The largest reptile on earth is lurking in the rivers of Australia's Northern Territory. A master predator, each year this cunning croc is tested by nature's harsh extremes and must battle for dominance with its own kind. The saltwater crocodile (Crocodylus porosus), also known as saltie, estuarine or Indo-Pacific crocodile, is the largest of all living reptiles, as well as the largest terrestrial and riparian predator in the world. The males of this species can reach sizes of up to 7 m (23 ft) and weigh as much as 2,000 kg (4,400 lb). However, an adult male saltwater crocodile is generally between 4.3 and 5.2 m (14 and 17 ft) in length and weighs 400--1,000 kg (880--2,200 lb), rarely growing larger. Females are much smaller and often do not surpass 3 m (9.8 ft). As its name implies, this crocodile can live in salt water, but usually resides in mangrove swamps, estuaries, deltas, lagoons, and lower stretches of rivers. They have the broadest distribution of any modern crocodile, ranging from the eastern coast of India, throughout most of Southeast Asia, stretching south to northern Australia, and historically ranging as far west as off the eastern coast of Africa and as far east as waters off the coast of Japan. The saltwater crocodile is a formidable, opportunistic, and adaptable predator capable of taking almost any animal that enters its territory. It is an apex predator which preys on a variety of fish, crustaceans, reptiles, birds and mammals, including other predators. It is an ambush predator, waiting for a suitable moment to attack. It has the strongest bite of any animal today, but its teeth are not designed to rip flesh, but to hold onto the prey item, which is an advantage that reduces the animal's chance of escape. These two properties allow the crocodile to catch and drag the animal into the water with the minimal possibility of losing its prey. Then, the prey item is swallowed whole or torn into pieces either by death roll or by sudden jerks of the head. Saltwater crocodiles are considered as the most dangerous species of crocodiles to humans, although attacks and killing are rare. Saltwater crocodiles are more territorial than other crocodilians, and are less tolerant of their own kind. Most crocodiles are social animals, sharing basking spots and food. Saltwater crocodiles do not fall into this category however, especially in the case of adult males of the species. They are extremely territorial and will fight off any intruders. The adult male will share his territory with a female. Saltwater crocodiles mate in the wet season, laying eggs in a nest made into a mound of mud and vegetation. The female guards the nest and hatchlings from predators. Conservation efforts were successful in this species, and it has recovered since the 1970s. Today, they aren't endangered in many countries. However, some populations are still at risk. Evolution Crocodylus porosus is believed to have a direct link to similar crocodilians that inhabited the shorelines of the supercontinent Gondwana (the ancient Australian continent) as long ago as 98 million years and survivors of the Cretaceous--Paleogene extinction event. Fossils of Isisfordia, discovered in outback western Queensland (once a vast inland sea) though smaller in size, show attributes of direct lineage to Crocodylus porosus, suggesting that it occupied a similar habitat and vertebra indicating that it shared the ability to death roll during feeding. Incomplete fossil records make it difficult to accurately trace the emergence of the species. The earliest fossil evidence of the species date to around 2 million years ago. Though scientists estimate that Crocodylus porosus is an ancient species that could have diverged anywhere from 39 and 9 million years ago

• published: 13 Dec 2013
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