Crocodylus porosus is most commonly found on the coasts of northern Australia, and the islands of New Guinea and Indonesia. It ranges west as far as the shores of Sri Lanka and eastern India, all along the shorelines and rivermouths of southeast Asia to central Vietnam, around Borneo and into the Philippines, and even out to Palau, Vanuatu, and the Solomon Islands. Saltwater Crocodiles are strong swimmers and can be found very far from land.
(Britton, 1995; Lanworn, 1972; Carr, 1972)
The Saltwater Crocodile shows a high tolerance for salinity, being found mostly in coastal waters or around rivers. It may also be found in freshwater rivers, billabongs and swamps.
Movement between habitats occurs during the wet season, when juveniles are raised in freshwater rivers. However, these juveniles are usually forced out of these areas, by dominant males who use the freshwater areas for breeding grounds, and into areas of low salinity. Males who are unable to establish a territory in the river system are either killed or forced out into the sea where they move around the coast in search of another river system.
(Britton, 1995; Pope, 1955)
Saltwater crocodiles are the largest reptilian species alive today. Adult males can reach up to sizes of 6 to 7 meters. Females are much smaller and do not generally exceed 3 meters, with 2.5 meters considered large. The head is very large and a pair of ridges run from the eyes along the center of the snout. The scales are oval in shape and the scutes are small compared to other species. Young saltwater crocodiles are pale yellow in color with black stripes and spots on the body and tail. This coloration lasts for several years until the crocodile matures into an adult. The color as an adult is much darker, with lighter tan or gray areas. The ventral surface is white or yellow in color. Stripes are present on the lower sides of the body but do not extend onto the belly. The tail is gray with dark bands. Saltwater crocodiles have a heavy set jaw which contains up to 68, and no less than 64, teeth. (Britton, 1995; Kondo, 1970; Lanworn, 1972)
The Saltwater Crocodile breeds during the wet season which falls between the months of November and March. Despite the fact that the Saltwater Crocodile is normally found in saltwater areas, breeding grounds are established in fresh water. Males mark out their territory and become defensive if another male tries to enter.
Females reach sexual maturity at around 10 to 12 years old. Males, on the other hand, do not reach sexual maturity until the age of 16 years.
The female crocodile normally lays 40 to 60 eggs, but she can lay up to 90 eggs. The eggs are placed in mounded nests made from plant matter and mud and then buried. Since the eggs are laid during the wet season, the nests must be elevated to prevent loss due to floods.
The male does not stay until the eggs are hatched, but the female stays and protects the nest from predators and humans. After incubation for 90 days, the offspring are hatched, although this time varies with nest temperature. Sex determination is directly related to nest temperature. Males are produced around 31.6 degrees Celsius. If this temperature is increased or decreased just a little, females will be produced. The female unearths the eggs when she hears the chirping sounds the offspring make after they hatch. She then assists the offspring into the water by carrying them in her mouth and tends to them until they learn how to swim. (Britton, 1995)
The Saltwater Crocodile has been thought of as one of the most intelligent and sophisticated of all reptiles. Their barks are a way of communicating with one another. The Saltwater Crocodile is thought to have four different calls. One is the distress call, which is normally only performed by juveniles. This call is higher pitched than most other calls and consists of short barks. They are also thought to have threat calls in which C. porosus makes a hissing or coughing sound at its intruder. There is also the hatching call. This call is only performed by newborns and is only one, short bark, high in tone. There is also the courtship bellow, which is a long, low growl.
The Saltwater Crocodile spends most of its time thermogulating to maintain its body temperature. If they become too hot they often go into the water with only their eyes and nostrils showing and stay submerged until they are cooled. If they become to cold, they lay in the sun on flat rocks until they warm up.
The Saltwater Crocodile is a predator and has many different types of prey. When young, Crocodylus porosus is restricted to smaller prey like insects, amphibians, crustaceans and small fish and reptiles. When they become an adult, they feed on larger prey such as mud crabs, turtles, snakes, birds, buffalo, wild boar, and monkeys. When the Saltwater Crocodile hunts for food, it usually hides in the water with only the nostrils, eyes, and part of the back exposed. When the prey approaches, it lunges out of the water and attacks, usually killing its prey with a single snap of the jaws. The Saltwater Crocodile then drags the prey under the water where it is more easily consumed.
