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Giraffe Giraffa camelopardalis

The giraffe (Giraffa) is an African artiodactyl mammal, the tallest living terrestrial animal and the largest ruminant. It is traditionally considered to be one species, Giraffa camelopardalis, with nine subspecies. However, the existence of up to eight extant giraffe species has been described, based upon research into the mitochondrial and nuclear DNA, as well as morphological measurements of Giraffa. Seven other species are extinct, prehistoric species known from fossils.

The giraffe's chief distinguishing characteristics are its extremely long neck and legs, its horn-like ossicones, and its distinctive coat patterns. It is classified under the family Giraffidae, along with its closest extant relative, the okapi. Its scattered range extends from Chad in the north to South Africa in the south, and from Niger in the west to Somalia in the east. Giraffes usually inhabit savannahs and woodlands. Their food source is leaves, fruits and flowers of woody plants, primarily acacia species, which they browse at heights most other herbivores cannot reach. They may be preyed on by lions, leopards, spotted hyenas and African wild dogs. Giraffes live in herds of related females and their offspring, or bachelor herds of unrelated adult males, but are gregarious and may gather in large aggregations. Males establish social hierarchies through "necking", which are combat bouts where the neck is used as a weapon. Dominant males gain mating access to females, which bear the sole responsibility for raising the young.

Description & appearance

Fully grown giraffes stand 4.3–5.7 m (14.1–18.7 ft) tall, with males taller than females. The tallest recorded male was 5.88 m (19.3 ft) and the tallest recorded female was 5.17 m (17.0 ft) tall. The average weight is 1,192 kg (2,628 lb) for an adult male and 828 kg (1,825 lb) for an adult female with maximum weights of 1,930 kg (4,250 lb) and 1,180 kg (2,600 lb) having been recorded for males and females, respectively. Despite its long neck and legs, the giraffe's body is relatively short. Located at both sides of the head, the giraffe's large, bulging eyes give it good all-round vision from its great height. Giraffes see in colour and their senses of hearing and smell are also sharp. The animal can close its muscular nostrils to protect against sandstorms and ants.
The giraffe's prehensile tongue is about 45 cm (18 in) long. It is purplish-black in colour, perhaps to protect against sunburn, and is useful for grasping foliage, as well as for grooming and cleaning the animal's nose. The upper lip of the giraffe is also prehensile and useful when foraging, and is covered in hair to protect against thorns. The tongue and inside of the mouth are covered in papillae.

The coat has dark blotches or patches (which can be orange, chestnut, brown, or nearly black in colour) separated by light hair (usually white or cream in colour.) Male giraffes become darker as they age. The coat pattern has been claimed to serve as camouflage in the light and shade patterns of savannah woodlands. When standing among trees and bushes, they are hard to see at even a few metres distance. However, adult giraffes move about to gain the best view of an approaching predator, relying on their size and ability to defend themselves rather than on camouflage, which may be more important for calves. Giraffe calves inherit some spot pattern traits from their mothers, and variation in some spot traits are correlated with neonatal survival. The skin underneath the dark areas may serve as windows for thermoregulation, being sites for complex blood vessel systems and large sweat glands. Each individual giraffe has a unique coat pattern.

The skin of a giraffe is mostly gray, or tan. Its thickness allows the animal to run through thorn bushes without being punctured. The fur may serve as a chemical defence, as its parasite repellents give the animal a characteristic scent. At least 11 main aromatic chemicals are in the fur, although indole and 3-methylindole are responsible for most of the smell. Because the males have a stronger odour than the females, the odour may also have sexual function. Along the animal's neck is a mane made of short, erect hairs. The one-metre (3.3-ft) tail ends in a long, dark tuft of hair and is used as a defense against insects.
Both sexes have prominent horn-like structures called ossicones, which are formed from ossified cartilage, covered in skin and fused to the skull at the parietal bones. Being vascularized, the ossicones may have a role in thermoregulation, and are also used in combat between males. Appearance is a reliable guide to the sex or age of a giraffe: the ossicones of females and young are thin and display tufts of hair on top, whereas those of adult males end in knobs and tend to be bald on top. Also, a median lump, which is more prominent in males, emerges at the front of the skull. Males develop calcium deposits that form bumps on their skulls as they age. A giraffe's skull is lightened by multiple sinuses. However, as males age, their skulls become heavier and more club-like, helping them become more dominant in combat. The upper jaw has a grooved palate and lacks front teeth. The giraffe's molars have a rough surface.
The front and back legs of a giraffe are about the same length. The radius and ulna of the front legs are articulated by the carpus, which, while structurally equivalent to the human wrist, functions as a knee. It appears that a suspensory ligament allows the lanky legs to support the animal's great weight. The foot of the giraffe reaches a diameter of 30 cm (12 in), and the hoof is 15 cm (5.9 in) high in males and 10 cm (3.9 in) in females. The rear of each hoof is low and the fetlock is close to the ground, allowing the foot to provide additional support to the animal's weight. Giraffes lack dewclaws and interdigital glands. The giraffe's pelvis, though relatively short, has an ilium that is outspread at the upper ends.

