domingo, 28 de septiembre de 2014

Marsupiales de ayer y hoy

`Marsupialia` obra en la que exploro aspectos de la maternidad, y que incluye un retrato, forzosamente póstumo, del tilacino (marsupial carnívoro extinto a principios de siglo) del Museo de Ciencias Naturales de Madrid. Debajo un boceto y una foto de archivo del último tilacino vivo.



-from wikipedia-
Thylacinus cynocephalus
El lobo marsupial o tilacino (nombre científico Thylacinus cynocephalus), también conocido como lobo de Tasmaniatigre de Tasmania y tilacín, fue unmarsupial carnívoro originado en el Holoceno. Era nativo de Australia y Nueva Guinea y se cree que se extinguió en el siglo XX. Se trataba del último miembro viviente de su género (Thylacinus), viviendo los otros miembros en tiempos prehistóricos a partir de principios del Mioceno.
El lobo marsupial se extinguió en el continente australiano miles de años antes de la llegada de los colonos europeos, pero sobrevivió en Tasmania junto con
otrasespecies endémicas, incluyendo el diablo de Tasmania. Generalmente suele culparse de su extinción a la caza intensiva, incentivada por recompensas, pero podrían haber contribuido otros factores, como por ejemplo las enfermedades, la introducción de los perros, o la ocupación de su hábitat por los humanos. Aún cuando se lo considera oficialmente extinto, todavía hay quienes dicen haberlo visto.
Como los tigres y lobos del Hemisferio Norte, de los cuales heredó dos de sus nombres comunes, el lobo marsupial era un depredador alfa. Siendo un marsupial, no tenía relación con estos mamíferos placentarios, pero debido a la evolución convergente, presentaba la misma forma general y las mismas adaptaciones. Su pariente vivo más próximo es el diablo de Tasmania.
Es probable que el lobo marsupial se extinguiera del continente australiano hace aproximadamente dos mil años (quizá en Nueva Guinea). Se culpa de la extinción a la competencia con los humanos y dingos. Aún así, hay dudas sobre el impacto de los dingos, pues las dos especies podrían no haber competido directamente dado que el dingo es principalmente un predador diurno, mientras que se cree que el lobo marsupial cazaba mayoritariamente por la noche, aunque, dado que compartían presas, sí que pudieron competir por el alimento. Ante una hipotética confrontación directa cabe destacar que el lobo marsupial era más robusto, cosa que le habría dado una ventaja en combates entre ejemplares de ambas especies.
Las pinturas rupestres del Parque Nacional Kakadu muestran claramente que los lobos marsupiales eran cazados por los humanos primitivos, y se cree que los dingos y lobos marsupiales podrían haber competido por las mismas presas, pese al distinto carácter cronobiológico de actividad de ambos. Sus hábitats se solapaban claramente: se han encontrado restos subfósiles de lobos marsupiales en proximidad a restos de dingos. La adopción del dingo como compañero de cacería por los aborígenes habría incrementado la presión sobre el lobo marsupial.
Aún cuando ya llevaban mucho tiempo extinguidos en el continente australiano cuando llegaron los colonos europeos, los lobos marsupiales sobrevivieron hasta la década de 1930 en Tasmania. En tiempos de la primera colonia europea, la zona de población más densa de los lobos marsupiales era el norte de la isla. Desde los primeros días de colonización europea, los lobos marsupiales eran poco comunes, pero poco a poco se los empezó a culpar de numerosos ataques a ovejas; esto llevó a ofrecer recompensas en un intento de controlar su número. Una compañía, la Van Diemen's Land Company, ofreció recompensas por matar lobos marsupiales desde 1830, y entre 1888 y 1909 el gobierno de Tasmania pagó 1 libra esterlina (£) por cabeza (10 chelines por los cachorros). En total se pagaron 2.184 recompensas, pero se cree que se mataron muchos más lobos marsupiales de los que se reclamaron. Su extinción suele atribuirse a estos esfuerzos constantes de los granjeros y cazadores de recompensas. Aun así, es probable que múltiples factores contribuyeran a su declive y eventual extinción, incluyendo la competencia con perros salvajes (introducidos por los colonos), la erosión de su hábitat, la extinción de especies que eran sus presas, y una enfermedad parecida al moquillo que afectaba a muchos ejemplares en cautiverio en aquellos tiempos.
