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One-horned rhinoceros

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One-horned rhinoceros

Indian rhinoceros[1]
Indian rhinoceros (Rhinoceros unicornis) in the Kaziranga National Park
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Rhinocerotidae
Genus: Rhinoceros
Species: R. unicornis
Binomial name
Rhinoceros unicornis
Linnaeus, 1758
Indian rhinoceros range

The Indian rhinoceros (Rhinoceros unicornis), also called the greater one-horned rhinoceros and Indian one-horned rhinoceros, belongs to the Rhinocerotidae family. Listed as a vulnerable species, the large mammal is primarily found in north-eastern India's Assam and in protected areas in the Terai of Nepal, where populations are confined to the riverine grasslands in the foothills of the Himalayas.[2]

The Indian rhinoceros once ranged throughout the entire stretch of the Indo-Gangetic Plain, but excessive hunting reduced the natural habitat drastically. Today, about 3,000 rhinos live in the wild, 2,000 of which are found in India's Assam alone.[3]

It is the fifth largest land animal.

Characteristics


Among terrestrial land mammals native to Asia, the Indian rhinoceros is second in size only to the Asian elephant. This heavily built species is also the second-largest living rhinoceros, behind only the white rhinoceros. Males have an average head and body length of 368–380 cm (12.07–12.47 ft) with a shoulder height of 163–193 cm (5.35–6.33 ft), while females have an average head and body length of 310–340 cm (10.2–11.2 ft) and a shoulder height of 147–173 cm (4.82–5.68 ft).[4][verification needed] The weights of captive individuals from the Basel Zoo were around 1,600 kg (3,500 lb) on average for the females and around 2,100 kg (4,600 lb) on average for the males. The skull is heavy with a basal length above 60 cm (24 in) and an occiput above 19 cm (7.5 in).[5]

The largest sized specimens can range up to 4,000 kg (8,800 lb).[6]

The rhino's single horn is present in both males and females, but not on newborn young. The black horn is pure keratin, like human fingernails, and starts to show after about six years. In most adults, the horn reaches a length of about 25 cm (9.8 in), but has been recorded up to 57.2 cm (22.5 in) in length.[7] The nasal horn is slightly back-curved with a base of about 18.5 cm (7.3 in) by 12 cm (4.7 in) that rapidly narrows until a smooth, even stem part begins about 55 mm (2.2 in) above base. In captive animals, the horn is frequently worn down to a thick knob.[5]

The Indian rhinoceros has thick, silver-brown skin, which becomes pinkish near the large skin folds that cover its body. Its upper legs and shoulders are covered in wart-like bumps. It has very little body hair, aside from eyelashes, ear fringes and tail brush. Males develop thick neck folds.[5]

Distribution and habitat


One-horned rhinos once ranged across the entire northern part of the Indian Subcontinent, along the Indus, Ganges and Brahmaputra River basins, from Pakistan to the Indian-Burmese border, including parts of Nepal, Bangladesh and Bhutan. They may have also existed in Myanmar, southern China and Indochina.They prefer the alluvial plain grasslands of the Terai and Brahmaputra basin.[8] As a result of habitat destruction and climatic changes their range has gradually been reduced so that by the 19th century, they only survived in the Terai grasslands of southern Nepal, northern Uttar Pradesh, northern Bihar, northern Bengal, and in the Brahmaputra Valley of Assam.[9]

On the former abundance of the species, Thomas C. Jerdon wrote in 1867:[10]

This huge rhinoceros is found in the Terai at the foot of the Himalayas, from Bhotan to Nepal. It is more common in the eastern portion of the Terai than the west, and is most abundant in Assam and the Bhotan Dooars. I have heard from sportsmen of its occurrence as far west as Rohilcund, but it is certainly rare there now, and indeed along the greater part of the Nepal Terai; ... Jelpigoree, a small military station near the Teesta River, was a favourite locality whence to hunt the Rhinoceros and it was from that station Captain Fortescue ... got his skulls, which were ... the first that Mr. Blyth had seen of this species, ...

Today, their range has further shrunk to a few pockets in southern Nepal, northern Bengal, and the Brahmaputra Valley. In the 1980s, rhinos were frequently seen in the narrow plain area of Royal Manas National Park in Bhutan. Today, they are restricted to habitats surrounded by human-dominated landscapes, so that they often occur in adjacent cultivated areas, pastures, and secondary forests.[9]

Rhinos are regionally extinct in Pakistan.[11]

Populations

In 2007, the total population was estimated to be 2,575 individuals, of which 2,200 lived in Indian protected areas:[12]

Pobitora Wildlife Sanctuary shelters the highest density of Indian rhinos in the world — with 84 individuals in 2009 in an area of 38.80 km2 (14.98 sq mi).[3]

The population of rhinos in Nepal increased by 99 individuals from 2008 to 2011 and in 2011 totaled 503. Of these, 145 were male, 183 female, and 175 of unidentified gender; 332 were adults, 111 were calves and 60 were of intermediate age.[13]

In Pakistan's Lal Suhanra National Park, two rhinos from Nepal were introduced in 1983 but have not bred so far.[2]

Ecology and behavior

Rhinos are mostly solitary creatures, with the exception of mothers and calves and breeding pairs, although they sometimes congregate at bathing areas. They have home ranges, those of males being usually 2 to 8 km2 (0.77 to 3.09 sq mi) and overlapping each other. Dominant males tolerate males passing through their territories except when they are in mating season, when dangerous fights break out. They are active at night and early morning. They spend the middle of the day wallowing in lakes, rivers, ponds, and puddles to cool down. They are very good swimmers. Over 10 distinct vocalizations have been recorded.

Indian rhinos have few natural enemies, except for tigers, which sometimes kill unguarded calves, but adult rhinos are less vulnerable due to their size. Mynahs and egrets both eat invertebrates from the rhino's skin and around its feet. Tabanus flies, a type of horse-fly, are known to bite rhinos. The rhinos are also vulnerable to diseases spread by parasites such as leeches, ticks, and nematodes. Anthrax and the blood-disease septicemia are known to occur.[5]

They can run at speeds of up to 55 km/h (34 mph) for short periods and are excellent swimmers. They have excellent senses of hearing and smell, but relatively poor eyesight.

Diet

Indian rhinoceros are grazers. Their diets consist almost entirely of grasses, but they also eat leaves, branches of shrubs and trees, fruits, and submerged and floating aquatic plants. They feed in the mornings and evenings. They use their prehensile lips to grasp grass stems, bend the stem down, bite off the top, and then eat the grass. They tackle very tall grasses or saplings by walking over the plant, with legs on both sides and using the weight of their bodies to push the end of the plant down to the level of the mouth. Mothers also use this technique to make food edible for their calves. They drink for a minute or two at a time, often imbibing water filled with rhinoceros urine.[5]

Social life

The Indian rhinoceros forms a variety of social groupings. Adult males are generally solitary, except for mating and fighting. Adult females are largely solitary when they are without calves. Mothers will stay close to their calves for up to four years after their birth, sometimes allowing an older calf to continue to accompany her once a newborn calf arrives. Subadult males and females form consistent groupings, as well. Groups of two or three young males will often form on the edge of the home ranges of dominant males, presumably for protection in numbers. Young females are slightly less social than the males. Indian rhinos also form short-term groupings, particularly at forest wallows during the monsoon season and in grasslands during March and April. Groups of up to 10 rhinos may gather in wallows—typically a dominant male with females and calves, but no subadult males.[7]

The Indian rhinoceros makes a wide variety of vocalizations. At least 10 distinct vocalizations have been identified: snorting, honking, bleating, roaring, squeak-panting, moo-grunting, shrieking, groaning, rumbling and humphing. In addition to noises, the rhino uses olfactory communication. Adult males urinate backwards, as far as 3–4 m behind them, often in response to being disturbed by observers. Like all rhinos, the Indian rhinoceros often defecates near other large dung piles. The Indian rhino has pedal scent glands which are used to mark their presence at these rhino latrines. Males have been observed walking with their heads to the ground as if sniffing, presumably following the scent of females.[7]

In aggregations, Indian rhinos are often friendly. They will often greet each other by waving or bobbing their heads, mounting flanks, nuzzling noses, or licking. Rhinos will playfully spar, run around, and play with twigs in their mouths. Adult males are the primary instigators in fights. Fights between dominant males are the most common cause of rhino mortality, and males are also very aggressive toward females during courtship. Males will chase females over long distances and even attack them face-to-face. Unlike African rhinos, the Indian rhino fights with its incisors, rather than its horns.[7]

Reproduction

Captive males breed at five years of age, but wild males attain dominance much later when they are larger. In one five-year field study, only one rhino estimated to be younger than 15 years mated successfully. Captive females breed as young as four years of age, but in the wild, they usually start breeding only when six years old, which likely indicates they need to be large enough to avoid being killed by aggressive males. Their gestation period is around 15.7 months, and birth interval ranges from 34–51 months.[7]

In captivity, four rhinos are known to have lived over 40 years, the oldest living to be 47.[5]

Threats

Sport hunting became common in the late 1800s and early 1900s.[2] Indian rhinos were hunted relentlessly and persistently. Reports from the middle of the 19th century claim that some military officers in Assam individually shot more than 200 rhinos. By 1908, the population in Kaziranga had decreased to around 12 individuals.[5] In the early 1900s, the species had declined to near extinction.[2]

