Fact Summary Taxonomy and Nomenclature Distribution and Habitat Physical Characteristics Behavior and Ecology Diet and Feeding Reproduction and Development Diseases and Pathology Captivity Population and Conservation Status Web Resources Bibliography

Kingdom: Animalia
    Phylum: Chordata
        Class: Reptilia
             Order: Crocodylia
                   Family: Alligatoridae (alligators and caimans)

                   Family: Crocodylidae (crocodiles and false gharials)
                           Genus: Crocodylus (crocodiles)
                           Genus: Tomistominae (false gharials)

                   Family: Gavialidae (gharials)
                           Genus: Gavialis
                                  Species: Gavialis gangeticus
                                        Subspecies: None

• Gavialidae:
  • G. gangeticus probably the only living species in the Family.
  • Fossil and morphological data on Tomistoma schlegelii (false gharial) show closest resemblance to Crocodylidae. But recent molecular data show closer resemblance to G. gangeticus, causing some authors to place it in the Gavialidae (Brochu, 2003).

• "Gharial" originates from the Hindi word "ghara" which is a clay pot with a long neck, much like the snout shape of an adult male gharial.
• Sometimes referred to as "gavial" which is probably a misspelling of gharial. The Family and Genus names have not been changed to reflect this error.
• "gangeticus" means "of the Ganges (River)."
• Other common names: long-nosed crocodile, gaviel du Ganges (Fr.), Schnabelkrokodil (Gr.), Sansar (Pakistan), Chimpta (Nepal).

• Oldest true crocodilian ancestor is 200 million years old; probably terrestrial.
• Crocodylia is the only living representative of the ancient group Archosauria, which includes dinosaurs.
• A very small number of crocodylians exist today -- 23 species. There are 9,000 species of birds, their closest relatives.
• Gavialidae is the oldest crocodilian family, dating back to the Cenozoic (~65 million years ago). Although 12 fossil species have been found in India, South America, Africa, and Europe, only one species survives today.

From Crocodilians: Natural History & Conservation Click on map for larger image.

• Northern Indian subcontinent in river drainages:   India, Pakistan, and Nepal. Numbers very low or extinct in Bangladesh, Bhutan, and Burma.
• The most important remaining populations occur in 3 tributaries of the Ganges River: Girwa and Chambal Rivers in India, and the Rapti-Narayani River in Nepal (Whitaker, 1987).
• Non-continuous distribution (isolated populations).

• Riverine habitats with deep, clear, fast-moving water and steep, sandy banks.
• Prefer still, deep pools, formed at sharp river bends.
• Use sandy banks (at river's edge or mid-river) and rocky outcrops for basking.
• Young up to a year old prefer to hide in thick vegetation, roots or branches in the water.

Body scales

• One of the largest crocodilians.
• Thick skin covered with smooth epidermal scales that do not overlap. Osteoderms (bony plates) on the dorsal side serve as armor. (None on belly).
• Light tan or olive color with darker bands along back and tail.
• Long, very narrow snout. Longest of all crocodilians.
• Sharp, slender teeth (all alike in form) along length of snout; upper teeth interlock with lower.
• Thecodont teeth (Crocodylia and Mammalia) =rooted and set in sockets. Unlike other reptiles, which are rootless and attached to the jaw, rather than set in sockets.
• Most aquatic crocodilian.Tail laterally compressed; back feet webbed; legs weak, can't lift body up off the ground.
  

  Heads of Crocodiles, showing snout lengths. From Bellairs, 1969.  A. Caiman latirostris. B. Alligator mississippiensis. C. Crocodylus porosus. D. Tomistoma schlegeli. E. Gavialis gangetius.

Bulbus nose of a male gharial

• Cartilaginous knob or ghara begins to develop at the tip of the male’s snout around age 10. Forms a lid over the nostrils in males larger than 3 m (9.8 ft)
• Males may be slightly larger than females.

• Integumentary Sense Organs, or ISO's:
• Tiny pits found on scales of entire body, including head and jaws.
• Thought to detect vibrations or changes in pressure or salinity.
• Probably assist in finding prey.
• Found in all crocodilians.

• Eyes:
  • Tapetum lucidum (reflective layer behind the retina) enables night vision.
  • Nictitating membrane:  transparent membrane that slides across the eye to protect it under water.
• Ears:
  • Muscles close the ear canal to prevent water from entering when submerged.
  • Hear mostly in low frequency or subsonic range.