En cuanto a la competencia con los zorros como uno de los factores implicados en la extinción, cabe destacar que estos animales fueron introducidos por vez primera en 1864 y de nuevo en 2000; su posible presencia en estado silvestre en Tasmania es muy seriamente tenida en cuenta, aún con los mínimos indicios de la misma. Claro que la Fox Free Tasmanian Taskforce, asociación implicada en la búsqueda de tilacinos y en la erradicación de los zorros, recibe financiación del gobierno y no realiza ya esfuerzos en la búsqueda del lobo marsupial. De este modo, se sugiere que la dificultad de encontrar zorros en las regiones salvajes de Tasmania parece indicar que hay alguna posibilidad de que el lobo marsupial haya sobrevivido lejos del contacto con los humanos.
Fuera por el motivo que fuese, el animal ya era extremamente raro en estado salvaje a finales de los años veinte. Hubo varios intentos de salvar la especie de la extinción. Los registros del comité de gestión de Wilsons Promontory de 1908 recomendaban la reintroducción de lobos marsupiales en diferentes lugares adecuados de Victoria. En 1928, el comité de consejo de la fauna nativa de Tasmania recomendó proteger a todos los lobos marsupiales que quedaban, en zonas como por ejemplo Arthur River y Pieman River, al oeste de Tasmania.
El último lobo marsupial salvaje conocido fue abatido en 1930 por un granjero denominado Wilf Batty a Mawbanna, al nordeste de Tasmania. El animal (supuestamente un macho) había sido visto cerca de los gallineros de Batty desde hacía algunas semanas.

http://www.arkive.org/thylacine/thylacinus-cynocephalus/
Thylacine description
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Dasyuromorphia
Family Thylacinidae
Genus Thylacinus (1)
The thylacine was the largest marsupial carnivore but it is now widely believed to be extinct (1). Despite similarities with canids such as the wolf, the thylacine was extremely distinctive, and the canine appearance was offset by the tapered hindquaters, relatively short legs and broad-based tail (2), which cannot be wagged from side-to-side (3). The short, coarse fur was a dirty yellow-brown with 13 to 19 transverse brown stripes running from the upper back to the base of the tail (4); animals from highland areas had a richer cinnamon-brown coat (3). There were lighter patches of fur (4) surrounding the eyes and near the erect, rounded ears (5). The belly was cream coloured, females carried a backwards-opening pouch (4), and males possessed a pseudo pouch in the form of a fold of skin that protected the testes when moving quickly through low bushland (3). The thylacine was renowned for its ability to open its jaw remarkably wide; whilst it is highly unlikely that this yawn was as wide as is sometimes quoted (180°), the gape was still the widest of any mammal (4), and is surpassed only by that of the snake (3). This species is a classic example of 'convergent evolution'; it is a marsupial mammal that closely resembles the placental canids, especially the wolf from which one of its common names is derived, due to the similarities in their way of life (6).Also known asTasmanian tiger, Tasmanian wolf.FrenchLoup Marsupial.SpanishLobo De Tasamania, Lobo Marsupial.SizeTail length: 50 - 65 cm (2)Head-body length: 1 - 1.3 m (2)Shoulder height: 56 cm (3)Weight25 - 35 kg (3)
Thylacinus cynocephalus — Thylacine
For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.
Legal Status and Documents
EPBC Act Listing Status Listed as Extinct
Adopted/Made Recovery Plans
Federal Register of
Legislative Instruments Declaration under s178, s181, and s183 of the Environment Protection and Biodiversity Conservation Act 1999 - List of threatened species, List of threatened ecological communities and List of threatening processes(Commonwealth of Australia, 2000) [Legislative Instrument].
State Government
Documents and Websites
TAS: Tasmanian Tiger or Thylacine (Department of Primary Industries, Parks, Water and Environment, 2014c) [Internet].
TAS: Thylacine, or Tasmanian tiger, Thylacinus cynocephalus (Tasmanian Parks and Wildlife Service (Tas. PWS), 2010) [Internet].
TAS: Thylacinus cynocephalus (Thylacine): Species Management Profile for Tasmania's Threatened Species Link (Threatened Species Section (TSS), 2014uq) [State Action Plan].
