My Science School

    Crocodiles and alligators are called 'loud-mouths' because, they are very noisy animals. Even before they hatch, baby crocodiles make calls from within the egg, signaling that hatching time is near. Baby crocodiles have a high pitched yelping cry which they use to call their mother. When an adult crocodile is angry, it makes a long hissing noise or growl.

The sound made by crocodiles and alligators range from coughs and hisses to roars and bellows. Bellowing seems to be contagious. If one animal in a group starts bellowing, others will soon join in and the chorus may go on for up to half an hour! Alligators are believed to recognize each other’s calls, so that they are able to keep track of their friends and foes. 

           Crocodiles can eat just about anything. Their long narrow snouts are rimmed with sharp teeth that can rip apart large pole or snatch anything tasty that happens to float by. A crocodile's fierce-looking teeth however, are not meant for chewing, They are meant for breaking up crab and turtle shells, or for crushing bones, even hooves and horns, so that they can slide down the crocodile's throat.

 The crocodile has a sturdy constitution, and doesn't seem to suffer from any indigestion. It has two chambers in its stomach. The first one grinds up those big chunks of food, while the second one absorbs the nutrients. The crocodile's digestive system is the most acidic of any animals, and that's why it can digest bones, shells and hooves.

Crocodiles also have an extraordinary ability to go without food. While other animals would die of starvation, some crocodiles can go for months without eating, and simply pick up where they left off when food becomes available again. This is because it stores about 60% of the energy contained in the food it eats. The energy is stored away as fat in the tail and other places- and this stored energy allows the crocodile to go without food for long periods. 

The period known as the Cretaceous Period ended 65 million years ago with the extinction of the dinosaurs and many, many other prehistoric life forms. No one knows exactly what brought on this disaster. One theory is that a huge asteroid hit the Earth, while another is that there was a rapid increase in volcanic activity. There were severe climate changes, and the Age of the Reptiles came to an end, to be followed by the Age of Mammals.

 Crocodiles and other members of the crocodile family were however, able to survive the disaster. One explanation for their survival is that, crocodiles belong to the community of freshwater vertebrates whose food chain was not so severely affected, since they did not depend on marine plankton or flowering plants that had completely disappeared. Whatever the reason, the fact remains that while huge dinosaurs were wiped off the face of the Earth, the hardy crocodile adjusted to the new conditions on Earth, and survived.

 

Crocodiles and alligators are very clever at stalking, capturing, and killing their prey. The gharial crocodile, which has a long narrow snout, eats mainly fish, and it captures its prey by a rapid sideways snap of its tooth lined jaw. Alligators and crocodiles with broader snouts also eat fish, but their diets vary according to their age. The young ones eat mainly insects, spiders, crabs and small frogs. They will circle their prey with their bodies and then snap them up with a sideways movement of their jaws.

Adult crocodiles and alligators feed on small mammals, birds, turtles and other reptiles. They will approach their prey stealthily with their bodies submerged under water and only their eyes and tip of their snout above the water. When they are near the prey, they submerge themselves completely... and then rear up with a few strokes of their powerful tails. Their vice like, tooth lined jaws snap shut with an enormous force that kills the smaller prey immediately. Larger animals are dragged underwater, drowned, and then killed and eaten - sometimes over the span of several days. 

 The dragon is a legendary creature that has been revered and worshipped by the Chinese since ancient times. In fact, the Chinese call themselves 'descendants of the dragon'. They believed that the dragon had supernatural powers, and that it could take on any number of forms. People in Ancient China offered sacrifices to the dragon for favourable weather and a good harvest.

 The dragon is described in ancient texts as having horns like a deer, the head of a camel, a neck like a snake's, and the body of a crocodile! It was imagined to be a mixture of many animals... possibly of the different animals that were once worshipped in different parts of China. Scholars feel the origin of the dragon lies in the respect that was given to crocodiles and alligators that were plentiful in the Yellow River around 2200 BC. The Chinese used to foretell rain by listening to the call of the alligator, which was also seen as a harbinger of war because of its heavy armour. Did you know that alligator flesh was a prized delicacy at Chinese weddings too? 

Do you know what a mummy is? A mummy is the body of a person or an animal that has been preserved after death by a special process called mummification. The Ancient Egyptian God Sobek was depicted as a crocodile, a mummified crocodile or a man with the head of a crocodile. The Egyptians mummified both infant and mature crocodiles, and even buried crocodile eggs with a dead person in order to enlist the protection of Sobek in the afterlife for that person!

Animals of all kinds were important to the Ancient Egyptians. The Egyptians both respected and feared the power of the crocodile as they were a real danger to them. The Nile, which was full of crocodiles, was important to the livelihood of the Egyptians. It therefore made good sense to have a God which could appease these ferocious beasts... and that God was Sobek.

Sobek was worshipped in order to appease the crocodiles, and to insure the fertility of their people and crops. Sobek possessed the strength and nature of a crocodile, and was a symbol of the Pharaoh's power. He was also considered the God who controlled the water - in this case, the Nile… and therefore both the crocodile god and crocodiles themselves were revered by the Egyptians.

 

         Alligators and crocodiles have ferocious looking jaws that they can snap shut with tremendous force. However, the muscles for opening the mouth are quite weak. In fact, you can keep a crocodile's mouth shut by just snapping an elastic band around it! Amazing, isn't it?

The temple of Kom Ombo dates back to the days of Ancient Egypt. It stands on the east bank of the Nile, right next to the river and was dedicated to two gods, Horus and Sobek, the Crocodile God. This temple became the centre for crocodile worship in Ancient Egypt. Crocodiles were kept in ponds and fed lavishly. They were even adorned with Jewels. Some of the crocodiles became quite tame, and the priests would feed them by hand, offering them meat, cakes, bread and honey. When they died, their bodies were embalmed and mummified and tourists who visit the temple today can see piles and piles of crocodile mummies! 

The skin of crocodiles is truly awesome. It is made of tough leathery scales, some of which are joined at the edges with more elastic skin. The skin on the head is fused directly on to the skull, while at the back of the neck; it forms a shield of large ridged projections. Embedded into the scales are horny plates like structures called scules that in effect act like tough armour. This armour is one of the reasons why it is very difficult to kill an adult crocodile. Unfortunately, the scales on the lower or belly surface are unarmoured- making the belly the most vulnerable part of the crocodile.

Unfortunately for the crocodile, its skin has long been recognized internationally for its durability and beauty, and is greatly in demand for making belts, bags, shoes and other products. Did you know that in Ancient Egypt, crocodiles were regarded as sacred and divine, and priests often wore robes made entirely of crocodile skin?

 

 Deinosuchus was one of the largest prehistoric crocodiles that ever lived, attaining lengths of about 10.5 metres and weighing around 4500 to 9000 kilogrammes. Ancient crocodiles were constantly growing...in the case of Deinosuchus, at the rate of about thirty centimetres per year. So, it's hard to know exactly how long the longest-lived specimens were. 

Crocodiles are cold blooded. This means they get the warmth that their body needs from the environment. They cannot generate body heat by shivering, or cool off by sweating. So, how do they get the heat they need?

The main method that crocodiles get the warmth necessary for their bodies is by basking in the sun. As their bodies warm up, they open their mouths to cool off by evaporative cooling. The membranes in their mouths play a major role in regulating their body temperature. If the temperature continues to rise, some species will seek the shade, or return to the water to cool off. They also love to wallow in the mud, and these mud baths provide a means to regulate the body temperature too.

Crocodiles also regulate the amount of heat that they receive by placing just the tip of their nose or one leg in the sun. Another method is to remain partly submerged while basking in the sunlight. When the temperature drops, crocodiles become more lethargic. If there is a cold spell, the animal will completely submerge itself in deeper water where the temperature is warmer, and breathe through holes in the ice. 

            The African dwarf crocodile is the smallest living crocodile in the world. The average length for adults is 1.5 metres and the largest known specimen was no bigger than 1.9 metres. The massive saltwater crocodile is three times its size! 

The alligator is a typical reptile. It is cold blooded- it gets its body heat from its surroundings. It lays eggs with shells, and though it cannot chew, it has a very efficient digestive system. Its brain is highly developed, and its heart has four chambers, though some reptiles have only three. Its lungs are also well developed, unlike the lungs of snakes, which are quite primitive. It differs from the crocodile in that its snout is broader and u shaped, and when its mouth is closed, you cannot see any of its teeth. On the other hand, a crocodile's teeth are visible even when its mouth is shut. 

On land, crocodiles belly crawl, walk high, and gallop. Belly crawling is lizard-like, belly-on-the-ground slithering. However, the muscles in its limbs are strong enough to allow the animal to lift its belly off the ground too. Walking high, crocodiles stand up on all four feet with their abdomens off the ground, moving their legs like a dog or cow. Galloping is walking high at highest speed, used for fast charges and quick escapes into water. Crocodiles can gallop ten miles an hour in short bursts and use speed and surprise for hunting and defense.

Crocodiles can move in several ways in the water. They swish their long tails side to side to propel themselves forward in the water. While swimming at low speeds or in shallows, they also use their webbed hind legs. When they swim fast, they fold their legs close to their bodies to become streamlined. By angling their body upwards, crocodiles can jump out of the water. They can launch themselves out of the water for over half its body length or more!