Utente:Marruz

Da Wikipedia, l'enciclopedia libera.

Salve a tutti! Sono un ragazzo livornese (per la precisione di Venturina) che, scoprendo Wikipedia, ha trovato un modo facile per imparare cose nuove e partecipare in prima persona all'edificazione di questo importante progetto culturale.

La mia passione principale sono gli animali (soprattutto i grandi predatori, dagli squali ai grandi felini e ai carnivori in generale), ma anche la geografia, specialmente quella inerente al continente asiatico.

(Scusate se sono stato un po' troppo sbrigativo, ma prima o poi migliorerò questa pagina di presentazione)

Paraceratherium, noto comunemente anche come Indricotherium o Baluchitherium (vedi sotto la discussione tassonomica), è un genere estinto di giganteschi mammiferi simili a rinoceronti senza corno, appartenenti alla famiglia degli Iracodontidi, i cui fossili sono stati ritrovati in molte parti dell'Asia, per la precisione in Kazakistan, Pakistan, India, Mongolia e Cina. Visse dall'Oligocene Medio al Miocene Inferiore, tra i 30 ed i 20 milioni di anni fa, quando queste regioni dell'Asia erano ricoperte da lussureggianti foreste (sub)tropicali e da aree boschive.

Paraceratherium è il più grande mammifero terrestre conosciuto, forse perfino più grosso delle più grandi specie di mammut (nonostante alcune di queste, come Mammuthus trogontherii, il mammut della steppa, si avvicinassero ad esso nelle dimensioni e nel peso). Le dimensioni che sono state stimate per gli adulti sono un'altezza al garrese di 5-5,5 m, oltre 8 m di lunghezza, altezza massima raggiunta dalla testa di 7 m e cranio lungo 1,35 m. Le stime sul suo peso variano moltissimo, ma quelle più realistiche indicano che quest'animale pesasse tra le 10 e le 20 tonnellate.

Era un erbivoro che strappava le foglie dagli alberi con i suoi denti superiori volti verso il basso simili a zanne, che andavano ad occludersi perfettamente con i denti inferiori rivolti in avanti. Aveva un cranio lungo e basso, privo di corno, ed ossa frontali e nasali a volta. Su entrambe le mascelle i denti davanti erano ridotti ad una singola coppia di incisivi di forma conica, tanto grandi che assomigliavano a piccole zanne. Le punte degli incisivi superiori erano rivolte all'indietro, mentre quelle degli inferiori lo erano verso l'esterno. Il labbro superiore era quasi sicuramente estremamente mobile. Il collo era molto lungo, il tronco robusto e gli arti, simili a colonne, erano lunghi e massicci. Il tipo di dentatura, il labbro superiore mobile e le zampe e il collo lunghi indicano che era un brucatore che si nutriva di foglie e di germogli degli alberi e dei grossi arbusti.

Indice 1 Tassonomia e specie di Paraceratherium 2 In popular culture and media 3 External links 4 References 5 Taxonomy and naming 5.1 Evolution 6 Description 7 Distribution and habitat 8 Behavior 8.1 Diet 8.2 Reproduction 9 Conservation 9.1 Ujung Kulon 9.2 Cat Tien 9.3 In captivity 10 References 11 External links 12 Tassonomia 12.1 Teoria delle tre specie di Eubalaena 12.2 Resti fossili di Balaena 12.3 Sinonimi e nomi comuni 13 Description 14 Diet 15 Sound production and hearing 16 Whaling 17 Population and distribution today 18 Conservation 19 Whale watching 20 Notes 21 References 22 External links

[modifica] Tassonomia e specie di Paraceratherium

Sebbene While more distinct at the species level, there is uncertainty and disagreement with regard to the genus level of taxonomy.

Paraceratherium fu descritto per la prima volta da Forster Cooper nel 1911, lo stesso che nel 1913 descrisse il genere Baluchitherium. Indricotherium, invece, venne descritto da Borissiak nel 1915.

Baluchitherium viene ora largamente accettato come sinonimo di Paraceratherium o Indricotherium.

Comunque, non tutti sono d'accordo nel considerare Indricotherium un genere distinto da Paraceratherium. Lucas e Sorbus, nel loro studio del 1989 sulla sottofamiglia degli Indricoterini (vedi sotto la bibliografia), propendono per una sinonimia e considerano le differenze tra i due generi come varietà specifica o perfino come risultato di dimorfismo sessuale all'interno di una singola specie: il più grande e più robusto Indricotherium, dagli incisivi più grandi, sarebbe probabilmente il maschio, e il più gracile Paraceratherium la femmina. Altri, però, hanno espresso dubbi su questa teoria (facendo appello soprattutto a delle differenze nella forma del cranio). Comunque, anche se si dovesse trattare di due generi distinti, questi animali sono molto simili per quanto riguarda dimensioni ed aspetto.

Se si considerano membri dello stesso genere, Indricotherium sarebbe un sinonimo minore di Paraceratherium, poiché, secondo il principio di priorità della classificazione scientifica, la prima pubblicazione, e quindi il nome valido più vecchio, prevale sulle altre. Per questo parliamo di Paraceratherium.

Qua seguiremo la classificazione di Lucas e Sobus, che ritengono Indricotherium, Baluchitherium, Thaumastotherium Forster Cooper, 1913a, Aralotherium Borissiak, 1939 e Dzungariotherium Xu e Wang, 1973 tutti sinonimi minori di Paraceratherium.

Lucas e Sobus riconobbero quattro specie valide di Paraceratherium. A queste se ne è aggiunta un'altra (P. zhajremensis). Le specie di Paraceratherium sono:

Paraceratherium bugtiense (Pilgrim, 1908), del Miocene Inferiore del Pakistan, è la specie tipo di Paraceratherium. Ne è un sinonimo Baluchitherium osborni Forster Cooper, 1913a. Venne scoperto per la prima volta nella formazione di Chitarwata, sulle colline di Bugti, in Belucistan, da cui prese originariamente il nome.

