Giraffe
Giraffe | |
Kingdom: | |
Phylum: | |
Class: | |
Order: | |
Family: | |
Genus: | |
Species: | G. camelopardalis |
The giraffe (Giraffa camelopardalis) is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant. Its scientific name, which is similar to its archaic English name of camelopard, refers to its irregular patches of color on a light background, which bear a token resemblance to a leopard's spots. The average mass for an adult male giraffe is 1,200 kilograms (2,600 lb) while the average mass for an adult female is 830 kilograms (1,800 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 other even-toed ungulates, such as deer and cattle, but is placed in a separate family, the Giraffidae, consisting of only the giraffe and its closest relative, the okapi, and their extinct relatives. 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 arid areas. The giraffe's fur may serve as a chemical defence, and is full of antibiotics and parasite repellents that gives the animal a characteristic scent. Old males are sometimes nicknamed "stink bulls". There are at least eleven main aromatic chemicals in the fur, although indole and 3-methylindole are responsible for most of their smell. Because the males have a stronger odour than the females, it is also suspected that it has a sexual function The giraffe has one of the shortest sleep requirements of any mammal, which averages 4.6 hours per 24 hours.
Etymology
The name giraffe has its earliest known origins in the Arabic word الزرافة ziraafa or zurapha, perhaps from an African name. It appears in English from the 16th century on, often in theItalianate form giraffa. The species name camelopardalis (camelopard) is derived from its earlyRoman name, where it was described as having characteristics of both a camel and a leopard.[8]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.
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 over 10 fossil genera described. The giraffids evolved from a 3 m (9.8 ft) tall antelope-like mammal that roamed Europe and Asia some 30–50 million years ag 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 genusGiraffa evolved during the Pliocene epoch, and included a number of other long-necked species, such as Giraffa jumae, that do not survive today.
The giraffe was one of the many species first described by Linnaeus in 1758. He gave it the binomial name of Cervus camelopardalis in the 10th edition of his Systema Naturae. Brissonerected the genus Giraffa in 1762.
Subspecies
Different authorities recognize different numbers of subspecies, differentiated by size, colour and pattern variations and range. Some of these subspecies may prove to be separate speciesas they appear to be reproductively isolated despite their mobility. The subspecies recognized by most recent authorities are:
§ G. c. camelopardalis, the nominate subspecies, is known as the Nubian Giraffe. Its coat pattern has 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. It is found in eastern Sudan and northeastern DR Congo. It has been estimated that fewer than 250 remain in the wild, but little is known about this subspecies and consequently this estimate is labelled with great uncertainty. It is very rare in captivity, although kept at Al Ain Zoo in the United Arab Emirates. G. c. reticulata known as the Reticulatedor Somali Giraffe, has a coat pattern of well defined patches that are normally a bright orange-brown colour. These patches have sharp edges and are separated by bold, bright white lines.[ It ranges from northeasternKenya, into southern Ethiopia and Somalia. It has been estimated that fewer than 5.000 remain in the wild, and based on ISIS records it is among the most common in zoos, with more than 450 kept.
§ G. c. angolensis, the Angolan or Smoky Giraffe, has large spots with some notches around the edges, extending down the entire lower leg. It is found in southern Angola, northern Namibia, southwestern Zambia, Botswana and western Zimbabwe. It has been estimated that fewer than 20,000 remain in the wild, and based on ISIS records approximately 20 are kept in zoos. G. c. antiquorum,[ the Kordofan Giraffe, has smaller, more irregular spots that cover the inner legs. Its distribution includes southernChad, Central African Republic and northern Cameroon. Populations in Cameroon were formerly included in G. c. peralta instead, but this was incorrect. Fewer than 3,000 are believed to remain in the wild Considerable confusion has existed over the status of this subspecies and G. c. peralta in zoos. In 2007 it was shown that all "G. c. peralta" in European zoos actually are G. c. antiquorum. Consequently, approximately 65 are kept in zoos based on ISIS records. G. c. tippelskirchi, known as the Maasai Giraffe or Kilimanjaro Giraffe, has jagged-edged, vine-leaf shaped spots of dark brown on a brownish-cream background. It is the darkest coloured subspecies. It occurs in central and southern Kenya and Tanzania. It is estimated that fewer than 40,000 remain in the wild, and based on ISIS records approximately 100 are kept in zoos. G. c. rothschildi, is known variously as the Rothschild Giraffeor Baringo Giraffe or Ugandan Giraffe. Its coats bears deep brown, blotched or rectangular spots with poorly defined cream lines. Its legs are mostly white with no pattern. Its range includes Uganda and west-central Kenya, especially near Lake Baringo. It may also occur in southern Sudan. Fewer than 700 are believed to remain in the wild and based on ISIS records more than 450 are kept in zoos.
