Saltwater Crocodile

The Saltwater crocodile (Crocodylus porosus) is the largest living reptile. It is also called the estuarine crocodile, Indo-Pacific crocodile, marine crocodile, sea crocodile and, informally, the saltie. Adult males typically measure 3.5 to 5 m and weigh 200 to 1,100 kg, while very old males can exceed 6 m. Females rarely pass 3 m, so males average about 4 to 5 times as massive as females.

Saltwater crocodiles have a wide snout with a pair of ridges running from the eyes along its centre, and relatively few armour plates on the neck. Young ones are pale yellow with black stripes and spots. Adults are a much darker greenish-drab, and some look almost blackish, with a white or yellow belly.

They live in coastal brackish mangrove swamps, river deltas and freshwater rivers from India's east coast across Southeast Asia to northern Australia. Australia alone is home to an estimated 100,000 to 200,000 adults. They are listed as Least Concern and are regarded as dangerous to humans.

The scientific name Crocodilus porosus was proposed by Johann Gottlob Theaenus Schneider, who described a specimen in 1801. Several later names were proposed for specimens from India, Borneo and Australia, but today the Saltwater crocodile is treated as a single species with no subspecies.

Fossil remains from northern Queensland date to the Pliocene. Their closest living relatives are the Siamese crocodile and the mugger crocodile. The crocodile genus likely originated in Africa and spread towards Southeast Asia and the Americas. It split from its closest recent relative, the extinct Voay of Madagascar, around 25 million years ago.

Saltwater crocodiles were hunted for their skin throughout their range until the 1970s. Their skin is the most commercially valuable of any crocodilian. In northern Australia the population fell by 95% by 1971, and full legal protection followed in Western Australia (1970), the Northern Territory (1971) and Queensland (1974). They have died out locally in places such as Cambodia, China, Thailand and Vietnam, and in the Seychelles about 200 years ago.

Saltwater crocodiles are large, opportunistic apex predators. They ambush prey by submerging and swimming quietly close, then striking suddenly. Small prey is swallowed whole, and larger animals are dragged into deep water and drowned. They have the strongest bite of any living animal. Their diet is the broadest of any modern crocodilian, from crabs and fish to birds and large mammals.

They are generally lethargic and can survive months without food. They bask or loiter in the water by day and prefer to hunt at night. They can stay underwater for long periods, with voluntary dives of up to two hours reported. They also ride ocean currents over long distances, and satellite-tagged crocodiles in Australia travelled up to 590 km along the coast.

They are the most territorial and aggressive crocodilians. Dominant males hold the best stretches of freshwater, which pushes younger crocodiles into marginal rivers or out to sea. They mate in the wet season, and females build a mound nest of mud and vegetation, lay 40 to 60 eggs, and guard them for around 80 to 98 days. Mothers carry the hatchlings to water and stay with them for several months. Only about 1% of hatchlings survive to adulthood.

Saltwater crocodiles that reach adulthood can live a very long time. Life expectancy is estimated at upwards of 70 years, and some may exceed 100, though no such age has been verified for any crocodilian.

Adults have no natural predators, but young ones may fall prey to monitor lizards, barramundi, wild boar, birds, pythons and others. Much egg loss comes from nest flooding. Barnacles can grow on the scales of crocodiles that spend long periods at sea.

They are partially resistant to the toxins of cane toads, which can kill freshwater crocodiles, though they can eat only small quantities. Their main threats are illegal killing and habitat loss.

This is general awareness only, not veterinary advice. If you find an injured or unwell wild animal, contact a vet or a wildlife rescue.

What is a saltwater crocodile?

It is the largest living reptile, found from India's east coast through Southeast Asia to northern Australia. Males can reach about 6 m in length. It is also called the estuarine crocodile or the saltie.

How long do saltwater crocodiles live?

Life expectancy is estimated at upwards of 70 years for those that reach adulthood. Some may exceed 100 years, but this has not been verified.

Are saltwater crocodiles dangerous to people?

Yes, they have a long history of attacking humans who enter their territory, and survival of a predatory attack is unlikely. Australia records one or two fatal attacks a year. Many wild crocodiles that have previously been harassed or persecuted are wary of humans, though, and claims of thousands of deaths a year are likely exaggerations.

Do saltwater crocodiles only live in the sea?

No. They live in mangrove swamps, estuaries and freshwater rivers. They tend to spend the wet season in freshwater swamps and move downstream to estuaries in the dry season. They are, though, more willing than most crocodiles to travel out to sea.

How big are saltwater crocodile hatchlings?

Newly hatched young measure about 28 cm and weigh around 71 g. They are pale yellow with black stripes and spots.

The largest confirmed saltwater crocodile on record drowned in a fishing net in Papua New Guinea in 1979. It was estimated at 6.3 m long.

The head of a large male can weigh over 200 kg. The muscles that close the jaw are very strong, but those that open it are small and weak.

The nest mound's covering of leaves and debris produces an astonishing amount of warmth for the eggs. The temperature at which the eggs develop determines the sex of the hatchlings.

The Alligator Rivers in Arnhem Land are misnamed, because early observers mistook the Saltwater crocodile for an alligator. Their broad bodies led to that early confusion.

Individuals have turned up far from their usual range, from Fiji to the Sea of Japan.