Temporal range: Eocene–Recent
|Black rhinoceros (Diceros bicornis) at the Saint Louis Zoo|
Rhinoceros //, often abbreviated as rhino, is a group of five extant species of knee-less, odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia.
The rhinoceros family is characterized by its large size (one of the largest remaining megafauna), with all of the species able to reach one tonne or more in weight; a herbivorous diet; a thick protective skin, 1.5–5 cm thick, formed from layers of collagen positioned in a lattice structure; relatively small brains for mammals this size (400–600 g); and a large horn. They generally eat leafy material, although their ability to ferment food in their hindgut allows them to subsist on more fibrous plant matter, if necessary. Unlike other perissodactyls, the African species of rhinoceros lack teeth at the front of their mouths, relying instead on their powerful premolar and molar teeth to grind up plant food.
Rhinoceros are killed by humans for their horns, which are bought and sold on the black market, and which are used by some cultures for ornamental or (pseudo-scientific) medicinal purposes. The horns are made of keratin, the same type of protein that makes up hair and fingernails. Both African species and the Sumatran rhinoceros have two horns, while the Indian and Javan rhinoceros have a single horn.
Taxonomy and naming
The word rhinoceros is derived through Latin from the Template:Lang-grc, which is composed of ῥῑνο- (rhino-, "nose") and κέρας (keras, "horn"). The plural in English is rhinoceros or rhinoceroses. The collective noun for a group of rhinoceroses is crash or herd.
The five living species fall into three categories. The two African species, the white rhinoceros and the black rhinoceros, diverged during the early Pliocene (about 5 million years ago) but the Dicerotini group to which they belong originated in the middle Miocene, about 14.2 million years ago. The main difference between black and white rhinos is the shape of their mouths. White rhinos have broad flat lips for grazing and black rhinos have long pointed lips for eating foliage. A popular — if unverified — theory claims that the name white rhinoceros was actually a mistake, or rather a corruption of the word weid ("wide" in Afrikaans), referring to their square lips.
White rhinoceros are divided into Northern and Southern subspecies. There are two living Rhinocerotini species, the Indian rhinoceros and the Javan rhinoceros, which diverged from one another about 10 million years ago. The Sumatran rhinoceros is the only surviving representative of the most primitive group, the Dicerorhinini, which emerged in the Miocene (about 20 million years ago). The extinct woolly rhinoceros of northern Europe and Asia was also a member of this tribe.
A subspecific hybrid white rhino (Ceratotherium s. simum × C. s. cottoni) was bred at the Dvůr Králové Zoo (Zoological Garden Dvur Kralove nad Labem) in the Czech Republic in 1977. Interspecific hybridisation of black and white rhinoceros has also been confirmed.
All rhinoceros species have 82 chromosomes (diploid number, 2N, per cell), except the black rhinoceros, which has 84.
The five extant species
There are two subspecies of white rhinos; as of 2005, South Africa has the most of the first subspecies, the southern white rhinoceros (Ceratotherium simum simum). The population of southern white rhinos is about 14,500, making them the most abundant subspecies of rhino in the world. However, the population of the second subspecies, the critically endangered northern white rhinoceros (Ceratotherium simum cottoni), is down to as few as four individuals in the wild, with the possibility of complete extinction in the wild having been noted since June 2008. Six are known to be held in captivity, two of which reside in a zoo in San Diego. There are currently four born in a zoo in the Czech Republic which were transferred to a wildlife refuge in Kenya in December 2009, in an effort to have the animals reproduce and save the subspecies.
The rhino receives its name not from its colour, but from the Dutch settlers that gave it the name "whyde", meaning wide referring to the animals square mouth. Confusion in translation then led to the to the name "white" being adopted
The white rhino has an immense body and large head, a short neck and broad chest. This rhino can exceed 3,500 kg (7,700 lb), have a head-and-body length of 3.5–4.6 m (11–15 ft) and a shoulder height of 1.8–2 m (5.9–6.6 ft). The record-sized white rhinoceros was about 4,500 kg (10,000 lb). On its snout it has two horns. The front horn is larger than the other horn and averages 90 cm (35 in) in length and can reach 150 cm (59 in). The white rhinoceros also has a prominent muscular hump that supports its relatively large head. The colour of this animal can range from yellowish brown to slate grey. Most of its body hair is found on the ear fringes and tail bristles with the rest distributed rather sparsely over the rest of the body. White rhinos have the distinctive flat broad mouth which is used for grazing.