Paraceratherium transouralicum (Pavlova, 1922). Noto anche come Indricotherium transouralicum, è la specie meglio nota e maggiormente diffusa, essendo stata ritrovata nei sedimenti dell'Oligocene Medio e Superiore di Kazakistan, Mongolia e Nei Monggol, in Cina settentrionale. Lucas e Sobus classificano le seguenti specie come sinonimi: Baluchitherium grangeri Osborn, 1923, Indricotherium asiaticum Borissiak, 1923, Indricotherium minus Borissiak, 1923.

Paraceratherium zhajremensis (Osborn, 1923), dell'Oligocene Medio e Superiore dell'India.

Paraceratherium prohorovi (Borissiak, 1939), dell'Oligocene Superiore e del Miocene Inferiore del Kazakistan orientale.

Paraceratherium orgosensis (Chiu, 1973) è la specie più grande, avendo i denti più grandi di almeno un quarto rispetto a quelli di P. transouralicum (vedi Lucas e Sobus p.363/fig.19.2). È noto da ritrovamenti dell'Oligocene Medio e Inferiore dello Xinjiang, in Cina nord-occidentale. I suoi tre sinonimi sono Dzungariotherium orgosensis Chiu, 1973, Dzungariotherium turfanensis Xu e Wang, 1978 e Paraceratherium lipidus Xu e Wang, 1978 (di ognuna di queste ultime due specie è noto un cranio distinto). While there is some variation in details of the proportions of the skull (perhaps due to sexual dimorphism), all occur in a close geographical region and have distinct first and second upper molar crochets.

Paraceratherium means "near horn animal" in old Greek, indicating the fact that is was hornless, but related to the rhinoceroses.

Indricotherium is named after a mythical Russian beast called the "indrik", considered the most powerful creature and the father of the animals.

Baluchitherium means "beast of Baluchistan", as it was first discovered in Baluchistan, western Province of Pakistan.

[modifica] In popular culture and media

• Paraceratherium appears, as Indricotherium, in episode 3 of Walking with Beasts as the main character.
• "Baluchitherium" is a Van Halen instrumental from their 10th studio album, Balance.
• The baluchitherium is a monster appearing in the computer game NetHack.
• Baluchitherium is also mentioned in the popular manga Air Gear when referring to a team called behemoth.
• In the They Might Be Giants song "Mammal", there is a line; "Dead uncle Baluchitherium".

[modifica] External links

• Indricotherium
• Discovery Channel - Answers from Dr. Mikael Fortelius
• Hyracodontidae: Indricotheriinae and Synonyms of Paraceratherium transouralicum - Mikko's Phylogeny Archive - follows Lucas and Sorbus
• sci.bio.paleontology newsgroup 20 July 1999

[modifica] References

• Lucas, S. G. & Sobus, J. C., (1989), The Systematics of Indricotheres. 358-378 in Prothero, D. R. & Schoch, R. M., (eds.) 1989: The Evolution of Perissodactyls, Oxford University Press, New York, New York & Oxford, England, ix-537 - argues that Indricotherium should be included under Paraceratherium

Il rinoceronte di Giava o rinoceronte unicorne minore (Rhinoceros sondaicus) è un membro della famiglia dei Rinocerotidi ed uno dei cinque rinoceronti esistenti. Appartiene allo stesso genere del rinoceronte indiano e presenta il simile aspetto a mosaico della pelle che ricorda un'armatura, ma con 3,1-3,2 m di lunghezza e 1,4-1,7 m d'altezza è più piccolo del rinoceronte indiano ed è più vicino nelle dimensioni al rinoceronte nero. Il suo corno solitamente è inferiore ai 25 cm di lunghezza ed è quindi più piccolo di quello delle altre specie di rinoceronte.

Un tempo il più diffuso dei rinoceronti asiatici, il rinoceronte di Giava era diffuso dalle isole dell'Indonesia, attraverso l'Asia sud-orientale, fino all'India e alla Cina. Questa specie è ora criticamente minacciata, dal momento che ne rimangono solo due popolazioni in natura e nessuna negli zoo. È forse il grande mammifero più raro della Terra^[3]. Una popolazione di almeno 40-50 esemplari vive nel Parco Nazionale di Ujung Kulon sull'isola di Giava ed una piccola popolazione, stimata nel 2007 a non più di otto esemplari, sopravvive nel Parco Nazionale di Cat Tien in Vietnam. Il declino del rinoceronte di Giava va attribuito al bracconaggio, soprattutto per il suo corno, di grande valore nella medicina tradizionale cinese, valutato sul mercato nero 30.000 dollari al chilogrammo^[3]. Anche la distruzione dell'habitat, soprattutto a causa delle guerre, come la guerra del Vietnam, in Asia sud-orientale, ha contribuito al declino della specie e ne ha ostacolato il recupero^[4]. Il suo areale rimanente giace soltanto all'interno di due aree nazionalmente protette, ma i rinoceronti sono ancora minacciati dai bracconieri, dalle malattie e dalla perdita di diversità genetica provocata dalla depressione da inincrocio.

In natura il rinoceronte di Giava può vivere approssimativamente 30-45 anni. It historically inhabited lowland rain forest, wet grasslands and large floodplains. The Javan Rhino is mostly solitary, except for courtship and child-rearing, though groups may occasionally congregate near wallows and salt licks. Aside from humans, adults have no predators in their range. The Javan Rhino usually avoids humans, but will attack when it feels threatened. Scientists and conservationists rarely study the animals directly due to their extreme rarity and the danger of interfering with such an endangered species. Researchers rely on camera traps and fecal samples to gauge health and behavior. Consequently, the Javan Rhino is the least studied of all rhino species.

[modifica] Taxonomy and naming

The first studies of the Javan Rhinoceros by naturalists from outside of its region took place in 1787 when two animals were shot in Java. The skulls were sent to the renowned Dutch naturalist Petrus Camper, who died in 1789 before he was able to publish his discovery that the rhinos of Java were a distinct species. Another Javan Rhinoceros was shot on the island of Sumatra by Alfred Duvaucel who sent the specimen to his stepfather Georges Cuvier, a famous French scientist. Cuvier recognized the animal as a distinct species in 1822, and in the same year it was identified by Anselme Gaëtan Desmarest as Rhinoceros sondaicus. It was the last species of rhinoceros to be identified.^[5] Desmarest initially identified the rhino as being from Sumatra, but later amended this to say his specimen was from Java.^[2]

The genus name Rhinoceros, which also includes the Indian Rhinoceros, is derived from Greek: rhino meaning nose, and ceros meaning horn; sondaicus is derived from sunda, the biogeographical region that comprises islands of Sumatra, Java, Borneo, and surrounding smaller islands. The Javan Rhino is also known as the Lesser One-Horned Rhinoceros (in contrast with the Greater One-Horned Rhinoceros, another name for the Indian Rhino).

