Saltwater crocodile
The saltwater crocodile is a crocodilian native to saltwater habitats, brackish wetlands and freshwater rivers from India's east coast across Southeast Asia and the Sundaland to northern Australia and Micronesia. It has been listed as Least Concern on the IUCN Red List since 1996. It was hunted for its skin throughout its range up to the 1970s, and is threatened by illegal killing and habitat loss. It is regarded as dangerous to humans.
The saltwater crocodile is the largest living reptile. Males can grow up to a weight of and a length of, rarely exceeding. Females are much smaller and rarely surpass. It is also called the estuarine crocodile, Indo-Pacific crocodile, marine crocodile, sea crocodile, and, informally, the saltie. A large and opportunistic hypercarnivorous apex predator, they ambush most of their prey and then drown or swallow it whole. They will prey on almost any animal that enters their territory, including other predators such as sharks, varieties of freshwater and saltwater fish including pelagic species, invertebrates such as crustaceans, various amphibians, other reptiles, birds, and mammals.
Taxonomy and evolution
Crocodilus porosus was the scientific name proposed by Johann Gottlob Theaenus Schneider who described a zoological specimen in 1801. In the 19th and 20th centuries, several saltwater crocodile specimens were described with the following names:- Crocodilus biporcatus proposed by Georges Cuvier in 1807 were 23 saltwater crocodile specimens from India, Java and Timor.
- Crocodilus biporcatus raninus proposed by Salomon Müller and Hermann Schlegel in 1844 was a crocodile from Borneo.
- Crocodylus porosus australis proposed by Paulus Edward Pieris Deraniyagala in 1953 was a specimen from Australia.
- Crocodylus pethericki proposed by Richard Wells and C. Ross Wellington in 1985 was a large-bodied, relatively large-headed and short-tailed crocodile specimen collected in 1979 in the Finnis River, Northern Territory. This purported species was later considered to be a misinterpretation of the physiological changes that very large male crocodiles undergo. However, Wells and Wellington's assertion that the Australian saltwater crocodiles may be distinctive enough from Asian saltwater crocodiles to warrant subspecies status has been considered to possibly bear validity.
Evolution
remains of a saltwater crocodile excavated in northern Queensland were dated to the Pliocene. The saltwater crocodile's closest extant relatives are the Siamese crocodile and the mugger crocodile.The genus Crocodylus was thought to have evolved in Australia and Asia. Results of a phylogenetic study supports its likely origin in Africa and later radiation towards Southeast Asia and the Americas; it genetically diverged from its closest recent relative, the extinct Voay of Madagascar, around near the boundary between the Oligocene and Miocene.
Phylogeny
Below is a cladogram based on a 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular, and stratigraphic data, as revised in 2021 after a paleogenomics study using DNA extracted from the extinct Voay. Hall's New Guinea crocodile placement suggested in 2023 study by Sales-Oliveira ''et al.''Description
The saltwater crocodile has a wide snout compared to most crocodiles. However, it has a longer snout than the mugger crocodile ; its length is twice its width at the base. A pair of ridges runs from the eyes along the centre of the snout. The scales are oval in shape and the scutes are either small compared to other species or commonly are entirely absent. In addition, an obvious gap is also present between the cervical and dorsal shields, and small, triangular scutes are present between the posterior edges of the large, transversely arranged scutes in the dorsal shield. The relative lack of scutes is considered an asset useful to distinguish saltwater crocodiles in captivity or in illicit leather trading, as well as in the few areas in the field where sub-adult or younger saltwater crocodiles may need to be distinguished from other crocodiles. It has fewer armour plates on its neck than other crocodilians.The adult saltwater crocodile's broad body contrasts with that of most other lean crocodiles, leading to early unverified assumptions the reptile was an alligator.
Young saltwater crocodiles are pale yellow in colour with black stripes and spots on their bodies and tails. This colouration lasts for several years until the crocodiles mature into adults. The colour as an adult is much darker greenish-drab, with a few lighter tan or grey areas sometimes apparent. Several colour variations are known and some adults may retain fairly pale skin, whereas others may be so dark as to appear blackish. The ventral surface is white or yellow in colour in saltwater crocodiles of all ages. Stripes are present on the lower sides of their bodies, but do not extend onto their bellies. Their tails are grey with dark bands.
Size
The weight of a crocodile increases approximately cubically as length increases. This explains why individuals at weigh more than twice as much as individuals at. In crocodiles, linear growth eventually decreases and they start getting bulkier at a certain point.Saltwater crocodiles are the largest extant riparian predators in the world. However, they start life fairly small. Newly hatched saltwater crocodiles measure about long and weigh an average of. These sizes and ages are almost identical to those at average sexual maturity in Nile crocodiles, despite the fact that average adult male saltwater crocodiles are considerably larger than average adult male Nile crocodiles.
The largest skull of a saltwater crocodile that could be scientifically verified was of a specimen in the Muséum national d'Histoire naturelle, collected in Cambodia. Its skull was long and wide near its base, with long mandibles; its length is not known, but based on skull-to-length ratios of large saltwater crocodiles its length was presumably in the range, though it could have had an exceptionally large skull or may not have the same skull-to-total-length ratios as other large saltwater crocodiles. If detached from the body, the head of a large male crocodile can weigh over, including the large muscles and tendons at the base of the skull that lend the crocodile its massive biting strength. The largest tooth measured in length.
Other crocodilians like the gharial and the false gharial have a proportionately longer skull, but both their skulls and their bodies are less massive than in the saltwater crocodile.
Male size
An adult male saltwater crocodile, from young adults to older individuals, typically ranges in length and weighs. On average, adult males range in length and weigh. However average size largely depends on the location, habitat, and human interactions and thus varies from one study to another. In 1993, in a study conducted, eleven saltwater crocodiles were found to have measured and weighed between. Very large, aged males can exceed in length and presumably weigh up to.The largest confirmed saltwater crocodile on record drowned in a fishing net in Papua New Guinea, in 1979. Its dried skin plus head measured in length and it was estimated to have been when accounting for shrinkage and a missing tail tip. Projected from their skull lengths, multiple specimens from Singapore were estimated to belong in life to male crocodiles measuring more than. A large Vietnamese saltwater crocodile was reliably estimated, based on its skull after its death, at. However, according to evidence in the form of skulls coming from some of the largest crocodiles ever shot, the maximum possible size attained by the largest members of this species is considered to be. A governmental study from Australia accepts that the very largest members of the species are likely to measure in length and weigh. Furthermore, a research paper on the morphology and physiology of crocodilians by the same organisation estimates that saltwater crocodiles reaching sizes of would weigh around. Due to the extreme size and highly aggressive nature of the species, weight in larger specimens is frequently poorly documented. A long individual named "Sweetheart" was found to have weighed. Another large crocodile named "Gomek", measuring in length weighed around. In 1992, a notorious man-eater, named "Bujang Senang" was killed in Sarawak, Malaysia. It measured in length and weighed more than. A saltwater–siamese hybrid named "Yai" at the Samutprakarn Crocodile Farm and Zoo, Thailand was claimed to be the largest crocodile ever held in captivity. It measured in length and weighed approximately. In 1962, a large male saltwater crocodile was shot in Adelaide River, Northern Territory. It was recorded to be long and weighed. A large male in the Philippines, named Lolong, was one of the largest saltwater crocodile ever caught and placed in captivity. He was long and weighed. Following his death in 2013, the largest living crocodile in captivity was "Cassius", who was kept at Marineland Crocodile Park, a zoo located at Green Island, Queensland, Australia. He measured 5.48 m in length and weighed approximately 1,300 kg before his death in November 2024.