The saltwater crocodile, also known as the estuarine or Indo-Pacific crocodile, is the largest of all living reptiles. They have a body length between 5 and 7 m (16 - 23 ft.) and they weigh between 400 and 700 Kgs (882 - 1,543 lbs), with males being much larger than females.
The smallest crocodile is the dwarf crocodile (Osteolaemus tetraspis) from central Africa, which has a maximum length of 1.9 m (6.5 ft). It is more terrestrial than other crocodiles.
They are grey or brown in colour and they have a broad, heavy set body with a large head. Their jaws are strong and they have short, strong limbs. They have ridges that run from their eyes to their nose and this is particularly prominent in older animals.
The Saltwater Crocodile is usually found in deep, dark murky water. It may inhabit fresh or saltwater but is most commonly found in the brackish estuary areas of Northern Australia.
The scientific name Crocodylus porosus is an allusion to the rugose and bumpy upper surface of the snout seen in large adult specimens. Porosus means "full of callosities" and is derived from, porosis, the Greek word for callosity, and osus, the Latin word for "full of".
In India, Saltwater crocodile restocking programs in the Bhitarkanika National Park in Orissa have been successful. Throughout the rest of India the species is still very rare.
Saltwater Crocodiles have a valve that seals off the mouth from the throat and this enables them to open their mouth while they are under water. However, they cannot eat their prey underwater as swallowing would allow water into their throat so they either have to drag their prey onto land or raise their head above the water to swallow.
They are capable of explosive bursts both on land and in the water but they are generally very lethargic with enables them to go for months without feeding.
Their legs are held flat against their body or slightly out to the side while they swim because all of their propulsion comes from their tail. They can also leap out of the water from a stationary position at the water's surface. It is more effective in deeper water as the crocodile can position its body better in order to get maximum propulsion from its tail.
Saltwater Crocodiles take a wide variety of prey, although juveniles are restricted to smaller items such as insects, amphibians, crustaceans, small reptiles and fish. The larger the animal becomes, the larger its prey items are. Although a large male crocodile could take on a food item as large as a 1 tonne Water Buffalo, the majority of their diet consists of relatively small prey items such as crustaceans, fish, turtles, small mammals and birds.
Around breeding season, which usually takes place during the wet season, large male crocodiles will patrol their stretches of water protecting their territory from intruding males. When Saltwater Crocodiles are courting one another, they will rub their heads and bodies together. Mating takes place in the water. Between 4-6 weeks after mating, the female will lay 40-60 eggs in her nest. The nest may be up to 80cm high and is made of vegetation broken off by the female's teeth and scraped together with her hind legs.