The cheetah (Acinonyx jubatus) is a large feline (family Felidae, subfamily Felinae) inhabiting most of Africa and parts of the Middle East. It is the only extant member of the genus Acinonyx. The cheetah can run faster than any other land animal— as fast as 112 to 120 km/h (70 to 75 mph) in short bursts covering distances up to 500 m (1,600 ft), and has the ability to accelerate from 0 to 100 km/h (62 mph) in three seconds. This cat is also notable for modifications in the species' paws. It is one of the few felids with semi-retractable claws. The word "cheetah" is derived from the Sanskrit word citrakāyaḥ, meaning "variegated", via the Hindi 'चीता' (cītā). The genus name, Acinonyx, means "no-move-claw" in Greek, while the species name, jubatus, means "maned" or "crested" in Latin, a reference to the dorsal crest found in cheetah cubs. The cheetah has unusually low genetic variability. This is accompanied by a very low sperm count, motility, and deformed flagella. Skin grafts between unrelated cheetahs illustrate the former point, in that there is no rejection of the donor skin. It is thought that the species went through a prolonged period of inbreeding following a genetic bottleneck during the last ice age. This suggests that genetic monomorphism did not prevent the cheetah from flourishing across two continents for thousands of years. The cheetah likely evolved in Africa during the Miocene epoch (26 million to 7.5 million years ago), before migrating to Asia. Recent research has placed the last common ancestor of all existing populations as living in Asia 11 million years ago, which may lead to revision and refinement of existing ideas about cheetah evolution. The now-extinct species include: Acinonyx pardinensis (Pliocene epoch), much larger than the modern cheetah and found in Europe, India, and China; Acinonyx intermedius (mid-Pleistocene period), found over the same range. The extinct genus Miracinonyx was extremely cheetah-like, but recent DNA analysis has shown that Miracinonyx inexpectatus, Miracinonyx studeri, and Miracinonyx trumani (early to late Pleistocene epoch), found in North America and called the "North American cheetah" are not true cheetahs, instead being close relatives to the cougar. Although many sources list six or more subspecies of cheetah, the taxonomic status of most of these subspecies is unresolved. Acinonyx rex—the king cheetah—was abandoned as a subspecies after it was discovered that the variation was caused by a single recessive gene. The subspecies Acinonyx jubatus guttatus, the woolly cheetah, may also have been a variation due to a recessive gene. Some of the most commonly recognized subspecies include: Asiatic cheetah (Acinonyx jubatus venaticus): Asia (Afghanistan, India, Iran, Iraq, Israel, Jordan, Oman, Pakistan, Saudi Arabia, Syria, Russia). Current range is in Iran, Pakistan and Afghanistan. Extinct in other Asian countries. Northwest African cheetah (Acinonyx jubatus hecki): Northwest Africa (Algeria, Djibouti, Egypt, Mali, Mauritania, Morocco, Niger, Tunisia) and western Africa (Benin, Burkina Faso, Ghana, Mali, Mauritania, Niger, and Senegal) Acinonyx jubatus raineyii: eastern Africa (Kenya, Somalia, Tanzania, and Uganda) Acinonyx jubatus jubatus: southern Africa (Angola, Botswana, Democratic Republic of the Congo, Mozambique, Malawi, South Africa, Tanzania, Zambia, Zimbabwe and Namibia) Acinonyx jubatus soemmeringii: central Africa (Cameroon, Chad, Central African Republic, Ethiopia, Nigeria, Niger, and Sudan) Acinonyx jubatus velox The cheetah's chest is deep and its waist is narrow. The coarse, short fur of the cheetah is tan with round black spots measuring from 2 to 3 cm (0.79 to 1.2 in) across, affording it some camouflage while hunting. There are no spots on its white underside, but the tail has spots, which merge to form four to six dark rings at the end. The tail usually ends in a bushy white tuft. The cheetah has a small head with high-set eyes. Black "tear marks" running from the corner of its eyes down the sides of the nose to its mouth keep sunlight out of its eyes and aid in hunting and seeing long distances. Its thin and fragile body make it well-suited to short bursts of high speed, but not to long-distance running. Agility, rather than raw speed, accounts for much of the cheetah's ability to catch prey. Cheetahs can accelerate four times as fast as a human (thanks to greater muscle power) and can slow down by 14 kilometers per hour in one stride. They can hunt successfully in dense forests. The adult cheetah weighs from 21 to 72 kg (46 to 160 lb). Its total head-and-body length is from 110 to 150 cm (43 to 59 in), while the tail can measure 60 to 84 cm (24 to 33 in) in length. Cheetahs are 66 to 94 cm (26 to 37 in) tall at the shoulder.

• published: 15 Dec 2013
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