Australian freshwater crocodile, Johnstone's crocodile, Freshie
The Australian freshwater crocodile is easily identified due to its unusual snout, which is tapered and narrow, reminding that of the gavial. The species is closely related to the Australian saltwater crocodile, being the latter's small cousin. This reptile possesses eyelid or a nictitating membrane, which protects the eyes of the animal under the water. The tail is powerful, legs are solid, and the feet are clawed and webbed. On both sides of the bottom jaw the animals display large, prominent fourth teeth. When the crocodiles close their mouths, these teeth fit into a notch on their upper jaw, remaining visible. The skin of the reptile exhibits brown with dark stripes along the body as well as on the tail and snout of the animal. The crocodile has large scales on its body, which have a form of wide plates on the back, bony plates on the belly, and pebbly scales on the flanks and outside of the animal's legs.
The freshwater crocodile is an Australian reptile. The species inhabits rivers, creeks, freshwater wetlands, swamps and billabongs of Western Australia, Queensland, and the Northern Territory.
Habits and lifestyle
These reptiles are night hunters, meanwhile being active by day. Freshwater crocodiles use so-called "sit-and-wait" technique of hunting, unexpectedly attacking the prey by quick sideways motion of the head. Those, living in areas with constant availability of water, are active throughout the year. In the meantime, those, exposed to drought during the dry winter season, tend to become dormant. During the winter, the crocodiles find shelter in dens, dug into the creek bank, where a group of these animals can be seen using the same den. Freshwater crocodiles, living in captivity, are not tolerant to their own kind, often showing extremely aggressive behavior towards one another. Those, living in the wild, are typically dominated by a large male, who tends to attack and bite the tails of lower-ranked crocodiles, thus establishing dominance. When threatened on land, the reptile quickly flees by fast gallop, entering into the water, where the animal feels safe.
bask, congregation, float, nest
Diet and nutrition
Adult freshwater crocodiles are carnivores, they usually feed upon reptiles, amphibians, insects, bats, crustaceans, fish as well as occasional land mammals, caught nearby water. Meanwhile, juveniles tend to consume smaller prey such as insects, crustaceans and smaller species of fish.
Freshwater crocodiles have a polygynous mating system, where each male mates with more than one female. About 3-6 weeks after mating, typically between August and September, the female digs a nest: she chooses a place along the river bank and digs a hole in a sand embankment. She usually lays the eggs at night. The amount of eggs per clutch varies from 13 to 20. As the offspring hatch out (in about 65-95 days), the female carries them to the water in its mouth. Over a short period of time, the female remains with the young, protecting and caring for them, after which she leaves her offspring on their own. Male freshwater crocodiles reach sexual maturity at 16-17 years old, whereas females - a little bit earlier - at 11-14 years of age.
The primary threat to these crocodiles is habitat destruction due to agricultural development. Freshwater crocodiles also suffer from illegal hunting, which significantly decreases the population of this species.
The Freshwater crocodile is fairly distributed throughout Australia, being classified on the IUCN Red List as Least Concern. The overall estimated population of these reptiles is around 100,000 individuals.
These reptiles form an important link in the food chain of freshwater and estuarine ecosystems of their habitat. Thus, they are top predators of their range, consuming a variety of animal species. On the other hand, their hatchlings and juveniles become prey for other animals of the area, including goannas, barramundi, feral pigs, sea eagles, turtles as well as other crocodiles. This makes Freshwater crocodile both predator and prey, due to which the animal helps keep a wetland ecosystem healthy, which, in turn, maintains the fishery healthy.
Fun facts for kids
- On land, these reptiles have so-called "high walk": this is when the animal moves around, holding the body high so that the belly and most part of the tail remains above the ground.
- Freshwater crocodiles are occasionally called "pulse nesters" due to the fact, that during each nesting season, all females in a population nest synchronously within a 3-week period.
- Along with powerful jaws, these animals have an extremely keen sense of hearing, allowing them to hear the calls of their offspring, coming from inside the egg.
- This crocodile has about 68 - 72 sharp teeth in its mouth.
- The bite of the Freshwater crocodile is the strongest of all living animals.
- The jaw of this crocodile is able to produce about 5,000 pounds of pressure per square inch. To compare, human’s jaw can produce no more than 100 pounds of pressure per square inch. The bite of the Freshwater crocodile is so powerful, that biting off a human arm or a leg will not require them much effort. However, despite tremendous closing power, their jaws have very little opening strength. A crocodile mouth can be kept shut wath a simple rubber band.