There are three distinct subspecies, of which only two are presumed to be extant:

• Rhinoceros sondaicus sondaicus, the type subspecies, known as the Indonesian Javan Rhinoceros, once lived on Java and Sumatra. The population is now confined to around 40–50 animals in the Ujung Kulon National Park on the western tip of the island of Java. One researcher has suggested that the Javan Rhino on Sumatra belonged to a distinct subspecies, R.s. floweri, but this is not widely accepted.^[6][7]
• Rhinoceros sondaicus annamiticus, known as the Vietnamese Javan Rhinoceros or Vietnamese Rhinoceros, once lived across Vietnam, Cambodia, Laos and into Thailand and Malaysia. Annamiticus is derived from the Annamite Mountain Range in Southeast Asia, part of this subspecies's range. A single population, estimated at less than 12 remaining rhinos, lives in an area of lowland forest in the Cat Tien National Park in Vietnam. Genetic analysis suggests that the two extant subspecies last shared a common ancestor between 300,000 and 2 million years ago.^[7][8]
• Rhinoceros sondaicus inermis, known as the Indian Javan Rhinoceros, once ranged from Bengal to Burma, but is presumed to have gone extinct in the first decade of the 1900s. Inermis means without horns, as the most distinctive characteristic of this sub-species is the small horns in males, and evident lack of horns in females. The original specimen of this species was a hornless female. The political situation in Burma has prevented assessment of the species in that country, but its survival is considered unlikely.^[9][10][11]

[modifica] Evolution

Per approfondire, vedi la voce Rhinoceros#Evolution.

Ancestral rhinoceroses first diverged from other Perissodactyls in the Early Eocene. Mitochondrial DNA comparison suggests that the ancestors of modern rhinos split from the ancestors of Equidae around 50 million years ago.^[12] 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.^[13]

The Indian and Javan Rhinoceros, 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.^[14][12] Although belonging to the type genus, the Indian and Javan Rhinoceros 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 Rhino. Other studies have suggested the Sumatran Rhinoceros is more closely related to the two African species.^[15] The Sumatran Rhino may have diverged from the other Asian rhinos as far back as 15 million years ago.^[13][3]

[modifica] Description

The Javan Rhino is smaller than its cousin, the Indian Rhinoceros, and is close in size to the Black Rhinoceros. The body length of the Javan Rhino (including its head) can be up to 3.1–3.2 m (10–10.5 feet), and it can reach a height of 1.4–1.7 m (4.6–5.8 ft). Adults are variously reported to weigh between 900 and 2,300 kg (2,000 and 5,100 lb), although because they are endangered, a study to collect accurate measurements of the animals has never been conducted and is not a priority.^[3] There is not a substantial size difference between genders, but females may be slightly bigger. The rhinos in Vietnam appear to be significantly smaller than those in Java, based on studies of photographic evidence and measurements of their footprints.^[16]

Like its Indian cousin, the Javan Rhinoceros has a single horn (the other extant species have two horns). Its horn is the smallest of all extant rhinos, usually less than 20 cm (7.9 inches) with the longest recorded only 27 cm (10½ in). The Javan Rhinoceros does not appear to often use its horn for fighting, but instead uses it to scrape mud away in wallows, to pull down plants for eating, and to open paths through thick vegetation. Similar to the other browsing species of rhino (the Black, Sumatran and Indian Rhinoceroses), the Javan Rhino has long, pointed, upper lips which help in grabbing food. Its lower incisors are long and sharp; when the Javan Rhino fights it uses these teeth. Behind the incisors, two rows of six low-crowned molars are used for chewing coarse plants. Like all rhinos, the Javan Rhino smells and hears well but has very poor vision. They are estimated to live for 30 to 45 years.^[16]

Its hairless, splotchy gray or gray-brown skin falls in folds to the shoulder, back and rump. The skin has a natural mosaic pattern which lends the rhino an armored appearance. The neck folds of the Javan Rhinoceros are smaller than those of the Indian Rhinoceros, but still form a saddle shape over the shoulder. Because of the risks of interfering with such an endangered species, however, the Javan Rhinoceros is primarily studied through fecal sampling and camera traps. They are rarely encountered, observed or measured directly.^[17]

[modifica] Distribution and habitat

Even the most optimistic estimate suggests there are fewer than 100 Javan Rhinos in the wild. They are considered possibly the most endangered of all large mammals; although there are more Sumatran Rhinos, their range is not as protected as that of the Javan Rhinos, and some conservationists consider them to be at greater risk. The Javan Rhinoceros is only known to survive in two places, the Ujung Kulon National Park on the western tip of Java and the Cat Tien National Park about 150 km (90 miles) north of Ho Chi Minh City.^[7][18]

The animal was once widespread from Assam and Bengal (where their range would have overlapped with both the Sumatran and Indian Rhino^[11]) eastward to Myanmar, Thailand, Cambodia, Laos, Vietnam, and southwards to the Malay Peninsula and the islands of Sumatra, Java and possibly Borneo.^[19] The Javan Rhino primarily inhabits dense lowland rain forests, tall grass and reed beds that are plentiful with rivers, large floodplains, or wet areas with many mud wallows. Although it historically preferred low-lying areas, the subspecies in Vietnam has been pushed onto much higher ground (up to 2,000 m or 6,561 ft), probably because of human encroachment and poaching.^[9]