State Listing Status
TAS: Listed as Extinct (Threatened Species Protection Act 1995 (Tasmania): September 2012 list)
Non-statutory Listing Status
IUCN: Listed as Extinct (Global Status: IUCN Red List of Threatened Species: 2014.3 list )
NGO: Listed as Extinct (The action plan for Australian mammals 2012)
Naming
Scientific name Thylacinus cynocephalus [342]
Family Thylacinidae:Polyprotodonta:Mammalia:Chordata:Animalia
Species author (Harris, 1808)
Infraspecies author
Reference
Distribution Map
Distribution map Species Distribution Map not available for this taxon.
Taxonomy
Scientific name: Thylacinus cynocephalus
Common name: Thylacine
Other names: Tasmanian Tiger
Description
The Thylacine was a marsupial that bore superficial resemblance to a dog. The most distinguishing feature of this animal were the 13–19 dark brown stripes over the back, beginning at the rear of the body and extending onto the tail. The tail was thick at the base and very stiff, giving the impression that it was a continuation of the body. The hair was short and dense, usually fawn to sandy brown, but varying in colour from deep brown to grey. The female had a large pouch. The species had prominent canine teeth as well as shearing molar teeth. There was some degree of sexual dimorphism, with males having a slightly longer body length than females. The average nose-to-tail length for adult males was 162.6 cm, compared to 153.7 cm for females (Guiler 1985; Paddle 2000; Tasmanian DPIW 2007).
The Thylacine was largely silent, its vocalisations being limited to an occasional 'terrier like' bark when hunting and a series of husky barks when excited in captivity. Adults could weigh anything from 15–35 kg (although recorded weights of live animals were few) (Flannery 1990a). The species was shy and secretive and always avoided contact with humans. Despite the common name, 'tiger', it had a quiet, nervous temperament. Captured animals generally gave up without a struggle and many died suddenly, apparently from shock (Guiler 1985; Tasmanian DPIW 2007).
Australian Distribution
Approximately 4000 years ago the Thylacine was widespread throughout New Guinea and most of mainland Australia, as well as Tasmania. Its extinction coincided closely with the arrival of the dingo in Australia and the wild dog in New Guinea. Dingoes never reached Tasmania, and most scientists see this as the main reason for the Thylacine's survival there. The most recent, well-dated occurrence of a Thylacine on the mainland is a carbon-dated fossil from Murray Cave in Western Australia, which is around 3100 years old. Further evidence for the previous presence of Thylacines on the mainland includes Aboriginal rock-paintings of a striped animal (almost certainly a Thylacine) in the Kimberley region of Western Australia and the Northern Territory (Flannery 1990a; Guiler 1985).
The Thylacine was widely distributed in Tasmania before European arrival. The first definite reference was that of Paterson in 1805, near Yorketown, on the Tamar River in northern Tasmania (Flannery 1990a). At the time of the first settlement, the heaviest distributions of this species were in the north-east, north-west and north-midland regions of Tasmania (Australian Museum 1999b).
Surveys Conducted
There have been numerous expeditions and searches for the Thylacine, beginning in 1937 and culminating in 1993. These included searches by leading Australian naturalists such as David Fleay, who searched for months in 1945–46, and notable Thylacine experts such as Eric Guiler (Flannery 1990a; Guiler 1980). None of these expeditions has produced evidence that Thylacines still exist. There have been hundreds of sightings since 1936, many of which may have been clear cases of misidentification. However, in a detailed study of sightings that occurred between 1934 and 1980, Smith (1980) concluded that of a total of 320 sightings, just under half could be considered good sightings. Nonetheless, all sightings have remained inconclusive (Tasmanian DPIW 2007). The results of a few of these searches are given below (Tasmanian DPIW 2007):
1937 - Sergeant Summers leads a search in the north-west of the State, recording many recent sightings by other persons in a large area between the Arthur and Pieman Rivers, although the party itself did not see any Thylacines. He recommends a sanctuary in that area.
1945 - Well-known naturalist David Fleay searches the Jane River to Lake St Clair area, finding possible Thylacine footprints.
1959 - Eric Guiler leads a search in the far north-west, an area which produced many bounties, and finds what appeared to be Thylacine footprints.
1963 - Eric Guiler leads a search in the Sandy Cape area but finds no evidence.
1968 - Jeremy Griffiths, James Malley and Bob Brown embark on a major search. Although they collect reports of sightings, they find no evidence of the Thylacine.
