The gharial (Gavialis gangeticus), sometimes called the Indian gavial or gavial, is one of two surviving members of the family Gavialidae, a long-established group of crocodile-like reptiles with long, narrow jaws. It is a critically endangered species. The gharial is the second-longest of all living crocodilians, after the saltwater crocodile.[1]
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 or may not 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.
Distribution
Northern Indian subcontinent: Bhutan (almost extinct), Bangladesh (close to extinction), India (present in small numbers and increasing), Myanmar (possibly extinct), Nepal (present and increasing), Pakistan (close to extinction). Usually found in the river systems of Indus (Pakistan) and the Brahmaputra (Bangladesh, Bhutan & North eastern India), the Ganges (Bangladesh, India & Nepal), and the Mahanadi (in the rainforest biome)(India), with small numbers in Kaladan and the Ayeyarwady River in Myanmar. It is sympatric, in respective areas, with the Mugger Crocodile (Crocodylus palustris) and the Saltwater Crocodile (Crocodylus porosus). There have been some small-scale projects to breed and release Gharials, for example in Nepal's Chitwan National Park[1].
Habitat
Riverine—most adapted to the calmer areas in the deep fast moving rivers. The physical attributes of the gharial do not make it very suited for moving about on land. In fact the only reasons the gharial leaves the water is either to bask in the sun or to nest on the sandbanks of the rivers.
[edit] Appearance
Characteristic elongated, narrow snout, similar only to the closely related False gharial, (Tomistoma schlegelii). The snout shape varies with the age of the saurian. The snout becomes progressively thinner the older the gharial gets. The bulbous growth on the tip of the male's snout is called a 'ghara' (after the Indian word meaning 'pot'), present in mature individuals. The bulbous growth is used for various activities, it is used to generate a resonant hum during vocalization, it acts as a visual lure for attracting females and it is also used to make bubbles which have been associated with the mating rituals of the species.
The elongated jaws are lined with many interlocking, razor-sharp teeth - an adaptation to the diet (predominantly fish in adults). This species is one of the largest of all crocodilian species, being the only crocodilian besides the saltwater crocodile (Crocodylus porosus) and nile crocodile (Crocodylus niloticus) with multiple records of attaining a length of 6 m (20 feet) and a weight of 1000 kg (2200 lbs)[2], although a majority of gharials do not grow past 5 m (16.5 feet) and about 680 kg (1500 lb).[3] The three largest examples reported were a 6.5 m (21.5 ft) gharial was killed in the Gogra River of Faizabad in August 1920; a 6.3 m (21 ft) individual shot in the Cheko River of Jalpaigur in 1934; and a giant taped at 7 m (23 ft) which was shot in the Kosi River of northern Bihar in January 1924.[4] The leg musculature of the gharial is not suited to enable the animal to raise the body off the ground (on land) in order to achieve the high-walk gait—being able only to 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 crocodiles in the world. The tail seems overdeveloped and is laterally flattened, more so than other crocodiles, this enables it to achieve the excellent water locomotive abilities.
The gharial has 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.[5]
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.
