agree that the dromedary was exploited as a pack animal sometime in the early Iron Age (not before the 12th century [BC])

and concludes:

Current data from copper smelting sites of the Arabah Valley enable us to pinpoint the introduction of domestic camels to the southern Levant more precisely based on stratigraphic contexts associated with an extensive suite of radiocarbon dates. The data indicate that this event occurred not earlier than the last third of the 10th century [BC] and most probably during this time. The coincidence of this event with a major reorganization of the copper industry of the region—attributed to the results of the campaign of Pharaoh Shoshenq I—raises the possibility that the two were connected, and that camels were introduced as part of the efforts to improve efficiency by facilitating trade.^[88]

• 
  A camel serving as a draft animal in Pakistan (2009)
• 
  A camel in a ceremonial procession, its rider playing kettledrums, Mughal Empire (c. 1840)
• 
  Petroglyph of a camel, Negev, southern Israel (prior to c. 5300 BC)
• 
  Joseph Sells Grain by Bartholomeus Breenbergh (1655), showing camel with rider at left