The saltwater or estuarine crocodile (Crocodylus porosus) is the largest of all living reptiles. It is found in suitable habitats in Northern Australia, the eastern coast of India and parts of Southeast Asia.
The saltwater crocodile has a longer muzzle than the mugger crocodile: its length is twice its breadth at the base. The saltwater crocodile has fewer armor plates on its neck than other crocodilians, and its broad body contrasts with that of most other lean crocodiles, leading to early unverified assumptions that the reptile was an alligator.
An adult male saltwater crocodile's weight is and length is normally , though mature males can be or more and weigh or larger. This species has the greatest sexual dimorphism of any modern crocodilian, with females being much smaller than males. Typical female body lengths in the range of . The largest female on record measured about . The mean weight of the species as a whole is roughly .
The largest size saltwater crocodiles can reach is the subject of considerable controversy. The longest crocodile ever measured snout-to-tail and verified was the skin of a dead crocodile, which was long. As skins tend to shrink slightly after removal from the carcass, this crocodile's living length was estimated at , and it probably weighed well over . Incomplete remains (the skull of a crocodile shot in Orissa) have been claimed to come from a crocodile, but scholarly examination suggested a length no greater than . There have been numerous claims of crocodiles in the range: the crocodile shot in the Bay of Bengal in 1840, reported at ; another killed in 1823 at Jala Jala on the main island of Luzon in the Philippines reported at ; a reported crocodile killed in the Hooghly River in the Alipore District of Calcutta. However, examinations of these animals' skulls actually indicated animals ranging from .
With recent restoration of saltwater crocodile habitat and reduced poaching, it is possible that crocodiles are alive today. Guinness has accepted a claim of a male saltwater crocodile living within Bhitarkanika Park in the state of Orissa, India, although, due to the difficulty of trapping and measuring a very large live crocodile, the accuracy of these dimensions has yet to be verified.
A crocodile shot in Queensland in 1957 was reported to be long, but no verified measurements were made and no remains of this crocodile exist. A "replica" of this crocodile has been made as a tourist attraction. Many other unconfirmed reports of 8+ metres (28+ ft) crocodiles have been made but these are highly unlikely.
The saltwater crocodile is one of the three crocodilians found in India, the others being the Mugger crocodile and the Gharial. Apart from the eastern coast of India, this crocodile is extremely rare in the Indian subcontinent. A huge population of saltwater crocodiles (consisting of many large adults, including a 7 meter male) is present within the Bhitarkanika Wildlife Sanctuary of Orissa and they are known to be present in smaller numbers throughout the Indian and Bangladesh portions of the Sundarbans.
In northern Australia (which includes the top ends of the Northern Territory, Western Australia and Queensland) the Saltwater Crocodile is thriving, particularly in the multiple river systems near Darwin (such as the Adelaide, Mary and Daly Rivers, along with their adjacent billabongs and estuaries) where large (6 metre +) individuals are common. The Australian Saltwater Crocodile population is estimated at somewhere between 100,000 and 200,000 adults. Their range extends from Broome in Western Australia through the entire Northern Territory coast all the way down to Rockhampton in Queensland. The Alligator Rivers of Northern Australia are misnamed due to the resemblance of the saltwater crocodile to alligators as compared to freshwater crocodiles, which also inhabit the Northern Territory. In New Guinea they are also common, existing within the coastal reaches of virtually every river system in the country, along with all estuaries and mangroves. They are also present in varying numbers throughout the Bismarck Archipelago, the Kai Islands, the Aru Islands, the Maluku Islands, and many other islands within the region including Timor, and most islands within the Torres Strait.
The saltwater crocodile was historically found throughout Southeast Asia but is now extinct throughout much of this range. This species has not been reported in the wild for decades in most of Indochina and is extinct in Thailand, Laos, Vietnam, and possibly Cambodia. The status of this species is critical within much of Myanmar, but there is a stable population of many large adults present in the Irrawaddy Delta. It is probable that the only country in Indochina still harboring wild populations of this species is Myanmar. Although Saltwater Crocodiles were once very common in the Mekong Delta (from where they disappeared in the 1980s) and other river systems, the future of this species in Indochina is now looking grim. However, it is also the least likely of crocodilians to become globally extinct due to its wide distribution and almost pre-colonial population sizes in Northern Australia and New Guinea.
The population is sporadic in Indonesia and Malaysia with some areas harboring large populations (Borneo, for example) and others with very small, at-risk populations (e.g., the Philippines). The status of this species is largely unknown within Sumatra and Java (although recent reports of attacks on humans by large crocodiles within isolated regions of Sumatra have been reported by news agencies and deemed reliable.) Despite the close proximity to the crocodile hot-bed of northern Australia, crocodiles no longer exist in Bali. The saltwater crocodile is also present in very limited parts of the South Pacific, with an average population in the Solomon Islands, a very small, invasive and soon to be extinct population in Vanuatu (where the population officially stands at only three) and a decent but at-risk population (which may be rebounding) in Palau. Saltwater crocodiles once ranged as far west as the east coast of Africa at the Seychelles Islands. These crocodiles were once believed to be a population of Nile crocodiles, but they were later proven to be Crocodylus porosus.
Due to this species' tendency to travel very long distances at sea, individual saltwater crocodiles occasionally show up in odd locales where they are not native. Vagrant individuals have historically been reported on New Caledonia, Iwo Jima, Fiji, and even in the relatively frigid Sea of Japan (thousands of miles from their native territory.) In late 2008/early 2009 a handful of wild saltwater crocodiles were verified to be living within the river systems of Fraser Island, hundreds of kilometers from and in much cooler water than their normal Queensland range. It was discovered that these crocodiles did indeed migrate south to the island from northern Queensland during the warmer wet season and presumably returned to the north upon the seasonal temperature drop. Despite the surprise and shock within the Fraser Island public, this is apparently not new behavior and in the distant past wild crocodiles had been reported occasionally appearing as far south as Brisbane during the warmer wet season.
Saltwater crocodiles generally spend the tropical wet season in freshwater swamps and rivers, moving downstream to estuaries in the dry season, and sometimes traveling far out to sea. Crocodiles compete fiercely with each other for territory, with dominant males in particular occupying the most eligible stretches of freshwater creeks and streams. Junior crocodiles are thus forced into the more marginal river systems and sometimes into the ocean. This explains the large distribution of the animal (ranging from the east coast of India to northern Australia) as well as its being found in odd places on occasion (such as the Sea of Japan). Saltwater crocodiles can swim in short bursts, but when cruising go .