Saltwater crocodile

• 1. Introduction

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  The saltwater crocodile, known to scientists as Crocodylus porosus, has jaws that can be held shut with several layers of duct tape. That detail sounds almost comic for the largest living reptile, an animal some people simply call the saltie. Its range stretches from India's east coast across Southeast Asia and the Sundaland to northern Australia and Micronesia. People also know it as the estuarine crocodile, the Indo-Pacific crocodile, the marine crocodile and the sea crocodile. How does a creature of that power cross open ocean and hunt almost anything that wanders near water? How big does it truly grow, and how much of its legend is exaggeration? What becomes of the tiny hatchlings that start life so small? And how have people come to treat it as both quarry and ancestor?

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• 2. Size and Strength

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  Newly hatched saltwater crocodiles measure about 28 cm and weigh an average of 71 g. From that modest start, adult males typically reach 3.5 to 5 m in length and 200 to 1100 kg in weight. The average adult male falls between 4.0 and 4.5 m and between 408 and 770 kg. Those averages shift with location, habitat and human interference. Because weight climbs roughly with the cube of length, an individual at 6 m weighs more than twice as much as one at 5 m.

  The largest confirmed saltwater crocodile on record drowned in a fishing net in Papua New Guinea in 1979. Its dried skin and head measured 6.2 m. Allowing for shrinkage and a missing tail tip, researchers estimated it at 6.3 m in life. Skulls from some of the largest crocodiles ever shot suggest a ceiling near 7 m. An Australian government study accepts that the very largest animals probably span 6 to 7 m and 900 to 1500 kg.

  Individual animals have earned names. Lolong, caught in the Philippines, measured 6.17 m and weighed 1075 kg, and he died in 2013. Cassius lived at Marineland Crocodile Park on Green Island in Queensland. He measured 5.48 m and weighed about 1300 kg before his death in November 2024. Gomek, at 5.42 m, weighed around 860 kg. Bujang Senang, a notorious man-eater killed in Sarawak, Malaysia, in 1992, measured 5.7 m and weighed more than 900 kg. A hybrid of saltwater and Siamese crocodiles named Yai was born on the 10th of June 1972 at the Samutprakarn Crocodile Farm and Zoo in Thailand. Yai measured 6 m, weighed about 1118 kg, and was claimed to be the largest crocodile ever held in captivity.

  Adult females are far smaller, typically measuring 2.7 to 3.1 m and weighing 76 to 103 kg. The largest female on record reached about 4.3 m. Males average four to five times the mass of females and can sometimes reach twice her length. That is the widest size gap of any living crocodilian. The cause is not definitively known, but it may relate to males needing to monopolise long stretches of habitat.

  A 4.59 m saltwater crocodile weighing 531 kg produced a bite force of 16414 N in a laboratory. That is the highest figure ever recorded for an animal in such a setting, and it topped the previous record of 13172 N set by an American alligator. Estimates based on body mass put individuals of 1308 kg at 27531 to 34424 N. The skull leaves a huge space for jaw muscle, which shows as a bulge on each side. That muscle is so stiff it feels almost like bone, and most of it is arranged for clamping down. The muscles that open the jaw are small and weak.

  At the Muséum national d'Histoire naturelle sits the largest skull the record treats as scientifically verified. It was collected in Cambodia and measures 76 cm long and 48 cm wide near the base, with mandibles 98.3 cm long. Detached from the body, the head of a large male can weigh over 200 kg, and the largest tooth measured reached 9 cm. Going by typical skull-to-body ratios, the Cambodian animal was presumably 6.7 to 7 m long, though it may simply have had an unusually large skull.

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• 3. Measuring Legends

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  A crocodile shot in the Bay of Bengal in 1840 was reported at 10.1 m, with a belly girth of 4.17 m and an estimated mass of 3000 kg. Its skull survived, and when Guinness Records examined it, the animal turned out to have probably measured no more than 5.89 m.

  James R. Montgomery ran a plantation near the Lower Kinabatangan Segama Wetlands in Borneo from 1926 to 1932. He claimed to have netted, killed and examined numerous crocodiles well over 6.1 m, including one of 10 m. No one scientifically confirmed any of them, and no voucher specimens are known.