The range of the Javan Rhinoceros has been shrinking for at least 3,000 years. Starting around 1000 BC, the northern range of the rhinoceros extended into China, but began moving southward at roughly 0.5 km (0.3 mile) per year, as human settlements increased in the region.^[20] It likely became locally extinct in India in the first decade of the 20th century.^[11] The Javan Rhino was hunted to extinction on the Malaysian peninsula by 1932.^[21] By the end of the Vietnam War, the Vietnamese Rhinoceros was believed extinct across all of mainland Asia. Local hunters and woodcutters in Cambodia claim to have seen Javan Rhinos in the Cardamom Mountains, but surveys of the area have failed to find any evidence of them.^[22] A population may have existed on the island of Borneo as well, though these specimens could have been the Sumatran Rhinoceros, a small population of which still lives there.^[19]

[modifica] Behavior

The Javan Rhinoceros is a solitary animal with the exception of breeding pairs and mothers with calves. They will sometimes congregate in small groups at salt licks and mud wallows. Wallowing in mud is a common behavior for all rhinos; the activity allows them to maintain a cool body temperature and helps prevent disease and parasite infestation. The Javan Rhinoceros does not generally dig its own mud wallows, preferring to use other animals' wallows or naturally occurring pits, which it will use its horns to enlarge. Salt licks are also very important because of the essential nutrients the rhino receives from the salt. Males's home ranges are larger at 12–20 km² (5–8 miles²) compared to the females's which are around 3–14 km² (1–5 mi²). Males's territories overlap each other less than those of females. It is not known if there are territorial fights.^[23]

Males mark their territory with dung piles and by urine spraying. Scrapes made by the feet in the ground and twisted saplings also seem to be used for communication. Members of other rhino species have a peculiar habit of defecating in massive rhino dung piles and then scraping their back feet in the dung. The Sumatran and Javan Rhinoceros, while defecating in piles, do not engage in the scraping. This adaptation in behavior is thought to be ecological; in the wet forests of Java and Sumatra, the method may not be useful for spreading odors.^[23]

The Javan Rhino is much less vocal than the Sumatran; very few Javan Rhino vocalizations have ever been recorded. Adult Javan Rhinos have no known predators other than humans. The species, particularly in Vietnam, is skittish and retreats into dense forests whenever humans are near. Though a valuable trait from a survival standpoint, it has made the rhinos difficult to study.^[4] Nevertheless, when humans approach too closely, the Javan Rhino becomes aggressive and will attack, stabbing with the incisors of its lower jaw while thrusting upward with its head.^[23] Its comparatively anti-social behavior may be a recent adaptation to population stresses; historical evidence suggests that, like other rhinos, the species was once more gregarious.^[7]

[modifica] Diet

The Javan Rhinoceros is herbivorous and eats diverse plant species, especially their shoots, twigs, young foliage and fallen fruit. Most of the plants favored by the species grow in sunny areas: in forest clearings, shrubland and other vegetation types with no large trees. The rhino knocks down saplings to reach its food and grabs it with its prehensile upper lip. It is the most adaptable feeder of all the rhino species. Currently it is a pure browser but probably once both browsed and grazed in its historical range. The rhino eats an estimated 50 kg (110 lb) of food daily. Like the Sumatran Rhino, it needs salt in its diet. The salt licks common in its historical range do not exist in Ujung Kulon, but the rhinos there have been observed drinking seawater, likely for the same nutritional need.^[16]

[modifica] Reproduction

The sexual habits of the Javan Rhinoceros are difficult to study as the species is rarely observed directly and no zoos have specimens. Females reach sexual maturity at 3–4 years of age while the males are sexually mature at 6. Gestation is estimated to occur over a period around 16–19 months. The birth interval for this species is 4–5 years and the calf is weaned at around 2 years. The other four species of rhino all have similar mating behaviors and the presumption is that the Javan Rhino follows suit.^[23]

[modifica] Conservation

Template:See also The main factor in the continued decline of the Javan Rhinoceros population has been poaching for horns, a problem that affects all rhino species. The horns have been a traded commodity in China for over 2,000 years where they are believed to have healing properties in Traditional Chinese Medicine. Historically, its hide was used to make armor for Chinese soldiers and some local tribes in Vietnam believed the hide can be used to make an antidote for snake venom.^[24] Because the rhinoceros's range encompasses many areas of poverty, it has been difficult to convince local people not to kill a seemingly useless animal which could be sold for a large sum of money.^[20] When the Convention on International Trade in Endangered Species of Wild Fauna and Flora first went into effect in 1975, the Javan Rhinoceros was placed under complete Appendix 1 protection: all international trade in the Javan Rhinoceros and products derived from it is illegal.^[25] Surveys of the rhinoceros horn black market have determined that Asian rhinoceros horn fetches a price as high as $30,000 per kilogram, three times the value of African rhinoceros horn.^[3]

Loss of habitat because of agriculture has also contributed to its decline, though this is no longer as significant a factor because the rhinoceros only lives in two nationally protected parks. Deteriorating habitats have hindered the recovery of rhino populations that fell victim to poaching. Even with all the conservation efforts, the prospects for the Javan Rhinoceros's survival are grim. Because the populations are restricted to two small areas, they are very susceptible to disease and the problems of inbreeding. Conservation geneticists estimate that a population of 100 rhinos would be needed to preserve the genetic diversity of the species.^[18]

[modifica] Ujung Kulon

The Ujung Kulon peninsula was devastated by the eruption of Krakatoa in 1883. The Javan Rhinoceros recolonized the peninsula after the explosion, but humans never returned in large numbers, thus creating a haven.^[18] In 1931, as the Javan Rhinoceros was on the brink of extinction in Sumatra, the government of Indonesia declared the rhino a legally protected species, which it has remained ever since.^[9] In 1967 when a census was first conducted of the rhinos in Ujung Kulon, only 25 animals were recorded. By 1980 that population had doubled, and has remained steady at about 50 ever since. Although the rhinos in Ujung Kulon have no natural predators, they have to compete for scarce resources with wild cattle which may keep the rhino's numbers below the peninsula's carrying capacity.^[26] Ujung Kulon is managed by the Indonesian Ministry of Forestry.^[9] Evidence of at least four baby rhinos was discovered in 2006, the most ever documented for the species.^[27]

