The Crocodile is a large aquatic reptile that lives throughout the Tropics in Africa, Asia, the Americas and Australia. Crocodiles tend to congregate in freshwater habitats like rivers, lakes, wetlands and sometimes in brackish water (water that is saltier than fresh water, but not as salty as seawater).
Some species, particularly the Saltwater Crocodile of Australia, Southeast Asia and the Pacific islands often live along the coastal areas. Crocodiles are also known to venture far out to sea. Crocodiles are an ancient lineage and are believed to have changed little since the time of the dinosaurs.
Crocodiles may look quite prehistoric, however, they are the most advanced reptile of our time. Unlike other reptiles they have a four-chambered heart, diaphragm and cerebral cortex (a structure within the vertebrate brain with distinct structural and functional properties).
A crocodiles physical traits allow it to be a successful predator. They have a streamlined body that enables them to swim faster. Crocodiles also tuck their feet to their sides while swimming, which helps the crocodile to swim fast, by decreasing the water resistance.
Crocodiles have webbed feet which, although not used to propel the animal through the water, allow it to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallower water where the crocodiles sometimes move around by walking.
Crocodiles are very fast over short distances, even out of water. Crocodiles have extremely powerful jaws capable of biting down with 3,000 pounds of pressure per square inch and sharp teeth for tearing flesh, however, a crocodile cannot open their mouth if it is being held closed. All large crocodiles also have sharp and powerful claws.
Crocodiles have limited lateral movement in their neck, therefore, on land protection can be found by getting even a small tree between the crocodiles jaws and oneself.
Size greatly varies between species, from the Dwarf Crocodile to the enormous Saltwater Crocodile. Large species can reach over 5 or 6 metres long and weigh well over 1200 kilograms (2,640 pounds). Despite their large adult size, crocodiles start their life at around 20 centimetres long. The largest species of crocodile, also Earths largest reptile, is the Saltwater Crocodile, found in northern Australia and throughout South-east Asia.
There is no reliable way of measuring the age of a crocodile, although several techniques can be used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth - each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons.
Crocodile Behaviour and Diet
Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they can survive long periods without food, and rarely need to actively go hunting. Despite their slow appearance, crocodiles are top predators in their environment and various species have been observed attacking and killing sharks. Crocodiles mostly feed on vertebrates like fish, reptiles, and mammals, sometimes with invertebrates like molluscs and crustaceans, depending on species.
The Crocodile breeding season is during January to May. For males, the onset of sexual maturity occurs when they are about 3 metres (10 feet) in length, while for females, it occurs when they reach 2 to 2.5 metres (6.5 to 8 feet) in length. This takes about 10 years for both male and females crocodiles to reach these lengths under normal conditions. During the mating season, males attract females by bellowing, slapping their snouts in the water, blowing water of out their noses and making a variety of vocalizations. The larger males of a population tend to be more successful. Once a female has been attracted, the pair warble and rub the underside of their jaws together.
After crocodiles mate, the female crocodile lays about 20 - 40 eggs (a clutch) in a nest she makes near a river bank once a year. She covers the nest with leaves and other vegetation. The rotting vegetation keeps the eggs warm and the nest moist. The incubation temperature for crocodile eggs is 28 - 32 degrees Celsius, relative humidity is 95 - 100 per cent, incubation period is 70 - 80 days. The female stays and guards the nest until the eggs hatch. The hatchlings call out and the female crocodile opens up the nest and carries them to the water, where they immediately start feeding on crabs, shrimps and insects. About half will not survive the first year due to predators.
Crocodile Life Span
The oldest crocodilians are estimated to have lived around 71 years on average and there is limited evidence that some individuals may exceed 100 years. One of the oldest crocodiles recorded died in a zoo in Russia apparently aged 115 years old.
Crocodiles and Humans
The larger species of crocodiles can be very dangerous to humans. The Saltwater and Nile Crocodiles are the most dangerous, killing hundreds of people each year in parts of South-East Asia and Africa. Mugger crocodiles and possibly the endangered Black Caiman, are also very dangerous to humans. American alligators are less aggressive and rarely assault humans without provocation.