Crocodile


Crocodiles are large and mostly aquatic Reptiles which are mostly found in the tropics. They are sometimes classified as the subfamily Crocodylinae. In general and broader sense, Crocodile includes all the members of the order Crocodilia: i.e. the 'True Crocodiles', the Alligators and Caimans (family Alligatoridae) and the Gharials (family Gavialidae). They have distinctive features such as long jaws, protective armour, streamlined body and long tail. These, together with various anatomical and physiological adaptations, make the Crocodile perfectly suited to an aquatic and predatory lifestyle. These features have changed very little from those of their prehistoric ancestors, and according to some experts the Crocodile, in its present form, has not changed for the last 100 million years. There are 23 different Crocodile Species that have been identified. They are found all over the world – in both salt water and fresh water. Out of the 23 Species, 17 Species of Crocodilians around the world are endangered. Crocodile life span varies between 70 to 100 years. Crocodiles are important for the environment as maintain the balance in the complex web of  life in freshwater and estuarine ecosystems.

Types of Crocodile

Basically there are two types of Crocodiles:

Freshwater Crocodiles - As the term goes 'Freshwater', Crocodiles of these type are found in Fresh Water Bodies like Lakes, Rivers and Marshes. The Freshwater Crocodile has a narrow snout and needle-like teeth and four large scales on their necks. The Freshwater Crocodile can grow up to 7 feet in length. They are mostly olive-green and brown in colour. They are ambush hunters but will not attack human beings unless provoked. These are found in India and Australia.

Saltwater or Estuarine Crocodiles - As the term goes 'Saltwater', Crocodiles of these type are found in fully or partially Saltwater bodies like Coasts, Estuaries, Marshes etc. The Saltwater Crocodile has a longer muzzle and has few armour plates on its neck. The Saltwater Crocodile can grow up to 19 feet in length. Saltwater Crocodiles are ambush hunters and are known to attack humans even when they are not provoked as they are more territorial and aggressive. These are found in Northern Australia, the eastern coast of India and parts of Southeast Asia. Saltwater Crocodiles have a protective translucent third eyelid called the 'Nictitating Membrane', which closes sideways across the eye. This allows them to see and swim at the same time.The tail of the estuarine Crocodile is 49.5% of its total body length, the longest of any Crocodile.

Crocodile Facts  

  • The first Crocodiles appeared on earth, around 240 million years ago, around the same time as Dinosaurs.
  • The first Crocodiles were once 40-foot-long terrestrial beasts that more closely resembled Lizards.
  • Crocodiles are much more closely related to Birds and dinosaurs than the other Reptiles.
  • Crocodiles have a four-chambered heart, which behaves like a three-chambered reptilian one, when underwater.
  • Crocodiles do not shed their skin, rather they grow into it.
  • Only the belly skin of Crocodiles is soft, the back skin is covered in bones which can reflect arrows, spears and even bullets.
  • Crocodiles sweat through their mouth and the gesture of lying with their mouth wide enables them to cool off.
  • The eyes of a Crocodile reflect light, making them appear red, and make night vision possible.
  • Each Crocodile jaw has 24 sharp teeth, used for grasping and crushing, but not chewing.
  • Crocodiles have very sharp teeth that help them in tearing and holding onto flesh. However, they cannot open their mouth if it is held closed as they have a very weak set of muscles. They will not be able to open it even if it is closed with an adhesive tape.
  • The teeth of a Crocodile get replaced continuously, throughout its life.
  • The bite force of a Crocodile is more than 5,000 pounds per square inch.
  • The eggs of a Crocodile are almost the same size as that of a Goose.
  • The sex of a Crocodile is determined on the basis of its temperature. Males are produced at around 31.6 deg C and females, at slightly lower or higher temperature.
  • At time,of hatching a female Crocodile may help the eggs hatch, by gently cracking the shells in her mouth.
  • A Crocodile can lunge more than half its body length into the air or out on the bank.
  • A number of Crocodile Species can gallop, including Cuban Crocodiles, New Guinea Crocodiles, African dwarf Crocodiles and Nile Crocodiles.
  • Crocodiles can produce sounds during distress and aggression.