A giraffe has only two gaits: walking and galloping. Walking is done by moving the legs on one side of the body at the same time, then doing the same on the other side. When galloping, the hind legs move around the front legs before the latter move forward, and the tail will curl up. The animal relies on the forward and backward motions of its head and neck to maintain balance and the counter momentum while galloping. The giraffe can reach a sprint speed of up to 60 km/h (37 mph), and can sustain 50 km/h (31 mph) for several kilometres.

A giraffe rests by lying with its body on top of its folded legs. To lie down, the animal kneels on its front legs and then lowers the rest of its body. To get back up, it first gets on its knees and spreads its hind legs to raise its hindquarters. It then straightens its front legs. With each step, the animal swings its head. In captivity, the giraffe sleeps intermittently around 4.6 hours per day, mostly at night. It usually sleeps lying down; however, standing sleeps have been recorded, particularly in older individuals. Intermittent short "deep sleep" phases while lying are characterised by the giraffe bending its neck backwards and resting its head on the hip or thigh, a position believed to indicate paradoxical sleep. If the giraffe wants to bend down to drink, it either spreads its front legs or bends its knees. Giraffes would probably not be competent swimmers as their long legs would be highly cumbersome in the water, although they could possibly float. When swimming, the thorax would be weighed down by the front legs, making it difficult for the animal to move its neck and legs in harmony or keep its head above the surface.
The giraffe has an extremely elongated neck, which can be up to 2–2.4 m (6.6–7.9 ft) in length, accounting for much of the animal's vertical height. The long neck results from a disproportionate lengthening of the cervical vertebrae, not from the addition of more vertebrae. Each cervical vertebra is over 28 cm (11 in) long. They comprise 52–54 per cent of the length of the giraffe's vertebral column, compared with the 27–33 percent typical of similar large ungulates, including the giraffe's closest living relative, the okapi. This elongation largely takes place after birth, perhaps because giraffe mothers would have a difficult time giving birth to young with the same neck proportions as adults.The giraffe's head and neck are held up by large muscles and a strengthened nuchal ligament, which are anchored by long dorsal spines on the anterior thoracic vertebrae, giving the animal a hump.

The giraffe's neck vertebrae have ball and socket joints. In particular, the atlas–axis joint (C1 and C2) allows the animal to tilt its head vertically and reach more branches with the tongue. The point of articulation between the cervical and thoracic vertebrae of giraffes is shifted to lie between the first and second thoracic vertebrae (T1 and T2), unlike most other ruminants where the articulation is between the seventh cervical vertebra (C7) and T1. This allows C7 to contribute directly to increased neck length and has given rise to the suggestion that T1 is actually C8, and that giraffes have added an extra cervical vertebra. However, this proposition is not generally accepted, as T1 has other morphological features, such as an articulating rib, deemed diagnostic of thoracic vertebrae, and because exceptions to the mammalian limit of seven cervical vertebrae are generally characterised by increased neurological anomalies and maladies.

There are several hypotheses regarding the evolutionary origin and maintenance of elongation in giraffe necks. The "competing browsers hypothesis" was originally suggested by Charles Darwin and challenged only recently. It suggests that competitive pressure from smaller browsers, such as kudu, steenbok and impala, encouraged the elongation of the neck, as it enabled giraffes to reach food that competitors could not. This advantage is real, as giraffes can and do feed up to 4.5 m (15 ft) high, while even quite large competitors, such as kudu, can feed up to only about 2 m (6 ft 7 in) high. There is also research suggesting that browsing competition is intense at lower levels, and giraffes feed more efficiently (gaining more leaf biomass with each mouthful) high in the canopy. However, scientists disagree about just how much time giraffes spend feeding at levels beyond the reach of other browsers, and a 2010 study found that adult giraffes with longer necks actually suffered higher mortality rates under drought conditions than their shorter-necked counterparts. This study suggests that maintaining a longer neck requires more nutrients, which puts longer-necked giraffes at risk during a food shortage.

