From the east of India, all through to the north of Australia, one fearsome, cold-blooded predator stalks the coasts. This hypercarnivore will contend with any that enters its watery domain, from birds to men to sharks, and almost always win that fight. Fossil evidence shows that this species has been plying its bloody trade for almost 5 million years, remaining virtually unchanged, a testament to just how efficient a killing machine it is. Looking it in the eye is the closest thing we have to staring down a carnivorous dinosaur.

This animal is the saltwater crocodile (Crocodylus porosus). It has the distinction of being the single largest reptile alive on the planet today, and one of the oldest species to still walk the Earth.

Predatory legacy

The earliest fossil evidence we have of this species dates back to the Pliocene Epoch, which spanned from 5.3 million to 2.6 million years ago.

But the crocodile family is much older. They draw their roots in the Mesozoic Era, some 250 million years ago, when they branched off of archosaurs (the common ancestor they share with modern birds). During those early days, they lived alongside dinosaurs.

Crocodiles began truly coming into their own some 55 million years ago, evolving into their own species in the shape we know them today. They have remained almost unchanged since, a testament to how well-adapted they are to their environments, and the sheer efficiency with which they hunt.

This makes the crocodile family, and the saltwater crocodile as one of its members, one of the oldest lineages alive on the planet today.

The saltwater crocodile

With adult males reaching up to 6 or 7 meters (around 20 to 23 ft) in length, this species is the largest reptile alive today. Females are smaller than males, generally not exceeding 3 meters in length (10 ft); 2.5 meters is considered large for these ladies.

The saltwater crocodile will grow up to its maximum size and then start increasing in bulk. The weight of these animals generally increases cubically (by a power of 3) as they age; an individual at 6 m long will weigh over twice as much as one at 5 m. All in all, they tend to be noticeably broader and more heavy-set than other crocodiles.

That being said, they are quite small as juveniles. Freshly-hatched crocs measure about 28 cm (11 in) in length and weigh an average of only 71 g — less than an average bag of chips.

Saltwater crocodiles have large heads, with a surprisingly wide snout compared to other species of croc. Their snout is usually twice as long overall as they are wide at the base. A pair of ridges adorn the animal’s eyes, running down the middle of their snout to the nose. Between 64 and 68 teeth line their powerful jaws.

Like their relatives, saltwater crocodiles are covered in scales. These are oval in shape. They tend to be smaller than the scales of other crocodiles and the species has small or completely absent scutes (larger, bony plates that reinforce certain areas of the animal’s armored cover) on their necks, which can serve as a quick identifier for the species.

Young individuals are pale yellow, which changes with age. Adults are a darker yellow with tan and gray spots and a white or yellow belly. Adults also have stripes on the lower sides of their bodies and dark bands on their tails.

That being said, several color variations are known to exist in the wild; some adults can maintain a pale coloration throughout their lives, while others can develop quite dark coats, almost black.

Behavior, feeding, mating

Saltwater crocodiles are ambush predators. They lie in wait just below the waterline, with only their raised brows and nostrils poking above the water. These reptiles capture unsuspecting prey from the shore as they come to drink, but are not shy to more actively hunt prey in the water, either. Their infamous ‘death roll’ — where they bite and then twist their unfortunate victim — is devastating, as is their habit of pulling animals into the water where they drown. But even their bite alone is terrifying. According to an analysis by Florida State University paleobiologist Gregory M. Erickson, saltwater crocodiles have the strongest bite of all their relatives, clocking in at 3,700 pounds per square inch (psi).

Apart from being the largest, the saltwater crocodile is also considered one of the most intelligent reptiles, showing sophisticated behavior. They have a relatively wide repertoire of sounds with which they communicate. They produce bark-like sounds in four known types of calls. The first, which is only performed by newborns, is a short, high-toned hatching call. Another is their distress call, typically only seen in juveniles, which is a series of short, high-pitched barks. The species also has a threat call — a hissing or coughing sound made toward an intruder — and a courtship call, which is a long and low growl.

Saltwater crocodiles will spend most of their time thermoregulating to maintain an ideal body temperature. This involves basking in the sun or taking dips into the water to cool down. Breaks are taken only to hunt or protect their territory. And they are quite territorial. These crocodiles live in coastal waters, freshwater rivers, billabongs (an isolated pond left behind after a river changes course), and swamps. While they are generally shy and avoidant of people, especially on land, encroaching on their territory is one of the few things what will make a saltwater crocodile attack humans. They’re not shy to fight anything that tresspasses, however, including sharks, monkeys, and buffalo.

This territoriality is also evident in between crocs. Juveniles are raised in freshwater rivers but are quickly forced out by dominant males. Males who fail to establish a territory of their own are either killed or forced out to sea. They just aren’t social souls at all.

Females lay clutches of about 50 eggs (though there are records of a single female laying up to 90 in extraordinary cases). They will incubate them in nests of mud and plant fibers for around 3 months. Interestingly, ambient temperatures dictate the sex of the hatchlings. If temperatures are cool, around 30 degrees Celsius, all of them will be female. Higher sustained temperatures, around 34 degrees Celsius, will produce an all-male litter.

Only around 1% of all hatchlings survive into adulthood.

Conservation status

Saltwater crocodiles have precious few natural predators. Still, their skins have historically been highly prized, and they have suffered quite a lot from hunting, both legal and illegal. Their eggs and meat are also consumed as food.

In the past, this species has been threatened with extinction. Recent conservation efforts have allowed them to make an impressive comeback, but the species as a whole is much rarer than in the past. They are currently considered at low risk for extinction, but they are still of especial interest for poachers due to their valuable meat, eggs, and skins.

Saltwater crocodiles are an ancient and fearsome predator. They have evolved to dominate their ecosystems, and do so by quietly lurking just out of sight. But, like many apex predators before them, pressure from humans — both directly, in the form of hunting, and indirectly, through environmental destruction and climate change — has left the species reeling.

Conservation efforts for this species are to be applauded and supported. Even though these crocodiles have shown themselves willing to attack humans if we are not careful, we have to bear in mind that what they want is to be left alone and unbothered. It would be a pity for this species, which has been around for millions of years, which has come from ancient titans, survived for millennia and through global catastrophe, to perish.