• Basking is the main activity while on land.
  • Amount of time spent basking is seasonal. More hours are spent basking in cooler winter months than during the hot summer, and this may occur more often on rocks than on sand.
  • Typical basking pattern: Winter months -bask from 9:00 AM until 4:00 PM. Summer months -come out several hours earlier, spend 10:00 AM - 5:00 PM (hottest time of day) in the water, return for a few hours in the evening.
  • Occasionally, very large animals have been observed basking at night during the hottest time of year.
  • Individuals often return to the same basking spot, making them more vulnerable to predators. But they are never far from the safety of the water.
• Gaping: Resting with jaws wide open.
  • Common among basking gharials (10-20 minute periods with head raised ~20 degrees).
  • At midday during the hot season, juveniles and adults remain submerged while holding heads out of water at a 20-30 ^o angle.
• Other activities: When not basking, time is spent in the water resting and foraging.

• Endothermic: must regulate body temperature by external means
• Bask in the sun to increase body temperature; results in better mobility and digestion
• Evaporative cooling
• Gaping: cool brain and head by
• Cool entire body by submerging under water and then lying on river bank

• Social group: single adult male with rostrum knob and several females
• Adult males are dominant to females and immatures.
• Size most important factor in dominance.
• Fairly social; bask in groups.

• Adult males become territorial during the breeding season, but will tolerate small and subadult males.
• Females slightly territorial during nesting season, and will defend nest and hatchlings. But nest communally and share nesting habitat with other females.

• Generally not aggressive towards one another, except during the breeding season.

• See Courtship.

• Hissing and buzzing: by males when protecting territory or during courtship. Bulbous growth on snout partially covers nostrils and sound is made during exhalation.
• Jawslap: most often under water, but occasionally above. By both males and females during courtship.
• Various types of "groans" and "bawling" have been described when animals are threatened or in pain.
• When ready to hatch, young make small grunting sounds which alerts the mother to start digging them out.

• Unlike other crocodilians, gharials do not move well on land, and can only slide on their belly.Cannot perform terrestrial locomotion described for other species- high walk, belly run, gallop.
• They usually come out only to bask, and to prepare and tend to nest.
• Swim with limbs folded next to body to reduce drag; undulating tail provides propulsion.

• Does not prey on people or other large mammals, but female may be aggressive when protecting her nest.
• Occasional aggressive encounters with the mugger (Crocodylus palustris) where ranges overlap. Mugger is usually the aggressor. Usually involves access to a particular basking spot.

• Diet
  • Primarily a fish eater. Also aquatic frogs.
  • Uncommon reports of other food items: soft shell turtles, birds, plant material, small mammals.
  • Young eat tadpoles and invertebrates, in addition to fish.
• Feeding strategies
• Sit and wait: anterior of body floating or completely submerged; remains motionless waiting for prey.
• Sweeping search: head and front of body slowly sweeps through the water back and forth looking for prey. Detection facilitated by presence of ISO's.
• Rapid strike: suddenly, swings snout to the side and grabs a fish in one swift motion. The narrow snout reduces drag in the water, allowing for a quick, whip-like motion.
• Gastroliths: occasionally swallow small stones (=gastroliths) to assist in grinding up food.

• Courtship begins in December. Mating occurs in  January and February (dry season).
• Female communicates readiness to mate by pointing snout upward.
• Bulbous knob on male's snout thought to be important in breeding. May act as visual identification for female, or as resonator of sound; see Vocalizations.
• The mating pair may stay under water for up to 30 minutes.
• Reproduction cycle determined by hormones as well as day length and rainfall.

• Occurs in March and April,between cold winter months and monsoon.
• Same approximate sites used each season.
• Females dig pitcher-shaped holes in steep, sandy river banks at night with hind feet.Eggs deposited, then covered with sand.
• Sometimes trial nest holes are dug before egg deposition.
• 1-10 m ( ft.) from water's edge, about 50 cm (20 in.) deep.
• Nest may be layered with sand in between.
• Female guards nest, but male does not.

