Rhinoceros And Hippopotamus

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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(HP Pavilion dv4 battery).

Members of the rhinoceros family are characterized by their large size (they are some of of the largest remaining megafauna, with all of the species able to reach one tonne or more in weight); as well as by 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 (HP PAVILION DV4000 battery) (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. (HP Pavilion dv5-1000 battery)

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.[2] Both African species and the Sumatran rhinoceros have two horns, while the Indian and Javan rhinoceros have a single horn(HP Pavilion dv6 battery).

The IUCN Red List identifies three of the species as critically endangered.

Taxonomy and naming

Comparison between living rhinoceroses species.

The word rhinoceros is derived through Latin from the Ancient Greek: ῥῑνόκερως, 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(HP Pavilion DV6-1210SA battery).

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(HP Pavilion dv6000 battery). 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. (HP Pavilion dv6200 battery)

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). (HP Pavilion dv6500 battery)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. (HP Pavilion dv8000 battery)

All rhinoceros species have 82 chromosomes (diploid number, 2N, per cell), except the black rhinoceros, which has 84.

The five extant species

The white rhinoceros is actually grey

The black rhinoceros has a beak shaped lip and is similar in color to the white rhinoceros

The Indian rhinoceros has a single horn

Smaller in size than the Indian rhinoceros, the Javan rhinoceros also have a single horn

The Sumatran rhinoceros is the smallest of the rhino species(HP Pavilion dv9000 battery)

White rhinoceros

Main article: White rhinoceros

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) (HP Pavilion dv9200 battery), 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.[6] 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. (HP Pavilion dv9500 battery)

There is no conclusive explanation of the name white rhinoceros. A popular theory that "white" is a distortion of the Dutch word wijd (or its other possible spellings whyde, weit, etc., all meaning wide) is not supported by linguistic studies.[8]

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) (HP Pavilion dv9700 battery). The record-sized white rhinoceros was about 4,500 kg (10,000 lb).[9] 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(HP Pavilion dv6-3000 battery). 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.

Black rhinoceros

Main article: Black rhinoceros

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(HP Pavilion dv6-3005sa battery). 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(HP Pavilion dv6-3005tx battery), 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.[10] 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. (HP Pavilion dv6-3006tx battery)

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.[12] An adult weighs from 850 to 1,600 kg (1,900 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(HP Pavilion dv6-3011tx battery). 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.

During the latter half of the 20th century their numbers were severely reduced from an estimated 70,000[13] in the late 1960s to only 2,410 in 1995.[14]

Indian rhinoceros

Main article: Indian rhinoceros

The Indian rhinoceros or the greater one-horned rhinoceros (Rhinoceros unicornis) is now found almost exclusively in Nepal and North-Eastern India(HP Pavilion dv6-3010sa battery). 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(HP Pavilion dv6-3015sa battery).

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)(HP Pavilion dv6-3020sa battery). 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.

Two-thirds of the world's Indian rhinoceroses are now confined to the Kaziranga National Park situated in the Golaghat district of Assam, India. (HP Pavilion dv6-3025sa battery)

Javan rhinoceros

Main article: Javan rhinoceros

The Javan rhinoceros (Rhinoceros sondaicus) is one of the rarest and most endangered large mammals anywhere in the world.[16] 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(HP Pavilion dv6-3026tx battery). 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. (HP Pavilion dv6-3030sa battery)

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 (4 ft 10 in–5 ft 7 in) tall. Adults are variously reported to weigh between 900–1,400 kg[18] or 1,360–2,000 kg. (HP Pavilion dv6-3030tx battery)Male horns can reach 26 cm in length while in females they are knobs or are not present at all.[19]

Sumatran rhinoceros

Main article: Sumatran rhinoceros

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(HP Pavilion dv6-3031sa battery).

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) (HP Pavilion dv6-3032sa battery), 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.

Evolution

The thick dermal armour of the Rhinoceros evolved at the same time as shearing tusks(HP Pavilion dv6-3032tx battery)

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(HP Pavilion dv6-3033sa battery).

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(HP Pavilion dv6-3035sa battery), 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(HP Pavilion dv6-3040sa battery).