1980 - Parks and Wildlife Officers, Steven Smith and Adrian Pyrke, search a wide area of the State using three automatic cameras. No evidence of Thylacines is found.
1982–83 - Parks and Wildlife Officer, Nick Mooney, undertakes an extensive but unsuccessful search to confirm the 1982 sighting reported by Hans Naarding near the Arthur River in the State's north-west.
1984 - A search in Tasmania's highlands by Tasmanian Wildlife Park owner, Peter Wright, fails to turn up conclusive evidence.
1988–93 - Separate photographic searches by wildlife photographer, Dave Watts and Ned Terry, fail to record a Thylacine.
Population Information
The Thylacine is presumed extinct. It was probably never an abundant species, despite its wide distribution, partly due to its position at the top of the food chain (Flannery 1990a).
Habitat
The Thylacine appeared to occupy most types of habitat except dense rainforest. Open eucalypt forest was thought to be prime habitat (Flannery 1990a).
Life Cycle
Little is known of the lifespan of the Thylacine. However, a captive individual lived in the London Zoo for nearly eight and a half years and was probably at least a year old when obtained, making it more than nine years old when it died. A second specimen lived for 12 years at Beaumaris Zoo, Tasmania (Flannery 1990a). Based on this information their life expectancy in the wild has been estimated at five to seven years (Tasmanian DPIW 2007). However, since the related Tasmanian Devil (Sarcophilus harrisii) lives longer in the wild than in captivity, it has been postulated that the lifespan of the Thylacine in the wild may have been 12–14 years (Guiler 1985).
The Thylacine had an extended breeding season from winter to spring, with indications that some breeding toook place through out the year (Guiler 1985). The maximum number of young in a season was four although the average litter was probably three. The Thylacine, like all marsupials, was tiny and hairless when born. Newborns crawled into the mother's pouch and attached themselves to one of the four teats (Tasmanian DPIW 2007). Females carried the young in the backwards-facing pouch for up to three months (Dixon 1989). The pouch enlarged and hung down low as the young grew (Flannery 1990a). Large pouch-young had fur with stripes. When old enough to leave the pouch, the young stayed in a lair such as a deep rocky cave, well-hidden nest or hollow log, whilst the mother hunted (Tasmanian DPIW 2007).
Much of the behaviour of this species is unknown. The Thylacine has been described as a social species, living and hunting in small family groups, but some texts state that the young left the mother once they were able to hunt independantly (Flannery 1990a; Paddle 2000).
Feeding
The Thylacine was exclusively carnivorous. Its stomach was muscular with an ability to distend to allow the animal to eat large amounts of food at one time, probably an adaptation to compensate for long periods when hunting was unsuccessful and food scarce (Dixon 1998). Its prey included Bennett's Wallaby (Macropus rufogriseus rufogriseus), the Long-nosed Potoroo (Potorous tridactylus), the Tasmanian Pademelon (Thylogale billardierii), the Eastern Grey Kangaroo (Macropus giganteus tasmaniensis), wombats, and a variety of bandicoots, bats and birds. A favourite prey animal may have been the once common Tasmanian Emu (Dromaius novaehollandiae diemenensis), as both dingoes and foxes have been noted to hunt the Emu on the mainland (Pople et al. 2000). They were said to eat carrion when live prey was not available, although some authorities dispute this. It was also said to have readily included domestic stock in its diet (Flannery 1990a).
The Thylacine was not a fast runner and probably caught its prey by exhausting it during a long pursuit. During long distance pursuits Thylacines probably relied more on scent than any other sense (Flannery 1990a; Guilder 1985). They emerged to hunt during the evening, night and early morning (Tasmanian DPIW 2007) and tended to retreat to the hills and forest for shelter during the day (Heberle 2004).
Movement Patterns
Although the Thylacine was mainly nocturnal, it was sighted moving during the day and captive animals were recorded basking in the sun (Flannery 1990a).
Thylacines had a typical home range of between 40 and 80 km² (Guiler 2006). It appears to have kept to its home range without being territorial (Guiler 1985; Paddle 2000).
Threats
The reasons for the Thylacine's extinction are still disputed. Some researchers have suggested that disease was instrumental in reducing its numbers although there is little evidence for this. The species decline was probably accelerated when they came into competition with domestic dogs and were hunted by humans (Flannery 1990a; Guiler 1985).
