Gharial

Appearance

The gharial is characterised by its extremely long, thin jaws, regarded as an adaptation to a predominantly fish diet. Males reach up to 6 m with an average weight of around 160 kg.

It is dark or light olive above with dark cross-bands and speckling on the head, body and tail. Dorsal surfaces become dark, almost grey-black, at about 20 years of age. Ventrals are yellowish-white. The neck is elongated and thick. The dorsals are more or less restricted to the median regions of the back. The fingers are extremely short and thickly emarginated with a web. Males develop a hollow bulbous nasal protuberance or at sexual maturity. The name gharial is derived from the resemblance of the nasal boss to an earthen pot known locally as "ghara". The boss is used to modify and amplify “hisses” snorted through the underlying nostrils. The resulting sound can be heard for nearly a kilometer on a still day. Gharials are the only extant crocodilian with visible sexual dimorphism. Although the function of the nasal boss is not well understood, it is apparently used as a visual sex indicator, as a sound resonator, or for bubbling or other associated sexual behaviours.

The average size of mature gharials is 3.5 to 4.5 m. The maximum recorded size is 6.25 m. Hatchlings approximate 37 cm. Young gharials can reach a length of 1 m in 18 months. The average body weight ranges from 159 to 250 kg. Males commonly attain a total length of 3 to 5 m, while females are smaller and reach a body length of up to 2.7 to 3.75 m.

The elongated, narrow snout is lined by 110 sharp interdigitated teeth, and becomes proportionally shorter and thicker as an animal ages. There are 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 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 lower anterior margin of the orbit 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. The length of the snout is 3.5 to 5.5 times the breadth of the snout's base. The 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 postoccipital scutes. The outer toes are two-thirds webbed, while the middle toe is only one-third webbed. They have a strong crest on the outer edge of the fore arm, leg, and foot. Typically, adult gharials have a dark olive colour tone, while young ones are pale olive, with dark brown spots or cross-bands.

The well-developed, laterally flattened tail and webbed rear feet provide tremendous manoeuvrability in deepwater habitat. On land, however, an adult gharial can only push itself forward and slide on its belly. The laterally compressed tail serves both to propel the animal and as a base from which to strike at prey.

The three largest examples reported were a 6.5-m gharial killed in the Gogra River of Faizabad in August 1920, a 6.3-m individual shot in the Cheko River of Jalpaiguri in 1934, and a giant of 7-m animal, which was shot in the Kosi River of northern Bihar in January 1924. Though specimens of over 6 m were not uncommon in the past, such large individuals are not known to exist today.* In the PlayStation 2 video game, "Metal Gear Solid 3: Snake Eater", one of the more noted animals that Naked Snake can consume for his survival is the Indian Gavial.
⤷  The "Ravnica: City of Guilds" expansion of the "Magic: The Gathering" trading card game features a "Crocodile" creature called Grayscaled Gharial, and the "Shards of Alara" expansion includes the creature Algae Gharial.
⤷  In the "Pokémon" series of video games, the pokémon "Krookodile" is meant to resemble a gavial. Part of the word "gavial" is used in its Japanese form, "Waruvial".

Naming

Common names include Indian gharial, Indian gavial, gavial del Ganges, gavial du Gange, long-nosed crocodile, bahsoolia, chimpta, lamthora, mecho kumhir, naka, nakar, shormon, thantia, thondre.

Distribution

Gharials once thrived in all the major river systems of the Indian Subcontinent, spanning the rivers of its northern part from the Indus River in Pakistan across the Gangetic floodplain to the Irrawaddy River in Myanmar. Today, they are extinct in the Indus River, in the Brahmaputra of Bhutan and Bangladesh, and in the Irrawaddy River. Their distribution is now limited to only 2% of their former range:
⤷  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, Odisha, where they apparently do not breed;
⤷  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.

They are sympatric with the mugger crocodile and formerly with the saltwater crocodile in the delta of Irrawaddy River.

In 1977, four nests were recorded in the Girwa River of Katarniaghat Wildlife Sanctuary, where 909 gharials were released until 2006. Twenty nests were recorded in 2006, so 16 nesting females resulted from 30 years of reintroductions, which is equivalent to 2% of the total pre-2006 releases. This is seemingly not a great achievement for the money and effort spent, and as several knowledgeable researchers have suggested, perhaps carrying capacity has been reached there. In 1978, twelve nests were recorded in the Chambal River in the National Chambal Sanctuary, where 3,776 gharials were released until 2006. By 2006, nesting had increased by over 500% to 68 nests, but the recruited mature, reproducing females constituted only about 2% of the total number released. The newly hatched young are especially prone to being flushed downstream out of the protected areas during the annual monsoonal flooding.

Status

"Gavialis gangeticus" is listed on CITES Appendix I.

By 1976, the estimated total population of wild gharials had declined from what is thought to have been 5,000 to 10,000 in the 1940s to less than 200, a decline of about 96%. The Indian government subsequently accorded protection under the Wildlife Protection Act of 1972.

In 1997, the total population was estimated at 436 adult gharials that had declined to 182 in 2006. This drastic decline has happened within a period of nine years, well within the span of one generation, and qualifies the gharial for Critically Endangered listing by the IUCN.
Estimates from population surveys carried out in 2007 indicated 200–300 breeding adults left in the world.

Behavior

Gharials are arguably the most thoroughly aquatic of the extant crocodilians, and adults apparently do not have the ability to walk in a semiupright stance as other crocodilians do. They are generally residents of flowing rivers with deep pools that have high sand banks and good fish stocks. Exposed sand banks are used for nesting.

