Freshwater Crocodiles can be found throughout the coastal and inland regions of northern Australia, from Western Australia to Queensland.
They are usually found upstream in rivers but can tolerate some saltwater. Their main habitats include wetlands, rivers, creeks and swamps, and they do not mind still water, fast flowing, muddy, shallow or deep water.
At the end of the wet season freshwater crocodiles usually move to more permanent water.
Mating occurs in the dry season during July, and nesting occurs over a two or three week period during August.
Freshwater crocodiles dig hole nests in sandy river banks. As the eggs are close to the ground water table, they are more susceptible to flooding at the start of the wet season.
Females tend to return to the same nesting sites year after year.
The female crocodile is not a good defender of her eggs. Almost 80% of nests are destroyed by predators such as monitor lizards and pigs.
The average size of the clutch is around 13 eggs. The largest clutches are laid at the start of the nesting period. The incubation period is around 74 to 80 days depending upon the outside temperature.
The sex of the baby crocodile is determined by the temperature during incubation. For example mostly males will be born if the temperature is between 31 and 32 degrees Celsius. If the temperature is warmer or cooler than 31 and 32 degrees Celsius the mostly females will be born.
Hatchlings weigh about 42 grams and measure about 24 cm at birth. They have one small tooth which that they use to split the egg to get out, and are often helped by their mothers. The mother will then carry the hatchlings to the water in her mouth. The mother stays with her little nursery of hatchlings for a few weeks.
The hatchlings’ rate of survival is less than 1% as birds, other crocodiles, turtles and large fish prey on both eggs and hatchlings.
Juvenile crocodiles eat insects, shellfish and small fish. Large adults prey on other reptiles, bats, birds and amphibians.
Freshwater crocodiles hunt by waiting at the water’s edge for prey to come within range. They do not hunt on land.
Freshwater crocodiles swallow small stones that help with digestion.
Crocodiles vary in size and are largely influenced by environment, habitat, genetics and diet. Males can reach from 2.4 to 3 metres and can weigh up to 53kg. Females are usually smaller getting to about 2 metres in length. It takes juvenile crocodiles about 20 years to reach their maximum size. Males reach sexual maturity at around 16-17 years and females at 11 – 14 years.
Freshwater crocodiles live for about 50 years.
The biggest threat to freshwater crocodiles is loss of habitat to farming or development.
Freshwater crocodiles only become dangerous when they are teased or irritated.Read More: Estuarine Crocodiles