Crocodile Saltwater & Freshwater Crocodiles

Crocodile sunbaking on beach

The crocodile is an aggressive amphibious, carnivorous reptile with an enormous mouth crammed full of large pointed teeth. It has a broad flattish body with scaly skin, a long streamlined, muscular tail and short limbs with clawed feet. It has the largest brain of any reptile and is thought to be the smartest reptile. A male saltwater crocodile can grow to over 6m and can weigh as much as 1,000kg.

There are two types of crocodiles. The larger and more dangerous of these is the Saltwater Crocodile which usually lives in brackish river estuaries that flow into the sea. The smaller Freshwater Crocodile inhabits rivers, lagoons, creeks, swamps and watering holes. Saltwater crocodiles have a lifespan of about 70 years. Other crocodiles live for 50-60 years.

The crocodile is an ambush hunter well adapted to its watery environment, where it lies in wait for its prey either partially or totally submerged. A crocodile can remain submerged for up to an hour. It does so by reducing its heartbeat to just 3-4 beats per minute, thereby reducing its metabolic rate and oxygen requirements.

Other names for the saltwater crocodile include Estuarine Crocodile, Indopacific Crocodile, Its scientific name is Crocodylus porosus.


Crocodile Description & Adaptations What Does a Crocodile Look Like?

Photo: Crocodile walking

A crocodile has a broad flattish body with a long streamlined muscular tail and short limbs with clawed feet. It has a long head with its eyes, ears, and nostrils set on top of its head so it can be active with its body submerged and only these parts of its body above water. A crocodile may appear slow and lethargic, but it can swim at speeds of up to 32 kph and run for short distances at speeds of up to 18 kph.

The Crocodile is Cold-Blooded

Crocodiles are cold-blooded. For this reason, they cannot regulate their internal body temperature. They rely on their habitat to provide them with an environment in which they can maintain a body temperature in the range of 30-33C. They regulate their body temperature by moving back and forth between warm and cool parts of their environment. In colder weather, they bask in the sun to heat up, and in hot weather, they seek shaded, cool areas to avoid overheating. When basking they position their bodies to optimise the heating or cooling they require. Crocodiles are frequently seen with their mouths agape. This mouth wide-open posture is used to keep their bodies, especially their brains, from overheating. By opening their mouths and exposing the skin inside, they cool themselves by evaporative cooling through their mouths. Mouth gaping is also a behavioural posture that is not fully understood.

Skin

A crocodile has rough, studded, scaly skin covering its entire body. The colour of the upper part of its body varies from tan, greenish-drab to almost black. It has a cream-coloured underside. A crocodile’s tail is usually grey with dark bands. Young crocodiles have bright patterns with dark spots and bars. These gradually disappear as the animal ages.

Photo: Crocodile eye and ear slit

Eyes

A crocodile's forward-facing eyes are located on top of its head so it can see above the waterline. Its eyesight is as good as an owl's. It can probably see some colour. Because of its vertical pupils which can open much wider to let in more light than round pupils, the crocodile also has very good night vision. Special transparent eyelids enable it to see underwater when submerged. It also has a second pair of eyelids that are transparent and protects its eyes while it is underwater.

Shedding Crocodile Tears

The crocodile produces tears to clean its eyes. It has been observed shedding tears while feeding. Hence the phrase "crying crocodile tears" means displaying insincere emotions such as crying fake tears of grief.

Ears

A crocodile’s ears are slits located just behind its eyes (see photo). These close when the crocodile submerges. Crocodiles have very good hearing. A mother can even hear its young calling from inside their eggs several meters away.

Nose

The crocodile's nostrils are located on top of its snout, which allows it to breath while keeping its body submerged underwater. It has nose flaps that close its nostrils to prevent water from entering its lungs when it submerges. It has special organs in its snout that gives it an excellent sense of smell.

Mouth

The crocodile has a wide rounded snout with a huge mouth. Its massive jaws, when closing, can exert a 'bite force' of as much as 2300 kilograms of pressure per square inch. (A human generates only 45). With this force, it can grasp and demolish almost any animal. While the crocodile has extremely powerful muscles to close its jaws, those to open them are very weak. So weak, in fact, that a person could literally hold them shut with his bare hands.