Crocodile Scientific Classification

Kingdom - Animalia.
Phylum - Chordata.
Class - Reptilia.
Order - Crocodilia.
Family - Crocodylidae.

Crocodile: Physical Features and Characteristics

  • Presence of Cerebral Cortex - Crocodiles have a cerebral cortex which is neural tissue in the brain that is used for memory, awareness, attention, thought and consciousness. The presence of Cerebral Cortex in Crocodile is unique amongst Reptiles.
  • Diapsids - Crocodilians are Diapsid, although their post-temporal fenestrae are reduced. The walls of the braincase are bony but they lack supratemporal and postfrontal bones. Their tongues are not free but held in place by a membrane which limits movement; as a result, Crocodiles are unable to stick out their tongues.
  • Four-Chambered Heart - All Crocodilians have a four-chambered heart, very similar in fact to Birds and of course Mammals. The four-chambered heart is the most efficient design because it separates the pulmonary and systemic circulations, there is no mixing of oxygenated blood from the lungs with deoxygenated blood from the body. Crocodiles are totally unique in that they have actively controlled muscular valves in the heart. This is important for Crocodilians because diving essentially makes the pulmonary system redundant until the Animal resurfaces and takes a breath. Hence, blood is diverted from the pulmonary system to the systemic to provide more blood and a greater aerobic capacity while submerged. This ability also allows the Crocodile to grow to much larger sizes than Animals with incomplete separation of pulmonary and systemic circulation.
  • High level of haemoglobin - Crocodiles have high levels of haemoglobin in the blood. Haemoglobin levels in the blood carry more oxygen and releases it to oxygen-starved tissues more readily. This allows the Crocodile to remain submerge for extended periods of time while still remaining active which is perfect for hunting in and around water.
  • Palatal Flap - Crocodiles have 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.
  • Scaly and Textured Skin - The skin of Crocodile Species is very textured and scaly as it is composed of bones. This protects the Crocodiles from any physical harm and from the hot sunlight as well.
  • Porous Scales - Crocodilian scales have pores that are considered to be sensory, analogous to the lateral line in fishes. They are particularly visible on their upper and lower jaws. It is also considered that these scales are secretory, as they produce an oily substance that appears to flush the mud off.
  • Webbed Feet - They have webbed feet that they use for making quick turns and movements in the water, more than they use them for propulsion. Their webbed feet also make it easier for them to move in shallower water where they may use them for walking rather than swimming.
  • Streamlined Body - They have a streamlined body that enables them to swim swiftly. Crocodiles also tuck their feet to their sides while swimming, which makes them faster by decreasing water resistance.
  • Tail - The tail is used to propel the Animal through the water and scutes (spikes) along the top of the tail are an important part of the tail. Not only do they increase the surface area and therefore thrust for the tail, they are made of cartilage, have a good blood supply and are an important device used for temperature regulation.
  • Slow Metabolism - They have an extremely slow metabolism due to the fact that they are cold blooded and which implies that they can survive long periods without food. In fact Crocodiles need to eat once every 7 days. Crocodiles don’t move very quickly at all on land. They have short appendages and this process drains their energy. They do go to land though to soak up the sun and to lay their eggs.
  • Short Stamina - Crocodiles can  maintain strenuous activity for only short periods of time, after which they become totally exhausted. This can happen when they are being captured or when fighting other Crocodiles. This extreme exertion is carried out anaerobically (without oxygen), and must be followed by a period of rest so that the "Oxygen Debt" can be repaid. The result of anaerobic activity is a build up of lactic acid in the blood, making it acidic.
  • Limited Neck Movement - They also have limited side-to-side movement in their neck.

Weight - Weight of Crocodiles vary from Species to Species. The heaviest Crocodile weighs up to 1 tonne and the smallest weighs up to 30-40 Kgs.

Size - The average length of Crocodiles vary from 1m to 5m depending upon the Species. The Largest grows up to to 7 m long and smallest grows up to 2 m long.

