Gavialis gangeticus

Gavialis gangeticus (*)

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Reptilia
Subclassis: Diapsida
Infraclassis: Archosauromorpha
Divisio: Archosauria
Subdivisio: Crurotarsi
Superordo: Crocodylomorpha
Ordo: Crocodilia
Subordo: Eusuchia
Familia: Gavialidae
Genus: Gavialis
Species: Gavialis gangeticus

Name

Gavialis gangeticus (Gmelin, 1789)

References

* IUCN link: Gavialis gangeticus (Gmelin, 1789) (Critically Endangered)
* Gmelin in Linnaeus, Syst. Nat., ed. 13, 1:1057.

Vernacular names
Internationalization
Česky: Gaviál indický
Deutsch: Gangesgavial
English: Gharial
Esperanto: Gavialo
Español: Gavial
Français: Gavial du Gange
עברית: גאביאל
Hrvatski: Gavijal, indijski gavijal
Italiano: Gaviale del Gange
日本語: インドガビアル
Nederlands: Gangesgaviaale
‪Norsk (bokmål)‬: Gangesgavial
Polski: Gawiale
Português: Gavial
Русский: Гавиал
Suomi: Gaviaali, gangesingaviaali
Svenska: Gavialer
ייִדיש: גאַװיאַל

The gharial (Gavialis gangeticus), (Hindi : घऱियाल, Marathi : सुसर Susar), also called Indian gavial or gavial, is the only surviving member of the once well-represented family Gavialidae, a long-established group of crocodilians with long, slender snouts.[2] The gharial is listed as a critically endangered species by IUCN.[1]

The gharial is one of the three crocodilians found in India, the others being the Mugger crocodile and the Saltwater crocodile.[3] It is one of the longest of all living crocodilians.[4]

Description


Gharials are exceeded in size only by the Saltwater Crocodile. Male individuals of up to 6 metres (20 ft) were commonly encountered in the past, but such large individuals are unknown today. Their well-developed laterally flattened tail and webbed rear feet provide tremendous maneuverability in their deepwater habitat. On land, however, an adult gharial can only push itself forward and slide on its belly. Its elongated, narrow snout becomes proportionally shorter and thicker as an animal ages. The bulbous growth on the tip of a male’s snout renders gharials the only visibly sexually dimorphic crocodilian. This growth is present in mature individuals and called ghara after the Indian word meaning “pot”. Males utilize the structure to modify and amplify “hisses” snorted through the underlying nostrils. The resultant sound can be heard for nearly a kilometer on a still day.[5] The ghara is used to generate a resonant hum during vocalization. It acts as a visual lure for attracting females, and is also used to make bubbles, which have been associated with the mating rituals of the species.

The Nepali word घड़ा ghaṛā means earthenware pot, pitcher, watervessel.[6]

There are multiple records of gharials having attained a weight of 1,000 kg (2,200 lb), but the majority do not grow past 680 kg (1,500 lb) and 5 m (16 ft) in size.[7][8] The average size of mature gharials is 3.6 to 4.5 m (12 to 15 ft).[9]

The three largest examples reported were a 6.5 m (21 ft) gharial killed in the Gogra River of Faizabad in August 1920; a 6.3 m (21 ft) individual shot in the Cheko River of Jalpaiguri in 1934; and a giant taped at 7 m (23 ft), which was shot in the Kosi River of northern Bihar in January 1924.[10]

The leg musculature of the gharial does not enable it to raise its body off the ground to achieve the high-walk gait on land, but can only push its body forward across the ground ('belly-sliding'), although it can do this with some speed when required. However, when in water, the gharial is the most nimble and quick of all the crocodilians in the world. The jaws are lined with many interlocking, razor-sharp teeth — 27 to 29 upper and 25 or 26 lower teeth on each side. These teeth are not received into interdental pits; the first, second, and third mandibular teeth fit into notches in the upper jaw. The front teeth are the largest. The gharial's snout is narrow and long, with a dilation at the end and its nasal bones are comparatively short and are widely separated from the pre-maxillaries. The nasal opening of a gharial is smaller than the supra-temporal fossae. The gharial's lower anterior margin of orbit (jugal) is raised and its mandibular symphysis is extremely long, extending to the 23rd or 24th tooth. A dorsal shield is formed from four longitudinal series of juxtaposed, keeled, and bony scutes.[11]

