The Australian saltwater crocodile is the largest reptile in the world with large head and ridges, stretching from each eye along the center of the animal's snout. The body is covered with oval scales while the scutes are smaller than these of other reptiles. Juveniles are identified by pale yellow coloration as well as black colored patches and markings on their tail and body. Usually, they retain this coloration for several years, until they become adults. Meanwhile, the body of adult crocodiles is darker, displaying lighter tan with gray spots. The ventral part is colored with white or yellow, and the gray tail has dark stripes. The lower side of their body is covered with bands, which do not reach their belly.
The area of their distribution covers a vast territory: they inhabit the islands of Indonesia and New Guinea as well as northern coasts of Australia; the crocodiles also occur along the shores of Sri Lanka and eastern India; they live at the estuaries of Southeast Asia to central Vietnam. The saltwater crocodiles can also be found on Borneo, the Philippines, Palau, Vanuatu and the Solomon Islands. At the dry season, they most frequently occur downstream at estuaries, sometimes living in the open sea. With the approaching of the wet season, they move to freshwater bodies, inhabiting swamps and rivers.
The Australian saltwater crocodile is a highly territorial but not at all social animal. These reptiles are not tolerant of their own kind; typically, they do not mind females on their territory, but will fiercely drive away rival males. The saltwater crocodiles are night hunters, spending the daytime hours moving through water or sunbathing. Being cold blooded animals, these reptiles have to constantly maintain their body temperature. When it gets too hot, they usually dive into the water, leaving their eyes and nostrils above the surface, until they cool down. When the temperature is low, they climb on flat rocks and busk in the sun to warm up. They use various forms of communication, including vocalizations as well as visual and chemical signals. Meanwhile, young crocodiles usually emit "chirping" sound in order to attract the attention of their mother or to keep members of the creche together.
Australian saltwater crocodiles are carnivorous. Their diet differs with the age. Thus, young crocodiles primarily feed upon small prey such as insects, amphibians, crustaceans as well as some small species of fish and reptile. Adult individuals consume larger prey, preferring mud crabs, snakes, turtles, birds, wild boars, monkeys and buffaloes.
The saltwater crocodiles have a polygynous mating system with males, mating with multiple females. The breeding season in this species matches the wet season, lasting from November to March. During this period, male crocodiles mark their territory, defending it from other males. Meanwhile, females become intolerant to each other, competing for dominance. Usually, 40-60 eggs are laid on the river bank, in a special mound of vegetation, and incubated for around 90 days. Then, hearing the identifying chirping sounds that the hatchlings usually emit, the mother digs the eggs out. After that, the female carries the young in her mouth, introducing them into the water and caring for them, until young crocodiles learn to swim. During the first eight months of their lives, the young live in creches under the supervision of the adults. Male crocodiles are sexually mature at 16 years old and females - by the age of 10-12 years.
The saltwater crocodile attracts hunters for its leather. In addition, the animal currently suffers from loss of its natural habitat as well as coastal development within its home range.
The total population of the species varies from 200,000 to 300,000 individuals. The saltwater crocodile population in Australia is estimated between 100,000 and 200,000 adults. On the IUCN Red List, the Australian Saltwater Crocodile is classified as Least Concern.
These reptiles are an important link in the ecosystem of their habitat. Being predators, they control distribution and numbers of prey species' populations. Juveniles of saltwater crocodile are a valuable source of food for other animals of the area, including birds and snakes. On the other hand, due to burrowing and constructing nests, these animals create aquatic habitat, which benefits various plant and animal species, helping them survive during dry and wet seasons.