Photo: Crocodile mouth full of teeth

Its mouth contains between 40-60 large teeth. The fourth tooth of its lower jaw is visible over the lip of its upper jaw. Its "holding teeth", designed for grasping and holding on to prey, are strong and pointed but not sharp. Other teeth are razor sharp and designed to chomp through its victim.

A crocodile replaces its teeth throughout its life. Teeth replacement occurs over time, in “waves”, starting from the back to the front in young crocodiles and front to back in older ones. Each alternate tooth is replaced in each wave. As many as 8,000 teeth may be replaced in a crocodile’s lifetime.

The crocodile's tongue, attached to the bottom of its mouth, does not move and has special glands to eliminate excess salt. The crocodile can block off the back of its throat with a large fleshy flap of skin. This is to prevent water from entering its lungs and stomach when it opens its mouth underwater.

Legs

How a Crocodile moves

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The crocodile has legs that protrude outwards from the side of its body. These legs are short with webbed rear feet. In water, it uses its feet only at very slow speeds for an occasional paddle, to steer, and maintain its position in the water. When floating on or just below the water surface, the front and back legs splay out to act as stabilisers to prevent the crocodile from tipping over and capsizing in the water. When swimming, the crocodile usually tucks its legs against its body to streamline its body and reduce drag but uses them like rudders for steering. On land, the crocodile slides along using its legs to propel itself or heaves itself up on its four legs to move. It can gallop for very short distances at speeds of up to 18 kilometres an hour.

Tail

The crocodile has a long, powerful and streamlined tail. This tail is laterally flattened—the tail is much taller than it is wide. This gives the tail a large surface area to push against the water when the crocodile whips its tail from side to side in an ‘S’ shaped pattern to propel itself through the water. It can also use its tail as a weapon to slash and disable its prey or knock it into the water. The crocodile stores fat in its tail and can draw down on it in hard times, going without eating for as long as two years in the case of large adults.


Crocodile Habitat Where Do Saltwater Crocodiles Live?

Photo: Crocodile distribution map

Saltwater crocodiles live in the coastal regions of Southeast Asia and northern Australia. They live in freshwater and saltwater habitats, including rivers, estuaries, creeks, mangrove swamps, coastal marshes lagoons and billabongs (waterholes). They are often found swimming along the coastline. Crocodiles do not live in regions higher than 250m above sea level.

Being cold-blooded, they move to warmer areas when temperatures are too cold. Australian saltwater crocodiles will generally spend the tropical wet season in freshwater areas such as swamps and river. As the weather warms up, they move downstream to estuaries, coastal areas, and even the open ocean. While a crocodile prefers travelling in water, there are instances where it will travel overland in search of new territory.

Crocodiles are territorial and will compete aggressively with others for territory. The most dominant male will usually occupy the prime “waterfront” real estate. Lesser crocodiles will inhabit more marginal areas. Crocodiles hibernate or become dormant in burrows dug in the sides of river banks during colder months or during periods of drought.

Crocodiles have excellent homing instincts. Some crocodiles relocated by humans to different habitats as far as 400km away were found to have returned home within three weeks. They have also been known to make epic ocean crossings, travelling many hundreds of kilometres in the open ocean. They will frequently swim up unobstructed rivers and streams to new areas, sometimes using seasonal flooding to get to hard to reach locations.


Crocodile Diet & Hunting Techniques What Do Crocodiles Eat?

Photo: Crocodile catching a flying bird

Crocodiles eat fish, turtles, frogs, crustaceans, pigs, buffaloes, dingoes, birds (sometimes snatched out of the air), domestic animals, sharks, dugongs, and kangaroos. Crocodiles will eat any animal. They will even eat humans if they get the opportunity.

The size of the prey a crocodile will attack is only limited by the crocodile's size and appetite. They have been opportunistic enough to try to snatch a baby elephant. Crocodiles are also cannibalistic. Dominant males may attack and eat smaller male crocodiles. Juvenile crocodiles start on a diet of insects, small fish and small mammals. As they grow older, they progress to larger and larger prey.