  In July 1957, Krystyna Pawlowski shot a crocodile in Queensland that became known as Krys the croc. It was reported at 8.63 m, but no verified measurements were made and no remains exist. A replica was later built as a tourist attraction. Records add that she was defending her three-year-old daughter.

  A crocodile killed in 1823 at Jalajala on Luzon in the Philippines was reported at 8.2 m. Its skull is 66.5 cm long, which points to an animal of about 6.1 m. In India, a crocodile shot in Odisha was claimed to measure 7.6 m. Scholars who examined its skull thought it came from an animal of no more than 7 m. Another reported 7.6 m crocodile, killed in the Hooghly River in Calcutta, left a skull of 75 cm. That is one of the largest known, and it implies roughly 6.7 m.

  In 2006, Guinness accepted a 7.01 m, 2000 kg male living in Bhitarkanika Park in Odisha. Park officials made those estimates over ten years, from 2006 to 2016. The figures remain unverified because trapping and measuring such an animal is so difficult, and visual estimates in the wild are uncertain. The region may hold up to four other crocodiles over 6.1 m.

  S. Baker claimed in 1874 that crocodiles of 6.7 m or more were commonplace in Sri Lanka during the 1800s. The largest Guinness considered authentic there was a suspected man-eater from the Eastern Province that measured exactly 6 m. For Papua New Guinea, Guinness accepted a 6.32 m crocodile shot by Herb Schweighofer in May 1966 along the northeastern coast. Its belly girth was 2.74 m.

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• 4. Riding the Currents

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  In Australia, 20 saltwater crocodiles were fitted with satellite transmitters, and 8 of them ventured into open ocean. One swam 590 km in 25 days, from the North Kennedy River on the eastern side of Far North Queensland, around Cape York Peninsula, to the Gulf of Carpentaria. Another covered 411 km in 20 days. The animals rode ocean currents, sometimes simply floating, which saves energy. When the current turned against them, they paused in sheltered bays for a few days.

  Salt glands let several crocodile species survive in the sea, a trait alligators lack. Yet most species rarely leave the coast except in extreme conditions. The saltwater crocodile goes to sea routinely, and barnacles have been seen growing on its scales, a sign of weeks spent at sea. It can also stay fully submerged for long periods by reducing its heart rate and oxygen consumption. Voluntary dives of up to two hours have been reported, and depths of 15 m have been recorded.

  On land and in the water, the animal is generally lethargic, which helps it survive months at a time without food. It loiters or basks through much of the day and prefers to hunt at night. Australian studies found it more active and more often in the water during summer, and more often basking in winter. Its brain can be as low as 0.05% of its body weight, yet it learns difficult tasks with little conditioning. It even learns to track the migratory route of its prey as the seasons change.

  Saltwater crocodiles generally spend the tropical wet season in freshwater swamps and rivers, then move downstream to estuaries in the dry season. Dominant males claim the best stretches of freshwater creeks and streams. Junior crocodiles are pushed into marginal river systems and sometimes into the ocean. That pressure helps explain the species' enormous range. Cold spells can make crocodiles seasonally vacate parts of Australia, and wanderers have appeared as far away as Fiji. The Seychelles once held the westernmost population.

  Japan has three historical records of the species in its coastal waters. One individual was found off Iwo Jima in 1744, and another off Amami Ōshima in 1800. In 1932, fishermen caught a third in Toyama Bay.

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• 5. Opportunistic Hunter

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  In Orissa, India, sub-adult saltwater crocodiles weighing only 8.7 to 15.8 kg and measuring 1.36 to 1.79 m have been recorded killing and eating goats. Those goats weighed 50 to 92% of the crocodile's own body mass. Young crocodiles can clearly tackle large prey from an early age.

  Hatchlings are limited to small fish, frogs, insects and small aquatic invertebrates. Juveniles add fish of both fresh and salt water, amphibians, crustaceans, molluscs, birds, small to medium-sized mammals, snakes and lizards. Once a crocodile passes 1.2 m, small vertebrates matter more than small invertebrates. Large mud crabs of the genus Scylla are frequent prey in mangroves. Among birds, the emu and the magpie goose are commonly taken. Prey recorded in the source includes crab-eating macaques, proboscis monkeys and gibbons.

