Gharial
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| Gavialis gangeticus (Gmelin, 1789) |
The gavial (Gavialis gangeticus) is one of two surviving members of the family Gavialidae, a long-established group of crocodile-like reptiles with long, narrow jaws. The gharial (sometimes Indian gharial, or gavial) is the second-longest of all living crocodilians: a large male can approach 6 meters in length.[1]
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[edit] 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 Gavialoidea 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 (about 35 million years ago). 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, are believed to have grown to an enormous 15 metres or more.
[edit] Distribution
Northern Indian subcontinent: Bhutan (possibly extinct), Bangladesh (close to extinction), India (present in small numbers and increasing), Myanmar (possibly extinct), Nepal, Pakistan (close to extinction). Usually found in the river systems of Indus (Pakistan) and the Brahmaputra (Bangladesh, Bhutan & 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.
[edit] 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 its relative, the 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, approaching the saltwater crocodile (Crocodylus porosus) and the Nile crocodile in maximum size - males reach at least 5 metres in length, and often approach 6 metres. Reports of 7 metre animals exist, but are unconfirmed. 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.
[edit] Diet
The young gharials prey primarily on small invertebrates such as insects, larvae, and also small frogs. The mature adults feed almost solely on fish. Their physiognomy is ideally suited for this diet and the obtaining of it. Their characteristic long narrow snouts afford very little resistance to water in swiping motions to snap up fish in the water. Their numerous needle-like teeth are perfect for holding on to struggling, slippery fish. Most adults are primarily fish eaters although some individuals have been known to scavenge dead animals. The Gharial is not thought to be a man-eater. Despite its immense size, its jaws make it physically incapable of devouring any large mammal, including a human being. However, specimens, especially some from the Ganges, have been found with jewelry in their stomachs, suggesting that they may have swallowed them while scavenging corpses that had been consecrated to the river.
[edit] Breeding
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 till they learn to fend for themselves.
[edit] Conservation
In the 1970s the gharial came to the brink of extinction and even now remains on the severely 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 as of 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) and then released back into the wild (the first being released in 1981). More than 3000 animals have been released through these programs, and 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.
[edit] Man-eaters
The gharial's structure is not conducive for it to be a maneater or to even launch an attack on a human on the river bank. In spite of this they have been called maneaters for some time. The reasons behind this myth are varied.
- They appear threatening to the average swimmer or fisherman since they have a similar appearance to Crocodiles.
- In many cases human jewelry has been found in the bellies of dead gharials (this is most likely from scavenging human corpses which are floated down river in the Ganges, or scavenging cremated remains that have been dumped into the Ganges). The gharial also swallows jewelry, stones, sticks, and the like to act as gastroliths: hard objects that aid in digestion and buoyancy management.
[edit] 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.
Janke et al. (2005), using molecular genetic evidence, found the gharial and the false gharial (Tomistoma) to be close relatives, and placed them together in the same family.
Common names include: Indian gharial, Indian gavial, Fish-eating crocodile, Gavial del Ganges, Gavial du Gange, Long-nosed crocodile, Bahsoolia, Nakar, Chimpta, Lamthora, Mecho Kumhir, Naka, Nakar, Shormon, Thantia, Thondre, Garial.
[edit] Classification
- Order Crocodilia
- Superfamily Gavialoidea
- Genus Eothoracosaurus
- Genus Thoracosaurus
- Genus Eosuchus
- Family Gavialidae
- Genus Eogavialis
- Genus Argochampsa
- Genus Gryposuchus
- Genus Ikanogavialis
- Genus Siquisiquesuchus
- Genus Piscogavialis
- Genus Rhamphosuchus
- Genus Hesperogavialis
- Genus Gavialis
- Gavialis curvirostris
- Gavialis breviceps
- Gavialis bengawanicus
- Gavialis lewisi
- Gavialis gangeticus - modern Gharial
- Superfamily Gavialoidea
[edit] Appearances in Popular Culture
- In the PlayStation2 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. It replenishes significant amounts of stamina, while causing Snake to express utmost satisfaction. A crocodile cap is also an obtainable item that can be used to scare away unsuspecting enemy soldiers. The Indian Gavials in the game are generally not too dangerous on land, inflicting only minor damage by striking the game's protagonist with their tails. However, if Naked Snake is attacked by one while in the water, it kills him instantly.
[edit] References
- Crocodile Specialist Group (1996). Gavialis gangeticus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Listed as Endangered (EN C2a, E v2.3)
- 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." J Mol Evol. 61(5):620-6.
[edit] See also
[edit] External links
- http://reptilis.net/crocodylia/gavies/gavialidae.html a less formal article, great photos
- http://www.vic.com/nepal/images/gharial.html photo of a large specimen in the wild
- http://www.flmnh.ufl.edu/cnhc/!ggan1.htm teeth and feeding
- http://www.whozoo.org/students/lydia/gharials.htm excellent photos from Fort Worth Zoo
- http://www.oneworldmagazine.org/tales/crocs/gharial.html a charming folk tale
- http://www.scz.org/animals/g/gharial.html species summary from Sedgwick County Zoo
- http://www.itis.usda.gov ITIS Taxonomic Serial No.: 202217
