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.).
[2]
Females are generally slightly shorter and weigh less.
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 .[3] 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
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 number of horns varies among the different giraffe subspecies,
with some having as many as five.
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 black. Giraffes have long necks, which they use to
browse the leaves of trees. Though usually stated to possess seven vertebrate in
the neck (the usual number for a mammal), it has in fact been argued that
giraffes might really have eight.
They also have slightly elongated forelegs, about 10% longer than their hind
legs. These bones produce bud-like horns called ossicorns.
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 a 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
extra vascular 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.[4]
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 behavior with another male. Females, on
the other hand, only appear to have same sex relations in 1% of mounting
incidents.[5]
Other behaviour
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 lay down andthat 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). 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.[6]
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Evolutionary perspectives
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 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. While the ecological niche which at least male giraffes utilize is only
used by a single other species, the African Elephant, there have been no
selective forces to maintain the length of the giraffe's neck.
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. Today, the maintenance of the giraffe's neck length
is more an example of neutralist selection than of "survival of the fittest".
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.
| The Somali Giraffe or Reticulated
Giraffe, Giraffa camelopardalis reticulata, is a
subspecies of giraffe native to Somalia, but is also widely found in
Northern Kenya and Southern Ethiopia. Reticulated giraffes can
interbreed with other giraffe subspecies in captivity or if
populations are low in the wild. The
reticulated giraffe is the most well-known of the nine giraffe
subspecies, and is by far the giraffe most commonly seen in zoos.
Its coat consists of 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.
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Giraffe subspecies
There are nine generally accepted subspecies, differentiated by color and
pattern variations and range:
- 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: Chad.
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.