  Buffalo herds offer a strategy for catching land animals. Mammals and birds appear only sporadically near water, so crocodiles seem to search out places where they gather. One example is the water beneath a tree holding a flying fox colony. Another is a spot where water buffaloes feed, where a large crocodile may take the weaker members of the herd. Adults take sambar deer, wild boar, Malayan tapirs, kangaroos, orangutans, dingos, tigers and large bovines such as banteng, water buffalo and gaur. They do so only sporadically, because most large mammals are thinly spread across the range.

  The sea adds another menu. Saltwater crocodiles prey on sea snakes, sea turtles, sea birds, dugongs, rays including large sawfish, and small sharks. Most witnessed attacks on marine animals took place in coastal waters, including on female sea turtles and their babies during the mating season. Bull sharks are the only largish sharks that regularly patrol brackish and fresh water. The remains of pelagic fish found in stomachs show that crocodiles also hunt in open seas. Unlike freshwater crocodiles, which can die from eating poisonous toads, saltwater crocodiles are partly resistant to cane toad toxins. They can eat the toads only in small quantities, however, so they offer no real natural control for that introduced pest.

  The method itself is simple. A crocodile submerges, swims quietly toward its target, then strikes upward. Young crocodiles can breach their entire body into the air to reach prey perched on low branches. When hunting rhesus macaques, they have been seen knocking the monkeys off a bank with a tail. Whether that is intentional is not clear. Unlike American alligators and Nile crocodiles, saltwater crocodiles are not known to hunt on dry land. Their peg-like teeth grip but do not shear, so small prey is swallowed whole. Larger animals are dragged into deep water and drowned or crushed. The crocodile then spins in a death roll to twist off pieces.

  Studying adults is difficult. The main capture tool is a huge pole with large hooks, meant for sharks, which restricts the jaws but can damage the snout. Even this is unproven for crocodiles over 4 m. Twentieth-century studies catalogued the stomach contents of many Nile crocodiles. Few did so for saltwater crocodiles, despite the many killed for the leather trade. The adult diet therefore rests largely on eyewitness accounts. When a crocodile stores leftovers for later, monitor lizards may scavenge them.

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• 6. Nests and Hatchlings

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  In Australia, courtship happens in September and October, and females lay eggs between November and March. Mating takes place in the wet season, when water levels are at their highest. Males reach sexual maturity at around 3.3 m and about 16 years of age. Females mature at 2.1 m and 12 to 14 years.

  The nest is a mound of mud and vegetation, usually 175 cm long and 53 cm high, with an entrance averaging 160 cm across. Nests are often in surprisingly exposed spots, such as bare mud with little protection from sun and wind. Debris scratched around the entrance is reported to produce an astonishing amount of warmth. Both parents defend the territory, and the female guards the nest for 80 to 98 days. A typical clutch holds 40 to 60 eggs, though some reach 90. Each egg averages 8 by 5 cm and weighs 113 g in Australia and 121 g in India.

  Temperature decides the sex of hatchlings. At 28 to 30 degrees, all hatchlings are female. At 30 to 32 degrees, 86% are male. At 33 degrees or more, 84% are female. Flooding causes most egg losses, while goannas take about 25% of the eggs. That is far lower than the 95% of a clutch that goannas may eat when they find freshwater crocodile eggs, because the mother is so vigilant.

  The mother shows remarkable care for a reptile. She excavates the nest in response to yelping calls from the hatchlings. She even rolls eggs gently in her mouth to help them hatch. She then carries the hatchlings to water in her mouth and stays with them for several months. Baby saltwater crocodiles are exceptionally aggressive to one another and often fight almost as soon as they reach water. Predators include barramundi, white-bellied sea eagles, black-necked storks, pythons, wild boars, larger crocodiles, and in places tigers and leopards. Only about 1% of hatchlings survive to adulthood.

  The survivors start dispersing after about 8 months and show territorial behaviour at around 2.5 years old. Females still need roughly another 10 years to reach sexual maturity. Adults have no natural predators, and life expectancy is estimated at upwards of 70 years. Some individuals may exceed 100, though no such age has been verified for any crocodilian.

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• 7. Near Collapse

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  By 1971, the saltwater crocodile population in northern Australia had been reduced by 95%. The years from 1940 to 1970 were the peak of unregulated hunting, which targeted meat, eggs and above all skin. Saltwater crocodile skin is the most commercially valuable of any crocodilian. Legal protection arrived in Western Australia in 1970, in the Northern Territory in 1971 and in Queensland in 1974. The IUCN Red List has listed the species as Least Concern since 1996.