Photo: Crocodile eating another crocodile

The crocodile is an opportunistic ambush hunter that prefers to hunt at night. But it will not let a good opportunity go by and will also catch prey during the day if they come by. It either cruises its waterway habitats or stays relatively motionless in the water until an unwitting animal comes within striking range. The crocodile will then move silently into position and launch itself with tremendous speed and power out of the water to grasp its prey in its powerful tooth-filled mouth.

A crocodile’s eating habits are best described as a ‘chomp and gulp’ approach. While it has a fearsome array of teeth, they are basically designed for grasping prey in a vice-like hold. A crocodile doesn't have shearing teeth to slice through a carcass, nor does it have tearing teeth with which and pull pieces of its victim’s body apart. (By comparison, a dog's small front teeth are for tearing, and its large back teeth are for shearing). Additionally, the crocodile has a fixed tongue and it cannot be used to move objects around in its mouth. The crocodile can only gulp its food down.

Photo: Crocodile thrashing its prey to kill it

For these reasons, a crocodile has two ways of consuming its prey.

1. Small prey are killed instantly by its pulverising bone-crushing bite and gulped down whole.
2. Larger prey are killed by grasping the victim by the arms, legs or head. The crocodile will then lift its prey high out of the water and flick its head like a whip exerting such tremendous tearing force on its victim’s body that it literately rips apart. It may even drag its victim underwater and drown it first. The crocodile also uses another tactic known as the death roll’; where the crocodile rolls rapidly in the water spinning the victim and slamming it against the water until the victim drowns and hunks of meat break off its body. As the crocodile cannot chew or bite off pieces of its prey, it will continue to dismember its victim into “bite-size” chunks that it can swallow. The crocodile will pick up these smaller pieces and will juggle the food around until it’s in the right position in its mouth and toss its head back, so the food slides down its throat.

A crocodile swallows small stones that help it grind up food in its stomach. Its stomach is highly acidic and can dissolve most of its food, including bone. However, it cannot digest some items such as fur, hooves and turtle shells. These items accumulate in its stomach and will be excreted in its faeces undigested or turned into ‘hairballs’ and regurgitated.

A crocodile can eat up to half its body in one meal when hungry. After filling its stomach, a crocodile may hide the remainder of its catch in mangroves or underwater to consume later. Because the crocodile does not exert itself searching for food, its energy requirements are extremely low. It can survive for months or even years without food.


Crocodile Reproduction & Life Cycle Crocodile Eggs & Babies

Photo: Crocodile mother baby and egg

The wet season's imminent arrival (November to April) is the signal for crocodiles to commence their courtship and mating. Males engage in posturing with conspicuous displays of virility intended on driving rival males away from possible receptive females. This male to male posturing may include chasing away, growling and head-slapping. This can soon escalate to serious confrontation leading to injury and even death. Females too become more aggressive towards other females during this time as they too jostle for dominance and the attention of a suitor. Courtship takes place around September and October, and copulation which may last up to 15 minutes, may occur underwater.

Sometime between November and March, the female selects a suitable location for her nest above any possible flood line and no further than 20 m from reliable freshwater such as a river, waterhole, creek or swamp. She clears an area and then scraps together plant matter, mud and earth to create an elliptical mound around 175- 220cm long and 53-80cm high. In some instances, nests are also built on floating mats of vegetation anchored to a riverbank.

The female crocodile lays between 40–60 eggs and covers them over with 8-28 cm of nest material. The rotting plant matter and heat from sunlight then warm the nest and usually keep the eggs at a relatively stable optimal incubation temperature of 31-32°C. The female crocodile will remain close by to protect the eggs, which hatch in about 90 days.

The incubation temperature in its nest determines the sex of a developing crocodile. Above 32°C and the hatchlings will be male. Below 30°C, the hatchlings will be female. (Note: We have not been able to find any credible scientific report of what the outcome would be if the temperature was between these two temperatures – say exactly 31°C).

Photo: Crocodile carrying its babies in its mouth

When baby crocodiles are ready to hatch, they make a chirping sound from inside their eggs, which alerts their mother that it is time to dig them out of their nest. She will carefully dig them out, and taking each hatching tenderly with her mouth; she will take them to the water’s edge and release them. There she will protect them until they disperse over the following months.