The length of the snout is 3.5 (in adults) to 5.5 times (in young) the breadth of the snout's base. Nuchal and dorsal scutes form a single continuous shield composed of 21 or 22 transverse series. Gharials have an outer row of soft, smooth, or feebly keeled scutes in addition to the bony dorsal scutes. They also have two small post-occipital scutes. The outer toes of a gharial are two-thirds webbed, while the middle toe is only one-third webbed. Gharials have a strong crest on the outer edge of the forearm, leg, and foot. Typically, adult gharials consist of a dark olive color tone while young ones are pale olive, with dark brown spots or cross-bands.[11]

Distribution and habitat

Gharials thrive in deep rivers. They are powerful swimmers but graceless on land, and will leave the water only to bask or to nest on sandy beaches. They were once distributed across approximately 20,000 square kilometres (7,700 sq mi) of riverine habitat of the Indus, Ganges, Brahmaputra, and Irrawady river systems. Today their distribution is limited to only 2% of their former range:[5]

In India, small populations are present and increasing in the rivers of the National Chambal Sanctuary, Katarniaghat Wildlife Sanctuary, Son River Sanctuary and the rainforest biome of Mahanadi in Satkosia Gorge Sanctuary, Orissa, where they apparently do not breed;[12]
In Nepal, small populations are present and slowly recovering in tributaries of the Ganges, such as the Narayani-Rapti river system in Chitwan National Park and the Karnali-Babai river system in Bardia National Park.[2][13]

They are extinct in Pakistan's Indus River, in the Brahmaputra of Bhutan and Bangladesh and in the Irrawaddy River in Myanmar.[5] They are sympatric with the Mugger crocodile (Crocodylus palustris) and formerly used to be with the Saltwater Crocodile (Crocodylus porosus) in the delta of Irrawaddy.[14]

There have been some small-scale projects to breed and rehabilitate gharials, like in Nepal's Chitwan National Park.

Ecology and behavior

Diet

Young gharials eat insects, larvae, and small frogs. Mature adults feed almost solely on fish, although some individuals have been known to scavenge dead animals. Their snout morphology is ideally suited for preying on fish. Their long, narrow snouts offer very little resistance to water in swiping motions to snap up fish in the water. Their numerous needle-like teeth are ideal for holding on to struggling, slippery fish. Gharials will often use their body to corral fish against the bank where they can be more easily snapped up.[15]

Reproduction

The mating season is during November through December and well into January. The nesting and laying of eggs takes place in the dry season of March, April, and May. This is because during the dry season the rivers shrink a bit and the sandy river banks are available for nesting. Between 30 and 50 eggs are deposited into the hole that the female digs up before it is covered over carefully. After about 90 days, the juveniles emerge, although there is no record of the female assisting the juveniles into the water after they hatch (probably because their jaws are not suited for carrying the young due to the needle like teeth). However, the mother does protect the young in the water for a few days until they learn to fend for themselves.

Gharials and humans
Gharial

The gharial is not a man-eater and is sensitive towards humans. Despite its immense size, its thin and fragile jaws make it physically incapable of consuming a large animal, especially a human being. The myth that gharials eat humans may come partly from their similar appearance to crocodiles and also since jewelry has been found in their stomachs. However, the gharial may have swallowed this jewelry while scavenging corpses or as gastroliths used to aid digestion or buoyancy management.

Threats

According to IUCN, there has been a population decline of 96–98% over a three-generation period since 1946, and the once widespread population of an estimated 5,000 to 10,000 individuals has been reduced to a very small number of widely spaced subpopulations of fewer than 235 individuals in 2006. The drastic decline in the gharial population can be attributed to a variety of causes including over-hunting for skins and trophies, egg collection for consumption, killing for indigenous medicine, and killing by fishermen. Hunting is no longer considered to be a significant threat. However, the wild population of gharials has undergone a drastic decline of about 58% within nine years between 1997 and 2006 due to

the increasing intensity of fishing and the use of gill nets, which is rapidly killing many of the scarce adults and many subadults — a threat prevalent throughout most of the present gharial habitat, even in protected areas;
the excessive, irreversible loss of riverine habitat caused by the construction of dams, barrages, irrigation canals, siltation, changes in river course, artificial embankments, sand-mining, riparian agriculture, and domestic and feral livestock, which have combined to cause an extreme limitation to gharial range.[1]


Conservation


Since 2007, the species is listed as Critically Endangered on the Red List of Threatened Species issued by IUCN, and protected by CITES Appendix I.[1][16]

Conservation programs have been undertaken in India and Nepal, based on the establishment of protected areas and restocking these with animals born in captivity, but nowhere has restocking re-established viable populations.[1]

