Animal Facts – Giraffe

The giraffe is a large African hoofed mammal belonging to the genus Giraffa. It is the tallest living terrestrial animal and the largest ruminant on Earth. Traditionally, giraffes have been thought of as one species, Giraffa camelopardalis, with nine subspecies. Most recently, researchers proposed dividing them into up to eight extant species due to new research into their mitochondrial and nuclear DNA, as well as morphological measurements. Seven other extinct species of Giraffa are known from the fossil record.

The giraffe’s chief distinguishing characteristics are its extremely long neck and legs, its horn-like ossicones, and its spotted 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.

Lions, leopards, spotted hyenas, and African wild dogs may prey upon giraffes. 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”, combat bouts where the neck is used as a weapon. Dominant males gain mating access to females, which bear sole responsibility for rearing the young.

The giraffe has intrigued various ancient and modern cultures 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 (IUCN) 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 there are approximately 97,500 members of Giraffa in the wild. More than 1,600 were kept in zoos in 2010.

Etymology

The name “giraffe” has its earliest known origins in the Arabic word zarāfah (زرافة), ultimately from Persian زُرنَاپَا‎ (zurnāpā), a compound of زُرنَا‎ (zurnā, “flute, zurna”) and پَا‎ (pā, “leg”). In early Modern English, the spellings jarraf and ziraph were used, probably directly from the Arabic, and in Middle English jarraf and ziraph, gerfauntz. The Italian form giraffa arose in the 1590s. The modern English form developed around 1600 from the French girafe.

“Camelopard” /kəˈmɛləˌpɑːrd/ is an archaic English name for the giraffe; it derives from the Ancient Greek καμηλοπάρδαλις (kamēlopárdalis), from κάμηλος (kámēlos), “camel”, and πάρδαλις (párdalis), “leopard”, referring to its camel-like shape and leopard-like coloration.

Taxonomy

Evolution

The giraffe is one of only two living genera of the family Giraffidae in the order Artiodactyla, the other being the okapi. They are ruminants of the clade Pecora, along with Antilocapridae (pronghorns), Cervidae (deer), Bovidae (cattle, antelope, goats and sheep) and Moschidae (musk deer). A 2019 genome study (cladogram below) finds that Giraffidae are a sister taxon to Antilocapridae, with an estimated split of over 20 million years ago.

Ruminantia	Tragulina Tragulidae Pecora Antilocapridae Giraffidae Cervidae Bovidae Moschidae

The family Giraffidae was once much more extensive, with over 10 fossil genera described. The elongation of the neck appears to have started early in the giraffe lineage. Comparisons between giraffes and their ancient relatives suggest vertebrae close to the skull lengthened earlier, followed by lengthening of vertebrae further down. One early giraffid ancestor was Canthumeryx, which has been dated variously to have lived 25 to 20 million years ago, 17–15 mya or 18–14.3 mya, and whose deposits have been found in Libya. This animal resembled an antelope and had a medium-sized, lightly built body. Giraffokeryx appeared 15–12 mya on the Indian subcontinent and resembled an okapi or a small giraffe, and had a longer neck and similar ossicones. Giraffokeryx may have shared a clade with more massively built giraffids like Sivatherium and Bramatherium.

Giraffids like Palaeotragus, Shansitherium, and Samotherium appeared 14 mya and lived throughout Africa and Eurasia. These animals had broader skulls with reduced frontal cavities. Paleotragus resembled the okapi and may have been its ancestor. Others find that the okapi lineage diverged earlier, before Giraffokeryx. Samotherium was a particularly important transitional fossil in the giraffe lineage, as the length and structure of its cervical vertebrae were between those of a modern giraffe and an okapi, and its neck posture was likely similar to the former’s. Bohlinia, which first appeared in southeastern Europe and lived 9–7 mya, was likely a direct ancestor of the giraffe. Bohlinia closely resembled modern giraffes, having a long neck and legs and similar ossicones and dentition.

Bohlinia colonized China and northern India and produced the Giraffa, which, around 7 million years ago, reached Africa. Climate changes led to the extinction of the Asian giraffes, while the African giraffes survived and radiated into new species. Living giraffes appear to have arisen around 1 million years ago in eastern Africa during the Pleistocene. Some biologists suggest that modern giraffes descended from G. jumae; others find G. gracilis a more likely candidate. G. jumae was larger and more robust, while G. gracilis was smaller and more slender.

