Sunday, June 20, 2004

Crocodiles are more closely related to birds and dinosaurs than lizards and snakes

When everything appears to sizzle in the summer heat and all living beings, man or beast, are trying to run away from the blistering weather the female crocodile lays her eggs on the river banks. The temperature decides whether the new born will be males or females. Like all reptiles, crocodiles are also cold-blooded and not equipped to incubate, so the female buries her eggs beneath the sand, usually under the shade of an overhanging branch and waits for them to hatch. This may take a few days. She keeps her watchful eyes open for egg thieves that may come nosing around.

Crocodiles have been around for about 300 million years and are more closely related to birds and dinosaurs than lizards, snakes and turtles. The ideal incubation temperature for them is 37 degrees C or 98 degrees F, but in natural conditions temperature never remains constant and the slight change brings about major impact not only on the size and vitality of the hatchlings but also on their sex. Eggs that incubate at a lower than ideal temperature or in cooler conditions, take longer to develop. Consequently, most of the food content is used up by the embryo in keeping itself alive. So when they hatch, the young are not only smaller in size but they will all be females. If the incubation is at an ideal temperature, the hatchlings will not only be larger and strong but they will all be males.

In crocodiles, the size of female is not important because her basic duty is to produce eggs. That a smaller female will produce a smaller clutch as compared to her larger relatives is the only disadvantage she has. But in males size and strength is crucial. They have to win ferocious fights that take place during the breeding season to lay claim on the females. The larger the male, more are the chances of winning fights and mates. Crocodiles are the largest group of living crocodilians of which 13 species survive. Some are near extinction. Of these long-snouted, fish-eating gharial (Gavialis gangeticus) is perhaps the most unique member of the group and is found in India and Nepal. This highly aquatic reptile inhabits slow-moving backwaters of large rivers like Ganga, Mahanadi, Brahmaputra and their tributaries. They are easily recognisable due to the long, slender, fragile-looking snout and are armed with small, but extremely sharp teeth. The characteristic feature in males is a distinctive pot-shaped protuberance or ghara at the tip of the snout, which has given them the name gharial. For years the ghara, its location and its function has been a matter of intense debate, but now it has been established that it is used to produce sounds and bubbles during courtship.

The other two species of these four-legged reptiles found in this region are the muggar or marsh crocodile (Crocodylus palustris) and the saltwater crocodile (Crocodylus porosus). Found in the Andaman and Nicobar Islands of India and in Sri Lanka, the saltwater crocodiles, also known as "salties", are notorious for taking cattle, goats and even humans to vary their diet. Muggar, which is also found in Nepal, is extremely adaptable and live in freshwater habitats. During summers, when there is extreme heat and drought, they make deep tunnels or even walk for miles overland in search of water.