• Clutch size: 12 - 100 eggs, but usually in the range of 28 to 60 . Number of eggs corresponds to size of female.
• Egg size: Largest of any crocodilian species, 100-160 g (3.5 - 5.6 oz).
• Incubation: Temperature dependent – 53-94 days (incubation period shorter when temperature is higher). Female stays nearby for the duration.

• Size: weight 75-130 g (2.6 - 4.6 oz), length 325-392 mm (12.8 - 15.4 in).
• Female does not bring the hatchlings to water in her mouth, as observed in other crocodilians.
• Group together, near the mother, for protection. Female protects hatchlings for several weeks, but will allow male to approach. Male does not actively protect hatchlings, but stays close and will carry them on his back.
• The sex of hatchlings is not determined by genes, but by temperature during incubation. Higher temperatures result in a higher percentage of males.
•  

• Maturity: Females ~3 m (9.8 ft) long at 7-10 years of age; males ~3.5 m (11.5 ft) long at 15-18 years of age; dependent on size more than age.
• Large knob at the tip of the rostrum in males begins to develop at about 10 years of age.
• Grow continuously until death.

• Only longevity record is from a female at the London Zoo. Estimated age 29 years.
• Fishermen living near gharials estimate ‘the age of man’ or ‘over 100 years.’
• Late maturity and large size suggests a long life span.

• See Threats to Survival.

• In Captivity
  • Hatchling or young crocodilians: gastroenteritis, mouth cankers
  • Stress causes lowered blood sugar levels (no appetite) and hormonal problems (hypoglycemic shock).
  • Metabolic bone disease (shortage of calcium and lack of sunlight).
  • Bacterial disease as secondary infections: Pasturella, Aeromonas, Salmonella, Pseudomonas, Klebsiella, Edwardsiella, Proteus, Arizona.
  • Respiratory disease.
  • Crocodilians of any age: wounds caused by fighting, dehydration.

• Captive Breeding
  • Successful breeding in captivity, requires a simulation of native temperature and humidity fluctuations during a 24 hour cycle and throughout the year.
• San Diego Zoo specimens
  • Received in 1990.Came from Nepal's captive breeding program (hatched from eggs).
  • Outgrew their enclosure in Tiger River (which opened in March, 1988), so new space was created for them in 2002 on Reptile Mesa. They now have deeper pools and steep sandy banks for basking and nesting.
  • If breeding is successful, San Diego Zoo will be one of only a few zoos in the U.S. to do so.

• Mid 1970's: Hunted almost to extinction. A survey conducted in 1974 concluded that only 50-60 individuals survived in India and a handful in Nepal, Pakistan and Bangladesh.
• Present population status: Most recent estimates given by Ross (1998); see also Whitaker & Whitaker (2003). New surveys are needed for areas of low population densities.
• India: ~1,500
• Nepal: ~130
• Pakistan: Few; exact number unknown
• Bangladesh: Once thought to be extinct, presence confirmed in upper Brahamputra.
• Bhutan: Declared extinct by Bustard (1980b) but recent reports confirm presence.
• Myanmar: Extinct.
• ISIS captive population (link requires Internet Explorer)

• IUCN Status: EN (Endangered)
• CITES Status: Appendix I
• 1970's: Active effort initiated to avoid extinction
  • Numerous sanctuaries created.
  • 1972: Indian Wildlife Protection Act; prohibited hunting.
  • Active management programs began in 1975 in India, and 1978 in Nepal. Captive rearing: Collect and incubate eggs; hand-rear hatchlings in captivity until they are big enough to avoid predation; release back into the wild.
• Present: Conservation efforts have been quite successful, but populations not self-sustained and continue to need active management.

• Poaching: for skin and meat; also for male's nasal knob (to be used as an aphrodisiac).
• Habitat destruction and competition due to rapidly growing human population, and development of hydroelectric dams.
• Heavy commercial net-fishing removes food source, blocks access to parts of the rivers, and entangles gharials.
• Threats to eggs
• Humans
• Rats
• Jackals
• Wild pigs
• Mongooses
• Monitor Lizards
• Monsoonal flooding

• Crocodilians Natural History and Conservation
• Gharial Species Account
• Crocodile Specialist Group
• Crocodile Specialist Group Newsletter
• The Bibliography of Crocodilian Biology
• Online CITES Identification Guide - Crocodilians.
• DigiMorph - 3D images of gharial skull. Slow to load but worth the effort. Must install QuickTime Viewer