The gharial (Gavialis gangeticus), also known as gavial or fish-eating crocodile, is a crocodilian in the family Gavialidae and among the longest of all living crocodilians. Mature females are long, and males . Adult males have a distinct boss at the end of the snout, which resembles an earthenware pot known as a ghara, hence the name "gharial". The gharial is well adapted to catching fish because of its long, narrow snout and 110 sharp, interlocking teeth.
The gharial probably evolved in the northern Indian subcontinent. Fossil gharial remains were excavated in Pliocene deposits in the Sivalik Hills and the Narmada River valley. It currently inhabits rivers in the plains of the northern part of the Indian subcontinent. It is the most thoroughly aquatic crocodilian, and leaves the water only for basking and building nests on moist sandbanks. Adults mate at the end of the cold season. Females congregate in spring to dig nests, in which they lay 20–95 eggs. They guard the nests and the young, which hatch before the onset of the monsoon. The hatchlings stay and forage in shallow water during their first year, but move to sites with deeper water as they grow.
The wild gharial population has declined drastically since the 1930s and is limited to only 2% of its historical range today. Conservation programmes initiated in India and Nepal focused on reintroducing captive-bred gharials since the early 1980s. Loss of habitat because of sand mining and conversion to agriculture, depletion of fish resources and detrimental fishing methods continue to threaten the population. It has been listed as critically endangered on the IUCN Red List since 2007.
The oldest known depictions of the gharial are about 4,000 years old and were found in the Indus Valley. Hindus regard it as the vehicle of the river deity Gaṅgā. Local people living near rivers attributed mystical and healing powers to the gharial, and used some of its body parts as ingredients of indigenous medicine.
Etymology The name 'gharial' is derived from the Hindustani word 'ghara' for an earthen pot, in reference to the nasal protuberance on the adult male's snout. It is also called 'gavial'. The name 'fish-eating crocodile' is a translation of its Bengali name 'mecho kumhir', with 'mecho' being derived from 'māch' meaning fish and 'kumhir' meaning crocodile. The name 'Indian gharial' has occasionally been used for gharial populations in India.
Taxonomy Lacerta gangetica was the scientific name proposed by Johann Friedrich Gmelin in 1789. Gmelin followed Carl Linnaeus who proposed Lacerta in 1758 to include other crocodiles and various lizards known at the time.
The gharial was placed in the genus Crocodilus by subsequent naturalists: Crocodilus gavial by Pierre Joseph Bonnaterre in 1789. Crocodilus longirostris by Johann Gottlob Theaenus Schneider in 1801. Crocodilus arctirostris by François Marie Daudin in 1802. Longirostres was a subgroup proposed by Georges Cuvier in 1807 for crocodiles with a long snout. He placed Crocodilus gangeticus with the type locality "Ganges" and Crocodilus tenuirostris without locality into this group.
The generic name Gavialis was proposed by Nicolaus Michael Oppel in 1811 for crocodiles with a cylindrical-shaped back. He placed this genus in the family Crocodilini. Rhamphostoma was proposed by Johann Georg Wagler in 1830 who considered this genus to contain two species, Crocodilus gangeticus and C. tenuirostris.
The family name Gavialidae was proposed by Arthur Adams in 1854 with Gavialis as the only genus in this family. Gavialis gangetica was the scientific name used by Albert Günther in 1864 who considered L. gangetica, C. longirostris and C. tenuirostris as synonyms and Gavialis a monotypic taxon. John Edward Gray reviewed zoological specimens in the collection of the Natural History Museum, London. He also considered the gharial monotypic in 1869. He placed it in the family Gavialidae together with the false gharial (Tomistoma schlegelii) because both have long, slender jaws and similar dentition.
Gharialis hysudricus proposed by Richard Lydekker in 1886 was based on a fossil skull from the Sivalik Hills that was larger than gharial fossil skulls known at the time. This name is considered to be a junior synonym of Gavialis gangeticus.
Evolution The evolution of the gharial and its relationship with and divergence from other crocodilians have been a subject of controversy. Some authors assumed that the gharial evolved earlier than the other crocodilians because of its distinct skull shape and dentition, indicating a more advanced level of specialization. Others suggested that it evolved much later than other crocodilians because of its low levels of blood protein divergence. As it shares this trait with the false gharial, it was suggested that they form a sister group. In contrast, it was suggested that the gharial and all the other crocodilians form a sister group as the structure of its tail muscles is unique. Sequencing of a ribosomal segment of mitochondrial DNAs of gharial and false gharial revealed that they share 22 unique nucleotides, a similarity of 94%, supporting the view that they are sister taxa. Analyses of nuclear gene sequences of both species also support the view that they are sister taxa. Molecular genetics and tip dating studies indicates a genetic divergence between the gharial and false gharial in the Eocene about .