Poaching for rhinoceros horn became the single most important reason for the decline of the Indian rhino after conservation measures were put in place from the beginning of the 20th century, when legal hunting ended. From 1980 to 1993, 692 rhinos were poached in India. In India's Laokhowa Wildlife Sanctuary, 41 rhinos were killed in 1983, virtually the entire population of the sanctuary.[14] By the mid-1990s, poaching had rendered the species extinct there.[8]

In 1950, Chitwan’s forest and grasslands extended over more than 2,600 km2 (1,000 sq mi) and were home to about 800 rhinos. When poor farmers from the mid-hills moved to the Chitwan Valley in search of arable land, the area was subsequently opened for settlement, and poaching of wildlife became rampant. The Chitwan population has repeatedly been jeopardized by poaching; in 2002 alone, poachers have killed 37 animals to saw off and sell their valuable horns.[15]

Six methods of killing rhinos have been recorded:[14]

  • Shooting is by far the most common method used; rhino horn traders hire sharpshooters and often supply them with rifles and ammunition.
  • Trapping in a pit depends largely on the terrain and availability of grass to cover it; pits are dug out in such a way that a fallen animal has little room to manoeuvre with its head slightly above the pit, so that it is easy to saw off the horn.
  • Electrocution is used where high voltage powerlines pass through or near a protected area, to which poachers hook a long, insulated rod connected to a wire, which is suspended above a rhino path.
  • Poisoning by smearing zinc phosphide rat poison or pesticides on salt licks frequently used by rhinos is sometimes used.
  • Spearing has only been recorded in Chitwan National Park.
  • A noose, which cuts through the rhino's skin, kills it by strangulation.

Poaching, mainly for the use of the horn in traditional Chinese medicine, has remained a constant and has led to decreases in several important populations. Apart from this, serious declines in quality of habitat have occurred in some areas, due to:

  • severe invasion by alien plants into grasslands affecting some populations;
  • demonstrated reductions in the extent of grasslands and wetland habitats due to woodland encroachment and silting up of beels;
  • grazing by domestic livestock.[2]

The species is inherently at risk because over 70% of its population occurs at a single site, Kaziranga National Park. Any catastrophic event such as disease, civil disorder, poaching, or habitat loss would have a devastating impact on the Indian rhino's status.However, small population of rhinos may be prone to inbreeding depression.[2]

Conservation

Rhinoceros unicornis is listed in CITES Appendix I since 1975. The Indian and Nepalese governments have taken major steps towards Indian rhinoceros conservation, especially with the help of the World Wide Fund for Nature (WWF) and other nongovernmental organizations.[2] In the early 1980s, a rhino translocation scheme was initiated. The first pair of rhinos was reintroduced from Nepal's Terai to Pakistan's Lal Suhanra National Park in Punjab in 1982.[9]

In India

In 1910, all rhino hunting in India became prohibited.[5] In 1984, five rhinos were relocated to Dudhwa National Park — four from the fields outside the Pabitora Wildlife Sanctuary and one from Goalpara.[9]

In Nepal

In 1957, the country's first conservation law insured the protection of rhinos and their habitat. In 1959, Edward Pritchard Gee undertook a survey of the Chitwan Valley, and recommended the creation of a protected area north of the Rapti River and of a wildlife sanctuary south of the river for a trial period of 10 years.[16] After his subsequent survey of Chitwan in 1963, he recommended extension of the sanctuary to the south.[17] By the end of the 1960s, only 95 rhinos remained in the Chitwan Valley. The dramatic decline of the rhino population and the extent of poaching prompted the government to institute the Gaida Gasti – a rhino reconnaissance patrol of 130 armed men and a network of guard posts all over Chitwan. To prevent the extinction of rhinos, the Chitwan National Park was gazetted in December 1970, with borders delineated the following year and established in 1973, initially encompassing an area of 544 km2 (210 sq mi). Since 1973, the population has recovered well and increased to 544 animals around the turn of the century. To ensure the survival of rhinos in case of epidemics, animals were translocated annually from Chitwan to the Bardia National Park and the Sukla Phanta Wildlife Reserve since 1986.[15]

In captivity


The Indian rhinoceros was initially difficult to breed in captivity. The first recorded captive birth of a rhinoceros was in Kathmandu in 1826, but another successful birth did not occur for nearly 100 years. In 1925, a rhino was born in Kolkata. No rhinoceros was successfully bred in Europe until 1956. On September 14, 1956, Rudra was born in Zoo Basel, Switzerland. In the second half of the 20th century, zoos became adept at breeding Indian rhinoceros. By 1983, nearly 40 babies had been born in captivity.[5] As of 2012, 33 Indian rhinos were born at Zoo Basel,[18] which means that most animals kept in a zoo are somehow related to the population in the zoo of Basel, Switzerland. Due to the success of Zoo Basel's breeding program, the International Studbook for the species has been kept there since 1972. Since 1990, the Indian rhino European Endangered Species Programme is being coordinated there, as well, which ensures that the captive global Indian rhinoceros population stays genetically as healthy as possible.[19] As of 2010, 174 rhinos are kept in zoos worldwide.