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(HP Pavilion dv6-3042tx battery). 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(HP Pavilion dv6-3044sa battery). 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(HP Pavilion dv6-3045sa battery). 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(HP Pavilion dv6-3046sa battery). 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.[21]

The origin of the two living African rhinos can be traced back to the late Miocene (6 mya) species Ceratotherium neumayri. The lineages containing the living species diverged by the early Pliocene (1.5 mya), when Diceros praecox, the likely ancestor of the black rhinoceros, appears in the fossil record. (HP Pavilion dv6-3047sa battery)The black and white rhinoceros remain so closely related that they can still mate and successfully produce offspring.[5]

Predators

Monk with rhinoceros horn. Samye, Tibet, 1938.

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(HP Pavilion dv6-3048sa battery). 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(HP Pavilion dv6-3048tx battery), which in turn provides a sales market. Nepal is apparently alone in avoiding the crisis while poacher-hunters grow ever more sophisticated.[26] 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.[27] Statistics from South African National Parks show a record 333 rhinoceros have been killed in 2010(HP Pavilion dv6-3050eo battery).

Horns

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. (HP Pavilion dv6-3050sa battery)

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.[30] 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.(HP Pavilion dv6-3055sa battery) 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.[32] A growing number of TCM educators have also spoken out against the practice. (HP Pavilion dv6-3056sa battery) 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(HP Pavilion dv6-3057sa battery). During 2011 448 rhino were killed for their horn in South Africa alone.[34] 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.(HP Pavilion dv6-3060sa battery)

Historical representations

Albrecht Dürer created a famous woodcut of a rhinoceros in 1515, based on a written description and brief sketch by an unknown artist of an Indian rhinoceros that had arrived in Lisbon earlier that year. Dürer never saw the animal itself, and as a result, Dürer's Rhinoceros is a somewhat inaccurate depiction(HP Pavilion dv6-3065ea battery).

There are legends about rhinoceros stamping out fire in Malaysia, India, and Burma. The mythical rhinoceros has a special name in Malay, badak api, where badak means rhinoceros and api means fire. The animal would come when a fire is lit in the forest and stamp it out.[38] There are no recent confirmations of this phenomenon. However, this legend has been reinforced by the film The Gods Must Be Crazy, where an African rhinoceros is shown to be putting out two campfires. (HP Pavilion dv6-3067ea battery)

The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl(HP Pavilion dv6-3068ea battery).

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land(HP Pavilion dv6-3070ea battery).

Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago.[3] The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago.[4] The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago(HP Pavilion dv6-3077la battery).

The hippopotamus is recognizable by its barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds (four legged mammals) [5] and despite its stocky shape and short legs(HP Pavilion dv6-3085ea battery), it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. There are an estimated 125,000 to 150,000 hippos throughout Sub-Saharan Africa; Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations. (HP Pavilion dv6-3100 battery)They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar.

Etymology

Look up hippopotamus in Wiktionary, the free dictionary.

The word "hippopotamus" is derived from the ancient Greek ἱπποπόταμος, hippopotamos, from ἵππος, hippos, "horse", and ποταμός, potamos, "river", meaning "horse of the river".[6] In English, the plural is hippopotamuses, but hippopotami is also used; (HP Pavilion dv6-3100sa battery) hippos can be used as a short plural. Hippopotamuses are gregarious, living in groups of up to 30 animals; such a name is called a pod, herd, dale, or bloat.

In Africa, the hippo is known by several names including Kiboko (Swahili), Ensherre (Nkore), Tomondo (Turu), Nvubu (Luganda), Ifuru (Luhya), Emiria (Ateso), Magawit (Sebei), Kibei (Kalenjin), Olmakau (Maasai) and Jir (Somali) in the east;[8]:256 and Seekoei (Afrikaans), Mvuvu (Venda), Kubu (Lozi) and Mvubu (Xhosa, Siswati and Zulu) in the south. (HP Pavilion dv6-3110ea battery)

Taxonomy and origins

Classification

The hippopotamus is the type genus of the family Hippopotamidae. The Pygmy Hippopotamus belongs to a different genus in Hippopotamidae, either Choeropsis or Hexaprotodon. Hippopotamidae are sometimes known as Hippopotamids. Sometimes the sub-family Hippopotaminae is used. Further, some taxonomists group hippopotamuses and anthracotheres in the super-family Anthracotheroidea or Hippopotamoidea(HP Pavilion dv6-3110sa battery).

A pygmy hippopotamus (Hexaprotodon liberiensis)

Hippopotamidae are classified along with other even-toed ungulates in the order Artiodactyla. Other artiodactyls include camels, cows, deer and pigs, although hippopotamuses are not closely related to these groups.