[modifica] Cat Tien

The few remaining members of R.s. annamiticus live in the Cat Tien National Park in Vietnam. Once widespread in Southeast Asia, after the Vietnam War, the Javan Rhinoceros was presumed extinct. The tactics used in the combat wrought havoc on the ecosystems of the region: use of napalm, extensive defoliation from Agent Orange, aerial bombing and use of landmines. The war also flooded the area with inexpensive weapons. After the war, many poor villagers, who previously relied on methods like pit traps, now had deadly weapons at their disposal, enabling them to become efficient poachers. The assumption of the subspecies extinction was challenged when, in 1988, a hunter shot an adult female, proving the species had somehow survived the war. In 1989, scientists surveyed Vietnam's southern forests to search for evidence of other survivors. Fresh rhinoceros tracks belonging to at least 15 rhinos were found along the Dong Nai River.^[28] Largely because of the rhinoceros, the region they inhabited became part of the Cat Tien National Park in 1992.^[24] Their population is feared to have declined in Vietnam, with some conservationists estimating that as few as 3–8 rhinos, and possibly no males, survive.^[27][18]

[modifica] In captivity

A Javan Rhinoceros has not been exhibited in zoos in a century. In the 1800s, at least four rhinos were exhibited in Adelaide, Calcutta and London. A total of at least 22 Javan Rhinos have been documented as having been kept in captivity, and it is possible that the number is greater as the species was sometimes confused with the Indian Rhinoceros.^[29] The Javan Rhinoceros never fared well in captivity: the oldest lived to be 20, about half the age the rhinos will reach in the wild. The last captive Javan Rhino died at the Adelaide Zoo in Australia in 1907 where the species was so little known that it had been exhibited as an Indian Rhinoceros.^[16] Because a lengthy and expensive program in the 1980s and 1990s to breed the Sumatran Rhinoceros in zoos failed badly, attempts to preserve the Javan species in zoos are unlikely.^[3]

[modifica] References

[modifica] External links

Template:Portal

• Javan Rhino Info & Javan Rhino Pictures on the Rhino Resource Center
• International Rhino Foundation dedicated to the conservation of rhinos: Javan Rhino
• ARKive - images and movies of the Javan Rhinoceros (Rhinoceros sondaicus)
• UNEP & WCMC species sheet on the Javan Rhinoceros.

Le balene franche sono balene con i fanoni appartenenti al genere Eubalaena. In questo genere vengono riconosciute tre specie di balena franca.

Talvolta la famiglia Balaenidae viene considerata la famiglia delle balene franche. Appartiene alla famiglia Balaenidae anche la balena della Groenlandia, unica specie del genere Balaena, che proprio per questo motivo viene talvolta considerata una balena franca. Comunque, questo articolo tratta solamente le specie di Eubalaena.

Le balene franche possono raggiungere i 18 m di lunghezza e le 100 tonnellate di peso. Il loro corpo arrotondato è quasi completamente nero, con caratteristiche callosità (zone di pelle ruvida) sulla testa. Vengono chiamate «balene franche» perché i balenieri ritenevano che queste fossero le balene «giuste» da cacciare, dal momento che galleggiano una volta uccise e spesso nuotano nei pressi della costa. Le popolazioni sono state enormemente ridotte a causa della caccia intensa negli anni dell'industria baleniera. Oggi, invece di cacciarle, l'uomo spesso osserva questi animali acrobatici per puro divertimento.

Le quattro specie di Balaenidae vivono in località distinte. Approssimativamente rimangono:

• 300 balene franche boreali dell'Atlantico nell'Atlantico settentrionale;
• 200 balene franche boreali del Pacifico nel Pacifico settentrionale;
• 7500 balene franche australi diffuse in tutta la parte meridionale dell'emisfero australe;
• 8000–9200 balene della Groenlandia nell'Oceano Artico.

[modifica] Tassonomia

Dopo molti anni di ipotesi discordanti sul numero delle specie di Balaenidae, le recenti indagini genetiche indicano che ne esistano quattro specie distinte. Queste specie sono state tradizionalmente suddivise in due generi.

La balena della Groenlandia viene attualmente considerata una specie individuale ed è stata classificata in un genere monotipico fin dagli studi di Gray nel 1821. Le tre specie rimanenti vengono classificate insieme in un genere separato. A supporto di questa suddivisione in due generi vi sono, comunque, delle piccole differenze genetiche. Infatti, gli scienziati individuano maggiori differenze tra le tre specie di Balaenoptera che tra la balena della Groenlandia e le balene franche. Tuttavia sembra probabile che tra pochi anni, dopo ulteriori ricerche, tutte e quattro le specie verranno classificate in un solo genere^[1]. Su come classificare le tre popolazioni di balene franche Eubalaena le autorità si sono da sempre trovate in disaccordo: infatti, a seconda degli autori, venivano riconosciute una, due o tre specie. Ai tempi della baleneria si riteneva che appartenessero tutte ad una sola specie diffusa in tutto il mondo. In seguito, alcuni fattori morfologici, come piccole differenze nella forma del cranio tra gli animali settentrionali e meridionali, indicarono la presenza di almeno due specie - una diffusa esclusivamente nell'emisfero boreale e l'altra diffusa nell'Oceano Meridionale^[2]. Tuttavia, non è mai stato osservato nessun gruppo di balene franche nuotare nelle calde acque equatoriali per prendere contatti con le altre (sotto)specie e (in)incrociarsi: il loro sottile strato di sego isolante rende loro impossibile dissipare il calore corporeo interno in acque tropicali.

In anni recenti, studi genetici hanno apportato prove inequivocabili indicanti che le popolazioni settentrionali e meridionali non si sono incrociate nel corso di un periodo che va dai 3 ai 12 milioni di anni, confermando la balena franca australe come una specie separata. Più sorprendente, poi, è stato scoprire che sono distinte tra loro anche le popolazioni pacifiche ed atlantiche dell'emisfera boreale e che la specie del Pacifico (nota ora come balena franca boreale del Pacifico) è infatti più strettamente imparentata con la balena franca australe che con la balena franca boreale dell'Atlantico. Tuttavia Rice, nella sua classificazione del 1998, continuò a considerare solo due specie^[3], fino a quando, nel 2000, questa classificazione venne messa in discussione da Rosenbaum ed altri^[4] e da Brownell ed altri (2001)^[5]. Nel 2005, Mammal Species of the World riconobbe tre specie, indicando apparentemente una preferenza per quest'ultima suddivisione^[6].