The changes from extensive forests to more open habitats, which began 8 mya, are believed to be the main driver for the evolution of giraffes. During this time, tropical plants disappeared and were replaced by arid C4 plants, and a dry savannah emerged across eastern and northern Africa and western India. Some researchers have hypothesized that this new habitat, coupled with a different diet, including acacia species, may have exposed giraffe ancestors to toxins that caused higher mutation rates and a higher rate of evolution. The coat patterns of modern giraffes may also have coincided with these habitat changes. Asian giraffes are hypothesized to have had more okapi-like colorations.

The giraffe genome is around 2.9 billion base pairs in length, compared to the 3.3 billion base pairs of the okapi. Of the proteins in giraffe and okapi genes, 19.4% are identical. The divergence of giraffe and okapi lineages dates to around 11.5 mya. A small group of regulatory genes in the giraffe appears to be responsible for the animal’s height and associated circulatory adaptations.

Species and subspecies

The International Union for Conservation of Nature (IUCN) currently recognizes only one species of giraffe with nine subspecies.

Carl Linnaeus originally classified living giraffes as one species in 1758. He gave it the binomial name Cervus camelopardalis. Mathurin Jacques Brisson coined the generic name Giraffa in 1762. During the 1900s, various taxonomies with two or three species were proposed. A 2007 study on the genetics of giraffes using mitochondrial DNA suggested at least six lineages could be recognized as species. A 2011 study using detailed analyses of the morphology of giraffes, and application of the phylogenetic species concept, described eight species of living giraffes. A 2016 study also concluded that living giraffes consist of multiple species. The researchers suggested the existence of four species, which have not exchanged genetic information between each other for 1 to 2 million years.

A 2020 study showed that depending on the method chosen, different taxonomic hypotheses recognizing from two to six species can be considered for the genus Giraffa. That study also found that multi-species coalescent methods can lead to taxonomic over-splitting, as those methods delimit geographic structures rather than species. The three-species hypothesis, which recognizes G. camelopardalis, G. giraffa, and G. tippelskirchi, is highly supported by phylogenetic analyses and also corroborated by most population genetic and multi-species coalescent analyses^. A 2021 whole genome sequencing study suggests the existence of four distinct species and seven subspecies.

The cladogram below shows the phylogenetic relationship between the four proposed species and seven subspecies based on the genome analysis. Note the eight lineages correspond to eight of the traditional subspecies in the one-species hypothesis. The Rothschild giraffe is subsumed into G. camelopardalis camelopardalis.

Anatomy

Fully grown giraffes stand 4.3–5.7 m (14–19 ft) tall, with males taller than females. The average weight is 1,192 kg (2,628 lb) for an adult male and 828 kg (1,825 lb) for an adult female. Despite its long neck and legs, its body is relatively short. The skin is mostly gray, or tan, and can reach a thickness of 20 mm (0.79 in). The 80–100 cm (31–39 in) long tail ends in a long, dark tuft of hair and is used as a defense against insects.

The coat has dark blotches or patches, which can be orange, chestnut, brown, or nearly black, surrounded by light hair, usually white or cream-colored. Male giraffes become darker as they grow old. 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 even a few meters 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. Each giraffe has a unique coat pattern. Calves inherit some coat pattern traits from their mothers, and variation in some spot traits is correlated with calf survival. The skin under the blotches may regulate the animal’s body temperature, being sites for complex blood vessel systems and large sweat glands.

The fur may give the animal chemical defense, as its parasite repellents give it 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 males have a stronger odor than females, it may also have a sexual function.

Habitat and feeding

Giraffes usually inhabit savannahs and open woodlands. They prefer areas dominated by Acacieae, Commiphora, Combretum, and Terminalia trees over Brachystegia which are more densely spaced. The Angolan giraffe can be found in desert environments. Giraffes browse on the twigs of trees, preferring those 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 plant matter daily. When stressed, giraffes may chew on large branches, stripping them of bark. Giraffes are also recorded to chew old 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. 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 feces come in the form of small pellets. When it has access to water, a giraffe will go no more than three days without drinking.

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 too-tall trees. 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.

~Wikipedia