Five subspecies of hippos have been described based on morphological differences in their skulls and geographical differences: (HP Pavilion dv6-3111sa battery)

H. a. amphibius – (the nominate subspecies) which stretched from Egypt, where they are now extinct, south up the Nile River to Tanzania and Mozambique.

H. a. kiboko – in the Horn of Africa, in Kenya and Somalia. Broader nasals and more hollowed interorbital region.

H. a. capensis – from Zambia to South Africa. Most flattened skull of the subspecies(HP Pavilion dv6-3112sa battery).

H. a. tschadensis – throughout Western Africa to, as the name suggests, Chad. Slightly shorter and wider face, with prominent orbits.

H. a. constrictus – in Angola, the southern Democratic Republic of Congo and Namibia. Named for its deeper preorbital constriction.

The suggested subspecies were never widely used or validated by field biologists; the described morphological differences were small enough that they could have resulted from simple variation in non-representative samples. (HP Pavilion dv6-3113sa battery)Genetic analyses have tested the existence of three of these putative subspecies. A study examining mitochondrial DNA from skin biopsies taken from 13 sampling locations, considered genetic diversity and structure among hippo populations across the continent. The authors found low but significant genetic differentiation among H. a. amphibius, H. a. capensis, and H. a. kiboko. Neither H.a.tschadensis nor H.a.constrictus have been tested. (HP Pavilion dv6-3114sa battery)

[edit]Evolution

Until 1909, naturalists grouped hippos with pigs, based on molar patterns. Several lines of evidence, first from blood proteins, then from molecular systematics[14] and DNA [15][16] and the fossil record, show that their closest living relatives are cetaceans—whales, dolphins and porpoises.[17][18] The common ancestor of hippos and whales branched off from Ruminantia and the rest of the even-toed ungulates(HP Pavilion dv6-3115sa battery); the cetacean and hippo lineages split soon afterwards.

The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[15][17] This hypothesized ancestral group likely split into two branches around 54 million years ago.[14] One branch would evolve into cetaceans(HP Pavilion dv6-3115tx battery), possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[19]

Hippopotamus madagascariensis skeleton with a modern hippopotamus skull.

The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads(HP Pavilion dv6-3116sa battery). All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[17]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[20] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos(HP Pavilion dv6-3116tx battery). Their common ancestor would have lived in the Miocene, about 20 million years ago.

Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe(HP Pavilion dv6-3117sa battery), no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[21]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon) (HP Pavilion dv6-3118sa battery), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus(HP Pavilion dv6-3119sa battery).

Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[22] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction. (HP Pavilion dv6-3120sa battery)Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[23]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene. (HP Pavilion dv6-3121sa battery) Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer.

The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene(HP Pavilion dv6-3122sa battery). Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man.[25][24]

Description

A hippo's skull, showing the large canine teeth used for fighting

Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river(HP Pavilion dv6-3123sa battery). Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[11]:3

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb) (HP Pavilion dv6-3125sa battery). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[11]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) and occasionally weighing 4,500 kg (9,900 lb).[26][27] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25. (HP Pavilion dv6-3127sa battery)

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[29][30] The range of hippopotamus sizes overlaps with the range of the White Rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land(HP Pavilion dv6-3130sa battery). Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. (HP Pavilion dv6-3131sa battery)

An open mouth signals that the hippo feels threatened.

The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) (HP Pavilion dv6-3140sa battery)because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[8]:260 The skin is 6 in (15 cm) thick,[31] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink. (HP Pavilion dv6-3141sa battery)

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[8]:259 The animal has a distinctive gape, which can reach 150°.[31] On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf) (HP Pavilion dv6-3150sa battery); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[32] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in). (HP Pavilion dv6-3163eo battery)

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) (HP Pavilion dv6-3180ea battery) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. (HP Pavilion dv6-3298ea battery)

A hippo's lifespan is typically 40–50 years.[8]:277 Donna the Hippo, 60, is the oldest living hippo in captivity. She lives at the Mesker Park Zoo in Evansville, Indiana, USA.[34][35] The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61. (HP Pavilion dv6-3299ea battery)

Distribution

Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[37] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region until historic times but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome; (HP Pavilion dv6-3300 battery) the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of Uganda, Sudan, Somalia, Kenya, northern Democratic Republic of the Congo and Ethiopia, west through Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia). A separate population exists in Tanzania and Mozambique(HP Pavilion dv6-3300sg battery).

