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Photo : Simon Maddock |
Reproduction
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Age at maturity: 10 yrs (females), 13 years (males) |
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Courtship: Begins December |
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Mating: January and February |
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Nesting: March and April |
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Nest type: Holes dug in sandy banks |
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Egg Clutch Size: 40-80 eggs |
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Incubation time: 70 days (average) |
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Females mature at around 10 years old and are usually about 3 m long. |
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Males mature at around 13 years old, which is when the ghara begins to grow on the snout. |
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The ghara may play an important role in reproduction, for mature males to be identified by females and by acting as a resonator for courtship and territorial male vocalization. |
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| Courtship/Mating |
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Males may have a harem of females, and defend their territory and females from rival males. |
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Courtship behaviour involves males and females following potential mates around, mounting, rubbing of snouts, and vocalizing by the males. |
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Female communicate their readiness to mate by raising their snout upwards. |
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Once mates are chosen gharials may submerge for up to 30 minutes during mating. |
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Mating gharials at Madras Crocodile Bank
Photo : Cyril Rufus |
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| Nesting |
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Nesting occurs during March and April. |
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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. |
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Females dig pitcher-shaped nest holes, about 50 cm(30 in) deep with their hind feet, where they then lay their eggs. |
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Gharials lay the largest eggs of any crocodile, weighing 160 g on average. |
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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. |
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Gharial nest hole in Katerniaghat Wildlife Sanctuary
Photo : Ramesh Pandey |
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| Incubation and Sex-Determination |
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The nest hole is a natural self-heating incubator – the sand heats up from the sun and helps the embryos develop. |
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The sex of crocodilians is not determined by genes, it is determined by incubation temperature. |
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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 |
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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. |
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The Mystery of Temperature-Dependent Sex-Determination in Gharials |
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There is no definitive knowledge of the exact temperatures which produce male and female gharials. It is possible that gharials follow the same rules as most other species (32 ºC produces males, higher or lower temperatures produce females). However the Australian freshwater crocodile (Crocodylus johnstoni) has a different pattern of sex-determining temperatures, and like gharials they lay their eggs in holes in the sand. In freshwater crocodiles all constant temperatures tend to produce more females, but gradually increasing incubation temperature tends to produce more males. It has been suggested this may be due to the increasing temperatures eggs are subjected to within natural nests in the sand. Is the sex of gharials determined the same way as freshwater crocs in their sandy nests? More research needs to be done to solve this mystery. |
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| Hatching |
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Incubation time for gharials is about 70 days. |
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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. |
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At hatching gharials weigh 75-130 g (2.6 - 4.6 oz) and are 325-392 mm (12.8 - 15.4 in) long. |
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| Photo : Ramesh Pandey |
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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. |
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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. |
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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. |
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In Katerniaghat Wildlife Sanctuary hatchlings have been observed sheltering from the swift monsoon currents in the grasses along the edge of the nesting banks. |
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| Photo : Ramesh Pandey; |
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