Another 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, necks are longer and heavier for males than females of the same age, and the former do not employ other forms of combat. However, one objection is that it fails to explain why female giraffes also have long necks. It has also been proposed that the neck serves to give the animal greater vigilance.

Distribution & habitat

Giraffes usually inhabit savannahs and open woodlands. They prefer Acacieae, Commiphora, Combretum and open Terminalia woodlands over denser environments like Brachystegia woodlands. The Angolan giraffe can be found in desert environments.

The giraffe has intrigued various cultures, both ancient and modern, for its peculiar appearance, and has often been featured in paintings, books, and cartoons. It is classified by the International Union for Conservation of Nature as vulnerable to extinction, and has been extirpated from many parts of its former range. Giraffes are still found in numerous national parks and game reserves but estimates as of 2016 indicate that there are approximately 97,500 members of Giraffa in the wild. More than 1,600 were kept in zoos in 2010.

Food

Giraffes browse on the twigs of trees, preferring trees of the subfamily Acacieae and the genera Commiphora and Terminalia, which are important sources of calcium and protein to sustain the giraffe's growth rate. They also feed on shrubs, grass and fruit. A giraffe eats around 34 kg (75 lb) of foliage daily. When stressed, giraffes may chew the bark off branches. Although herbivorous, the giraffe has been known to visit carcasses and lick dried meat off bones.
During the wet season, food is abundant and giraffes are more spread out, while during the dry season, they gather around the remaining evergreen trees and bushes. Mothers tend to feed in open areas, presumably to make it easier to detect predators, although this may reduce their feeding efficiency. As a ruminant, the giraffe first chews its food, then swallows it for processing and then visibly passes the half-digested cud up the neck and back into the mouth to chew again. It is common for a giraffe to salivate while feeding. The giraffe requires less food than many other herbivores because the foliage it eats has more concentrated nutrients and it has a more efficient digestive system. The animal's faeces come in the form of small pellets. When it has access to water, a giraffe drinks at intervals no longer than three days.

Giraffes have a great effect on the trees that they feed on, delaying the growth of young trees for some years and giving "waistlines" to trees that are too tall. Feeding is at its highest during the first and last hours of daytime. Between these hours, giraffes mostly stand and ruminate. Rumination is the dominant activity during the night, when it is mostly done lying down.

Reproduction

Reproduction in giraffes is broadly polygamous: a few older males mate with the fertile females. Male giraffes assess female fertility by tasting the female's urine to detect oestrus, in a multi-step process known as the flehmen response. Males prefer young adult females over juveniles and older adults. Once an oestrous female is detected, the male will attempt to court her. When courting, dominant males will keep subordinate ones at bay. A courting male may lick a female's tail, rest his head and neck on her body or nudge her with his horns. During copulation, the male stands on his hind legs with his head held up and his front legs resting on the female's sides.

Giraffe gestation lasts 400–460 days, after which a single calf is normally born, although twins occur on rare occasions. The mother gives birth standing up. The calf emerges head and front legs first, having broken through the fetal membranes, and falls to the ground, severing the umbilical cord. The mother then grooms the newborn and helps it stand up. A newborn giraffe is 1.7–2 m (5.6–6.6 ft) tall. Within a few hours of birth, the calf can run around and is almost indistinguishable from a one-week-old. However, for the first 1–3 weeks, it spends most of its time hiding; its coat pattern providing camouflage. The ossicones, which have lain flat while it was in the womb, become erect within a few days.

Mothers with calves will gather in nursery herds, moving or browsing together. Mothers in such a group may sometimes leave their calves with one female while they forage and drink elsewhere. This is known as a "calving pool". Adult males play almost no role in raising the young, although they appear to have friendly interactions. Calves are at risk of predation, and a mother giraffe will stand over her calf and kick at an approaching predator. Females watching calving pools will only alert their own young if they detect a disturbance, although the others will take notice and follow.

The length time in which offspring stay with their mother varies, though it can last until the female's next calving. Likewise, calves may suckle for only a month or as long as a year. Females become sexually mature when they are four years old, while males become mature at four or five years. Spermatogenesis in male giraffes begins at three to four years of age. Males must wait until they are at least seven years old to gain the opportunity to mate.

Important Note:

This text is based on the article Giraffe from the free encyclopedia Wikipedia and is licensed under the Creative Commons CC-BY-SA 3.0 Unported (short version). A list of the authors is available on Wikipedia.