The Ultimate Guide to Crocodiles: Fascinating facts and their secrets revealed

There are different Australian animal characters in our children’s book about Kevin the kangaroo. We’ve already explored the topics of wombats and kangaroos on our blog, so now it’s time to talk about crocodiles.

Let’s unveil the secrets behind their unique physiology, from remarkable respiratory capabilities to an immune system that holds promise for scientific discovery.

1. What's the difference between alligators and crocodiles?

Though similar looking, alligators and crocodiles are different groups of animals (species), like distant relatives sharing the same family name ‘Crocodilia’ (order). There are similarities in their look, but they generally prefer living in different parts of the world. Although in some regions they inhabit the same areas.

Snout shape: One of the easiest ways to tell an alligator apart from a crocodile is by looking at the shape of their snout. Alligators have a wide, rounded snout, while crocodiles have a longer, more pointed snout.

Habitat: Alligators are freshwater enthusiasts and like to swim in swamps, marshes, and rivers, while crocodiles are fond of both freshwater and saltwater, such as rivers, lakes, and coastal areas.

Geographic range: Alligators are found in the south-eastern United States and parts of China, while crocodiles are found in many other parts of the world, including Africa and Australia. In South America the Cayman, another, smaller cousin is the Crocodilia ‘representative’.

Tooth arrangement: When an alligator grins, only the upper teeth show; the lower ones stay hidden. But when a crocodile grins, it’s a toothy extravaganza — both upper and lower sets of teeth are out in the open.

Size: Crocs are the heavyweight champions. The largest crocodile species, the saltwater crocodile, can grow up to 23 feet long and weigh over a ton, while the largest alligator species, the American alligator, typically grows up to 14 feet long and weighs up to 1,000 pounds.

A Crocodile
An Aligator

2. What is so special about a crocodile's heart?

Crocodiles have a heart that’s more highly efficient than most other reptiles, and even some mammals.

A four-chambered heart helps them separate the good, oxygen-rich blood from the not-so-great, oxygen-poor blood making their system more efficient.

Additionally, crocodiles have special bypasses called shunts that activate, and redirect the blood away from their lungs, when they decide it’s time to hold their breath underwater.

They can also slow down their heart rate for serious energy conservation.

3. Why do crocodiles swallow stones?

Crocodiles have a habit known as gastroliths, which is where they swallow stones. It’s actually a common activity among various animals, including birds, lizards, and certain fish.

The exact reason why crocodiles swallow stones is not fully understood, but it’s almost certainly to aid digestion. Crocodiles do not have teeth suitable for grinding food, so they likely swallow stones to help break down tough pieces of food in their stomachs, making them easier to digest.

4. What are crocodiles afraid of?

Crocodiles are apex predators, which means they are top-of-the-group hunters and not generally afraid of other animals, except hippos! A hippo’s bite is strong enough to tear a crocodile in half. Smaller crocodiles are also afraid of larger crocodiles that might eat them!

Source: BBC

There are other things that can scare crocodiles:

Noise and vibrations: Crocodiles are tuned in to the smallest ripples and echoes in the water, and making any disturbance will often cause them to slip away.

Bright lights: Crocodiles have sensitive eyes, especially at night. Flashing a bright light will scare them enough to make them dive underwater.

Disturbances in their habitat: Crocs are creatures of habit and like their environment quiet and constant. If humans or other creatures disturb it they will often change location.

Sudden movements: Crocodiles are known to be attracted to movement, but unexpected, sudden movements can also spook them,

If you spot a crocodile, keep your distance; though sometimes it might already be too late! These are powerful, ambush predators, and VERY, VERY DANGEROUS!!!

Source: Viral List

5. What is a crocodile's weakness?

Crocodiles have few natural enemies. However, like all animals, they have weaknesses and vulnerabilities. Here are some factors that could be considered a weakness for crocodiles:

Temperature: if the temperature drops and it gets too chilly, crocodiles become lethargic and can go into a state known as torpor; which means they fall half asleep and find it very hard to move

Limited mobility on land: Though they can move startlingly fast over very short distances on land, most crocodiles tire very quickly and are then, generally, very slow; but not all:

Source: Enjoy It

Vulnerable young: Crocodile babies are quite cute but defenceless. They’re vulnerable to attacks from birds, mammals, and reptiles. It’s a tough world for them until they grow up.

Human activities: Crocs might rule in the water, but humans rule over it. Habitat loss, hunting, and other human activities have a big effect on crocodiles, often not in their favour.

Dependence on water: Crocs live mainly in water. If there is a drought it can hit them hard, but crocs are very adaptive and resilient. Many burrow holes deep into river banks and lie in them, without eating, for up to 9 months – they survive by slowing down their bodily functions to almost nil and almost go into a coma.