Geographical Range and Habitat

Crocodiles are found throughout the in aquatic Habitats like Lakes, Rivers etc. in Africa, Asia, the Americas and Australia.

Behaviour

Crocodile Attack - Crocodiles are ambush hunters i.e they wait for their prey which maybe a fish or a land Animal, to come close, then rushing out to attack. This ability also poses a threat to Humans and their domestic Animals especially in a natural environment. Sometimes Crocodiles stray into inhabited areas where they pose a threat to domestic Animals, children, and adults. On rare occasions, they have eaten humans but humans are not part of their diet. Humans are eaten up by Crocodiles only if the Crocodile happens to be hungry and some Humans happen to be in the same area. Statistics show that the Saltwater Crocodile and the Nile Crocodile are the most dangerous to human beings. At least a dozen people have been killed in Crocodile attacks since 1990. Most of these incidents occurred while the victims were in the water or were on a boat. The Crocodiles tended to drag their victims under the water and drown them. Between 1980 and 1990 Crocodiles attacked 8 people and 11 sharks in the Western world. There are two main types of Crocodile that are likely to attack humans. Nile Crocodiles live in Africa and can reach a length of up to 6 meters and a weight around 500 kilos. They will attack without warning and have the patience to guard and to observe their potential victims for weeks on end. This exceptional Animal also has the ability to gallop, making it difficult for its prey to run away. Nile Crocodiles are responsible for more human deaths than any other Crocodile Species. Mugger Crocodiles and possibly the Black Caiman are also very dangerous to humans. American alligators are less aggressive and rarely assault humans without provocation. Nile Crocodiles in particular are viewed as a menace by many African people their lives depend upon access to water. This brings them in contact with Crocodiles which results in injury or death. In some areas like Florida and Northern Australia, Crocodile populations have increased many fold causing Human-Crocodile conflict. Careful management, education and awareness have greatly reduced the danger to people, who now view Crocodiles with a little more respect.

Rolling Mechanism
- The Crocodile exhibits a Rolling Mechanism which is known as the 'death Roll'. Once the Crocodile has a grip on it's prey, it will roll to throw the prey off balance so it can be dragged into deeper water and drowned. Because the stomach of the Crocodile is small relative to the size of some prey taken, head shaking, thrashing and rolling is used to dismember large prey into smaller pieces for eating.

Regulating Body Temperature - With a preferred body temperature of 30° to 33° C, Crocodiles use the water, sun and shade to regulate their body temperature and move between these warm and cool parts of their environment to adjust it.

Swallowing of stones - Many large Crocodilians swallow stones which are known as Gastroliths or stomach stones. These are considered to act as ballast to balance their body or assist in crushing food, similar to grit in Birds.

Belly Run - The fastest means by which most Crocodile Species can move is known 'Belly Run'. It involves the movement of the body in a snake-like fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of 10 or 11 km/h (around 7 mph) when they 'Belly Run', and often faster if they're slipping down muddy riverbanks. Another form of locomotion is the ''  where the body is raised clear off the ground whilst walking on land.

Sleeping with Mouth open - Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may even pant like a dog.

Diet

Crocodile diet mostly includes fish, Reptiles, Mammals, Birds and sometimes Mollusks and Crustaceans, depending on the Species. Some Crocodiles display cannibalistic behaviour i.e they eat their own kind. This is considered to be an important population controlling mechanism.

Crocodile: Predators

Adult Crocodiles rarely have any Predators. However, hatchings do fall prey to Birds, Mammals, Reptiles, big Fish and even large Frogs. Lions, Tigers, Anaconda, Pythons and Leopards can sometimes kill smaller Crocodiles under 7 feet. This is primarily because Crocodiles do not have enough stamina.

