Crocodiles and alligators:

Powerful hunters

Crocodiles and alligators are top-notch hunters and will eat just about anything they can get their teeth on, from fish and turtles to monkeys and buffalo. With teeth specialised just for spearing, neither family even bothers to chew the food -- they swallow large chunks or the entire animal whole.

All alligators are crocodiles, but not all crocodiles are alligators.Both alligators and crocodiles are members of the reptilian order Crocodylia. But the families they belong to, Alligatoridae and Crocodylidae respectively, differ. Often, when people use the word "crocodile" what they really mean is "crocodilian." This term encompasses not just the common alligators and crocodiles you might already know, but also the lesser known Gavialidae family that contains the lone gavial, or gharial. All told, there are 23 species of crocodilians. As a group, crocodilians are pretty impressive animals: Their lineage goes back 240 million years, meaning they've outlived the dinosaurs by a good 65 million years. Crocodylidae is classified as a biological family or subfamily.The term can also be used more loosely to include all extant members of the order Crocodilia: which includes the crocodiles of Crocodylidae, the alligators and caimans (family Alligatoridae) and the gharials (family Gavialidae), and the rest of Crocodylomorpha, which includes prehistoric crocodile relatives and ancestors.

Crocodilians have incredibly powerful senses to detect their prey. Their eyesight above water is excellant, and thanks to vertical pupils that can open up extra wide to let in additional light. They also have keen night vision. And even though you can't see their ears, don't be fooled. These small slits are sensitive enough to hear offspring calling from inside their eggs! Even their sense of smell is highly developed due to special organs in their snouts. Ideally suited for life in water and on land, members of the order can swim up to 20 mph (32 kph) and run up to 11 mph (17.6 kph). Eyes situated atop their heads enable them to keep a lookout for prey, while their powerful tails swiftly propel them through the water.

Caiman

Gharial

American alliga

Crocodile

Crocodiles are found in large numbers in Sri Lanka and most of you must be familiar with their appearance. However, their cousin, the alligators are not found in our country. They live mostly in America and China. Even though they live in different parts of the world, the two species are very similar in appearance. The other species, the caimans and gharials also resemble the crocodile, but the gharial's snout is different to the rest of them. Its snout is long and thin.

So, as crocodiles and alligators look so much alike, how do you tell them apart if ever you spot them together somewhere - perhaps in a zoo? By their smile of course ! Have you noticed how a crocodile seems to be smiling when its jaws which are crammed with sharp, pointed teeth are fully closed? Well, if you look at photographs of the two species with their mouths closed (two smiling faces) you will notice that their teeth are visible on either side.

However, if you look closely it will be evident that the sharp, pointed teeth in the lower jaw are visible only in crocodiles and not alligators or the other members of the family .

The alligators lower teeth are not visible because they are hidden inside its mouth. It is the same with a caiman. So, the best way to tell an alligator apart from a crocodile is to look for the big lower jaw tooth sticking out at either side of its long jaws.

However, this is just one way of telling them apart, at a glance. There are many other physical traits that set them apart ,if only you take time to study their appearance.

Alligators have a broad snout, while crocodiles have a thinner snout. Alligators tend to be grayish black in colour, whereas crocodiles have a light tan appearance. Alligators can only be found in the southeastern United States and in some parts of China. Crocodiles can be found all over the world. In the wild, alligators tend to run away.

Crocodiles tend to congregate in freshwater habitats such as rivers, lakes, wetlands and sometimes in brackish water. They feed mostly on vertebrates - fish, reptiles, and mammals, and sometimes on invertebrates - molluscs and crustaceans, depending on species. They first appeared during the Eocene epoch, about 55 million years ago.

Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they have a very slow metabolism, so they can survive long periods without food.

Despite their appearance of being slow, crocodiles are top predators in their environment, and various species have been observed attacking and killing sharks.

A crocodile's physical traits allow it to be a successful predator. Its streamlined body enables it to swim swiftly, A crocodile has the ability to stay submerged in the water and wait for prey to come near due to a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water.

The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence.

It is no secret that a crocodile has very powerful jaws and sharp teeth. Here's an interesting fact you should keep in mind. Unlike humans, crocodiles never have to worry about getting dentures (a set of false teeth). Would you believe that as the animal grows and its teeth wear down, they are replaced by sharp new ones already growing in its jaws? According to scientists, by the time a Nile crocodile is a young adult, it would probably have used up about 45 sets of teeth! Unbelievable isn't it? And this is despite all the dental care they take by using even 'bird toothbrushes' to clean their long, spiky teeth.

The Nile crocodile is often seen resting on the banks of the river, with its huge mouth wide open. Birds, especially the spur - winged plover acts as its 'toothbrush' by picking at the food and especially the meat stuck in between the teeth and also eating the parasites lurking in its mouth.

The crocodile seems to like the symbiotic relationship (see page 15)because it doesn't have to suffer from 'toothaches' thanks to all the cleaning work done by the birds. A useful agreement. However, the birds have to be watchful because the crocodile can suddenly snap shut its jaws. You need not be told what the bird's fate would be if it doesn't fly out on time. Crocodiles are flesh-eating animals so they are called carnivores. They are dangerous because they prey on many animals including humans. They are powerful hunters and intelligent too when it comes to catching prey. They are good hunters because they lie in wait for their prey with great patience.

Some of you may remember a recent incident where a crocodile attacked a girl bathing in the river after watching her bathing in that particular spot with her mother, for many days. Perhaps, the crocodile waited for a good opportunity to attack the girl.

[Fast facts]

* With teeth specialised just for spearing, neither family Alligatoridae and Crocodylidae, even bothers to chew the food -- they swallow large chunks or the entire animal whole.

* They have vertical pupils that can open up extra wide to let in additional light.They also have keen night vision.

* Their ears are not visible but the slits are sensitive enough to hear offspring calling from inside their eggs.

* Crocodiles tend to congregate in freshwater habitats such as rivers, lakes, wetlands and sometimes in brackish water.

* They feed mostly on vertebrates - fish, reptiles, and mammals, and sometimes on invertebrates - molluscs and crustaceans, depending on species.

* As cold-blooded predators, they have a very slow metabolism, so they can survive long periods without food.

* Some species of crocodiles, have legendary tempers. The Salt Water Crocodile and the Nile Crocodile have been known to eat people.

* Alligators, caimans, crocodiles and gharials are all referred to as crocodilians.

Facts and pix: Internet