Tropical freshwater lakes, rivers and swamps.
Crocodilians are the most advanced surviving reptiles; many of their features are more similar to mammals or birds than to other reptiles. All crocodilians have a similar body shape, with a head held horizontally in front of the body, four legs which project from the sides, heavy scales which function as armor, and a heavy muscular tail. Their front feet have five separate toes and their rear feet have four partially-webbed toes. Their eyes are on the top of their head, close together to allow for binocular vision. A "third eyelid" sweeps sideways across the eye to give more protection while diving. This eyelid is transparent and does not interfere with the crocodiles sharp vision. The nostrils are crescent-shaped and set at the end of the snout, which allows breathing even when the animal is almost entirely submerged. Unlike an alligator, the crocodile's fourth tooth of the lower jaw sticks up over the upper jaw.
Adults are territorial, and mark their territory by loudly slapping their head down on the water or snapping their jaws on the surface of the water. Dominant animals tend to swim higher in the water; other crocodilians of the same species communicate their submission by swimming lower in the water. Dominant animals control access to mates, choice nesting sites, food, basking sites, and living space. During drought, territories are forgotten as crocodilians crowd into the smaller remaining inhabitable area, although hierarchies are still observed. In some species and in some areas, territories are only maintained by males or only during mating season. Combat between crocodilians is rare, but does sometimes occur between animals of the same size competing for dominance. They bang the sides of their heads together or sometimes bite each other, but in either case they rarely cause any lasting damage. Crocodilians communicate with each other by means of sounds, postures, motions, odors released by four scent glands, and by touch. Vocal sounds are made by forcing air through a voice box (larynx) in the throat. Young call to adults when in danger, but also are very vocal while being fed. Sounds (by the hatchlings themselves or by adults) also seem to keep young together. Adults also produce sounds to communicate with other adults. The most common adult sound is a loud, low roar which is repeated, and may be echoed by other adults. When hunting mammals, crocodiles wait near the water's edge with only the tip of their snout and eyes above the water. When an animal comes to drink, the crocodile attacks suddenly, dragging the prey down into the water where it is drowned and eaten.
Breeding occurs during the wet season (April and May). 20 to 50 eggs are layed in a mound nest which is then guarded by the female. Hatching occurs after around 80 days, at which time the female will open the nest and carry the hatchlings to the water.
The Siamese crocodile is virtually extinct in the wild, because it was hunted and killed for its skin, However, the highly prized skin has probably saved this species. To satisfy the need for crocodile skin, many crocodile farms have been created. Large numbers of Siamese crocodiles thrive and breed on these farms. This has caused the price of skins to drop and made it less profitable for hunters to kill crocodiles in the wild.