In June 2009, an Indian rhino was artificially inseminated using sperm collected four years previously and cryopreserved at the Cincinnati Zoo’s CryoBioBank before being thawed and used. She gave birth to a male calf in October 2010.[20] The calf died 12 hours after birth.

Taxonomy

The modern scientific designation Rhinoceros unicornis is adopted from the Greek: ρινό- ("rhino-" — nose) and -κερος ("-keros" — horn of an animal) and Latin: "uni-" meaning single and "-cornis" meaning horn.[21]

Rhinoceros unicornis was the type species for the rhinoceros family, first described by Carolus Linnaeus in 1758.[22]

The one-horned rhinoceros is monotypic. Several specimen were described since the end of the 18th century under different scientific names, which are all considered synonyms of Rhinoceros unicornis today:[23]

  • R. indicus by Cuvier, 1817
  • R. asiaticus by Blumenbach, 1830
  • R. stenocephalus by Gray, 1867
  • R. jamrachi by Sclatter, 1876
  • R. bengalensis by Kourist, 1970[1]

Evolution

Ancestral rhinoceroses first diverged from other Perissodactyls in the Early Eocene. Mitochondrial DNA comparison suggests the ancestors of modern rhinos split from the ancestors of Equidae around 50 million years ago.[24] The extant family, the Rhinocerotidae, first appeared in the Late Eocene in Eurasia, and the ancestors of the extant rhino species dispersed from Asia beginning in the Miocene.[25]

Fossils of R. unicornis appear in the Middle Pleistocene. In the Pleistocene, the genus Rhinoceros ranged throughout South and Southeast Asia, with specimens located on Sri Lanka. Into the Holocene, some rhinoceros lived as far west as Gujarat and Pakistan until as recently as 3,200 years ago.[5]

The Indian and Javan rhinoceroses, the only members of the genus Rhinoceros, first appear in the fossil record in Asia around 1.6 million–3.3 million years ago. Molecular estimates, however, suggest the species may have diverged much earlier, around 11.7 million years ago.[24][26] Although belonging to the type genus, the Indian and Javan rhinoceroses are not believed to be closely related to other rhino species. Different studies have hypothesized that they may be closely related to the extinct Gaindetherium or Punjabitherium. A detailed cladistic analysis of the Rhinocerotidae placed Rhinoceros and the extinct Punjabitherium in a clade with Dicerorhinus, the Sumatran rhinoceros. Other studies have suggested the Sumatran rhinoceros is more closely related to the two African species.[27] The Sumatran rhino may have diverged from the other Asian rhinos as long as 15 million years ago.[7][25]

In culture

The Rhinoceros
Artist Albrecht Dürer
Year 1515
Type woodcut
Dimensions 24.8 cm × 31.7 cm (9.8 in × 12.5 in)

The Indian rhinoceros was the first rhino widely known outside its range. The first rhinoceros to reach Europe in modern times arrived in Lisbon on May 20, 1515. King Manuel I of Portugal planned to send the rhinoceros to Pope Leo X, but the rhino perished in a shipwreck. Before dying, the rhino had been sketched by an unknown artist. The German artist Albrecht Dürer saw the sketches and descriptions and carved a woodcut of the rhino, known ever after as Dürer's Rhinoceros. Though the drawing had some anatomical inaccuracies (notably the hornlet protruding from the rhino's shoulder), his sketch became the enduring image of a rhinoceros in western culture for centuries.

The British public had their first chance to view a rhinoceros (presumably this species) in 1683; it unknowingly caused a political row when the notorious Judge Jeffreys, in one of his lighter moments, spread a rumour that his chief rival, Lord Guildford, had been seen riding on it.

The Assam state of India uses the one-horned rhino as its official state animal. It is also the organizational logo for Assam Oil Company Ltd.

See also

References

Further reading

External links

  • The Rhino Resource Center
  • Nepal Rhino Conservation
  • Indian Rhino in Kaziranga National Park Official website
  • Indian Rhino page at AnimalInfo.org
  • Indian Rhinoceros page at nature.ca
  • Page Rhinocéros indien à nature.ca
  • Indian Rhinoceros page at UltimateUngulate.com
  • Images, videos and information on the Indian Rhinoceros
  • Asian Rhino Foundation
  • Indian army to help prevent rhino poaching

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