[modifica] Teoria delle tre specie di Eubalaena

I pidocchi delle balene, crostacei ciamidi parassiti che vivono sulla pelle di questi animali, offrono ulteriori informazioni sulle popolazioni di balene franche Eubalaena tramite l'analisi del loro pattern genetico. Poiché i pidocchi si riproducono molto più velocemente delle balene, la loro diversità genetica è maggiore. I biologi marini dell'Università dello Utah hanno esaminato i geni di questi pidocchi ed hanno determinato che i loro padroni di casa si sono suddivisi in tre specie 5-6 milioni di anni fa e che queste specie erano tutte ugualmente abbondanti prima degli inizi della baleneria nell'XI secolo^[7]. Queste comunità si suddivisero per la prima volta dopo la congiunzione del Nordamerica con il Sudamerica. In seguito il caldo dell'equatore le suddivise ulteriormente in gruppi settentrionali e meridionali. Jon Seger, il direttore di questi studi, su BBC News disse «Ciò pone fine al lungo dibattito su quante specie di balena franca [Eubalaena] esistano. Sono veramente separate tra loro oltre ogni dubbio»^[8].

[modifica] Resti fossili di Balaena

Voci correlate: Evoluzione dei cetacei

In Europa ed in Nordamerica, in depositi che vanno dal Miocene superiore (circa 10 milioni di anni fa) al Pleistocene inferiore (circa 1,5 milioni di anni fa), sono stati trovati cinque resti fossili di Balaena. Questi cinque ritrovamenti sono stati indicati ciascuno come appartenenti ad una specie distinta - B. affinis, B. etrusca, B. montalionis, B. primigenius e B. prisca. I resti di quest'ultima, comunque, potrebbero essere quelli di una moderna balena della Groenlandia. Oltre a queste specie bisogna risalire indietro per un lungo intervallo di tempo prima di trovare altri fossili a nostra disposizione - Morenocetus, ritrovato in un deposito sudamericano, risale a 23 milioni di anni fa.

[modifica] Sinonimi e nomi comuni

In seguito alla loro familiarità con i balenieri per un certo numero di secoli alle balene franche sono stati dati molti nomi. Questi nomi vennero applicati alle balene franche di tutto il mondo, riflettendo il fatto che a quei tempi veniva riconosciuta solamente una sola specie. Nel romanzo Moby-Dick, Herman Melville scrisse: "Among the fishermen, the whale regularly hunted for oil is indiscriminately designated by all the following titles: The Whale; the Greenland Whale; the Black Whale; the Great Whale; the True Whale; the Right Whale."

Halibalaena (Gray, 1873) ed Hunterius (Gray, 1866) sono sinonimi minori per indicare il genere Eubalaena. La specie tipo è E. australis.

I sinonimi, in ordine di tempo, per le varie specie sono:^[6]

• per E. australis: antarctica (Lesson, 1828), antipodarum (Gray, 1843), temminckii (Gray, 1864)
• per E. glacialis: biscayensis (Eschricht, 1860), nordcaper (Lacepede, 1804)
• per E. japonica: sieboldii (Gray, 1864)

[modifica] Description

A North Atlantic Right Whale, clearly showing the distinctive callosities and curved mouth

A Southern Right Whale in the breeding grounds at Peninsula Valdés in Patagonia

Drawing of a North Pacific Right Whale

A North Atlantic Right Whale on a Faroese stamp

Right whales are easily distinguished from other whales by the callosities on their heads, a broad back without a dorsal fin, and a long arching mouth that begins above the eye. The body of the whale is very dark grey or black, occasionally with some white patches on the belly. The right whale's callosities appear white, not due to skin pigmentation, but to large colonies of cyamids or whale lice.

Adults may be between 11–18 m (36–59 ft) in length and typically weigh 60–80 tonnes. The most typical lengths are 13–16 m (42–52 ft). The body is extremely robust with girth as much as 60% of total body length in some cases. The tail fluke is also broad (up to 40% of body length). The North Pacific species is on average the largest of the three Eubalaena right whales. The largest specimens of these may weigh 100 tonnes.

Right whales have between 200 and 300 baleen plates on each side of the mouth. These are narrow and approximately 2 m long, and are covered in very thin hairs. The plates enable the whale to feed (see Diet below). The testicles of the right whale are likely to be the largest of any animal, each weighing around 500 kg (1,100 lbs). At 1% of the whale's total body weight, this size is very large even taking into account the size of the whale. This suggests that sperm competition is important in the mating process.^[9] Right whales have a distinctive wide V-shaped blow, caused by the widely-spaced blowholes on the top of the head. The blow rises to 5 m (16 ft) above the ocean's surface.^[9]

Females reach sexual maturity at 6–12 years and breed every 3–5 years. Both reproduction and calving take place during the winter months. Calves are approximately 1 tonne (1.1 short tons) in weight and 4–6 m in length at birth following a gestation period of 1 year. The right whale grows rapidly in its first year, typically doubling in length. Weaning occurs after eight months to one year and the growth rate in later years is not well understood—it may be highly dependent on whether a calf stays with its mother for a second year.^[1]

Very little is known about the life span of right whales because they are so scarce scientists can't really study them. One of the few pieces of evidence is the case of a mother North Atlantic right whale that was photographed with a baby in 1935, then photographed again in 1959, 1980, 1985 and 1992; callosity patterns were used to ensure that it was the same animal. Finally, she was photographed in 1995 with a seemingly fatal head wound that is presumed to have been caused by a ship strike. The animal was around 70 years of age at death. Research on Bowhead Whales suggest reaching this age is not uncommon and may even be exceeded.^[1][10]

Right whales are slow swimmers, reaching only 5 knots (9 km/h) at top speed, but are highly acrobatic and frequently breach (jump clear of the sea surface), tail-slap and lobtail. Like other baleen whales, the species is not gregarious and the typical group size is only two. Larger groups of up to twelve have been reported, but these were not close-knit and may have been transitory.