6. How big is the largest crocodile?

The heavyweight champion of crocodiles goes by the name Lolong, a saltwater crocodile which was caught in the Philippines in 2011. Lolong was a huge 6.17 meters long (that’s 20 feet 3 inches) and tipped the scales at 1,075 kilograms (that’s 2,370 pounds). The Guinness Book of World Records gave Lolong the crown for the largest captive crocodile, a title he held until he died, in 2013.

7. Do crocodiles communicate with each other?

Crocodiles are often portrayed as silent predators, but they’re not as quiet as we might think.

Vocalizations: Crocodiles use vocal throat vibrations to communicate.

Body language: Crocodiles often ‘talk’ with their bodies, using postures, head nods, tail wiggles, and jaw manoeuvres to communicate.

Crocs have scent glands for marking territory or sending mass messages to fellow crocodiles. Nile crocodiles often throw head-slaps on the water, to show dominance or warn other crocs to stay away! 

8. How do crocodiles detect prey in the water?

Crocodiles have a variety of ways to detect potential prey.

Sensitive skin: Crocodile skin is super sensitive. It can feel changes in water pressure and pick up on vibrations caused by movement, which could indicate the presence of prey nearby. 

Ears and eyes: Crocodiles have keen eyes and ears. In dim light their eyes are like night vision goggles, spotting any movement near the surface.

Chemical receptors: Crocs have special receptors on their jaws, which can detect chemicals from other animals, helping them locate their prey even if it’s hiding in the mud & sediment.

Lateral line system: Crocodiles have a lateral line system. It’s a series of sensory organs along their bodies, called the Line of Corti, that can pick up changes in water pressure and vibrations. This system helps give crocodiles the location and movement of potential prey.

9. How do crocodiles hunt and kill their prey?

Crocodiles are supreme hunters!

Ambush hunting: Crocs are very, very patient and will lurk patiently, underwater, for hours, waiting for their unsuspecting prey to walk by.

Quick strike: When the moment is right, the crocodile will launch itself forward with incredible speed, snapping shut its jaws with the force of a hydraulic press. Those powerful jaws can crush bones and tear through muscle like it’s made of tissue paper.

Drowning: Once the prey is caught, the crocodile drags it underwater, keeping it submerged until it drowns.

Death roll: This is a powerful dismembering technique. The crocodile clamps a limb or other section of its dead prey and then rolls repeatedly until it tears off. Crocodiles often use ‘team effort’ for this manoeuvre, with two crocodiles holding and bracing the dead prey still, to stop it ‘from slipping, whilst the third performs the move.

In a nutshell, crocodiles are a deadly combination of stealth, strength, and speed. Their jaws are like vice grips, and their ability to play the waiting game is legendary. Add in their underwater acrobatics, and you’ve got a predator that’s the stuff of nightmares for many creatures.

10. How long the crocodile can hold its breath underwater?

On average, most crocodiles can hold their breath for 20-30 minutes underwater, but saltwater crocodiles can do so for up to (a staggering) two hours!

So, how? Well, they’ve got lungs which are incredibly elastic and stretchy, allowing them to stock up on lots more oxygen than other animals, and that, along with their incredibly slow metabolism, means that one breath can last them a very long time.

11. Why do crocodiles thermoregulate their body temperature?

Crocodiles, being reptiles, are the cold-blooded. That means they have no internal means of heating themselves up or cooling themselves down, meaning they rely on external heat sources to keep them warm or cool. This is called being ectothermic.

To alter their temperature, crocodiles lie in the sun to heat up and dip in cool river water to cool down.

Image by Herbert Bieser from Pixabay

12. Are crocodiles intelligent?

Crocodiles are highly intelligent.

Research has shown that crocodiles are very quick learners and are extremely good at retaining information. They can learn how to navigate mazes, remember where food has been hidden, and even use tools to catch their prey. They also have extremely good memories.

13. What does a crocodile's nest look like?

The nest is crafted from an array of materials like vegetation, sticks, and soil. These are skilfully compacted and sculpted into a mound. The size of this mound can differ, based on the female crocodile’s size and the number of eggs laid.

Crocodile nests are often nestled in locations that offer good protection against egg predators and other dangers.

Once the nest is prepared, the female crocodile delicately places her eggs inside. A layer of soil and vegetation serves as a protective blanket, shielding the precious cargo from the elements and any unwelcome visitors. The exact egg count varies depending on the species and the female size. Larger females typically lay more eggs.

14. Do crocodiles care for their offspring?

Crocodiles stay around to ward off predators and look after their young, once the eggs finally hatch. They are unusually gentle and caring parents.

