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Last updated date: 16th May 2024
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Introduction to Crocodile

Crocodiles (subfamily Crocodylinae), also known as true crocodiles, are massive semi-aquatic reptiles found in Africa, Asia, the Americas, and Australia. Crocodylinae is a biological subfamily whose members are all called true crocodiles. The word crocodile in its broadest sense means Crocodylidae (which includes Tomistoma). Only the animals of the Crocodylinae subfamily are referred to as crocodiles in this context. The term is sometimes used to refer to all extant members of the order Crocodilia, which includes alligators and caimans (family Alligatoridae), gharials, and false gharials (family Gavialidae), and all other Crocodylomorpha, both living and extinct. Despite their appearance, crocodiles, alligators, and gharials are all members of different biological groups. The gharial, with its short snout, is easier to discern, although morphological distinctions between crocodiles and alligators are more difficult to detect. Crocodiles have shorter and broader heads, with a V-shaped snout rather than a U-shaped snout than alligators and caimans. Another noticeable feature is that the crocodiles' upper and lower jaws are the same width, and the crocodile teeth in the lower jaw fall around the edge or beyond the upper jaw while the mouth is closed.

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General Crocodile Features

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  • Size Range and Diversity of Structure

The physical crocodile characteristics of a crocodile allow it to be a good predator. Its external morphology indicates that it lives an aquatic and predatory lifestyle. Its sleek body allows it to swim quickly; it also tucks its feet to the left when swimming, which increases speed by reducing water resistance. Crocodiles have webbed feet that, while not used to drive them across the water, allow them to make quick turns and rapid movements in the water, as well as begin swimming. Webbed feet help animals navigate about in deeper water, where they often walk. In contrast, the smooth-fronted caiman (Paleosuchus) and the dwarf crocodile (Osteolaemus tetraspis) grow to be about 1.7 meters (about 6 feet) long as adults. Crocodiles have a palatal flap, which is a stiff tissue at the back of the mouth that prevents water from entering. The palate has a unique journey from the nostril to the glottis that avoids the mouth entirely. During submergence, the nostrils close. Crocodilians, like other archosaurs, are diapsid, but their post-temporal fenestrae are reduced.

  • Distribution and Abundance

Crocodiles are mostly found in the Northern and Southern hemispheres' lowland, tropical tropics. Many “true crocodiles” live in Africa south of the Sahara, Madagascar, India, Sri Lanka, Southeast Asia, the East Indies, northern Australia, Mexico and Central America, the West Indies, and northern South America (family Crocodylidae). Temperate areas are also home to the American alligator (Alligator mississippiensis) and the Chinese alligator (Alligator sinensis). The Indian gavial (Gavialis gangeticus) is a gavial species native to Pakistan, northern India, Nepal, Bhutan, Bangladesh, and Myanmar. Crocodile populations have diminished across their range due to human encroachment and land-use change, which have reduced crocodile habitat. Overhunting for their precious skins—which provide leather for handbags, accessories, belts, and other articles—has severely depleted many crocodilian species. Crocodiles are still widely used for meat and medicine in the local community.

Natural History

Crocodiles have existed for over 240 million years, occurring 25 million years before dinosaurs and 100 million years before birds and mammals. Crocodiles from 230 million years ago could grow to be 40 feet tall. Dr. Perran Ross, a crocodile expert and professor of wildlife ecology and restoration at the University of Florida, told the New York Times, "Our primate ancestors were ratty little creatures that went about stealing eggs." "Ancestral crocodiles had essentially the same body plan as modern crocodiles, which works." Crocodiles are the closest surviving descendants of dinosaurs. They have certain dinosaur-like crocodile characteristics, such as bird-like hip bone structures and crocodile teeth fixed in sockets rather than glued straight to the jawbone. Dinosaurs, crocodiles, and birds can all be included in the same branch of mammals, according to recent taxonomic research. Crocodiles have more in common with birds than with frogs, geckos, and other reptiles. Birds and crocodiles, for example, have four-chambered hearts, while lizards and snakes only have three-chambered hearts. A four-chamber heart outperforms a three-chamber heart in terms of brain performance and adaptability to changing conditions. Crocodiles are admired by the Egyptians. Sobek, their river deity, is based on one. Families of crocodiles were mummified and raised in holy tombs, their ankles adorned with gold bracelets. Priests fed them honey wine and cakes, according to a Greek historian who visited an Egyptian Crocodileopolis. 

