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Gharial

Gharial
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Reptilia
Order:Crocodylia
Family:Gavialidae
Genus:Gavialis
Species:gangeticus
Binomial name
Gavialis gangeticus

The Gharial (Gavialis gangeticus) is the only surviving member 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-largest of all surviving crocodilians: a large individual can be 6 or 7 metres long.

Gharials are not dangerous to humans but are themselves classified as endangered: a major effort to prevent their extinction began in the 1970s and has been moderately successful, however loss of habitat remains a significant threat to them.

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

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 Cretacious), others survived until the early Eocene (about 35 million years ago). The modern forms apeared 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, Ramphosuchus crassidens of India, grew to an enormous size: 15 metres or more.

Although the Gavialoidea appear to have been largely coastal and estuarine, the sole remaining species lives only in fresh water. Once more widespread, it is now restricted to the Indus, Ganges and Brahmaputra river systems, where human hunting, competition for food, and above all habitat depletion reduced it to critically endangered status.

An intensive conservation effort in India began in the 1970s: Gharials were protected by law (although poaching continued and, to a lesser extent, still continues today); 9 areas of habitat were set aside for them; captive breeding programs began; and eggs were collected from the wild, the young raised in safety, then released. A total of over 3000 Gharials have been restored to the wild in these ways, but the total population in India is still estimated at only 1500 animals, and the shortage of suitable habitat suggests that increasing the population to a safe number will be difficult. It is now thought that any increase in gharial numbers may well help restore the diminished fisheries yield of the river systems of India, as Gharials tend to prey mostly on carnivorous fish species rather than on the species that are of interest to humans. Outside India, there are probably only about 200 wild Gharials left.

The Gharial is a large, slender crocodilian. Males can grow to almost a tonne in weight and over 6 metres in length, but are more commonly about 4 metres long. Females are usually under 4 metres. The snout is very long and slender and has between 27 and 29 evenly-sized, slightly forward and outward pointing teeth on either side, which mesh fully top and bottom and are well adapted to catching slippery fish.

Mature males have a bulbous knob on the end of their snout, apparently used for vocalising during courtship and called a ghara—the Indian word for pot. The name gharial derives from this; gavial is a common misspelling of it. The very tough armoured hide is pale olive or tan, with irregular darker blotches.

Gavials have long but weakly-muscled legs; the hind toes are webbed to aid swimming. They are unable to raise their bellies clear of the surface to run on dry land and almost never leave the water except to lay their eggs, but they can belly-slither rapidly if need be. In the water, however, they are fast-moving and agile, swimming with their long, streamlined tails.

Although the very thin, elongated snout and altered jaw musculature is a trademark of the Gavialoidea, several other crocidilians have gone at least part-way to adopting the same fish-catching strategy. The Freshwater Crocodile of Australia is one example. Another, the False Gharial of Indonesia, provides one of the major evolutionary mysteries of the crocodile order: it appears at first sight to be one of the gharial family. Closer examination, however, suggests that it is in fact a crocodile, and the fossil record appears to suport this view. Recent molecular data, however, indicates that it may well be most closely related to the Indian Ghavial after all. Research is continuing.

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