However, once they’re able to swim and feed themselves the juvenile crocodiles are despatched to fend for themselves!

15. How can a crocodile breathe when its mouth is underwater?

Because a crocodile’s snout has the nostrils positioned right at the top.

Image by Angelo Giordano from Pixabay

16. How can crocodiles see at night?

Crocodiles have large, spherical eyes with lots of light-sensitive cells called rods. These rods are extremely sensitive to light and, together with a reflective layer at the back of their eyes, called tapetum lucidum – which amplifies any available light, giving the rods an extra efficiency /performance boost — make the crocs eyesight extremely efficient and effective.

17. Can crocodiles see underwater?

Crocodiles can definitely see underwater. This is aided by a thin, transparent membrane called a nictating lens. These membranes can be moved, at will by the crocodile, across its eyeballs to clean or protect them and act like inbuilt swimming goggles whilst the crocs are underwater.

18. How hard crocodile’s skin is?

Crocodile skin is extremely tough and resilient.

What makes it so formidable are skin spots called scutes – these are bony nodules covering the crocodile’s body. Made of osteoderms, these scutes provide a tough shield against predators. Along with these, the crocodile’s skin also has scales, made of keratin (the same as human hair and nails), packed tight, making the croc’s skin almost tear-proof.

19. What do crocodiles eat?

Crocodiles eat almost anything, literally. They will eat fish, birds, reptiles, mammals and, unfortunately, humans.

Crocodiles are opportunistic hunters.. They’re not picky, and, as said, will dine on whatever’s available to them at the time. They often stash previously caught food to eat later, by burying it in mud or vegetation along the riverbank.

The crocodiles play an important role in maintaining the balance of ecosystems. They keep things in check and balance the populations of their prey species.

20. How strong is a crocodile bite?

Crocodiles’ bite force intensity varies based on a few factors – their size, their species, and the circumstances surrounding the bite.

A mature, full-grown Saltwater crocodile has a bite force of around 3,700 pounds per square inch (psi). This is much stronger than the bite force of other large predators such as lions, tigers, and bears.

21. How fast do crocodiles swim?

Crocodiles are fast, powerful swimmers. 

Crocodiles can cruise at speeds ranging from 20 to 30 kilometres per hour (12 to 19 miles per hour), but the Saltwater crocodile has been known to reach speeds of up to 40 kilometres per hour (25 miles per hour), in short, powerful bursts.

22. Do crocodiles cry?

Contrary to popular belief, crocodiles don’t shed tears of sorrow whilst eating their prey; however, they do have glands near their eyes that play a practical role. These glands produce a lubricating fluid, keeping the crocs eyes moist and shielded from any debris floating in the water. It’s this fluid that is often mistaken for ‘crocodile tears’!

23. How long can a crocodile survive without food?

Crocodiles can survive without food for several months, sometimes, unbelievably, for up to a year.

Their secret to surviving for long periods without food lies in their low metabolism and ability to stockpile energy.

24. What so special has been found in crocodile blood?

Crocodiles have the strongest immune system in the World. Their blood is almost like a secret weapon against infections, all thanks to special germ-killing pathogens known as antimicrobial peptides. Their immune system is so strong that, a crocodile can live in raw sewage, with deep cuts and open wounds and not contract any infections.

Scientists have been busy isolating and studying these peptides, as possible replacements for antibiotics. One especially interesting peptide is crocodylin, which can kill dangerous bacteria like E. coli and Staphylococcus aureus. There’s also crocosin, another peptide, which has antiviral capabilities and can block the growth of viruses like herpes simplex.

25. How to spot a crocodile in the water?

The short answer is, it’s very difficult to do so and not recommended, except from a safe distance, because, as said, they are the ultimate and most deadly ambush predator.


Source: Viral Hog

 There’s no special way or technique to spot crocodiles. Often, they will be very nearby the whole time you’re in their territory, and you’ll (sometimes hopefully) never see them!

26. Do crocodiles have a second joint in their jaws?

Crocs have what we call a “second joint” – not your regular human-type joint, but an epic anatomical feature that allows crocodiles to open their mouths extremely wide.

They have a moveable area in their skulls called the gular fold, or gular sac. It’s tucked near the base of their lower jaw. This flexible tissue lets the lower jaw swing wide and pivot, creating the effect of opening their mouths extremely wide.

27. Are crocodile jaws weak when opening?

Crocodile jaw mechanics are a tale of two strengths. When it comes to closing, their jaws are an absolute powerhouse, delivering a bite that’s phenomenally powerful and a vice-like grip. But, the opposite is true when it comes to opening them.

If you want to find out more interesting and sometimes very weird facts about Australian animals, check our blog!


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Crocodile Eyes: what makes them so unique? A-Z Animals

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