§ G. c. giraffa, the South African Giraffe, has rounded or blotched spots, some with star-like extensions on a light tan background, running down to the hooves. It is found in northern South Africa, southern Botswana, southern Zimbabwe and southwestern Mozambique. It is estimated that fewer than 12,000 remain in the wild, and based on ISIS records approximately 45 are kept in zoos.
§ G. c. thornicrofti, called the Thornicroft Giraffe or Rhodesian Giraffe, has star-shaped or leafy spots extend to the lower leg. It is restricted to the Luangwa Valley in eastern Zambia. Fewer than 1,500 remain in the wild and based on ISIS records none are kept in zoos.
§ G. c. peralta, commonly known as the West African Giraffe or Nigerian Giraffe, has numerous pale, yellowish red spots. It isendemic to southern Niger. With fewer than 220 individuals remaining in the wild, it is the rarest giraffe subspecies. Giraffes in Cameroon were formerly believed to be this subspecies, but are actually G. c. antiquorum. This has also resulted in some confusion over its status in zoos, but in 2007 it was established that all "G. c. peralta" kept in European zoos actually are G. c. antiquorum. Formerly, the Kordofan and West African Giraffes were regarded as a single subspecies, but genetic evidence has confirmed that they represent two separate subspecies. Comparably, the Rothschild's Giraffe has been considered a hybrid population, but genetic evidence has confirmed that it is a valid 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 today none of these is widely accepted. One genetic study on Smoky Giraffes suggests that the northern Namib Desert and Etosha National Park populations are distinct subspecies. Although 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. 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 ago, judging from genetic driftin nuclear and mitochondrial DNA. The implications for conservation of as many as eleven such cryptic species and subspecies 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
Anatomy and morphology
Male giraffes are up to 5.5 metres (18 ft) tall at the horn tips, and weigh between 800 and 1,930 kilograms (1,800 and 4,300 lb). Females are between 4 and 4.5 metres (13 and 14.8 ft) tall and weigh between 550 and 1,180 kilograms (1,200 and 2,600 lb). The coat is made up of brown blotches or patches separated by lighter hair. Each giraffe has a unique coat pattern.
Horns
Both sexes have prominent horns, formed from ossified cartilage, and known as ossicones. The appearance of horns is a reliable method of identifying the sex of giraffes, with the females displaying tufts of hair on the top of the horns, whereas males' horns are larger and tend to be bald on top — the hairs worn away due to necking in combat. Males sometimes develop calcium deposits which form bumps on their skull as they age, which can give the appearance of up to three additional horns.
Legs and locomotion
Giraffes also have slightly elongated forelegs, about 10% longer than their hind legs, and can reach a sprint speed of up to 60 km/h (37 mph). It cannot sustain a lengthy chase. The apparent inflexibility of its legs give it a stiff gait when walking. When running the giraffe thrusts its front legs into the air and when they touch the ground they push off again. When the hind legs land together the process starts over.[ The giraffe is briefly airborne when running. When hunting adult giraffes, lions try to knock the lanky animal off its feet and pull it down. Giraffes are difficult and dangerous prey. The giraffe defends itself with a powerful kick. A single well-placed kick from an adult giraffe can kill a predator. Lions are the only predators which pose a serious threat to an adult giraffe.
Swimming
Although no definitive study has been publicly conducted, giraffes are assumed to be unable to swim. It has been estimated that the giraffe's proportionally larger limbs have very high rotational inertias making rapid swimming motions strenuous. A swimming giraffe – forced into a posture where the neck is sub-horizontal and with a thorax that is pulled downwards by the large fore limbs – would not be able to move the neck and limbs synchronously as giraffes do when moving on land, possibly further hampering the animal's ability to move its limbs effectively underwater. A computer simulation conducted by Scientific American suggested that while a giraffe could float, "they would be clumsy and unstable in water" The simulation suggests the giraffe's high density in its limb bones would make it slow and suffer from high drag.[ Furthermore, the weight of the forelimbs and shoulder would pull the front of the giraffe down, straining its neck.
