Overview
Background
The Gharial (Gavialis gangeticus) is a unique species of crocodilian, characterized by its long, thin snout and the bulbous growth at the end of its snout. Though millions of years ago there were several similar species, today the Gharial is the last remaining species of this ancient line, the last surviving species of the family Gavialidae.Gharials eat fish and live in deep, fast-moving rivers. They are the most aquatic of all crocodilians, spending most of their time in the water and coming out onto land only to lay eggs and bask in the sun. They were once found in India, Pakistan, Nepal, Bangladesh, Bhutan, and Myanmar but are now extinct from most of these areas. Gharials now exist in the wild in only a few small areas of India and Nepal. Recent surveys indicate there may be less than 200 mature breeding adults left in the wild. Gharials are listed as “Critically Endangered” in the IUCN Red List of Endangered Species
Physical Description
Size:
- The Gharial is one of the largest crocodiles, ranked closely behind the salt-water crocodile (Crocodylus porosus).
- Males can grow 5-6 meters, females can grow 3.5 - 4.5 meters long.
Body Length
Males: 3-6m (9.8-19.6 ft)
Females: 2.7-3.75 m (8.8 ft-12.3 ft)
Hatchlings (at time of hatching): 32.5 -37.5 cm (12.8-14.8 in)
Diet
AdultsFish (primary food source)
Small crustaceans (mud crabs)
Juveniles
Insects, tadpoles, small fish, frogs
Reproduction
Age at maturity: 10 yrs (females), 13 years (males)Courtship: Begins December
Mating: January and February
Nesting: March and April
Nest type: Holes dug in sandy banks
Egg Clutch Size: 40-80 eggs
Incubation time: 70 days (average)
Courtship/Mating
- Males may have a harem of females, and defend their territory and females from rival males.
- Courtship behaviour involves males and females following potential mates around, mounting, rubbing of snouts, and vocalizing by the males.
- Female communicate their readiness to mate by raising their snout upwards.
- Once mates are chosen gharials may submerge for up to 30 minutes during mating.
- Nesting occurs during March and April. Females dig trial nest holes on sandy banks.
- They may make one every night until the night they actually lay the eggs in one of these nest holes.
- Females dig pitcher-shaped nest holes, about 50 cm(30 in) deep with their hind feet, where they then lay their eggs.
- Gharials lay the largest eggs of any crocodile, weighing 160 g on average.
- After laying between 40 to 80 eggs, mother gharials cover the hole and remain close by to guard their nests against egg predators like pigs, jackals, monitor lizards, and mongooses.ul
- The nest hole is a natural self-heating incubator – the sand heats up from the sun and helps the embryos develop.
- The sex of crocodilians is not determined by genes, it is determined by incubation temperature.
- In most species studied to date incubation temperatures of 31 ºC or less and 33 ºC or greater produce females. Constant incubation temperature of 32 ºC produces males.
- The incubation temperature also affects the time it takes for eggs to develop. Higher temperatures cause faster development than lower temperatures. However the optimal temperature range for crocodilians is narrow (around 30-34ºC). Higher or lower temperatures can cause defects or death.
- Incubation time for gharials is about 70 days.
- When the hatchling gharials are ready to emerge they call from inside the egg – a signal to their mother, who stands guard close by to dig them out.
- At hatching gharials weigh 75-130 g (2.6 - 4.6 oz) and are 325-392 mm (12.8 - 15.4 in) long.
- Because of their unique snout and teeth, gharials may not be able to help the babies hatch, as many other crocodile species do. Instead female gharials must wait for the young to hatch unaided and will lead the young to the water.
- Female gharials will stay near their young and protect them for a period of several weeks to several months. During this time the hatchlings usually stay together in groups near the female.
- Often the monsoon forces the separation of the mother from her young, as the rising waters often wash the young juveniles downriver away from the protection of their mother.This may be a significant source of mortality in young gharials.
