Crocodiles

A Bit About Them:

Crocodiles; Fearsome, mysterious, ancient lizards.
These guys have been around a long long long time and aren't here to be messed with.
Practically having maxed out their evolution, they are very well adapted at living across the planet and can survive on quite little food for extended periods.
While they are rightly feared, they needn't be punished for doing what evolution has taught them is right for millions of years.

Common Name:

Crocodile or Croc

Scientific name:

Kingdom:

Animalia

Phylum:

Chordata

Class:

Reptilia

Order:

Crocodilia

Family:

crocodylidae

Genus:

X

Species:

X

Closely related to/Family tree:

In the Crocodilia order there are three families:

Alligatoridae (Alligators and Caimans) (8)

Gavialidae (Gharials) (1)

Crocodylidae (Crocodiles) (14)

Of these, the Gharial is the closest relative to crocs, but alligators look the most similar.

Alligators and crocodile families diverged nearly 100 Million years ago and usually given that much time, the two families would be very different to each other. The thing with crocodiles however, is that they evolve very conservatively. So as far as external features go, they are pretty similar.

This isn't, however, a consistent rule as some crocodiles have broader snouts than some Alligators.

Gharials are much easier to tell apart because while Alligator and Crocodile jaws are U or V shaped, Gharial jaws are I-shaped.

Additionally, the 4th tooth from the front on a crocodile protrudes into a slot in the upper jaw just behind the nose. So if you were to see one from above, they would have a mushroom tipped snout!

A group is called:

A bask when on land and a Float when in the water.

Status:

Appearance:

Crocodiles vary in size greatly, with the smallest (Dwarf Crocodile) measuring up to 2m and weighing 25Kg, and the largest (Australian Saltwater Crocodile) measuring up to 7m and weighing a literal ton!

Varying in colour between species, but with an overall dark green or brown hue for most species. The underside in every species however is always some variant of a light tan colour.

In rows of lumps along their backside are osteoderms. These work as extra armour to their already thick scaly hide, but also in temperature regulation (We'll go into this later)

Surrounding the mouth and along  the underside of the body on crocs, are many small lumps, which not yet entirely researched, are thought to be for oil secretion (Which keeps mud off their hide and out of their mouth) or are sensory receptors, detecting minute pressure changes while underwater (Helping them to better find prey underwater). An alligator only has these around their mouth.

Reptile ears are often overlooked as they can seem just like another scale. But croc ears are a bit more visible, if not oddly placed. Situated right behind each eye is an ear slit which can open or close to cover the ear membrane within. This extra attention to ear detail could be why crocs are known for having quite good hearing.

History:

In the early 90's of Australia, crocs were hunted and killed often for their meat and hide. They were hunted to endangered levels as low as 3000 adults but were given full protection in 1971 (WA) and 1974 (QL). Their numbers have since increased to more stable levels.

Common world round, these perfect predators have been a prominent feature in many cultures and religions.
Ancient Egyptians had two gods with Crocodile physical atributes; Sobek and Taweret. Both being attributed gods of fertility, Sobek also being attributed with power and military prowess.

Some Madagascan people see crocodiles as ancestor spirits and under superstition will offer them food.

In Hinduism, Varuna, a god of the sky and seas, rides a Crocodile as his Makkara (Legendary sea creature) and several rivers throughout India have goddess representations who ride crocodiles. 

Goa even has a crocodile worship ceremony, Mannge Thapnee, where they make a mud crocodile, filled with offerings and sacrifices (A young chicken and egg) to appease Varuna and encourage a good harvest.

In Latin America, there was Cipactli, the giant crocodile resembling monster of the Aztecs, whose death was involved in the creation of the world. It's head becoming the 13 heavens, its tail becoming the 9 underworlds and its midsection becoming Earth.

Malay superstition often prevents the killing of crocodiles as some believe that when a crocodile is killed, another will come take a family member as punishment.

Range:

Crocs are found all throughout the tropics of the world, different species often overlapping in their own ranges.

Two types of Crocodile live in Australia;

Freshwater Croc (Freshie or fish eating croc)

Saltwater croc (Saltie or man eating croc)

Being quite different in some ways, salties are much larger and dangerous. The Saltwater crocodile is the largest reptile in the world and unlike freshies are highly territorial and won't tolerate another croc in its area. Some common differences are listed below:

Habitat:

Crocodiles live in a variety of waterbodies and despite the differentiation between freshwater and saltwater crocs, you can find either type in just about any body of water that is in their global range. This is because salties have better functioning salt glands on their tongues than freshies do. So while salties can tolerate the 35% salinity of the Sea, freshies can only tolerate up to 24% salinity.