The giraffe's extreme altitude is a consequence of its extremely elongated neck, which can be over 2 m (7 ft) in length, accounting for nearly half of the giraffe's vertical height. The increase in neck length results from the disproportionate elongation of the cervical vertebrae, rather than the addition of more vertebrae. The cervical vertebrae comprise about 45–50% of the giraffe vertebral column, compared to the 30% typical of similar large ungulates, including the giraffe’s closest extant relative, the okapi. This elongation, which occurs in large part after birth, is a 150% increase in vertebrae length over similar sized animals – in fact, the non-cervical sections of the giraffe vertebral column exhibit identical proportions to those in okapi.
In addition to their elongated cervical vertebrae, in giraffes the point of articulation between the cervical and thoracic vertebrae is shifted to lie between T1 and T2, the first and secondthoracic vertebrae, rather than between C7 and T1, as in most other ruminants. This allows C7 to contribute directly to increased neck length, and has sparked the suggestion that T1 is actually C8, and giraffes have added an extra cervical vertebra. However, this proposition is generally not accepted, as T1 has other morphological features, such as an articulating rib, deemed diagnostic of thoracic vertebrae. Also, the exceptions to the mammalian constraint of seven cervical vertebrae are generally characterized by increasedneurological anomalies and maladies, symptoms that have not been observed in giraffes.
There are two main hypotheses regarding the evolutionary origin and maintenance of elongation in giraffe necks The “competing browsers hypothesis” was originally suggested by Charles Darwin and only challenged recently. It suggests that competitive pressure from smaller browsers, such as kudu, steenbok, and impala, drove the elongation of the neck so giraffes could reach nutrients competitors could not. This advantage is real – giraffes can and do feed up to 5 m, while most of their competitors, kudu, can only feed up to about 2 m (7 ft). There is also research suggesting that browsing competition below 2 m is intense, and giraffes feed more efficiently (gaining more leaf biomass per bite) higher in the canopy However, scientists disagree about just how much time giraffes spend feeding at levels unreachable to other browsers. Although giraffes can feed as low as 0.5 m and as high as 6 m off the ground, it appears that they most often feed between 2 and 4 m (7–14 ft). However, elephants also routinely feed at heights up to 5 m (they knock down only a minority of the trees they feed on), and are likely competitors at these heights. Competition for food with other giraffes could also favor the evolution of tall necks.
The other main theory, the sexual selection hypothesis, 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. In support of this theory, males have proportionally larger necks than females, and males with longer, bigger necks are more successful in dominance displays and courtship behavior.[ However, a major criticism of this theory is that it fails to adequately explain why female giraffes also have long necks
Circulatory system
Modifications to the giraffe's structure have evolved, particularly to the circulatory system. A giraffe's heart, which can weigh up to 10 kg (22 lb) and measure about 60 cm (2 ft) long, must generate approximately double the normal blood pressure for an average large mammal to maintain blood flow to the brain. In the upper neck, a complex pressure-regulation system called the rete mirabile prevents excess blood flow to the brain when the giraffe lowers its head to drink.
The jugular veins also contain several (most commonly seven) valves to minimise blood flowing back into the head and assist it getting to the inferior vena cava and right atrium in the same situationConversely, the blood vessels in the lower legs are under great pressure (because of the weight of fluid pressing down on them). In other animals such pressure would force the blood out through the capillary walls; giraffes, however, have a very tight sheath of thick skin over their lower limbs which maintains high extravascular pressure in the same way as a pilot's g-suit.