The introduction of sheep in 1824 led to conflict between the settlers and Thylacines (Guiler 1985; Tasmanian DPIW 2007). It seems likely that hunting by Europeans, firstly by the Van Dieman Land Company and private landowners, and then as a result of bounties paid by the Tasmanian government, was a significant factor in the extinction of the Thylacine. The Tasmanian government bounty was one pound for each adult scalp and ten shillings for sub-adults. Bounties were collected on 2184 animals. The government bounty numbers quoted do not include those Thylacines killed for private landholders, who also offered rewards (Flannery 1990a; Guiler 1985).
The list below records the decline of the species (Tasmanian DPIW 2007):
1830 - Van Diemens Land Company introduced a Thylacine bounty
1888 - Tasmanian Parliament placed a price of £1 on Thylacine's head
1909 - Government bounty scheme terminated: 2184 bounties paid
1910 - Thylacines rare - sought by zoos around the world
1926 - London Zoo bought its last Thylacine for £150
1933 - Last Thylacine captured, Florentine Valley, sold to Hobart Zoo
1936 - World's last captive Thylacine died in Hobart Zoo (7 September 1936)
1936 - Thylacine added to the list of protected wildlife
1986 - Thylacine declared extinct by international standards
Although its extinction is generally attributed to these relentless efforts by farmers and bounty hunters (Tasmanian PWS 2006), it is likely that multiple factors led to its decline and eventual extinction. These include competition with wild dogs introduced by settlers (Boyce 2006), loss of habitat, the concurrent extinction of prey species, and a distemper-like disease may also have affected the species (Guiler 2006; Paddle 2000; Tasmanian DPIW 2007).
There seems to have been little public pressure to preserve the Thylacine, nor was much concern expressed by scientists at the decline of this species. A notable exception was T.T. Flynn, professor of biology at the University of Tasmania. In 1914, he was sufficiently concerned about the scarcity of the Thylacine to suggest that some should be captured and placed on an island. However, it was not until 1929, with the species on the very edge of extinction, that the Animals and Birds Protection Board passed a motion protecting Thylacines only for the month of December, which was thought to be their prime breeding season (Flannery 1990a). Official protection of the species by the Tasmanian government was introduced on 10 July 1936, 59 days before the last known specimen died in captivity (Paddle 2000).
There was only one successful attempt to breed Thylacines in captivity, at Melbourne Zoo in 1899 (Paddle 2000). This was despite the large numbers that went through some zoos, particularly those in Hobart and London. The famous naturalist John Gould foresaw the Thylacine's demise when he published his Mammals of Australia between 1848 and 1863: 'When the comparatively small island of Tasmania becomes more densely populated, and its primitive forests are intersected with roads from the eastern to the western coasts, the numbers of this singular animal will speedily diminish, extermination will have its full sway, and it will then, like the wolf of England and Scotland, be recorded as an animal of the past' (Gould 1863). The last known wild Thylacine to be killed was shot by a farmer in the north-east of the state in 1930 (The Thylacine Museum 2006). The last known Thylacine died in Hobart Zoo on 7th September, 1936 (Tasmanian DPIW 2007).
Threat Abatement and Recovery
The Australian Museum in Sydney began a cloning project in 1999 (Leigh 2002). The goal was to use genetic material from specimens taken and preserved in the early 20th century to clone new individuals and restore the species. Several noted microbiologists dismissed the project as a public relations stunt (Miller 2002).
The researchers had some initial success as they were able to extract good-quality DNA from the specimens (Salleh 2000). However, on 15 February 2005, the museum announced that it was stopping the project after tests showed the DNA retrieved from the specimens had been too badly degraded to be usable (ABC News Online 2005; Smith 2005). In May 2005, Professor Michael Archer, the University of NSW Dean of Science, former director of the Australian Museum and evolutionary biologist, announced that the project was being restarted by a group of interested universities and a research institute (Dasey 2005; Skatssoon 2005). A Thylacine gene has since been extracted from alcohol-preserved Thylacine pouch young and a dried adult skin. This gene was inserted into a mouse genome, where it was able to function normally as the mouse fetus developed (Pask et al. 2008).
The International Thylacine Specimen Database (ITSD) was completed in April 2005 and is the culmination of a four-year research project to catalogue and digitally photograph, if possible, all known surviving Thylacine specimen material held within museum, university and private collections. The master records are held by the Zoological Society of London (World Conservation Monitoring Centre 1996).