Life Cycle

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With a length of 20–30 cm, the juvenile crocodile emerges from the shell. To escape numerous predators, it initially hides with its siblings at the edge of its water crocodile habitat. Fish and birds are the most common prey, but larger crocodiles also prey on the young. Cannibalism and social isolation are thought to have a significant impact on demographic patterns and development. The young grow about 30 cm (about 1 foot) each year over the first three to four years of their lives. The rate of growth slows down after that, but growth will continue for the rest of one's life. At around the age of ten, and with a body length of 1.5–3 meters (5–10 feet), sexual maturity develops. Crocodiles in captivity have lived to be 70 years old or more, but their lifespan in the wild is unknown. Development rates are used to measure life spans in the wild, and limited analyses of bone growth rings show that wild and captive crocodiles have identical lifespans. A Nile crocodile (Crocodylus niloticus) or an estuarine (or saltwater) crocodile (Crocodylus porosus) measuring 6 meters (20 feet) in length will live for up to 80 years. Alligators and caimans have a lifespan of 30 to 60 years on average, while true crocodiles have a lifespan of 50 to 75 years.


Crocodiles are thought to be more evolved than other reptiles in terms of behavioural, social, and physical development. They are the only reptiles capable of making noisy noises and master things better than other reptiles. Crocodiles communicate with hisses, grunts, chirps, burps, and growls, as well as infrared sounds. Head slapping, body arching, and bubble blowing are examples of physical demonstrations. Crocodilians, according to Natalie Angier of the New York Times, "can partake in an advanced activity that leaves other reptiles in the cold." They communicate with each other by vocalizations. They argue over social standing and can tell the difference between a polite hominid and an irritating graduate student with a dart gun.


Crocodile locomotion is the product of a distinct body shape. Complex ligaments connect the lateral processes of the spine to the interlocking bony plates of the dorsal scales. The back muscles are encased in a semirigid "I-beam" formation as a result of this configuration. This arrangement is rigid but flexible, allowing for effective energy transfer from the crocodile tail while swimming and maintaining an upright body stance while walking. When swimming, the crocodile rests its legs against the body's sides and propels itself forward with lateral wavelike movements of the crocodile tail. Crocodiles keep themselves up on all four legs while stepping on the ground. The rotation of a front leg in tandem with the opposite hind leg during each motion causes the body's characteristic sinusoidal (side-to-side) flexure. The body is also balanced by a cantilevered tail. Crocodiles slip on their bellies and propel themselves along with the fee while going swiftly into the water from a bank.


Crocodiles lay eggs in a variety of places, including holes and mound nests, depending on the species. A pit nest is normally dug in the sand, whereas a mound nest is usually made of grass. The duration of the nesting cycle varies from a few weeks to six months. Courtship is a long process that involves a number of behavioural behaviours that include a combination of snout rubbing and submissive displays. Mating is often done in water, and the couple can be seen mating many times. Females may build or dig a number of trial nests, one of which seems to be unfinished and discarded later. The egg-laying period is normally 30–40 minutes long and takes place at night. Females guard their nests and young with their lives. The eggs have a rigid shell, but they are transparent when they are laid. 7 to 95 eggs are laid depending on the crocodile genus. Crocodile embryos lack sex chromosomes, and sex is not determined genetically, unlike humans. Temperature determines sex; most hatchlings are females at 30 °C (86 °F) or less, and offspring of both sexes at 31 °C (88 °F).


Swamps, wetlands, and rivers are home to crocodiles, while some animals migrate to brackish water or the sea. The estuarine (or saltwater) crocodile (Crocodylus porosus) and the American crocodile (Crocodylus acutus) are also capable of swimming miles out to sea, but they prefer brackish and freshwater environments. Excess salt is excreted by the tongue's glands. The smooth-fronted caiman (Paleosuchus trigonatus) favours rocky, fast-flowing rivers in South America. The dwarf crocodile (Osteolaemus tetraspis) is mostly found in the rivers of West Africa's woodland regions. In the areas where they live, crocodiles can have an effect on nitrogen cycles, crocodile habitat structure, and fisheries productivity. 

Form and Function

The crocodilian type has evolved to live in an amphibious environment. The body is elongated, and the long, slender tail is ideal for swimming quickly. The highest areas of the head are the external nostril openings, pupils, and ear openings. And when the remainder of the head and body is underwater, these vital sense organs remain above the water's surface. On a raised section at the muzzle's point, the two nostril openings are close together. When the animal dives, membranous flaps will close these openings to keep water out. From the outer nostril openings to the internal nostril openings, or choanae, situated at the extreme posterior end of the palate, a long bone-enclosed nasal passage leads; a membranous flap in front of the choanae forms the posterior closing of the mouth cavity.

