Giraffe

The giraffe (Giraffa camelopardalis) is an African even-toed ungulate mammal, the tallest of all land-living animal species, and the largest ruminant. It is covered in large, irregular patches of yellow to black fur separated by white, off-white, or dark yellowish brown background. The average mass for an adult male giraffe is 1,191 kilograms (2,630 lb) while the average mass for an adult female is 828 kilograms (1,830 lb). It is approximately 4.3 metres (14 ft) to 5.2 metres (17 ft) tall, although the tallest male recorded stood almost 6 metres (20 ft).

The giraffe is related to deer and cattle, but is placed in a separate family, the Giraffidae, consisting of only the giraffe and its closest relative, the okapi. Its range extends from Chad in Central Africa to South Africa.

Giraffes usually inhabit savannas, grasslands, or open woodlands. However, when food is scarce they will venture into areas with denser vegetation. They prefer areas with plenty of acacia growth. They will drink large quantities of water when available which enables them to live for extended periods in dry, arid areas.

Etymology

The species name camelopardalis (camelopard) is derived from its early Roman name, where it was described as having characteristics of both a camel and a leopard. The English word camelopard first appeared in the 14th century and survived in common usage well into the 19th century. The Afrikaans language retained it. The Arabic word الزرافة ziraafa or zurapha, meaning "assemblage" (of animals), or just "tall", was used in English from the sixteenth century on, often in the Italianate form giraffa.

Taxonomy and evolution

The giraffe is one of only two living species of the family Giraffidae, along with the okapi. The family was once much more extensive, with numerous other species. The giraffids evolved from a 3 metres (9.8 ft) tall antelope-like mammal that roamed Europe and Asia some 30-50 million years ago.

The earliest known giraffid was Climacoceras, which still resembled deer, having large antler-like ossicones. It first appeared in the early Miocene epoch. Later examples include the genera Palaeotragus and Samotherium, which appeared in the early to mid-Miocene. They were both tall at the shoulder, and had developed the simple, unbranched ossicones of modern giraffids, but still had relatively short necks.

From the late Pliocene onwards, the variety of giraffids drastically declined, until only the two surviving species remained. The modern genus Giraffa evolved during the Pliocene epoch, and included a number of other long-necked species, such as Giraffa jumae, that do not survive today. Alan Turner proposes, in the 2004 book Evolving Eden, that giraffe ancestors initially had a dark coat with pale spots, and that the spots gradually became star-shaped, before eventually forming the reticulated pattern found today. The modern species, Giraffa camelopardalis, appeared during the Pleistocene 1 million years ago.

The evolution of the long necks of giraffes has been the subject of much debate. The standard story is that they were evolved to allow the giraffes to browse vegetation that was out of the reach of other herbivores in the vicinity, giving them a competitive advantage. However, an alternative theory proposes that the long necks evolved as a secondary sexual characteristic, giving males an advantage in "necking" contests (see below) to establish dominance and obtain access to sexually receptive females. This theory notes that giraffes frequently feed from relatively low-lying shrubs, and that the necks of males are significantly longer than those of females. However, this theory is not universally accepted, and some of the data supporting it has recently been challenged, lending support to the original proposal that neck length is related to browsing habits.

Subspecies

Different authorities recognize different numbers of subspecies, differentiated by colour and pattern variations and range. Some of these species may prove to in fact be separate species. The subspecies recognized by various authorities include:

• Reticulated or Somali Giraffe (G. c. reticulata) — large, polygonal liver-coloured spots outlined by a network of bright white lines. The blocks may sometimes appear deep red and may also cover the legs. Range: northeastern Kenya, Ethiopia, Somalia.
• Angolan or Smoky Giraffe (G. c. angolensis) — large spots and some notches around the edges, extending down the entire lower leg. Range: Angola, Zambia.
• Kordofan Giraffe (G. c. antiquorum) — smaller, more irregular spots that cover the inner legs. Range: western and southwestern Sudan.

• Masai or Kilimanjaro Giraffe (G. c. tippelskirchi) — jagged-edged, vine-leaf shaped spots of dark chocolate on a yellowish background. Range: central and southern Kenya, Tanzania.
• Nubian Giraffe (G. c. camelopardalis) — large, four-sided spots of chestnut brown on an off-white background and no spots on inner sides of the legs or below the hocks. Range: eastern Sudan, northeast Congo.
• Rothschild Giraffe or Baringo Giraffe or Ugandan Giraffe (G. c. rothschildi) — deep brown, blotched or rectangular spots with poorly defined cream lines. Hocks may be spotted. Range: Uganda, north-central Kenya.
• South African Giraffe (G. c. giraffa) — rounded or blotched spots, some with star-like extensions on a light tan background, running down to the hooves. Range: South Africa, Namibia, Botswana, Zimbabwe, Mozambique.
• Thornicroft or Rhodesian Giraffe (G. c. thornicrofti) — star-shaped or leafy spots extend to the lower leg. Range: eastern Zambia.
• West African or Nigerian Giraffe (G. c. peralta) — numerous pale, yellowish red spots. Range: Niger, Cameroon.

Some scientists regard Kordofan and West African Giraffes as a single subspecies; similarly with Nubian and Rothschild's Giraffes, and with Angolan and South African Giraffes. Further, some scientists regard all populations except the Masai Giraffes as a single subspecies. By contrast, scientists have proposed four other subspecies — Cape Giraffe (G. c. capensis), Lado Giraffe (G. c. cottoni), Congo Giraffe (G. c. congoensis), and Transvaal Giraffe (G. c. wardi) — but none of these is widely accepted.

Though giraffes of these populations interbreed freely under conditions of captivity, suggesting that they are subspecific populations, genetic testing published in 2007 has been interpreted to show that there may be at least six species of giraffe that are reproductively isolated and not interbreeding, even though no natural obstacles, like mountain ranges or impassable rivers block their mutual access. In fact, the study found that the two giraffe populations that live closest to each other— the reticulated giraffe (G. camelopardalis reticulata) of north Kenya, and the Masai giraffe (G. c. tippelskirchi) in south Kenya— separated genetically between 0.13 and 1.62 million years BP, judging from genetic drift in nuclear and mitochondrial DNA.

The implications for conservation of as many as eleven such cryptic species and sub-species were summarised by David Brown for BBC News: "Lumping all giraffes into one species obscures the reality that some kinds of giraffe are on the brink. Some of these populations number only a few hundred individuals and need immediate protection."

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