In the 1970s the gharial came to the brink of extinction and even now remains on the critically endangered list. The conservation efforts of the environmentalists in cooperation with several governments has led to some reduction in the threat of extinction. Some hope lies with the conservation and management programs in place since 2004. Full protection was granted in the 1970s in the hope of reducing poaching losses, although these measures were slow to be implemented at first. Now there are 9 protected areas for this species in India, which are linked to both captive breeding and 'ranching' operations, where eggs collected from the wild are raised in captivity to reduce mortality due to natural predators. Since 1981, more than 3000 young gharial have been released into the wild. The wild population in India is estimated at around 1500 animals — with perhaps between one and two hundred animals in the remainder of its range. The release of captive gharials was not as successful as expected. Recently, more than 100 gharials died in India in the Chambal River from an unknown cause with gout-like symptoms. This recent death toll is expected to have decreased the number of breeding pairs to less than 400. Tests of the carcasses conducted at the IVRI suggest the possibility of poisoning by metal pollutants.
[edit] In situ initiatives
Gharial and Turtles

On December 27, 2010, the then Indian Minister for Environment and Forests, Jairam Ramesh, during a visit with Romulus Whitaker at the Madras Crocodile Bank, announced the formation of a National Tri-State Chambal Sanctuary Management and Coordination Committee for gharial conservation on 1,600 km2 (620 sq mi) of the National Chambal Sanctuary along the Chambal River in Madhya Pradesh, Rajasthan and Uttar Pradesh. The Committee will comprise representatives of three states' Water Resources Ministries, states' Departments of Irrigation and Power, Wildlife Institute of India, Madras Crocodile Bank Trust, the Gharial Conservation Alliance, Development Alternatives, Ashoka Trust for Research in Ecology and the Environment, Worldwide Fund for Nature and the Divisional Forest officers of the three states. The Committee will plan strategies for protection of gharials and their habitat. This will involve further research on the species and its ecology and socio-economic evaluation of dependent riparian communities. Funding for this new initiative will be mobilized as a sub-scheme of the ‘Integrated Development of Wildlife Habitats’ in the amount of INR 50 to 80 million (USD 1 million to 1.7 million) each year for five years. This project has long been advocated by Rom Whitaker.[17][18]

In captivity

Gharials are bred in captivity in the National Chambal Sanctuary in Uttar Pradesh, and in the Gharial Breeding Centre in Nepal's Chitwan National Park, where they are generally grown for two to three years and average about one meter, when released.[1] They are also kept at the Honolulu Zoo on Oahu, the Cleveland Metroparks Zoo, the Fort Worth Zoo in Texas, the San Diego Zoo in San Diego, the La Ferme aux Crocodiles in France and at the Prague Zoo in the Czech Republic.

Ancestry

The fossil history of the Gavialoidea is quite well known, with the earliest examples diverging from the other crocodilians in the late Cretaceous. The most distinctive feature of the group is the very long, narrow snout, which is an adaptation to a diet of small fish. Although gharials have sacrificed the great mechanical strength of the robust skull and jaw that most crocodiles and alligators have, and in consequence cannot prey on large creatures, the reduced weight and water resistance of their lighter skull and very narrow jaw gives gharials the ability to catch rapidly moving fish, using a side-to-side snapping motion.

The earliest gharial may have been related to the modern types: some died out at the same time as the dinosaurs (at the end of the Cretaceous), others survived until the early Eocene. The modern forms appeared at much the same time, evolving in the estuaries and coastal waters of Africa, but crossing the Atlantic to reach South America as well. At their peak, the Gavialoidea were numerous and diverse; they occupied much of Asia and America up until the Pliocene. One species, Rhamphosuchus crassidens of India, is believed to have grown to an enormous 15 metres (~50 feet) or more.

Taxonomy

The gharial and its extinct relatives are grouped together by taxonomists in several different ways:

If the three surviving groups of crocodilians are regarded as separate families, then the gharial becomes one of two members of the Gavialidae, which is related to the families Crocodylidae (crocodiles) and Alligatoridae (alligators and caymans).
Alternatively, the three groups are all classed together as the family Crocodylidae, but belong to the subfamilies Gavialinae, Crocodylinae, and Alligatorinae.
Finally, palaentologists tend to speak of the broad lineage of gharial-like creatures over time using the term Gavialoidea.

