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Giraffe

2007 Schools Wikipedia Selection. Related subjects: Mammals

                     iGiraffe

                             Conservation status

   Conservation dependent (LR/cd)
            Scientific classification

   Kingdom: Animalia
   Phylum:  Chordata
   Class:   Mammalia
   Order:   Artiodactyla
   Family:  Giraffidae
   Genus:   Giraffa
   Species: G. camelopardalis

                                Binomial name

   Giraffa camelopardalis
   Linnaeus, 1758

   The Giraffe (Giraffa camelopardalis) is an African even-toed ungulate
   mammal, the tallest of all land-living animal species. Males can be 4.8
   to 5.5 metres (16 to 18 feet) tall and weigh up to 1,360 kilograms
   (3,000 pounds). The record-sized bull was 5.87 m (19.2 feet) tall and
   weighed approximately 2,000 kg (4,400 lbs.). Females are generally
   slightly shorter and weigh less than the males do.

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

Etymology and history

   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.
   A number of European languages retain 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.

Physical characteristics

   Giraffes use their long, prehensile tongues to extend their reach.
   Specimen at the National Museum of Natural History, Washington, DC.
   Enlarge
   Giraffes use their long, prehensile tongues to extend their reach.
   Specimen at the National Museum of Natural History, Washington, DC.

   Male giraffes are around 15–17 feet tall at the horn tips, and weigh
   1700–4200 lb. Females are one to two feet shorter and weigh several
   hundred pounds less than males. Both sexes have horns, although the
   horns of a female are smaller. The prominent horns are formed from
   ossified cartilage and are called ossicones. Males sometimes develop
   calcium deposits which form bumps on their skull as they age, which can
   give the appearance of up to three further horns.

   Giraffes have spots covering their entire bodies, except their
   underbellies, with each giraffe having a unique pattern of spots. They
   have long, prehensile tongues that are distinctly blue-black to protect
   from sunburn. Giraffes have long necks, which they use to browse the
   leaves of trees. They possess seven vertebrae in the neck (the usual
   number for a mammal). They also have slightly elongated forelegs, about
   10% longer than their hind legs.

   Modifications to the giraffe's structure have evolved, particularly to
   the circulatory system. A giraffe's heart, which can weigh up to 10 kg
   (24 lb), has to generate around double the normal blood pressure for an
   average large mammal in order to maintain blood flow to the brain
   against gravity. 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. Conversely, 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 exactly the same way as
   a pilot's g-suit.

Social structure, reproduction and sexuality

   Female giraffes associate in groups of a dozen or so members,
   occasionally including a few younger males. Males tend to live in
   "bachelor" herds, with older males often leading solitary lives.
   Reproduction is polygamous, with a few older males impregnating all the
   fertile females in a herd. Male giraffes determine female fertility by
   tasting the female's urine to detect estrus in a multi-step process
   known as the flehmen response.

   Giraffe gestation lasts between 14 and 15 months, after which a single
   calf is born. The mother gives birth standing up and the embryonic sack
   actually bursts when the baby falls to the ground. Newborn giraffes are
   about 1.8 metres 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. While adult giraffes are too large to be attacked by most
   predators, the young can fall prey to lions, leopards, hyenas, and
   African Wild Dogs. It has been speculated that their characteristic
   spotted pattern provides a certain degree of camouflage. Only 25 to 50%
   of giraffe calves reach adulthood; the life expectancy is between 20
   and 25 years in the wild and 28 years in captivity (Encyclopedia of
   Animals).

   The males often engage in necking, which has been described as having
   various functions. One of these is combat. These battles can be fatal,
   but are more often less severe. The longer a neck is, and the heavier
   the head at the end of the neck, the greater force a giraffe will be
   able to deliver in a blow. It has also been observed that males that
   are successful in necking have greater access to estrous females, so
   that the length of the neck may be a product of sexual selection.

   Another function of necking is affectionate and sexual, in which two
   males will caress and court each other, leading up to mounting and
   climax. Same sex relations are more frequent than heterosexual
   behavior. In one area 94% of mounting incidents were of a homosexual
   nature. The proportion of same sex courtships varies between 30 and
   75%, and at any given time one in twenty males will be engaged in
   affectionate necking behaviour with another male. Females, on the other
   hand, only appear to have same sex relations in 1% of mounting
   incidents.

Other behaviour

   Giraffe, Melbourne Zoo
   Enlarge
   Giraffe, Melbourne Zoo

   The giraffe browses on the twigs of trees, preferring plants of the
   Mimosa genus; but it appears that it can live without inconvenience on
   other vegetable food. A giraffe can eat 63 kg (140 lb) of leaves and
   twigs daily.

   The pace of the giraffe is an amble, though when pursued it can run
   extremely fast. It can not sustain a lengthened chase. Its leg length
   compels an unusual gait with the left legs moving together followed by
   right (similar to pacing) at low speed, and the back legs crossing
   outside the front at high speed.

   The giraffe defends itself against threats by kicking with great force.
   A single well-placed kick of an adult giraffe can shatter a lion's
   skull or break its spine.

   The giraffe has one of the shortest sleep requirement of any mammal,
   which is between 10 minutes and two hours in a 24-hour period. This has
   led to the myth that giraffes cannot lie down and that if they do so,
   they will die.

   A giraffe will clean off any bugs that appear on its face with its
   extremely long tongue (about 18 inches/45 centimeter). The tongue is
   tough on account of the giraffe's diet, which includes thorns from the
   tree it is making a meal of. In Southern Africa, giraffes are partial
   to all acacias — especially Acacia erioloba — and possess a
   specially-adapted tongue and lips that appear to be immune to the
   vicious thorns.

   Giraffes are thought to be mute; however, although generally quiet,
   they have been heard to grunt, snort and bleat and also recent research
   has shown evidence that the animal communicates at an infrasound level.

   The instinct of some other African animals is to stay close to the
   giraffe, for the giraffe's high vantage point can see predators from
   far away.

Evolutionary perspectives

   Female Giraffe with calf, in Kenya.
   Enlarge
   Female Giraffe with calf, in Kenya.

   The long neck allows a giraffe to eat from the tops of trees. However,
   since female giraffes are not as tall as male giraffes and tend to feed
   from much lower heights than their male counterparts, it is hard to say
   that they need the long necks purely for metabolic reasons.
   Furthermore, the additional length that helps a giraffe reach the top
   food sources makes it difficult for the same creature to drink. The
   ecological niche which at least male giraffes utilize is only used by a
   single other species, the African Elephant. It may be that the long
   neck originally evolved when the benefit of filling the ecological
   niche was more pronounced due to the presence of other, now extinct,
   giant ungulates in Africa.

   It has been observed that males use their long necks not only for
   feeding, but also for combat and competition. Indeed, sexual dimorphism
   is strongly represented among giraffes, with females having shorter,
   lighter necks than males. A female's neck and head mass will level off
   after about ten years of age, while a male's will continue to increase
   throughout its twenty-plus years of life.

Giraffe subspecies

   There are nine generally accepted subspecies, differentiated by colour
   and pattern variations and range:
   Giraffe subspecies range map
   Enlarge
   Giraffe subspecies range map
     * Reticulated or Somali Giraffe (G.c. reticulata) — large, polygonal
       liver-colored 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 do 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's or Baringo 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.

Gallery

   Reticulated Giraffe

                      Angolan giraffes
   Retrieved from " http://en.wikipedia.org/wiki/Giraffe"
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   with only minor checks and changes (see www.wikipedia.org for details
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