Crocodile: Reproduction

The Crocodile breeding season is during January to May. For males, the onset of sexual maturity occurs when they are about 3 metres (10 feet) in length, while for females, it occurs when they reach 2 to 2.5 metres (6.5 to 8 feet) in length. This takes about 10 years for both male and females Crocodiles to reach these lengths under normal conditions. During the mating season, males attract females by bellowing, slapping their snouts in the water, blowing water of out their noses and making a variety of vocalizations. The larger males of a population tend to be more successful. Once a female has been attracted, the pair warble and rub the underside of their jaws together. After Crocodiles mate, the female Crocodile lays about 20 - 40 eggs (a clutch) in a nest she makes near a river bank once a year. She covers the nest with leaves and other vegetation. The rotting vegetation keeps the eggs warm and the nest moist. The incubation temperature for Crocodile eggs is 28 - 32 degrees Celsius, relative humidity is 95 - 100 per cent, incubation period is 70 - 80 days. The female stays and guards the nest until the eggs hatch. The hatchlings call out and the female Crocodile opens up the nest and carries them to the water, where they immediately start feeding on crabs, shrimps and insects. About half do not survive the first year due to predators.

In Folklore and Culture

Crocodile Myth - The Crocodile plays a prominent part in many of the myths of creation of Papua New Guinea. For example, some Kiwaians believe that their father was a Crocodile. The myth tells how a being called Ipila carved a human figure out of wood and brought it to life by painting the face with sago milk. First the eyes opened, then the nostrils quivered and the "man" made a noise like a Crocodile. His name was Nugu and he was not satisfied until Ipila made three more men as companions for him. These men refused to learn the things Ipila wanted to teach them and after a while two of them became tired of only eating sago and started to kill Animals for food. Almost at once they turned into half-Crocodiles. They then tried to make some of their own kind but they found that they could only make men because Ipila secretly altered their work. It is from these new men that their descendants claim the Crocodile as their father.  

Crocodile Tears - There is a an Idiom which goes by the name 'Crocodile Tears' which means to describe false displays of sadness or other deep emotions. There was ancient allusion that Crocodiles weep while devouring their prey. They do have Lachrymal Glands and produce tears to lubricate the eyes as humans do. But they don't cry with emotion rather they shed tears when these glands are stimulated as the Crocodile works its jaws during a meal.

Television Series - The Crocodile Hunter is a wildlife documentary television series that was hosted by Steve Irwin and his wife Terri.

Crocodile Belts - The skin of the Crocodile, especially from the belly surfaces, is the most prized of all Crocodilian skins for fashion leather. There is a considerable demand for Crocodile skins for use in shoes, belts, suitcases, briefcases and handbags. Lacoste is a high-end apparel company which has a Logo featuring a Green Crocodile.

Crocodile Art - Crocodile based Art used in various forms. Some apply Tattos, while some paintings on cave depict them while others are in the form of Tribal Art.

Some of the Crocodile Art Images are available at:

http://www.fotosearch.com/clip-art/crocodile.html
http://www.clipartguide.com/_search_terms/crocodile.html
http://www.artistshelpingchildren.org/alligators-crocodilescraftsideasactivitieskids.html
http://fineartamerica.com/art/all/crocodile/all

Crocodile Games - Various Crocodile based games have been mad for the entertainment of the kids. Croc 2, called Croc Adventure in Japan (working title Croc 2: Kingdoms of the Gobbos), is a video game released in 1999, is the sequel to Croc: Legend of the Gobbos, developed by Argonaut Software between 1998 and 1999, and published by Fox Interactive. Croc 2 was released on Game Boy Color, Windows, PlayStation. Sega Saturn and Nintendo 64. For more info -  Some of the Crocodile based games are available to be played online.

Crocodile Game Links

http://en.yupis.org/crocodile-games/
http://movies.yahoo.com/feature/crochuntergamepopup.html
http://noolmusic.com/games/crocodile.php
http://www.crocodilegames.com/

Crocodile Toys - Some kids like to play with Crocodile Toys. There are a variety of Crocodile Toys like Stuffed Crocodiles available in the market as well as online. There is also a Toy making company named after Crocodile located in Cirencester, Gloucestershire, United Kingdom. Example of a Crocodile Toy - http://www.dealextreme.com/details.dx/sku.12581


Crocodile Clips - Crocodile Clips is a company that develops and sells educational software and hardware. For more info - http://www.crocodile-clips.com/en/Crocodile_Chemistry/

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