According to molecular genetic studies the gharial and the false gharial (Tomistoma) are close relatives, which would support to place them in the same family.[19]

Classification

Order Crocodilia
Superfamily Gavialoidea
Genus †Eothoracosaurus
Genus †Thoracosaurus
Genus †Eosuchus
Genus †Argochampsa
Family Gavialidae
Subfamily Gavialinae
Genus Gavialis
Gavialis gangeticus – modern gharial
†Gavialis curvirostris
†Gavialis breviceps
†Gavialis bengawanicus
†Gavialis lewisi
Subfamily Tomistominae
Genus Tomistoma
Tomistoma schlegelii, false gharial or Malayan gharial
†Tomistoma lusitanica
†Tomistoma cairense
Genus †Eogavialis
†Eogavialis africanus
†Eogavialis andrewsi
Genus †Kentisuchus
Genus †Gavialosuchus
Genus †Paratomistoma
Genus †Thecachampsa
Genus †Rhamphosuchus
Genus †Toyotamaphimeia
Subfamily †Gryposuchinae
Genus †Aktiogavialis
Genus †Gryposuchus
Genus †Ikanogavialis
Genus †Siquisiquesuchus
Genus †Piscogavialis
Genus †Hesperogavialis


Vernacular names

Common names include Indian gharial, Indian gavial, Fish-eating crocodile, Gavial del Ganges, Gavial du Gange, Long-nosed crocodile, Bahsoolia, Chimpta, Lamthora, Mecho Kumhir, Naka, Nakar, Shormon, Thantia, Thondre, Garial.

References

^ a b c d e f Choudhury, B.C., Singh, L.A.K., Rao, R.J., Basu, D., Sharma, R.K., Hussain, S.A., Andrews, H.V., Whitaker, N., Whitaker, R., Lenin, J., Maskey, T., Cadi, A., Rashid, S.M.A., Choudhury, A.A., Dahal, B., Win Ko Ko, U., Thorbjarnarson, J., Ross, J.P. (2010). "Gavialis gangeticus". IUCN Red List of Threatened Species. Version 2010.4. International Union for Conservation of Nature.
^ a b Maskey, T.M., Percival, H.F. (1994) Status and Conservation of Gharial in Nepal. Presented at the 12th Working Meeting of the Crocodile Specialist Group, Thailand.
^ Hiremath, K.G.. Recent advances in environmental science. Discovery Publishing House, 2003. ISBN 8171416799, 9788171416790.
^ "Crocodilian species – Gharial". Flmnh.ufl.edu. Retrieved 2010-03-16.
^ a b c Whitaker, R., Members of the Gharial Multi-Task Force, Madras Crocodile Bank (2007). "The Gharial: Going Extinct Again". Iguana 14 (1): 24–33.
^ Turner, R.L.. "A Comparative and Etymological Dictionary of the Nepali Language".
^ Gavial (Gharial). Gavialis gangeticus. National Geographic
^ "San Diego Zoo's Animal Bytes: Alligator & Crocodile". Sandiegozoo.org. Retrieved 2010-03-16.
^ Gavialis gangeticus. "Gavials (Gharials), Gavial (Gharial) Pictures, Gavial (Gharial) Facts – National Geographic". Animals.nationalgeographic.com. Retrieved 2010-03-16.
^ Wood, The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc (1983), ISBN 978-0851122359
^ a b Boulenger, G. A. (1890) Fauna of British India. Reptilia and Batrachia.
^ Bustard, H.R. (1983). "Movement of wild Gharial, Gavialis gangeticus (Gmelin) in the River Mahanadi, Orissa (India)". British Journal of Herpetology 6: 287–291.
^ Priol, P. (2003) Gharial field study report. A report submitted to Department of National Parks and Wildlife Conservation, Kathmandu, Nepal.
^ Rao, R.J., Choudhury, B.C. (1990). "Sympatric distribution of Gharial Gavialis gangeticus and Mugger Crocodylus palustris in India". Journal of the Bombay Natural History Society 89: 313–314.
^ Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
^ Raaj, N. (2007) At 200, gharials now on critically-endangered list. The Times of India.
^ Lenin, Janaki (1010-12-27). "New Government of India initiative for gharial conservation". Janaki Lenin's Facebook Notes (Madras Crocodile Bank, Chennai, India).
^ Oppilli, P. (2010-12-27). "A sanctuary Coming Up for Ghariyals". S & T, Energy and Environment (The Hindu, Chennai). Retrieved 2010-12-27.
^ Janke, A; Gullberg, A; Hughes, S; Aggarwal, RK; Arnason, U (2005). "Mitogenomic analyses place the gharial (Gavialis gangeticus) on the crocodile tree and provide pre-K/T divergence times for most crocodilians". Journal of molecular evolution 61 (5): 620–6. doi:10.1007/s00239-004-0336-9. PMID 16211427.
^ Grayscaled Gharial image
^ "Algae Gharial (Shards of Alara) – Gatherer – Magic: The Gathering". Gatherer.wizards.com. Retrieved 2010-03-16.

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