The name black rhinoceros (Diceros bicornis) was chosen to distinguish this species from the white rhinoceros (Ceratotherium simum). This can be confusing, as those two species are not really distinguishable by color. There are four subspecies of black rhino: South-central (Diceros bicornis minor), the most numerous, which once ranged from central Tanzania south through Zambia, Zimbabwe and Mozambique to northern and eastern South Africa; South-western (Diceros bicornis bicornis) which are better adapted to the arid and semi-arid savannas of Namibia, southern Angola, western Botswana and western South Africa; East African (Diceros bicornis michaeli), primarily in Tanzania; and West African (Diceros bicornis longipes) which was declared extinct in November 2011. The native Tswanan name Keitloa is used to describe a South African variation of the black rhino in which the posterior horn is equal to or longer than the anterior horn.
An adult black rhinoceros stands 150–175 cm (59–69 in) high at the shoulder and is 3.5–3.9 m (11–13 ft) in length. An adult weighs from 850 to 1,600 kg (1,870 to 3,500 lb), exceptionally to 1,800 kg (4,000 lb), with the females being smaller than the males. Two horns on the skull are made of keratin with the larger front horn typically 50 cm long, exceptionally up to 140 cm. Sometimes, a third smaller horn may develop. The black rhino is much smaller than the white rhino, and has a pointed mouth, which they use to grasp leaves and twigs when feeding.
The Indian rhinoceros or the greater one-horned rhinoceros (Rhinoceros unicornis) is now found almost exclusively in Nepal and North-Eastern India. The rhino once inhabited many areas of Pakistan to Burma and may have even roamed in China. But because of human influence their range has shrunk and now they only exist in several protected areas of India (in Assam, West Bengal, Gujarat and a few pairs in Uttar Pradesh) and Nepal, plus a few pairs in Lal Suhanra National Park in Pakistan. It is confined to the tall grasslands and forests in the foothills of the Himalayas.
The Indian rhinoceros has thick, silver-brown skin which creates huge folds all over its body. Its upper legs and shoulders are covered in wart-like bumps, and it has very little body hair. Fully grown males are larger than females in the wild, weighing from 2,500–3,200 kg (5,500–7,100 lb).The Indian rhino stands at 1.75–2.0 metres (5.75–6.5 ft). Female Indian rhinos weigh about 1,900 kg and are 3–4 metres long. The record-sized specimen of this rhino was approximately 3,800 kg. The Indian rhino has a single horn that reaches a length of between 20 and 100 cm. Its size is comparable to that of the white rhino in Africa.
The Javan rhinoceros (Rhinoceros sondaicus) is one of the rarest and most endangered large mammals anywhere in the world. According to 2002 estimates, only about 60 remain, in Java (Indonesia) and Vietnam. Of all the rhino species, the least is known of the Javan Rhino. These animals prefer dense lowland rain forest, tall grass and reed beds that are plentiful with large floodplains and mud wallows. Though once widespread throughout Asia, by the 1930s the rhinoceros was nearly hunted to extinction in India, Burma, Peninsular Malaysia, and Sumatra for the supposed medical powers of its horn and blood. As of 2009, there are only 40 of them remaining in Ujung Kulon Conservation, Java, Indonesia. The last rhinoceros in Vietnam was reportedly killed in 2010.
Like the closely related larger Indian rhinoceros, the Javan rhinoceros has only a single horn. Its hairless, hazy gray skin falls into folds into the shoulder, back, and rump giving it an armored-like appearance. The Javan rhino's body length reaches up to 3.1–3.2 m (10–10 ft), including its head and a height of 1.5–1.7 m (Template:Convert/Dual/LoffAnd) tall. Adults are variously reported to weigh between 900–1,400 kg or 1,360–2,000 kg. Male horns can reach 26 cm in length while in females they are knobs or are not present at all.