Conservation status

The Hippopotamus Hunt (1617), by Peter Paul Rubens

Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water. (HP Pavilion dv6-3350ef battery) Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. (HP Pavilion dv6-3350sf battery)

The hippo population declined most dramatically in the Democratic Republic of the Congo.[39] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[40] The decline is attributed to the disruptions caused by the Second Congo War.[40] The poachers are believed to be former Hutu rebels(HP Pavilion dv6-3351ef battery), poorly paid Congolese soldiers, and local militia groups.[40] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[41] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track.

[edit]Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans(HP Pavilion dv6-3351sf battery). They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[42] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") (HP Pavilion dv6-3355ef battery)was killed by hunters under authorization of the local authorities.[43][44] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities(HP Pavilion dv6-3355sf battery).

Behavior

A bull hippo out of water during daylight

Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water(HP Pavilion dv6-3362ef battery).

Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[45] Like almost any herbivore, they will consume many other plants if presented with them(HP Pavilion dv6-3362sf battery), but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[46] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[47] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress. HP Pavilion dv6-6000 battery 

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[46] Because of their size and their habit of taking the same paths to feedHP Pavilion dv6-6000eg battery, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[48]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes. HP Pavilion dv6-6001ea batteryThe process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges.

As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food. HP Pavilion dv6-6001eg battery

[edit]Social life

A hippopotamus pod

Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[50] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown. HP Pavilion dv6-6001sg battery

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[11]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by genderHP Pavilion dv6-6002eg battery. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[11]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond. HP Pavilion dv6-6002sg battery

Reproduction

Hippos are born underwater.

Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[52] Males reach maturity at around 7.5 years.

A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summerHP Pavilion dv6-6003eg battery, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[11]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months. HP Pavilion dv6-6004sa battery

Mating occurs in the water with the female submerged for most of the encounter,[11]:63 her head emerging periodically to draw breath. Hippos are one of the few mammals that give birth under water, along with Cetaceans and Sirenians (manatees and dugongs). Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) HP Pavilion dv6-6005ea battery and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a yearHP Pavilion dv6-6005eg battery.

Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents) HP Pavilion dv6-6005sg battery.

Aggression

Male hippos fighting

Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[54] Hippos are very aggressive towards humansHP Pavilion dv6-6006ea battery, whom they commonly attack whether in boats or on land with no apparent provocation.[55] They are widely considered to be one of the most dangerous large animals in Africa.[56][57]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[58] Likely for the same reason, hippos are retromingent – that is, they urinate backwards. HP Pavilion dv6-6007sg battery

When in combat, male hippos use their incisors to parry each others attacks, and their lower canines to inflict damage.[8] Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrinkHP Pavilion dv6-6007tx battery, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[53] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior.[11]:82–83

Hippos and humans

A faience sculpture, from the New Kingdom of Egypt, 18th/19th dynasty, c. 1500–1300 BC, when hippos were still widespread along the NileHP Pavilion dv6-6008eg battery

Obaysch lounging at the London Zoo in 1852

The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[60] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer MountainsHP Pavilion dv6-6008sa battery. Hippos were also well-known to the ancient Egyptians, where the hippo was recognized as a ferocious denizen of the Nile.

The Hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD). HP Pavilion dv6-6008tx batteryHippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief DinizuluHP Pavilion dv6-6011tu battery, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [62]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus." HP Pavilion dv6-6012tu battery

[edit]Hippos in zoos

Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[64] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivityHP Pavilion dv6-6013cl battery. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive anim

als to maintain.[11]:129[64]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitatsHP Pavilion dv6-6013tu battery. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[65] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo.[66]

Cultural depictions

The cover of the Hippopotamus Polka. The unlikely portrayal of dancing hippos was echoed in Disney's FantasiaHP Pavilion dv6-6022eg battery.

A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[67] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young. HP Pavilion dv6-6023tx battery The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[70]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fishHP Pavilion dv6-6024tx battery. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so he can inspect it for fish bones. [71] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water. HP Pavilion dv6-6025tx battery

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[64] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[72] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandiseHP Pavilion dv6-6026tx battery, and many a stuffed hippo toy.[73][74] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[75] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. HP Pavilion dv6-6027tx battery

Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[39] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the AnimaniacsHP Pavilion dv6-6029tx battery, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [78] based in MunichHP Pavilion dv6-6042sf battery, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each timeHP Pavilion dv6-6051sf battery. The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.CHP Pavilion dv6-6051xx battery.

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