This information is one of the Northern territories key points in their CrocWise campaign; That just because there wasn't a Croc there last time, doesn't mean there won't be one again.
Even in water bodies considered too high up or far away from other water bodies, a heavy downpour especially in the wet season, could bring Crocs to new waters.

Waterbodies include; Ocean, estuary, lake, rivers and creeks, pools, billabongs and swamps.

Feeding style:

The downward bite force of a crocodile is greater than 22,000 N (Sometimes up to 34,000 N). Compare this not only to the bite force of a rottweiler (3,600 N) but also to the latest estimate of a T-rex's biteforce (57,000 N). They have around half the force of a T-rex bite, but by far the greatest bite force of any living animal. The 2nd greatest belonging to the Great White Sharks (18,220 N).This bite force is made more deadly by the 66 odd teeth that fill the mouth of a crocodile. Conical in shape and up to 13cm long, a crocs teeth are a pretty good warning sign to not get too close. They can replace their teeth if they break or fall out, having 8000 teeth in their lifetime.

If you do happen to be face to face with one of these prehistoric beasts, your best bet is to give it a hug.... Around the mouth.

Despite their astounding bite force, they have very little strength to open their mouths. So holding their mouth shut with just your hands proves to be quite easy. This gave rise to the, kind of true, fact that you could hold a crocodile mouth shut with a rubber band. Now you're everyday rubber band won't quite do the trick on an adult croc, but use a slightly thicker, robust version and you'll be a-ok. (I'm going off other people's word for this one so please don't try this on your own!)

Once a croc has grabbed its prey however, there isn't much hope. They don't have the dexterity to accurately bite off pieces of its dinner, nor does it know how to use a knife and fork. Instead, they choose the very refined method of shaking their head side to side rapidly, letting whiplash tear their meal apart. If their prey is resisting too strongly, they can engage their notorious death roll. This is to disorientate and drown their prey. This is all if they don't have a feeding buddy nearby to play tug of war with of course.

Crocs are the ultimate generalist predator. Eating whatever they can find, including: Birds, crabs, large herbivores such as deer and buffalo, fish, other younger crocodiles.
Even other large apex predators aren't safe, as crocs have been noted to prey on big cats (Lions and Leopards) and sharks.
They will also contend other predators for a meal, stealing others prey or feeding on carrion left by another predator.
They will eat almost anything and will absorb almost all of the nutrients from its food.

Because they can't chew or take measured bites, large chunks of animals are swallowed at once. Not a problem for the crocodile.
They have very acidic stomachs which quite easily break down anything they could swallow, including bones, hooves, beaks and shells.
Much like birds, crocs have gastroliths (Stomach stones) in their bellies which help to break down a meal better and faster. It is also speculated that these gastroliths help crocodiles stay balanced and upright in the water.
If they need to digest even faster, a crocodile who has been underwater for some time can build up CO2 in their blood. Redirecting this acidic blood heading to the heart into the stomach, will increase their stomach acidity even further!
Because their stomachs are rather small, if they can't rapidly digest a full meal, they will store their meal on the water banks for later.

Crocs are excellent at conserving energy, with very slow metabolism and very little energy needed to regulate their temperature (Because they're ectotherms). They can go a whole year comfortably without a meal.
 Past this point they start to shut down and feed off themselves internally, pushing the extremes to survive even longer without a meal.

You can check out some cool (Albeit gory) videos of Crocs catching and eating prey from this website: 
Crocs Eating

Predators:

Nesting/sleeping:

Crocodiles are sexually mature at a certain size, not necessarily an age. Varying between species, females mature at 110cm and males mature at 160cm and the 'woo'ing' of females begins at different times for different species and location.

Freshwater crocs mate during the dry-season (Mid-summer in southern hemisphere, Mid-winter in Northern Hemisphere) and Saltwater crocs mate during the wet season (Opposite of freshies).

Being reptiles, crocs lay eggs. The female will construct a nest for her eggs, either in sand on water banks (Freshies) or in a mound of vegetation just up from the water's edge (Salties). These nests can be 5m wide and 80cm deep!

She lays around 50 eggs in her nest (Up to 70) over half an hour and will guard them fiercely. A 'Wallow' is often found nearby where the female lays during the day to watch over her eggs.

Interestingly though, is that the sex of the crocodile isn't determined immediately when the gametes fuse. Instead the temperature of the eggs during incubation determines the sex.
Varying between species, but as a general rule of thumb, warmer eggs produce males and cooler eggs produce females. Just like a good cake, baking a crocodile egg at too great or too little of a temperature and the end product will not be something you want to keep around.


Depending on temperature, species and location, incubation period can be 65-95 days. The young will start to call before they've even hatched, calling for their mum to help. While mum is on the way, the hatchlings begin getting their own way out with a special egg cracking tooth on the tip of their snouts. When mum arrives, she rolls the eggs about to help them along. Newly hatched crocs are then scooped up into the mouth of their mother, who is very gentle in doing so, and carried down to the water where they will be safer from predators.