Threat Class Summary
The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.

http://www.parks.tas.gov.au
Thylacine, or Tasmanian Tiger, Thylacinus cynocephalus
The thylacine is one of the most fabled animals in the world. Yet, despite its fame, it is one of the least understood of Tasmania's native animals. European settlers were puzzled by it, feared it and killed it when they could. After only a century of white settlement the animal had been pushed to the brink of extinction. Full details of the demise of the thylacine can be found at ourthreatened species site.
Description
The thylacine looked like a large, long dog, with stripes, a heavy stiff tail and a big head. Its scientific name, Thylacinus cynocephalus, means pouched dog with a wolfs head. Fully grown it measured about 180 cm (6 ft) from nose to tail tip, stood about 58 cm (2 ft) high at the shoulder and weighed up to 30 kg. The short, soft fur was brown except for 13 - 20 dark brown-black stripes that extended from the base of the tail to almost the shoulders. The stiff tail became thicker towards the base and appeared to merge with the body.
Thylacines were usually mute, but when anxious or excited made a series of husky, coughing barks. When hunting, they gave a distinctive terrier-like, double yap, repeated every few seconds. Unfortunately there are no recordings.
The thylacine was shy and secretive and always avoided contact with humans. Despite its common name, 'tiger' it had a quiet, nervous temperament compared to its little cousin, the Tasmanian devil. Captured animals generally gave up without a struggle, and many died suddenly, apparently from shock. When hunting, the thylacine relied on a good sense of smell, and stamina. It was said to pursue its prey relentlessly, until the prey was exhausted. The thylacine was rarely seen to move fast, but when it did it appeared awkward. It trotted stiffly, and when pursued, broke into a kind of shambling canter.
Breeding
Aboriginal art depicting thylacine, Kakadu,
Northern Australia (Photo by Ina Johnson)
Breeding is believed to have occurred during winter and spring. A thylacine, like all marsupials, was tiny and hairless when born. It crawled into the mother's rear-opening pouch, and attached itself to one of four teats. Four young could be carried at a time, but the usual litter size was probably three. As the pouch-young grew, the pouch expanded, and became so big that it reached almost to the ground. Large pouch-young had fur with stripes. When old enough to leave the pouch, the young stayed in a lair such as a deep rocky cave, well-hidden nest or hollow log, whilst the mother hunted. Thylacines lived in zoos for up to 9 years, but never bred in captivity. Their life expectancy in the wild was probably 5-7 years.
Diet
The thylacine was a meat-eater. In fact, the world's largest marsupial carnivore since the extinction ofThylacoleo the marsupial 'lion'. Its diet is believed to have consisted largely of wallabies, but included various small animals and birds. Since European settlement, the thylacine also preyed upon sheep and poultry, although the extent of this was much exaggerated. Occasionally, the thylacine scavenged. In captivity, thylacines were fed on dead rabbits and wallabies, which they devoured entirely, as well as beef and mutton.
Distribution and habitat
Fossils and Aboriginal rock paintings show that the thylacine once lived throughout Australia and New Guinea. The most recent thylacine remains have been dated as being about 2 200 years old. Predation and competition from the dingo may have contributed to the thylacine's disappearance from mainland Australia and New Guinea.
Bass Strait protected a relict population of thylacines in Tasmania. When Europeans arrived in 1803, thylacines were widespread in Tasmania. Their preferred habitat was a mosaic of dry eucalypt forest, wetlands and grasslands. They emerged to hunt on grassy plains and open woodlands during the evening, night and early morning.
Why are they extinct?
The arrival of European settlers marked the start of a tragic period of conflict that led to the thylacine's extinction. The introduction of sheep in 1824 led to conflict between the settlers and thylacines.
1830 Van Diemens Land Co. introduced a thylacine bounties.
1888 Tasmanian Parliament placed a price of £1 on thylacine's head.
1909 Government bounty scheme terminated. 2184 bounties paid.
1910 Thylacines rare -- sought by zoos around the world.
1926 London Zoo bought its last thylacine for £150.
1933 Last thylacine captured, Florentine Valley, sold Hobart Zoo.
1936 World's last captive thylacine died in Hobart Zoo, ( 7/9/36).
1936 Tasmanian tiger added to the list of protected Wildlife.
1986 Thylacine declared extinct by international standards.
Do they still exist?