The right whale's only predators are the orca and humans. When danger lurks, a group of right whales may come together in a circle, with their tails pointing outwards, to deter a predator. This defence is not always successful and calves are occasionally separated from their mother and killed.

[modifica] Diet

The right whale's diet consists primarily of zooplankton and tiny crustaceans such as copepods, as well as krill, and pteropods, although they are occasionally opportunistic feeders. They feed by "skimming" along with their mouth open. Water and prey enters the mouth but only the water can pass through the baleen and out again into the open sea. Thus, for a right whale to feed, the prey must occur in sufficient numbers to trigger the whale's interest; be large enough that the baleen plates can filter it; and be small enough that it does not have the speed to escape.^[1] The "skimming" may take place on the surface, underwater, or even close to the ocean's bottom, indicated by mud occasionally observed on right whales' bodies.^[1]

[modifica] Sound production and hearing

See also: Whale song

Vocalizations made by right whales are not elaborate compared to those made by other whale species. The whales make groans, pops and belches that are typically around 500 Hz. The purpose of the sounds is not known but is likely to be a form of communication between whales within the same group.

A report published in the Proceedings of the Royal Society B in December 2003 found that Northern Right Whales responded rapidly on hearing sounds similar to police sirens—sounds of much higher frequency than those made by whales. On hearing the sounds they moved rapidly to the surface. The research was of particular interest because it is known that Northern Rights ignore most sounds, including those of approaching boats. Researchers speculate that this information may be useful in attempts to reduce the number of ship-whale collisions or to encourage the whales to surface for ease of harvesting.^[11][12]

[modifica] Whaling

Per approfondire, vedi la voce History of whaling.

Template:See also Right whales were so named because whalers thought they were the "right" whale to hunt. 40% of a right whale's body weight is blubber, which is of relatively low density. Consequently, unlike many other species of whale, deceased right whales float. Combined with the right whale's slowness through water they were easy to catch even for whalers equipped only with wooden boats and hand-held harpoons.

The Basques were the first to commercially hunt right whales. They began doing so as early as the 11th century in the Bay of Biscay. The whales were hunted initially for their oil but, as meat preservation technology improved, the animal was also used for food. They reached eastern Canada by 1530^[1] and the shores of Todos os Santos Bay (in Bahia, Brazil) by 1602. The last Basque whaling voyages were made prior to the commencement of the Seven Year's War (1756-1763). A few attempts were made to revive the trade, but they all failed. Basque shore whaling continued sporadically into the 19th century.

Basques were replaced by the whalers from the new American colonies: the "Yankee whalers". Setting out from Nantucket, Massachusetts and Long Island, New York, the Americans were able to take up to 100 right whales in good years. By 1750 the North Atlantic Right Whale was as good as extinct for commercial purposes and the Yankee whalers moved into the South Atlantic before the end of the 18th century. The southernmost Brazilian whaling station was established in 1796, in Imbituba. Over the next one hundred years, Yankee whaling spread into the Southern and Pacific Oceans, where the Americans were joined by fleets from several European nations. The beginning of the 20th century saw much greater industrialization of whaling, and the takes grew rapidly. By 1937, there had been, according to whalers' records, 38,000 takes in the South Atlantic, 39,000 in the South Pacific, 1,300 in the Indian Ocean, and 15,000 in the north Pacific. Given the incompleteness of these records, the actual take was somewhat higher.^[13]

As it became clear that stocks were nearly depleted, a worldwide total ban on right whaling was agreed upon in 1937. The ban was largely successful, although some whaling continued in violation of the ban for several decades. Madeira took its last two right whales in 1968. Japan took 23 Pacific right whales in the 1940s and more under scientific permit in the 1960s. Illegal whaling continued off the coast of Brazil for many years and the Imbituba land station processed right whales until 1973. The Soviet Union is now known to have illegally taken at least 3,212 Southern Right Whales during the 1950s and '60s, although it only reported taking 4.^[14]

[modifica] Population and distribution today

Estimating whale abundance

Because the oceans are so large, it is very difficult to accurately gauge the size of a whale population. The estimate of 7,000 Southern Right Whales came about following an IWC workshop held in Cape Town in March 1998. Researchers used data about adult female populations from three surveys (one in each of Argentina, South Africa and Australia collected during the 1990s) and extrapolated to include unsurveyed areas, number of males and calves using available male:female and adult:calf ratios to give an estimated 1999 figure of 7,000 animals. Further information may be obtained from the May 1998 edition of "Right Whale News" available online.

Today, the three Eubalaena species inhabit three distinct areas of the globe: the North Atlantic in the western Atlantic Ocean, the North Pacific in a band from Japan to Alaska and the Southern in all areas of the Southern Ocean. The whales can only cope with the moderate temperatures found between 20 and 60 degrees in latitude. Thus the warm waters of the equatorial region form a barrier and prevent the northern and southern groups' inter-mixing. Although the Southern species in particular must travel across open ocean to reach its feeding grounds, the species is not considered to be pelagic. In general, they prefer to stay close to peninsulas and bays and on continental shelves, as these areas offer greater shelter and an abundance of their preferred foods.

There are about 400 North Atlantic Right Whales, almost all living in the Western North Atlantic Ocean. In spring, summer and autumn, they feed in areas off the Canadian and north-east US coasts in a range stretching from New York to Nova Scotia. Particularly popular feeding areas are the Bay of Fundy and Cape Cod Bay. In winter, they head south towards Georgia and Florida to give birth.

There have been a smattering of sightings further east over the past few decades—several sightings were made close to Iceland in 2003. It is possible that these are the remains of a virtually extinct eastern Atlantic stock, but examination of old whalers records suggest that they are more likely to be strays from further west.^[1] However, a few sightings are regular between Norway, Ireland, Spain, Portugal, the Canary Islands and even Sicily^[15] and at least the Norway individuals come from the Western stock.^[16]

Only about 200 North Pacific right whales survive.^[8] Thus, the two northern right whale species are the most endangered of all large whales and two of the most endangered animals in the world. Based on current population density trends, both species are predicted to become extinct within 200 years.^[12] The Pacific species was historically found from the southern tip of Japan, across the Bering Strait and down the North American coast as far as California. Today, sightings are very rare and generally occur in the mouth of the Sea of Okhotsk and in the eastern Bering Sea. Although this species is very likely to be migratory like the other two species, its movement patterns over the year are not known.