The hide of the Saltwater crocodile is considered very valuable. Many people will pay large amounts of money to have crocodilian products, and Saltwater Crocodile leather products are the most prized. Farms are run for this specific purpose. The crocodile is raised until it is ready to be skinned for leather products. This is a contrversial topic as many people do not find it fit to kill the crocodiles to obtain a small amount of the hide, while the rest of the crocodile is thrown aside.
The Saltwater Crocodile can be a very dangerous animal to encounter, and humans are attacked and killed by this species every year. Many of these attacks could be prevented by increased awareness and education.
Although the population of saltwater crocodiles is not stable everywhere, it is in no immediate danger. However, in some countries where the crocodile once thrived, it is now rare or extirpated. Habitat loss associated with coastal development and intensive hunting for hides has drastically reduced populations throughout much of the range. In Sri Lanka and Thailand, habitat destruction is so rapid that the saltwater crocodile has been virtually unseen, with only two saltwater crocodiles being sighted in 1999. In southern Vietnam, where the species once thrived by the thousands, there are but an estimated 100 crocodiles alive in the wild. This is due to the rapid degradation of habitat and the poaching of the animal for leather products. The global population will not be stable until all the countries which have habitats that support the saltwater crocodile have laws that prevent poaching, and programs that create reserves.
A number of such programs have been begun to ensure that C. porosus will not become extinct. In India, a restocking program was introduced in Bhitarkinaka National Park. More than 1,400 saltwater crocodiles were released, with approximately 580 surviving. The population has now become moderately stable at around 1,000 total crocodiles in India. In Burma, crocodile farms are controlling the breeding and conservation of crocodiles. The Australian management program is the world's leader in conservation of the saltwater crocodile. This program focuses its attention on educating the public on precautions to take if they encounter a crocodile, thus discourage unnecessary killing. Crocodile farms were opened to maintain a breeding population, and national sanctuaries have been established, ensuring an undisturbed habitat. Yearly population counts are conducted, monitoring the number of saltwater crocodiles in Australia, making sure that the population does not become dangerously low. In New Papua Guinea, programs that ensure an undisturbed habitat stabilize the population. The Papua New Guinean management system involves a combination of wild cropping, egg and hatchling harvest, and ranching. (Britton, 1995; Carr, 1972)
The IUCN rates the species as a whole as "Low Risk." The U.S. Fish and Wildlife Service rates the Australian population of this species as "Threatened," does not rate the population in Papua New Guinea, and rates the populations in other countries as "Endangered." Saltwater crocodiles from Australia, Indonesia, and Papua New Guinea are included in Appendix II of the CITES treaty, which limits international trade. Members of the species from all other countries are listed in Appendix I, which means they may not be traded internationally.
Erin Wayman (author), Milford High School, George Campbell (editor), Milford High School.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
the nearshore aquatic habitats near a coast, or shoreline.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
The term is used in the 1994 IUCN Red List of Threatened Animals to refer collectively to species categorized as Endangered (E), Vulnerable (V), Rare (R), Indeterminate (I), or Insufficiently Known (K) and in the 1996 IUCN Red List of Threatened Animals to refer collectively to species categorized as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU).
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
Britton, A. 1995. "Species Account: C. Porosus" (On-line). Accessed March 4, 2001 at http://www.flmnh.ufl.edu/cnhc/csp_cpor.htm.
Carr, A. 1972. The Reptiles. New York City, NY, USA: Time-Life Books Inc.
Kondo, H. 1970. Grolier's Amazing World of Reptiles. New York, NY: Grolier Interprises Inc.
Lanworn, R. 1972. The Book of Reptiles. New York, NY: The Hamlyn Publishing Group Ltd.
Pope, C. 1955. The Reptile World. New York, NY: Alfred A Knopf.