Habitat

Gharials once thrived in all the major river systems of the Indian Subcontinent, spanning the rivers of its northern part from the Indus River in Pakistan across the Gangetic floodplain to the Irrawaddy River in Myanmar. Today, they are extinct in the Indus River, in the Brahmaputra of Bhutan and Bangladesh, and in the Irrawaddy River. Their distribution is now limited to only 2% of their former range:
⤷  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, Odisha, where they apparently do not breed;
⤷  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.

They are sympatric with the mugger crocodile and formerly with the saltwater crocodile in the delta of Irrawaddy River.

In 1977, four nests were recorded in the Girwa River of Katarniaghat Wildlife Sanctuary, where 909 gharials were released until 2006. Twenty nests were recorded in 2006, so 16 nesting females resulted from 30 years of reintroductions, which is equivalent to 2% of the total pre-2006 releases. This is seemingly not a great achievement for the money and effort spent, and as several knowledgeable researchers have suggested, perhaps carrying capacity has been reached there. In 1978, twelve nests were recorded in the Chambal River in the National Chambal Sanctuary, where 3,776 gharials were released until 2006. By 2006, nesting had increased by over 500% to 68 nests, but the recruited mature, reproducing females constituted only about 2% of the total number released. The newly hatched young are especially prone to being flushed downstream out of the protected areas during the annual monsoonal flooding.Gharials are arguably the most thoroughly aquatic of the extant crocodilians, and adults apparently do not have the ability to walk in a semiupright stance as other crocodilians do. They are generally residents of flowing rivers with deep pools that have high sand banks and good fish stocks. Exposed sand banks are used for nesting.

Reproduction

Males mature at around 13 years old, which is when the ghara begins to grow on the snout. They advertise for mates by making hissing and buzzing noises as they patrol their territories, and may have a harem of females within a territory which they aggressively defend from other males. Females communicate their readiness to mate by raising their snouts upwards. During courtship, males and females follow prospective mates around until a suitable mate is chosen. Courtship also involves head and snout rubbing and mounting by both males and females.

Mating usually occurs during December and January.
In India, gharials nest in March and April, the dry season; the female lays 20–95 eggs in a hole 50–60 cm deep, dug with the hind feet in a riverside sand or silt bank, 1–5 m from the waterline.
The eggs are the largest of any crocodilian species, weighing an average of 160 g.
After 71 to 93 days of incubation, young gharials hatch in July just before the monsoon. Temperature is likely an important influence on determining gender.
Female gharials dig up the young in response to hatching chirps, but do not assist the hatchlings to the water. They will, however, guard the hatchlings for some time.

Food

The elongated, narrow snout reduces resistance to water when snagging fish, and the very sharp interdigitated teeth are well adapted for capturing fish. Young gharials eat insects, tadpoles, small fish and frogs. Adults feed on fish and small crustaceans. Their jaws are too thin and delicate to grab larger prey, especially a person. They catch fish by lying in wait for fish to swim by, and then catch the fish by quickly whipping their heads sideways and grabbing it in their jaws. They herd fish with their bodies against the shore, and stun fish using their underwater jaw clap. They do not chew their prey, but swallow it whole.

Gharials do not kill and eat humans. Jewellery found in their stomachs may have been the reason for the myth that gharials are man-eaters. They may have swallowed this jewellery as gastroliths used to aid digestion or buoyancy management.

Predators

According to IUCN, a population decline of 96–98% has occurred 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 overhunting 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 declined by about 58% between 1997 and 2006 because of:
⤷  the increasing intensity of fishing and the use of gill nets throughout most of the present gharial habitat, even in protected areas;
⤷  the loss of riverine habitat to dams, barrages, irrigation canals, siltation, changes in river course, artificial embankments, sand-mining, riparian agriculture, and domestic and feral livestock.

In December 2007, several gharials were found dead in the Chambal River. Initially, it was suspected that fishermen illegally had caught fish using nets, in which gharials became trapped and subsequently drowned. Later "post mortem" pathological testing of tissue samples from the dead gharials revealed high levels of heavy metals such as lead and cadmium, which together with stomach ulcers and protozoan parasites reported in most necropsies were thought to have caused their deaths.

Evolution

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, and crossing the Atlantic to reach South America as well. The discovery of the fossil remains of the Puerto Rican Gharial "Aktiogavialis puertorisensis" in a cave located in San Sebastián, Puerto Rico, suggested that the Caribbean served as the link between the two continents.

Gharials have sacrificed the great mechanical strength of the robust skull and jaw that most crocodiles and alligators have, and consequently are unable to prey on larger creatures. The reduced weight and water resistance of their lighter skull and very narrow jaw enables gharials to catch rapidly moving fish, using a side-to-side snapping motion. 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 or more.

Cultural

* In the PlayStation 2 video game, "Metal Gear Solid 3: Snake Eater", one of the more noted animals that Naked Snake can consume for his survival is the Indian Gavial.
⤷  The "Ravnica: City of Guilds" expansion of the "Magic: The Gathering" trading card game features a "Crocodile" creature called Grayscaled Gharial, and the "Shards of Alara" expansion includes the creature Algae Gharial.
⤷  In the "Pokémon" series of video games, the pokémon "Krookodile" is meant to resemble a gavial. Part of the word "gavial" is used in its Japanese form, "Waruvial".