Evolution and Classification

  • Palaeontology

Crocodiles, like all snakes, are diapsids, meaning they have two holes on either side of their skull. Crocodiles also exhibit the most significant traits of the dinosaur family (subclass Archosauria). The upper and lower temporal fenestrae (openings behind the eye sockets) of the skull are separate, the crocodile teeth emerge from sockets, and the roof of the skull lacks an opening for the parietal gland, a median, a dorsal outgrowth of the brain. Crocodiles are a distinct order within the Archosauria since they also evolved a secondary bony palate that encloses the nasal passage from the exterior nasal openings to the choanae (internal nostrils). 

Distinguishing Taxonomic Features

External crocodile features such as the proportions of the snout, the bony surfaces on the dorsal side of the snout, the number of crocodile teeth, the number and configuration of the large knobs on the nape of the neck, and the crocodile characteristics of the dorsal plates are used to classify each species. The order Crocodylia is divided into families and genera based on the anatomical crocodile characteristics of their skulls. Alligators, for example, have a long, U-shaped snout and an "overbite," which means that all of the lower jaw's teeth fit inside (are closer to the tongue than) the upper jaw's teeth, while crocodiles have a short, V-shaped snout. While the alligator's mouth is closed, the big fourth tooth on either side of the lower jaw fits into a socket in the upper jaw; when the mouth is closed, no lower crocodile teeth are visible. When the crocodile's mouth is closed, the broad fourth tooth on either side of the lower jaw extends beyond the snout.

Critical Appraisal

Regarding the grouping of Eusuchia's living groups— alligators and caimans, true crocodiles, and gavials—a variety of viewpoints exist. Within the suborder Eusuchia, the three classes have been treated as separate families. Alligators and true crocodiles are the most closely related of these, and they are also considered as two separate subfamilies of the Crocodilidae family. The gavials are considered a third subfamily by some scholars. Some writers place Tomistoma schlegelii, the Malaysian false gharial, in the Crocodilidae family, while others place it in the Gavialidae family. In addition, the order Crocodilomorpha has been divided into two suborders: Crocodylia (or Crocodilia) and Paracrocododylia, according to one authority. The Crocodylia, according to this scheme, contain as infraorders the classes mentioned above as suborders. Thalattosuchia is an order of this system. 


The word crocodile is derived from the Ancient Greek krokódilos, which means 'lizard,' and is used in the sentence ho krokódilos tou potamo, which means "the lizard of the (Nile) river." There are many different Greek spellings for this word, including the later form krokódeilos, which is quoted in several English reference works. Crocodile hides, meat, oil, and claws are all derived from hunting this animal. The over-catching of this specimen has resulted in the extinction of this species in the wild. Breeding this animal in captivity is a growing business in some parts of the world, even though it is not a modern concept. Crocodiles are ancient marine snakes that have existed for millions of years. Crocodilians have been found in a variety of water sources, from freshwater to somewhat brackish. They have unique crocodile adaptations, which are features that help animals live in their natural environment, which is in and near water. Males have a higher growth rate than females. Temperatures relative to the environment and the available food supplies in the area they live in determine growth rates and maturity of crocodiles.

FAQs on Crocodile

1. Crocodile is Which Type of Animal?

Answer: Crocodile, (order Crocodylia, or Crocodilia), is one of the 23 species of lizard-like amphibian animals with a carnivorous diet that belongs to the reptile order Crocodylia. Crocodiles have slender legs with clawed webbed toes and sturdy jaws with many conical teeth.

2. What Makes a Crocodile So Dangerous?

Answer: The most aggressive crocodiles are the Nile and saltwater crocodiles. Humans are not attacked by all animals. Many animals are afraid of humans and can only bite if they are startled. Around the same time, crocodiles that threaten humans need protection as well.

3. Where Do You Find Alligators and Crocodiles?


In Water: These creatures can be found all over the world, particularly where there are slow-moving rivers and grasslands. Alligators prefer freshwater marshes, while crocodiles prefer saline lakes.

Geographical Distribution: Alligators can be found in China and the southeastern United States, especially in Florida and the Gulf Coast states. Crocodiles can be found in North, Central, and South America, Africa, Australia, and in a small portion of Asia. The Florida Everglades is unique in that it is the only location on the planet where both alligators and crocodiles coexist.