Lifestyle
Social structure and breeding habits
While giraffes are usually found in groups, the composition of these groups is more fluid than in other social ungulates. They are a largely transient species with few strong social bonds and aggregations usually disband every few hours, although calving groups can last weeks to months.[ For research purposes, a "group" has been defined as "a collection of individuals that are less than a kilometre apart and moving in the same general direction." Giraffe groups can range from over 40 individuals to only a few individuals with the latter being more common. Female giraffes associate in groups of a dozen or so members, occasionally including a few younger males. Calves and sub-adults are rarely alone. Giraffe groups with young tend to feed in more open areas, presumably to provide better visibility to detect predators. This may reduce their feeding efficiency. Reproduction is broadly polygamous, with a few older males impregnating the fertile females. Male giraffes determine female fertility by tasting the female's urine in order to detect estrus, in a multi-step process known as the Flehmen response. Once a estrous female is detected, the male will them attempt to court her. Males prefer younger females, possibly became the latter are more fertile, while females prefer older, more dominant males. During courtship, dominant males will displace subordinates from the presence of the females, by staring and walking towards them. Thus the female prolongs the courtship process for as long as possible so only the most dominant male remains and copulation will follow.
Although generally quiet and non-vocal, giraffes have been heard to communicate with various sounds. Courting males will emit loud coughs. Females will call their young by whistling or bellowing. Calves will bleat, moo, or make mewing sounds. In addition, giraffes will grunt, snort, hiss, or make strange flute-like sounds. Recent research has provided evidence that the giraffes produce infrasound.
Birthing, parental care, and lifespan
Giraffe gestation lasts between 400 and 460 days, after which a single calf is normally born, although twins occasionally occur. The mother gives birth standing up and the embryonic sack usually bursts when the baby falls to the ground. Newborn giraffes are about 1.8 m (5 ft. 11 in.) tall.
Within a few hours of being born, calves can run around and are indistinguishable from a week-old calf; however, for the first two weeks, they spend most of their time lying down, guarded by the mother. It has been speculated that their characteristic spotted pattern provides a certain degree of camouflage. Mothers with calves will gather in nursery herds which are usually made up of two or more infants and/or juveniles and their mothers moving or browsing together. Mothers in a groups may sometimes leave their calves with one female while they travelled to other areas. It is what’s known as a "calving pool".Males largely play no role in raising the young.
The young can fall prey to lions, leopards, spotted hyenas, and wild dogs. Mother giraffes will defend their young by placing themselves between the young and the predator and kicking the predator. Giraffes only defend their own young and form calving herds for selfish reasons.[ Only 25 to 50% of giraffe calves reach adulthood. Maximum lifespan is ~25 years in the wild and 28 years in captivity
Necking
Male giraffes often engage in necking, which has been described as having various functions. One of these is combat. Battles can be fatal, but are more often less severe, generally ending when one giraffe surrenders to the other. The longer the neck, and the heavier the head at the end of the neck, the greater the force a giraffe is able to deliver in a blow. It has also been observed that males that are successful in necking have greater access to estrousfemales, so the length of the neck may be a product of sexual selection. After a necking duel, a giraffe can land a powerful blow with his head — occasionally knocking a male opponent to the ground. These fights rarely last more than a few minutes or end in physical harm.
Another function of necking is sexual, in which two males caress and court each other, leading up to mounting and climax. Such interactions between males are more frequent than heterosexual coupling. In one study, up to 94% of observed mounting incidents took place between two males. The proportion of same sex activities varied between 30 and 75%, and at any given time one in twenty males were engaged in non-combative necking behaviour with another male. Only 1% of same-sex mounting incidents occurred between females.
Diet
Giraffes browse on the twigs of trees, preferring trees of the genera Acacia, Commiphora andTerminalia, and also eat grass and fruit. The tongue, lips and palate are tough, which allows them to feed on trees with sharp thorns. In Southern Africa, giraffes feed on all acacias, especiallyAcacia erioloba. A giraffe can eat 65 pounds (29 kg) of leaves and twigs daily, but can survive on just 15 pounds (6.8 kg). The giraffe requires less food than typical grazing animals because the foliage it eats has more concentrated nutrition and it has a more efficient digestive system. During the wet season, food is abundant and giraffes disperse widely, but during the dry season they need to congragate around evergreen trees and bushes As a ruminant, it first chews its food, then swallows for processing and then visibly regurgitates the semi-digested cud up their necks and back into the mouth, in order to chew again. This process is usually repeated several times for each mouthful. The giraffe can survive without water for extended periods. Compared with domestic cattle, giraffes have a comparatively short small intestine and a comparatively long large intestine, with a resulting small ratio of small:large intestine. A giraffe can clean off bugs (like acacia ants) on its face with its extremely long tongue (about 45 centimetres (18 in)).
