Giraffe
Giraffes are large African hoofed mammals. They are the tallest living terrestrial animals and the largest ruminants on Earth. They are classified under the family Giraffidae, along with their closest extant relative, the okapi. Traditionally, giraffes have been thought of as one species, Giraffa camelopardalis, with nine subspecies. Most recently, researchers proposed dividing them into four extant species, with seven subspecies, which can be distinguished morphologically by their fur coat patterns. Six valid extinct species of Giraffa are known from the fossil record.
The distinguishing characteristics of giraffes are their extremely long neck and legs, horn-like ossicones, and spotted coat patterns. Their 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 ground-based 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 groups. 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.
Giraffes have intrigued various ancient and modern cultures for their peculiar appearance and has often been featured in paintings, books, and cartoons. They have been extirpated from many parts of their former range. Giraffes are still found in many 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 in many 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 , of an ultimately unclear Sub-Saharan African language origin. The Middle English and early Modern English spellings, jarraf and ziraph, derive from the Arabic form-based Spanish and Portuguese girafa. The modern English form developed around 1600 from the French girafe."Camelopard" is an archaic English name for the giraffe; it derives from the Ancient Greek καμηλοπάρδαλις, from κάμηλος, "camel", and πάρδαλις, "leopard", referring to its camel-like shape and leopard-like colouration.
Taxonomy
Evolution
Giraffes, along with the okapi, are the only living members of family Giraffidae in the order Artiodactyla. They are ruminants of the clade Pecora, along with Antilocapridae, Cervidae, Bovidae and Moschidae. A 2019 genome study finds that Giraffidae are a sister taxon to Antilocapridae, with an estimated split of over 20 million years ago.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, 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.
File:Giraffidcomparison.jpg|thumb|upright|The extinct giraffid Samotherium in comparison with the okapi and giraffe. The anatomy of Samotherium appears to have shown a transition to a giraffe-like neck.
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 Giraffa. Bohlinia closely resembled modern giraffes, having a long neck and legs and similar ossicones and dentition.
Bohlinia colonised China and northern India and produced the Giraffa, which, around, 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 in eastern Africa during the Pleistocene. Some biologists suggest the 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 hypothesised 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 hypothesised to have had more okapi-like colourations.
The Masai 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 responsible for the animal's height and associated circulatory adaptations.
Species and subspecies
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 recognised 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 one to two 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 recognises 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, which was supported by a 2024 study of cranial morphology. A 2024 study found a higher amount of ancient gene flow than expected between populations.
The cladogram below shows the phylogenetic relationship between the four species and seven subspecies based on a 2021 genome analysis. The eight lineages correspond to eight traditional subspecies in the one-species hypothesis. The Rothschild giraffe is subsumed into G. camelopardalis camelopardalis.
The following table compares the different hypotheses for giraffe species. The description column shows the traditional nine subspecies in the one-species hypothesis.
The first extinct species to be described was Giraffa sivalensis from Pakistan, the holotype of which was reevaluated as a vertebra of separate species within the genus that was initially described as a fossil of the living giraffe. Another extinct species Giraffa punjabiensis is known from Pakistan. Four other valid extinct species of Giraffa known from Africa are Giraffa gracilis, Giraffa jumae, Giraffa pygmaea and Giraffa stillei. "G." pomeli from Algeria and Tunisia is not a species of Giraffinae, but a species of Palaeotraginae related to Mitilanotherium.
Anatomy
Fully grown giraffes stand tall, with males taller than females. The average weight is for an adult male and 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. The 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 coloured. 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 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. 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. Spotless or solid-colour giraffes are very rare, but have been observed.
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 odour than females, it may also have a sexual function.