Young hatchlings are about 28cm long and weigh an average of 71g. They are brightly patterned with dark and light bans and spots covering their bodies. These bright colours fade as the crocodile grows. They are exceptionally aggressive will fend for themselves soon after birth, feeding mainly on small insects and other invertebrates.

Only about 1% of hatchlings will survive to reach adulthood. Male crocodiles reach sexual maturity at about 16 years of age and females at around 12.

Only about 1% of hatchlings will survive to reach adulthood. Male crocodiles reach sexual maturity at about 16 years of age and females at around 12.

Crocodiles keep growing throughout their lives, and their weight increases exponentially as their length increases. A mere one meter increase in length could see as much as a doubling in weight. They can live for up to 70-80 years. A crocodile in captivity named “Cassius” is at least 112 years old (in 2018).


Crocodile Predators & Threats What Threatens Saltwater Crocodiles?

Adult saltwater crocodiles do not have any natural predator (with the exception of a rare shark and humans). Young crocodiles are frequently eaten by fish, monitor lizards, turtles, and other crocodiles. Up to 75% of all crocodile eggs laid in a season do not hatch. The reasons for this may include, flooding, overheating and under-heating of the nest before hatching, infertility, poor gas exchange and desiccation of the eggs (eggs drying out).

Human encroachment into areas inhabited by crocodiles is the biggest threat to their survival. Waterfront homes, draining of swamps and mangroves and the property developments along the shorelines are displacing crocodiles from their natural environment and increase the risk of crocodile-human conflicts. Introduced animals such as feral buffaloes and feral pig are also responsible for destroying wetland habitats by increasing drainage, reducing vegetation, trampling crocodile nesting sites. Many crocodiles, especially juveniles are caught in fishing nets and drown each year.


Crocodile Conservation Status Are Saltwater Crocodile Endangered?

There are many of saltwater crocodiles across their vast Southeast Asian habitat, with some becoming extinct (China) and near extinct (Philippines). The IUCN conservation status for it is one of least concern.

Until 1974 saltwater crocodiles were hunted to near extinction for their skins and meat. Crocodile populations plummeted to just 3,000 in all of the Northern Territory in Australia. Their numbers have increased over the subsequent years, and it is estimated that there are about 150,000 crocodiles in the Northern Territory alone today. Crocodiles are now a protected species throughout Australia.


25 Crocodile Facts

  1. Crocodiles are cold-blooded reptiles that live in northern Australia and south-eastern Asia.
  2. The saltwater crocodile is the largest crocodile species. It can grow to 1200 kg and over 6m.
  3. The largest crocodile ever captured was 6.17m long and weighed 1,075kg!
  4. They can swim speeds up to 32 kph.
  5. Crocodiles can hold their breath underwater for about one hour.
  6. A crocodile’s eyes, ears, and nostrils are at the highest points on its head so it can be active with its body underwater.
  7. Crocodiles eat almost any living thing and can go without food for long periods.
  8. They have a tremendous bite force when closing their mouths.
  9. But if you were brave enough to try, you could hold a crocodile’s mouth shut using your bare hands.
  10. That’s because they have very weak muscles to open their mouths.
  11. A crocodile’s eating habits are best described as a ‘chomp and gulp’.
  12. They swallow their prey whole or tear it to pieces and swallow the pieces.
  13. Crocodiles cannot eat underwater, or they will drown.
  14. They swallow small stones to help it grind up food in their stomachs.
  15. Crocodiles do “cry crocodile tears” while eating.
  16. Crocodiles don’t sweat. They use “mouth gaping”, which is a lot like panting, to control their body temperature.
  17. Also, a crocodile’s teeth protrude over their cheeks.
  18. The temperature of the nest determines the sex of the babies. Above 32°C for male. And below 30°C for female.
  19. A crocodile mother carries her babies in her mouth when moving them.
  20. Crocodiles have excellent homing instincts and will find their way back to their original location.
  21. Crocodiles are classified as reptiles, but are more closely related to dinosaurs and birds.
  22. They can live for up to 100 years.
  23. A crocodile has a V-shaped jaw, an alligator U-shaped one.
  24. Crocodiles are 10-20% larger than alligators and are far more dangerous.
  25. A group of crocodiles on land are called a 'a bask of crocodiles'. In water, they are called 'a float of crocodiles'.