Stereotypic behavior
Many animals when kept in captivity, such as in zoos, display abnormal behaviours. Such unnatural behaviours are known as stereotypic behaviours. In particular, giraffes show distinct patterns of stereotypic behaviours when removed from their natural environment. Due to a subconscious response to suckle milk from their mother, something which many human-reared giraffes and other captive animals do not experience, giraffes resort instead to excessive tongue use on inanimate objects
Human interactions
In art and culture
The giraffe was considered the "queen of beasts" by Arab prophets and poet for what they considered to be its delicate features and fragile form. Eastern sultans prized them as special pets. Giraffes were also known to the people of the Mediterranean region duringantiquity. Pompey apparently kept ten at his theater in Rome. Giraffes were apparently mostly forgotten by the Middle Ages except in legends from Arab travelers. The Medici giraffe was a giraffe presented to Lorenzo de' Medici in 1486. It caused a great stir on its arrival inFlorence,[62] being reputedly the first living giraffe to be seen in Italy since the days of Ancient Rome. Another famous giraffe, called Zarafa, was brought from Africa to Paris in the early 19th century and kept in a menagerie for 18 years.
Giraffe is a novel by the author J. M. Ledgard. The work concerns a true incident in which 49 giraffes were slaughtered in the Czech Republic (then Czechoslovakia) in 1975 following the suspected outbreak of disease amongst the group. The novel contains extensive information about the species, including the long history of European fascination with the beast and its captivity in zoos.
Giraffes can be seen in paintings, including the famous painting of a giraffe which was taken from Somaliato China in 1414. The giraffe was placed in a Ming Dynasty zoo. At one point the giraffe was associated with the mythical Qilin, and a derivative of that name (kirin) is still used as the word for giraffe in Japan, Taiwan, and Korea.
Giraffes continue to have a presence in modern popular culture; most notably Toys "R" Us mascotGeoffrey the Giraffe. They also appear as miscellaneous characters in films like The Lion King and Dumbo. They have had more prominent roles with Melman from Madagascar and Longrack from the Transformersuniverse.
Scientific inspiration
Giraffes have been used as examples for introducing ideas in evolution, especially to illustrate the ideas ofLamarck. Lamarck believed that the giraffe's long neck developed as a result of ancestral giraffe's reaching to browse on the leaves of tall trees. In addition the coat patterns of several subspecies of giraffe have been modelled using reaction-diffusion mechanisms[ The giraffe's circulatory system has been studied by NASA which hopes to replicate the the giraffe's ability to keep blood from pooling in its lower body for astronauts returning from space.
Conservation
Overall, the giraffe is regarded as Least Concern from a conservation perspective by theInternational Union for Conservation of Nature (IUCN), as it still is widespread and occurs in numerous reserves. However, the giraffe has been extirpated from many parts of its former range, including Burkina Faso, Eritrea, Guinea, Malawi, Mauritania and Senegal. It may also have disappeared from Angola, Mali and Nigeria. Two subspecies, the West African Giraffe (G. c. peralta) and the Rothschild Giraffe (G. c. rothschildi), have been classified as endangeredwith wild populations of each of these numbering in the hundreds. Additionally, it has been suggested that the Nubian Giraffe (G. c. camelopardalis) is the most threatened of all giraffesand may number fewer than 250, but little recent information is available and consequently that estimate is labelled with considerable uncertainty. Giraffes are hunted for their tails, hides and meat. The tails are used as good luck charms, thread and flyswatters. In addition, habitat destruction also hurts the giraffe. In the Sahel trees are cut down for firewood and to make way for livestock. Normally, giraffes are able to cope with livestock since they feed in the trees above their heads. The giraffe is a protected species in most of its range. The total African giraffe population has been estimated to range from 110,000 to 150,000. Kenya (45,000), Tanzania (30,000), and Botswana (12,000), have the largest national population More recent estimates suggest fewer than 80,000 remain in total
0 Response to "The Giraffe"
Post a Comment