Not many crocs reach a mature age as competition from other crocs for food is high and predation rates of hatchlings is high.

Habits/behaviours:

Crocs are most active at dusk, night and dawn. Also during warmer months of the wet season

Being nocturnal, crocs have good night vision, and have an eyeball similar to a cat, a long thin vertical slit of a pupal.

Crocs are exceptionally smart, especially for reptiles!

 In the water, Crocs are well adjusted to hunting. Using their incredibly strong muscular tails to swim and tucking their legs up and to the side to be more streamlined, they can reach swimming speeds of up to 32km/h.
Although their feet are webbed, they aren't used to paddle, but more so like rudders for quick direction changes.
Closing their nostrils over and shifting a rigid plate over their throat, Crocs have no trouble keeping watertight.
They have a third eyelid (nictitating membrane) which is semitransparent and can "close" over the eye whilst the other two eyelids are open. This helps protect their sensitive eyes during the day, but also from the saltwater when submerged. 

All of this combined makes them very formidable predators in the water.

Using its powerful tail to launch itself out of the water and quickly grabbing onto the unsuspecting prey, there isn't much hope of escape. Within a 5m distance from the waters edge a Croc has a very good chance of catching its prey.

Outside of this range Crocs have to do a little running to catch up to their prey. Fortunately for the 'to-be-meal', a Croc is relatively slow on land.
Reaching 17.6km/h on land, the average human (Running at 24km/h) could easily out run a crocodile on land. If you're a below average human, it is advised to run in increasingly wide arcs as a Croc is less agile on land and will waste time turning.

Crocs have also been noted for placing traps. Again utilising their ability to remember prey behaviour and patterns, catching a bird can be too easy for a Croc who knows how. A Croc will deliberately place branches and sticks in the water and wait submerged nearby. When a bird comes to perch on the branch to fish, its only too easy for the Croc to snap it away.

However, this works too well for them sometimes. Believe it or not, Crocs can get too hot! 

A very serious risk for crocodiles is their blood being too warm and swelling their head, leading to exploding their brains.
Not to worry, cooling of is not much of an issue.
Seeking shade and gaping their mouths allows the moisture from their mouths to cool their head evaporatively. Combined with panting like a dog, this generally does the trick.
You won't however, find the same smile like face of a panting dog on a panting crocodile as they can't stick out their tongue.

If this still doesn't cut it, a quick dip in the pool will bring their temperature down a lot.

Cool tricks:

Can communicate 20 messages through sound alone!

You can have a listen to some on this website: 

Croc Sounds

Unlike any other reptile, crocs have a four chambered heart, just like mammals!

Crocs have the most acidic stomach of any living vertebrate.

Some species can scale the more horizontal of trees to bask on outstretched branches

The Jamieson organ that reptiles have in their mouths to help with their sense of smell disappears in older crocs. Relying completely on their nose, they move their pharynx to pump air through their nose for more advanced smelling.

Saying someone is crying crocodile tears is to say they are being insincere. Based on the myth that crocs don't have tears (They do actually have tears but can be hard to see if they aren't very dry)

Salties can tolerate poisonous toads and fish better than freshies, due to their extended range into Asia where poisonous sea life is abundant.

Crocs are thought to have some kind of homing ability as there have been several cases of crocs being shifted out of trouble areas only to make their way back again over a matter of weeks or even years. One particular case moved a bunch of crocs to a site 26km away (Straight line distance)(67km coastal trip) and within 10 days, several had already returned.

A croc can stay underwater for up to 3 hours! This is possible as they can slow their heart rate down to 1-2 beats per minute.

Being CrocWise:

The Northern Territory is home to many crocodiles, both fresh and saltwater based. As such they have increased risk of Croc attacks and the need for more awareness of them. The NT government launched their CrocWise campaign to teach not only tourists but also locals of the very real danger of encountering a Croc. Some of their tips include:

Don't feed Crocs

Be extra cautious at dusk/night/dawn

Don't fetch water from the same point along the bank

Keep an eye on pet dogs as these are attractive prey for a hungry Croc

Females will defend their nests aggressively, so stay away if you see one

Be extra cautious after floods or rain as Crocs may appear in unusual areas

Crocs are more active during the warmer months so be more aware

If you fail to remember any or all of these little tips and tricks, then this catchy song might help!

Conservation:

Crocodiles have a bad rep for being vicious, scary, sneaky or even downright evil. While some of these views are warranted as crocs are truly dangerous, many of them stem from superstition or bad media representation. While they are secure as a species currently, fear mongering and neglect could easily force these ancient animals closer to extinction.