The genus Gavialis probably originated in the region of India and Pakistan in the Early Miocene. Fossil gharial remains excavated in the Sivalik Hills of Haryana and Himachal Pradesh are dated to between the Pliocene and the Early Pleistocene. Fossil gharial remains were also found at two sites in the Ayeyarwady River valley in central Myanmar, which are dated to the Late Pleistocene. During the Quaternary, Gavialis dispersed as far as Java via the Siva–Malayan route, which did not require saltwater crossings. Fossil remains of Gavialis bengawanicus found on Java were dated to the Early Pleistocene. G. bengawanicus fossils found in Thailand's Nakhon Ratchasima Province support the hypothesis of gharial dispersal through riverine systems. It represents the only valid extinct Gavialis species.
Phylogeny The below cladogram of the major extant crocodile groups is based on the latest molecular studies and shows the gharial's close relationship to the false gharial, and how the gavialids and crocodiles are more closely related than the alligatoroids:
Here is a more detailed cladogram that shows the gharial's proposed placement within Gavialidae, including extinct members:
Characteristics
The gharial is olive-coloured, with adults being darker than young, which have dark brown cross bands and speckles. Its back turns almost black at 20 years of age, but its belly is yellowish-white. It has four transverse rows of two scales on the neck, which continue along the back. Scutes on the head, neck and back form a single continuous plate composed of 21 to 22 transverse series, and four longitudinal series. Scutes on the back are bony, but softer and feebly keeled on the sides. The outer edges of the forearms, legs, and feet have crests jutting out; fingers and toes are partly webbed.
Its snout is very long and narrow, widened at the end, and has 27 to 29 upper teeth and 25 or 26 lower teeth on each side. The front teeth are the largest. The first, second, and third lower jaw teeth fit into spaces in the upper jaw. The extremely long mandibular symphysis extends to the 23rd or 24th tooth. The snout of adult gharials is 3.5 times longer than the width of the skull's base. Because of this long snout, the gharial is especially adapted to catching and eating fish. The nasal bones are rather short and widely spaced from the premaxillae. The jugal bone is raised. It becomes proportionally thicker with age. Two individuals in the weight range of had an average measured bite force of .
Male gharials develop a hollow bulbous nasal protuberance at the tip of the snout upon reaching sexual maturity. This protuberance resembles an earthen pot known locally as "ghara". The male's ghara starts growing over the nostrils at an age of 11.5 years and measures about at an age of 15.5 years. It enables the males to emit a hissing sound that can be heard away; this sound is thought to attract females. The gharial is the only living crocodilian with such visible sexual dimorphism. Mature male gharials have larger skulls than females, exceeding a basal length of and a width of .
Female gharials reach sexual maturity at a body length of and grow up to . Males mature at a body length of at least and grow up to a length of . Adult males weigh about on average, but large males can reach a weight of . The gharial is among the largest living crocodilians, with the heaviest recorded male weighing . A long gharial was claimed to have been killed in the Ghaghara River in Faizabad in August 1920, though no reliable measurements were taken. Male gharials with an alleged length of were sighted around the turn of the 20th century in Indian rivers. Overall, the gharial is less massive when compared to other crocodilians of similar length; a long gharial weighed around , while a long Nile crocodile weighed .
Distribution and habitat
The gharial once thrived in all the major river systems of the northern Indian subcontinent, from the Indus River in Pakistan, the Ganges in India, the Brahmaputra River in northeastern India and Bangladesh to the Irrawaddy River in Myanmar. In the early 20th century, it was considered common in the Indus River and its Punjabi tributaries. By the early 1980s, it was almost extinct in the Indus. During surveys in 2008 and 2009, no gharial was sighted in the river. It was also present in India's Godavari River but was hunted to extinction between the late 1940s and the 1960s. It was considered extinct in the Koshi River since 1970. In the 1940s, it was numerous in the Barak River in Assam, which held big fish at the time including golden mahseer (Tor putitora). A few individuals were also sighted in tributaries of the Barak River in Assam, Mizoram and Manipur up to 1988, but surveys were not carried out. In 1927, a gharial was shot in the Shweli River in Myanmar, a tributary of the Ayeyawady River. This is the only authenticated record in the country attesting the survival of gharials into the 20th century. Whether gharials still live in the Shweli River today is possible but remained unclear in 2012.
By 1976, its global range had decreased to only 2% of its historical range, and fewer than 200 gharials were estimated to survive. It is locally extinct in Bhutan and Myanmar.
In Pakistan, fishermen reported several sightings of adult and juvenile gharials in the Sutlej River in 2023; a strip of the river was notified as Gharial Wildlife Sanctuary in July 2023. A survey in 2023 in an area of along a river stretch revealed two breeding sites and 27 individuals.
Since the early 1980s, the population has been reinforced with captive-bred gharials that were released into wild habitats in India and Nepal. As of 2019, the global population was estimated to comprise at maximum 900 individuals, including about 600 mature adults in six major subpopulations along of river courses and another 50 mature adults in eight minor subpopulations along of river courses.
In Nepal, small populations are present and slowly recovering in tributaries of the Ganges, such as the Karnali–Babai River system in Bardia National Park and the Narayani–Rapti river system in Chitwan National Park. In spring 2017, the Babai River was surveyed using an unmanned aerial vehicle, which detected 33 gharials on a stretch of .
In India, gharial populations are present in the: