Crocodiles, Silent killers, How they help environment? Part 1

The idiom ‘crocodile tears’ came from an old myth that crocodiles shed tears while eating their prey and cry out of grief for the prey’s death.

A French writer brought the story of crocodile tears to Europe in the 14th century, and Shakespeare used the term Crocodile Tears in his plays for the first time in English in the 16th century. But when it was tested experimentally, scientists found it not to be true.

If crocodiles stay out of water for a longer time, their eyes become dry, and the tear glands in the eyes also release water to lubricate them and remove debris from them. Hot air from the nose while eating out of water can also bring tears to the eyes. A disease known as Crocodile tear syndrome also derived its name from Crocodile tears because patients shed tears while eating. The major cause behind this syndrome is facial paralysis when nerve fibres destined for a salivary gland are damaged and then by mistake regrow into a tear gland.

Crocodilia an order of many animals:

Crocodile belongs to a large order known as Crocodilia which is the collection of three families given below.;

1. True crocodiles

2. Alligators

3. Gharials and false gharials

Distribution:

They are found on all the continents, except Europe and Antarctica, in tropical (marsh and swamps) areas with natural forests. They are found in rivers, running water, seasonal lakes and ponds. They are also found in the lagoons of the warm oceanic regions.

They are not found in all kinds of rivers, but where there is a large number of fish, birds of prey, and other animals who often come to drink water. They live mostly in brackish stagnant water but can also be found in running and fresh water.

Physical features:

✓A crocodile has a strong sense of smell and can smell both in water and on land. Its eyes resemble to that of the snake with a vertical pupil which controls the amount of light entering the eye, unlike our round eyes. They have a nictating membrane which protects the eye. Besides this, there is a layer known as Tapetum Lucidum behind the retina which makes them able to see in the dark as well. This layer is also found in the eyes of cats and dogs.

✓Just behind its eyes are ears, which are not visible, but function normally.

✓They have 80 polyphyodont teeth, i.e. their teeth are continually replaced. As they do not have lips, teeth are always visible from the outside.

Teeth are sharp and pointed and are used to kill their prey.

✓They have small black spots around their mouths. These are body sensors and they can sense even the slightest ripple in the water.

✓The bumps, spines or scales that appear on the body are called Osteoderm. They are made of Keratin, the same substance that makes up our nails and hair.

Inside the mouth, there is a membrane in the throat that seals in the water so that the water does not flow into the stomach.

✓The claws on their feet help them to make burrows, and the webs between them help in swimming.

Behaviour:

While swimming, the crocodile places its legs back against the sides of the body to reduce energy consumption and open them to change their direction.

They can also walk on land and can run by lifting their bodies above the ground. They are good swimmers and can also climb trees.

You have often seen them sitting on the dry land with their mouths open, because they do not have sweat glands in their body, so they lie outside with their mouths open. Vapours come out of their mouths and hence body temperature is normalized.

Crocodile as a predator:

A crocodile is an ambush predator and waits for its prey to come close to water, then rushes out to attack. It can hold its breath for 2 hours.

It clamps down on prey with its massive jaws, then crushes it with its powerful jaws, and then swallows the whole prey. A crocodile cannot chew its food so it has to swallow small stones and pieces of rocks that help it to grind up food in the stomach.

You have often seen crocodiles catch and flip their prey in water or on land. This is its most powerful attack. Flipping movement helps crocodiles in breaking the bone and tearing the skin of the prey.

What is special about digestive system of a crocodile?

The digestive system of a crocodile consists of two main parts. A muscular part where it keeps the swollen stones and other which has digestive acid and juices. Stones help to break off food into small pieces which are now available for the mechanism of digestive acid. The acid is so strong that it can digest the bones, hair and even nails of the prey.

Their metabolism rate is very slow, which means that energy from food is released very slowly. Animals with such a slow metabolism rate reduce their body movements in order to conserve energy.

Mode of reproduction:

During mating season the male use different tactics to attract female, it vibrates the water with its back, blows into the water with its nose, and splashes the water with its claws.

The female lays lots of eggs, out of which 1 or 2% survive. The hatchlings are about 7 to 10 inches in length and can grow up to 20 feet in size.

(to be continued..)

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