The Sumatran rhinoceros (Dicerorhinus sumatrensis) is the smallest extant rhinoceros species, as well as the one with the most fur, which allows it to survive at very high altitudes in Borneo and Sumatra. Due to habitat loss and poaching, its numbers have declined and it is the most threatened rhinoceros. About 275 Sumatran rhinos are believed to remain.
Typically a mature Sumatran rhino stands about 130 cm (51 in) high at the shoulder, a body length of 240–315 cm (94–124 in) and weighs around 700 kg (1,500 lb), though the largest individuals have been known to weigh as much as 1,000 kilograms. Like the African species, it has two horns; the larger is the front (25–79 cm), with the smaller second usually less than 10 cm long. The males have much larger horns than the females. Hair can range from dense (the densest hair in young calves) to scarce. The color of these rhinos is reddish brown. The body is short and has stubby legs. They also have a prehensile lip.
Rhinocerotoids diverged from other perissodactyls by the early Eocene. Fossils of Hyrachyus eximus found in North America date to this period. This small hornless ancestor resembled a tapir or small horse more than a rhino. Three families, sometimes grouped together as the superfamily Rhinocerotoidea, evolved in the late Eocene: Hyracodontidae, Amynodontidae and Rhinocerotidae.
Hyracodontidae, also known as 'running rhinos', showed adaptations for speed, and would have looked more like horses than modern rhinos. The smallest hyracodontids were dog-sized; the largest was Indricotherium, believed to be one of the largest land mammals that ever existed. The hornless Indricotherium was almost seven metres high, ten metres long, and weighed as much as 15 tons. Like a giraffe, it ate leaves from trees. The hyracodontids spread across Eurasia from the mid-Eocene to early Miocene.
The family Amynodontidae, also known as "aquatic rhinos", dispersed across North America and Eurasia, from the late Eocene to early Oligocene. The amynodontids were hippopotamus-like in their ecology and appearance, inhabiting rivers and lakes, and sharing many of the same adaptations to aquatic life as hippos.
The family of all the modern rhinoceros, the Rhinocerotidae, first appeared in the Late Eocene in Eurasia. The earliest members of Rhinocerotidae were small and numerous; at least 26 genera lived in Eurasia and North America until a wave of extinctions in the middle Oligocene wiped out most of the smaller species. Several independent lineages survived, however. Menoceras, a pig-sized rhinoceros had two horns side-by-side and Teleoceras of North America had short legs and a barrel chest and lived until about 5 million years ago. The last rhinos in the Americas became extinct during the Pliocene.
Modern rhinos are believed to have dispersed from Asia beginning in the Miocene. Two species survived the most recent period of glaciation and inhabited Europe as recently as 10,000 years ago. The woolly rhinoceros appeared in China around 1 million years ago and first arrived in Europe around 600,000 years ago and again 200,000 years ago, where alongside the woolly mammoth, they became numerous but eventually were hunted to extinction by early humans. Another species of enormous rhino, Elasmotherium, survived through the middle Pleistocene. Also known as the giant rhinoceros, Elasmotherium was two meters tall, five meters long and weighed around five tons, with a single enormous horn, hypsodont teeth and long legs for running.
Of the extant rhinoceros species, the Sumatran rhino is the most archaic, first emerging more than 15 million years ago. The Sumatran rhino was closely related to the woolly rhinoceros, but not to the other modern species. The Indian rhino and Javan rhino are closely related and from a more recent lineage of Asian rhino. The ancestors of early Indian and Javan rhino diverged 2–4 million years ago.
The origin of the two living African rhinos can be traced back to the late Miocene ( ) species Ceratotherium neumayri. The lineages containing the living species diverged by the early Pliocene ( ), when Diceros praecox, the likely ancestor of the black rhinoceros, appears in the fossil record. The black and white rhinoceros remain so closely related that they can still mate and successfully produce offspring.