  Northern Australia is now thriving, with an estimated 100,000 to 200,000 adults, particularly in river systems near Darwin such as the Adelaide, Mary and Daly Rivers. Part of the credit goes to a taste for feral pigs and buffalo. Dr. Marianna Campbell and colleagues published studies in 2022 comparing isotopes in bones collected over five decades ago with modern specimens. They found that crocodiles originally ate a more estuarine diet. After hunting and the loss of aquatic prey, they switched to more terrestrial prey, which let them recover faster.

  Other regions have fared worse. Population surveys in Sri Lanka and Palau found that fewer than 10% of the crocodiles spotted were adults, and none were particularly large males. That points to a breeding population that has not recovered. In Bhitarkanika National Park and in Sabah on Borneo, 28% and 24.2% of observed crocodiles were adults over 3 m. The species is locally extinct in Cambodia, China, Seychelles, Thailand and Vietnam.

  CITES places all wild populations under Appendix I, which prohibits commercial trade, except those of Australia, Indonesia and Papua New Guinea. Those three, plus captive-bred populations bred for commercial purposes, fall under Appendix II, which allows trade with an export permit. Illegal hunting persists in some areas, and trade is hard to monitor across such a vast range.

  Habitat loss remains a major problem. In northern Australia, feral water buffalo trample nesting habitat, although eradication programs have reduced this considerably. In the Andaman Islands, freshwater nesting areas are increasingly converted to agriculture. Once the commercial value of skins waned, perhaps the greatest immediate obstacle to conservation became the danger the animal poses to people and the negative view that follows.

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• 8. Crocodiles and People

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  From 1971 to 2013, Australia reported 106 deaths from saltwater crocodile attacks, or one or two fatal attacks a year. Wildlife officials have posted warning signs at many billabongs, rivers, lakes and beaches. In Sarawak, the reported average was 2.8 fatal attacks a year from 2000 to 2003. Attacks have also been reported in Sumatra, the Andaman Islands and Burma. One study posits that 20 to 30 attacks happen yearly outside Australia and often go unreported. Past claims of thousands of deaths a year were probably exaggerations that benefited leather companies and hunting organisations.

  Crocodiles older than two years often attack anything that enters their area, including boats. About half of all attacks seem territorial, and humans can usually escape those alive. Non-fatal attacks usually involve crocodiles of 3 m or less. Fatal attacks, more likely to be predatory, typically involve animals averaging 4.3 m. In the Northern Territory, relocating aggressive crocodiles failed because the animals found their way back. In the Darwin area from 2007 to 2009-67 to 78% of problem crocodiles were male.

  Some episodes have become infamous. The Battle of Ramree Island reached its retreat on the 19th of February 1945. British soldiers encircled the swampland through which Japanese troops were retreating, and the men spent a night in mangroves holding thousands of saltwater crocodiles. Crocodiles may have killed over 400 of them, although many doubt that most of the deaths came from crocodiles. In 1985, the ecofeminist Val Plumwood survived an attack. She learned that the advice she had received, that crocodiles do not attack canoes, was wrong. In July 2018, a mob of 600 killed 292 saltwater and New Guinea crocodiles in Papua province, Indonesia, in revenge for a man devoured after he entered a sanctuary.

  On Timor, the saltwater crocodile is considered holy, and legend says a giant crocodile formed the island. The Papuan people hold a similar myth, and traditionally described the crocodile as a relative, normally a father or grandfather. In the Wondjina mythology of Indigenous Australians, the saltwater crocodile was banished from fresh water for growing too large and becoming full of bad spirits. Rare rock art of the species, up to 3,000 years old, survives in caves in Kakadu and Arnhem Land. The Larrakia people regard themselves as crocodile descendants and the animal as their totem, and they do not eat its meat. The Alligator Rivers in Arnhem Land are misnamed because of the animal's resemblance to an alligator.

  Postage stamps have featured the species repeatedly. They include an 1894 North Borneo 12-cent stamp, a 1948 Australian 2 shilling stamp showing Aboriginal rock art, a 1966 Indonesian stamp, a 1994 Palau 20-cent stamp, and a 1997 Australian 22-cent stamp. The latest listed is a 2005 Malaysian one-ringgit stamp.

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