Southern Right Whales spend the summer months in the far Southern Ocean feeding, probably close to Antarctica. They migrate north in winter for breeding and can be seen around the coasts of Argentina, Australia, Brazil, Chile, Mozambique, New Zealand and South Africa. The total population is estimated to be between seven and eight thousand. Since hunting of the Southern Right Whale ceased, stocks are estimated to have grown by 7% a year. It appears that the South American, South African and Australasian groups intermix very little, if at all, because the fidelity of a mother to its feeding and calving habitats is very strong. The mother also passes these instincts to her calves.^[1]

In Brazil, more than 300 individuals have been cataloged through photo identification (using their distinctive head callosities) by the Brazilian Right Whale Project, maintained jointly by Petrobras (the Brazilian state-owned oil company) and the International Wildlife Coalition. The State of Santa Catarina hosts a concentration of breeding and calving right whales from June to November, and females from this population are also known to calve off Argentinian Patagonia.

[modifica] Conservation

The leading cause of death among North Atlantic right whales, which migrate through some of the world's busiest shipping lanes whilst journeying off the east coast of the United States and Canada, is injury sustained from colliding with ships.^[17] At least 16 reported deaths due to ship strikes were reported between 1970 and 1999, and probably many more remain unreported.^[1] Recognising that this toll could tip the balance of the already delicately poised species towards extinction, the United States government introduced measures to curb the decline. The National Oceanic and Atmospheric Administration's Atlantic Large Whale Take Reduction Plan^[18] was introduced in 1997. A key part of the plan was the introduction of mandatory reporting of large whale sightings by ships using U.S. ports. This requirement was implemented in July 1999.

Whilst environmental campaigners were, as reported in 2001, pleased that the reporting plan has a positive effect, they wanted the government to do more.^[19] In particular they demanded that ships within 40 km (25 miles) of U.S. ports in times of known high right whale conservation be forced to maintain a speed of no more than 12 knots (22 km/h). The United States government, citing concerns about excessive disruption to trade, did not enforce such measures. The conservation groups Defenders of Wildlife, the Humane Society of the United States and the Ocean Conservancy thus sued the National Marine Fisheries Service (a sub-agency of the NOAA) in September 2005 for "failing to protect the critically endangered North Atlantic Right Whale, which the agency acknowledges is 'the rarest of all large whale species' and which federal agencies are required to protect by both the Marine Mammal Protection Act and the Endangered Species Act," and demanded that emergency measures be put in place to protect the whales.^[20] Both the North Atlantic and North Pacific species are listed as a "species threatened with extinction which [is] or may be affected by trade" (Appendix I) by CITES, and as Conservation Dependent by the IUCN Red List, and as endangered under the U.S. Endangered Species Act.

A second major cause of morbidity and mortality in North Atlantic right whales is entanglement in fishing gear. Right whales filter feed plankton with their mouths wide open, exposing themselves to the risk of entanglement in any rope or net fixed in the water column. They commonly wrap rope around their upper jaws, flippers and tails. Most manage to escape with minor scarring, but some get seriously and persistently entangled. Such cases if sighted are sometimes successfully disentangled, but others are not and they die a most gruesome death over a period of months. There has been a major focus on the conservation status of the right whale in terms of an endangered species. However, equally significant is the extreme animal welfare concern such chronic fatal entanglements represent.

The Southern Right Whale, listed as "endangered" by CITES and "lower risk - conservation dependent" by the IUCN, is protected in the jurisdictional waters of all countries with known breeding populations (Argentina, Australia, Brazil, Chile, New Zealand, South Africa and Uruguay). In Brazil, a federal Environmental Protection Area encompassing some 1,560 km² (602 miles²)and 130 km (80 miles)of coastline in Santa Catarina State was established in 2000 to protect the species' main breeding grounds in Brazil and promote regulated whale watching.^[21]

On June 26, 2006, NOAA proposed the Strategy to Reduce Ship Strikes to North Atlantic Right Whales.^[22] The proposal, which is opposed by the shipping industry, envisages imposing a speed cap of 10 knots (11.5 miles per hour; 18.5 km per hour) on specific routes during calving season for vessels 20 m (65 ft) or longer. The proposal is open for comments until August 25, 2006. According to the NOAA, 25 of the 71 right whale deaths reported since 1970 resulted from ship strikes.

The Stellwagen Bank area has implemented an autobuoy (AB) program to acoustically detect right whales in the Boston Approaches and notify mariners of right whale detections via the Right Whale Listening Network website.

[modifica] Whale watching

See also: Whale watching

Southern Right Whales have made Hermanus, South Africa one of the world centers for whale watching. During the winter months (July–October), Southern Right Whales come so close to the shoreline that visitors can watch whales from strategically-placed hotels. The town employs a "whale crier" (cf. town crier) to walk through the town announcing where whales have been seen. Southern Right Whales can also be watched at other winter breeding grounds.

In Brazil, Imbituba in Santa Catarina has been recognized as the National Right Whale Capital and holds annual Right Whale Week celebrations in September, when mothers and calves are more often seen. The old whaling station there has been converted to a museum documenting the history of right whales in Brazil. In Argentina, Península Valdés in Patagonia hosts (in winter) the largest breeding population of the species, with more than 2,000 animals catalogued by the Whale Conservation Institute and Ocean Alliance.^[23]

[modifica] Notes

• Wikimedia Commons contiene file multimediali su Marruz

Template:Cetaceaportal

[modifica] References

• Collins Gem : Whales and Dolphins, ISBN 0-00-472273-6.
• Carwardine, Mark. Whales, Dolphins and Porpoises, ISBN 0-7513-2781-6.
• Congressional Research Service (CRS).Northern Right Whale

[modifica] External links

• Right whale information from Woods Hole Oceanographic Institution, Woods Hole Oceanographic Institution
• Description and sightings of Right Whales
• IUCN Red List entry
• earthOCEAN documentary film about Southern Right Whales of Argentina
• Whale & Dolphin Conservation Society (WDCS)