- Family Rhinocerotidae
- Subfamily Rhinocerotinae
- Tribe Aceratheriini
- †Aceratherium lived from 33.9—3.4 Ma
- †Acerorhinus 13.6—7.0 Ma
- †Alicornops 13.7—5.33 Ma
- †Aphelops 20.430—5.330 Ma
- †Chilotheridium 23.03—11.610 Ma
- †Chilotherium 13.7—3.4 Ma
- †Dromoceratherium 15.97—7.25 Ma
- †Floridaceras 20.43—16.3 Ma
- †Hoploaceratherium 16.9—16.0 Ma
- †Peraceras 20.6—10.3 Ma
- †Plesiaceratherium 20.0—11.6 Ma
- †Proaceratherium 16.9—16.0 Ma
- Tribe Teleoceratini
- Tribe Rhinocerotini 40.4—11.1 Ma—Present
- Tribe Dicerorhinini
- Tribe Dicerotini 23.03—Present
- Tribe Aceratheriini
- Subfamily Elasmotheriinae
- †Gulfoceras 23.030—20.430 Ma
- Tribe Diceratheriini
- Tribe Elasmotheriini 20.0—0.126 Ma
- †Bugtirhinus 20.0—16.9 Ma
- †Elasmotherium – Giant rhinoceros 3.6—0.126 Ma
- †Hispanotherium synonymized with Huaqingtherium 16.0—7.250 Ma
- †Menoceras 23.03—16.3 Ma
- †Ougandatherium 20.0—16.9 Ma
- †Sinotherium 9.0—5.3 Ma
- Subfamily Rhinocerotinae
In the wild, adult rhinoceros have few natural predators other than humans. Young rhinos can fall prey to predators such as big cats, crocodiles, wild dogs, and hyena. Although rhinos are of large size and have a reputation of being tough, they are actually very easily poached, because it visits water holes daily, the rhinoceros is easily killed while taking a drink. As of December 2009 poaching has been on a global increase whilst efforts to protect the rhinoceros are being considered increasingly ineffective. The worst estimate, that only 3% of poachers are successfully countered, is reported of Zimbabwe. Rhino horn is considered to be particularly effective on fevers and even "life saving" by traditional Chinese medicine practitioners, which in turn provides a sales market. Nepal is apparently alone in avoiding the crisis while poacher-hunters grow ever more sophisticated. South African officials are calling for urgent action against rhinoceros poaching after poachers killed the last female rhinoceros in the Krugersdorp Game Reserve near Johannesburg. Statistics from South African National Parks show a record 333 rhinoceros have been killed in 2010.
Rhinoceros horns, unlike those of other horned mammals, consist of keratin only and lack a bony core, such as bovine horns. Rhinoceros horns are used in traditional Asian medicine, and for dagger handles in Yemen and Oman. Esmond Bradley Martin has reported on the trade for dagger handles in Yemen.
One repeated misconception is that rhinoceros horn in powdered form is used as an aphrodisiac in Traditional Chinese Medicine (TCM) as Cornu Rhinoceri Asiatici (犀角). It is, in fact, prescribed for fevers and convulsions. Neither have been proven by evidence-based medicine. Discussions with TCM practitioners to reduce its use have met with mixed results since some TCM doctors see rhinoceros horn as a life-saving medicine of better quality than substitutes. China has signed the CITES treaty however, and removed rhinoceros horn from the Chinese medicine pharmacopeia, administered by the Ministry of Health, in 1993. In 2011 in the United Kingdom, the Register of Chinese Herbal Medicine issued a formal statement condemning the use of rhinoceros horn. A growing number of TCM educators have also spoken out against the practice. To prevent poaching, in certain areas, rhinos have been tranquilized and their horns removed. Armed park rangers, particularly in South Africa, are also working on the front lines to combat poaching, sometimes killing poachers who are caught in the act. A recent spike in rhino killings has made conservationaists concerned about the future of rhino species. During 2011 448 rhino were killed for their horn in South African alone. The horn is incredibly valuable: an average sized horn can bring in much as a quarter of a million dollars in Vietnam and many rhino range States have stockpiles of rhino horn. Still, poaching is hitting record levels due to demands from China and Vietnam.
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