In 1863, John Gould, a famous naturalist, predicted that the Tasmanian tiger was doomed to extinction:
When the comparatively small island of Tasmania becomes more densely populated, and its primitive forests are intersected with roads from the eastern to the western coast, the numbers of this singular animal will speedily diminish, extermination will have its full sway, and it will then, like the Wolf in England and Scotland, be recorded as an animal of the past...John Gould, 1863
Every effort was made, by snaring, trapping, poisoning and shooting, to fulfil his prophecy. Bounty records indicate that a sudden decline in thylacine numbers occurred early in the 20th century. Hunting and habitat destruction leading to population fragmentation, are believed to have been the main causes of extinction. The remnant population was further weakened by a distemper-like disease.
The last known thylacine died in Hobart Zoo on 7th September, 1936.
Sightings and Searches
Since 1936, no conclusive evidence of a thylacine has been found. However, the incidence of reported thylacine sightings has continued. Most sightings occur at night, in the north of the State, in or near areas where suitable habitat is still available. Although the species is now considered to be 'probably extinct', these sightings provide some hope that the thylacine may still exist.
There have been hundreds of sightings since 1936, many of which may have been clear cases of mis-identification. However, in a detailed study of sightings between 1934 and 1980, Steven Smith concluded that of a total of 320 sightings, just under half could be considered good sightings. Nonetheless, all sightings have remained inconclusive.
Interestingly, just as many sightings of equally good quality are reported from mainland Australia -- perhaps a comment on the poor evidence that sightings alone represent.
There have been a number of searches for the animal. None of these searches have been successful in proving the continued existence of the animal. The results of a few of these searches are given below:
1937 - Seargent Summers leads a search in the north-west of he state, recording many recent sightings by other persons in a large area between the Arthur and Pieman Rivers, although the party itself did not see any thylacines. He recommends a sanctuary in that area.
1945 - Well-known naturalist David Fleay searches the Jane River to Lake St Clair area, finding possible thylacine footprints.
1959 - Eric Guiler leads a search in the far north-west, an area which produced many bounties and finds what appeared to be thylacine footprints.
1963 - Eric Guiler leads a search in the Sandy Cape area but finds no evidence.
1968 - Jeremy Griffiths, James Malley and Bob Brown embark on a major search. Although they collect reports of sightings, they find no evidence of the thylacine.
1980 - Parks and Wildlife Officers, Steven Smith and Adrian Pyrke, search a wide area of the State using three automatic cameras. No evidence of thylacines is found.
1982-83 - Parks and Wildlife Officer, Nick Mooney, undertakes an extensive but unsuccessful search to confirm the 1982 sighting reported by Hans Naarding near the Arthur River in the State's north-west.
1984 - A search in Tasmania's highlands by Tasmanian Wildlife Park owner, Peter Wright, fails to turn up conclusive evidence.
1988-93 - Separate photographic searches by wildlife photographer, Dave Watts and Ned Terry fail to record a thylacine.
Hope for the Future?
The thylacine is the only mammal to have (possibly) become extinct in Tasmania since European settlement. This is in vivid contrast to mainland Australia, which has the worst record of mammalian extinctions of any country on Earth, with nearly 50% of its native mammals becoming extinct in the past 200 years. Tasmania is unique in that our fauna is abundant, and that the State acts as a refuge - a final hope -- for many species that have recently become extinct on mainland Australia.
Despite our wishes to have a perfect record, the lack of any hard evidence of the thylacine's continued existence supports the increasingly held notion that the species is extinct. Nonetheless, the incidence of sightings introduces a reluctance among some authorities to make empahatic statements on the status of the species. Even if there did exist a few remaining individuals, it is unlikely that such a tiny population would be able to maintain a sufficient genetic diversity to allow for the viable perpetuation of the species in the long-term.
Recent attention has been given to the possibility of cloning the species. However, it is very unlikely to be achievable from a single individual preserved in alchohol. Even if cloning were possible, it should be asked whether such effort and expense is justifiable when many other species are currently threatened with extinction, and when we allow the same processes that threatenen habitats and wildlife to continue.
Perhaps the lesson to be learned from the loss of the thylacine is to ensure that the rich natural heritage of our island State is no longer jeopardised.

No hay comentarios:

Publicar un comentario en la entrada