Our Animals - Giraffe
Our Animals > 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 1,200 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 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.
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 15 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. Wild giraffes have a lifespan close to 13 years while those in captivity live up to 25 years.
Both sexes have horns, although the horns of a female are smaller. The prominent horns are formed from ossified cartilage, and are called 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 tend to be bald on top — an effect of 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.
Giraffes have long necks which they use to browse tree leaves. The neck has seven highly lengthened vertebrae, otherwise the usual number of vertebrae for a mammal. Moreover, the vertebrae are separated by very flexible joints, the base of the neck has spines which project upward to form a hump over the shoulders and anchor muscles hold the neck upright.
Legs and pacing
Giraffes also have slightly elongated forelegs, about 10% longer than their hind legs. The pace of the giraffe is an amble, though when pursued it can run extremely fast, up to 55 km/h. It cannot sustain a lengthy 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. 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 shatter a lion's skull or break its spine. Lions are the only predators which pose a serious threat to an adult giraffe.
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. 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 the same way as a pilot's g-suit.
Female giraffes associate in groups of a dozen or so members, occasionally including a few younger males. Younger males tend to live in "bachelor" herds, with older males often leading solitary lives. While research from the 1970s concluded that giraffes did not socialize, later research found that giraffes did form attachments to other giraffes, with giraffes spending 15% of their time grazing with the giraffes they are close to and only 5% of their time grazing with giraffes who are strangers.
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 in order to detect estrus, in a multi-step process known as the Flehmen response.
Giraffes will mingle with the other herbivores in the African bush. Their company is beneficial, since they are tall enough to have a much wider scope of an area and will watch for predators.
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 (6 ft) 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. The young can fall prey to lions, leopards, spotted hyenas, and 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.
Males 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 estrous females, 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.
The giraffe browses on the twigs of trees, preferring trees of the genera Acacia, Commiphora and Terminalia, and also eats grass and fruit. The tongue is tough due to the giraffe's diet, which can include tree thorns. In Southern Africa, giraffes feed on all acacias, especially Acacia erioloba, and possess a specially-adapted tongue and lips that are tough enough to withstand the vicious thorns of this plant. 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. A giraffe will clean off any bugs that appear on its face with its extremely long tongue (about 45 centimeter (18 in).
The giraffe has one of the shortest sleep requirements of any mammal, which is between ten minutes and two hours in a 24-hour period, averaging 1.9 hours per day.
Although generally quiet and non-vocal, giraffes have been heard to make 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 shown evidence that the animal communicates at an infrasound level.