Crocodilians are an ancient group of reptiles. They include crocodiles, alligators, caimans and gharials. They all live in or near water. Most crocodilians in North and South America belong to the alligator and caiman group. In fact only one type of alligator - the Chinese alligator - lives outside of the Americas. American crocodiles tend to be larger than their alligator and caiman cousins, and most are very rare.
The last living members of an ancient group known as the archosaurs, crocodiles are little changed from the days of the dinosaurs. The 25 surviving species stand as testament to the success of the crocodilian body design. Thick, scaly skin keeps predators at bay, a special respiratory system allows them to keep hidden underwater for up to five hours at a time, and powerful jaws make them fearsome predators.
These caimans live in a wide range of habitats from rivers to coastal wetlands. They prefer stiller waters than the black caimans that share parts of their range, and consequently they have taken up residence in many reservoirs.
Spectacled caimans rarely come out of the water, only attacking land animals when they come to the water's edge. They spend the day floating on the surface and hunt mainly at night. During periods of drought, they aestivate - enter a period of dormancy to avoid desiccation -in cool burrows dug deep into mud.
Spectacled caimans are smaller than most crocodilians. They get their name from ridges of bone located on their snouts between their eyes. The ridges appear to join the eyes together, looking similar to the frames of a large pair of spectacles.
The breeding season coincides with the wet season in May and June. The dominant males get the best territories and attract most females. Females lay eggs in mounds of vegetation that they build on banks or rafts of plants. Several females may lay eggs in a single nest, which they guard together. The young live in large groups called creches.
Distribution: Central America and northern South America.
Habitat: Areas of still water.
Food: Fish, wild pigs and water birds.
Size: 1.5 - 2.5 m (5 - 8.25 ft).
Maturity: 4 - 7 years.
Breeding: Eggs laid in nests during wet season.
Life span: 40 years.
Schneider's dwarf caiman is the world's second smallest crocodile species. Males can reach more than twice the size of females, but are generally only slightly larger. This caiman prefers colder water than most crocodiles, which is why it is often found in the cooler, fast-flowing water under waterfalls and in rapids.
Schneider's dwarf caiman is also known as the smooth-fronted caiman, because it lacks the characteristic ridge between the eyes seen in other South American crocodiles. Hatchlings emerge from the eggs with a golden patch on their heads - hence the species' alternative name of crowned caiman.
Schneider's dwarf caimans only gather together for breeding. This ensures that the eggs - of which there are rarely more than 15 in a nest - hatch as the rains arrive, giving the young a better chance of survival. The nests are often built next to termite mounds, so that the heat from the mound helps to incubate the eggs. (This may be to compensate for the reduced incubating effect of the sun's rays in their shady rainforest habitat.) Female dwarf caimans become sexually mature when they reach 1.3 m (4.2 ft), which may take between 10 and 20 years. They do not breed every year.
Distribution: Amazon and Orinoco Basins from Venezuela south to Bahia state in Brazil.
Habitat: Fast-flowing water.
Food: Fish, birds, lizards and snakes, plus rodents and similar small mammals.
Size: 1.4 - 2 m (4.5 - 7.5 ft).
Maturity: 10 - 20 years.
Breeding: Eggs laid in nests before rainy season in early summer.
Life span: 25 years.
This medium-sized caiman has an even broader snout than the American alligator. It is found from Bolivia to southern Brazil and northern Argentina, in freshwater habitats and brackish coastal mangroves. Broad-snouted caimans eat aquatic snails, amphibians, small fish and even turtles. The female lays 20 - 60 eggs in a nest, sometimes on a river island. She guards them for 70 days, then breaks open the nest and carries the hatchlings to water.
Size: 2 - 3 m (6.5 - 11.5 ft).
This species lives in the rivers, lakes and wetlands of northern Argentina, Paraguay, southern Brazil and Bolivia. Its alternative name, piranha caiman, refers the many teeth visible in its mouth. It feeds on water snails, fish and snakes. The female guards her 20 - 40 eggs, which she lays in an earthen nest.
Size: 2.5 - 3 m (8.25 - 9.75 ft).