Crocodiles and Alligators

Crocodylia - genus Crocodylus
The smallest crocodile is Cuviers Dwarf Cayman(Caiman).
The largest crocodile is the Salt Water Crocodile.
Size ranges from about 1.5m up to 9m.
Crocodiles have a narrow snout and jaw with a lower tooth that juts out when the jaw is closed. The snout is V shaped.
They are covered with non-overlapping scales which are shed individually. Feet are webbed as they are aquatic. Eyes and nostrils are set high on the head, which allows the croc to be almost completely submerged and still keep an eye on everything. They have very good night vision like a cat, and their sense of hearing and smell is excellent. The jaw is very powerful on closing, not so powerful on opening as the biting down muscles are stronger. This allows handlers to tape the jaw closed and be confident that the croc is unable to open the jaw to break the tape. The croc has a powerful tail, it is broad, heavy and thick and acts like a rudder when they are swimming. The legs are short and can move very quickly on land. The crocs walk in two ways, a low belly walk and a semi-erect high walk that helps them to move quickly.
The teeth of crocodiles grow continually until old age. As one falls out it is soon replaced by one that is growing inside the old tooth. They go through about 3,000 teeth per lifetime.
Crocodiles can live over 50 years.
Crocodiles can be seen quite often lying with the mouth wide open, this is called gaping, and believed to be a way of cooling down.

Crocodylia - genus Alligator family Alligatoridae
The alligator was originally named by Spanish explorers and settlers in Florida. They called the alligator el lagarto (the lizard).
There are two species of alligator.
The American alligator(Alligator mississippiensis)
The Chinese alligator(Alligator sinensis)
The American alligator is much larger, about 4m to 5m long and weighs about 360kg. The chinese alligator is only about 2m long.
Alligators look very much like crocodiles. They have a broad, wide snout that is U shaped.
They don't have the protruding lower tooth that crocodiles have, and they are not as aggressive as crocodiles.
Alligators also have a heavy body with a slow metabolism but can move very quickly.
Crocodiles and alligators also have a stomach with two chambers. The first stomach is powerful and muscular and contains gastroliths (stomach stones which the croc has swallowed) The other stomach is very acidic, (more than any other animal) this enables the digestion of just about anything including bones and feathers.

Crocodiles and Alligators live in warmer continents. They like hot, humid, swampy conditions (temperatures over 30 deg C).

CROCODILES:-

Crocodiles are found in America, Africa, Australia, Asia, Mexico, Central America and South America.

American Crocodiles:- found in the Florida Keys, the Everglades, Mexico and Central America.
African Crocodiles: found in the Nile river and surrounds.
Indo-Pacific Crocodiles:- found in South-East Asia, Australia, Phillipines and Indonesia.
The Cayman(Caiman):- Central and South America and Southern Mexico

ALLIGATORS:-

Alligators are found in the USA and China

American alligators:- found in Florida, Louisiana, Alabama, Mississippi, Georgia, North and South Carolina, Texas, Oklahoma and Arkansas
Chinese alligators:- These alligators are endangered. Found in the Yangtse River Valley.

Florida has both crocodiles and alligators.

Alligators prefer freshwater and live in wetlands, rivers, lakes and swamps.
Crocodiles usually live in saltwater, but can survive in freshwater. They also have special glands to filter out the salt. Alligators don't have this gland.
Crocodiles live in swamps and rivers and have been seen quite far out at sea.

Crocodiles and Alligators are territorial and will defend against intruders. Females will defend their nests. Crocodiles especially are very aggressive and will kill and eat humans.
Crocodiles and alligators ambush their prey by stealth. The prey is grabbed and dragged underwater to drown. The crocodile rolls in the water with the prey, this is called the 'death roll'. They are carnivores and will eat other reptiles, birds, antelopes, large fish, mammals, turtles and even baby crocs.
Baby crocs and alligators eat fish, insects, snails, crustaceans and worms.

Human deaths from crocodiles are on the increase due to intrusions on their habitat. The Nile river crocodiles have the worst record for human fatalities.

REPRODUCTION

Mating occurs in eary spring. Crocodiles and alligators lay between 20 and 100 eggs.
Nests are buried in the sand above the water line or built out of mud, leaves and other vegetation.
Eggs hatch in two to three months. The sex of the offspring is determined by the temperature of the nest between days 7 to 21 of incubation. Temperatures less than 30 deg C. result in female offspring, higher temperatures result in male offspring. Mum protects the nest against intruders and then helps the hatchlings to the water. Few hatchlings survive as they are eaten by predators including adult crocs and alligators.

Visit the Crocodiles at Australia Zoo

Jaws - Crocodiles - same width
Alligators - upper jaw is wider than the lower jaw, although I wouldn't get close enough to check that one out!
Snout - Crocodiles V shaped
Alligators U shaped
Teeth - Crocodiles have an exposed lower 4th tooth
- Alligators don't have this
Feet - Crocodiles have jagged fringes on hind legs and feet
- Alligators don't have this
Water - Crocodiles found in saltwater
- Alligators found in freshwater
Gland - Crocodiles have a special gland to filter out salt from the water
- Alligators don't have this
Colour - Alligators are usually darker in colour than crocodiles. This is due to the quality of the water in which they live.
Behaviour - Crocodiles are more aggressive
- Alligators will retreat from danger and are more timid.

FARMING

Alligators - Alligator farms exist in Georgia, Louisiana, Florida and Texas. Hides are sold for good prices.
Alligator meat is used in jambalayas, soups and stews. Alligator meat is low in kilojoules.

Crocodiles - Crocodile farms exist in Australia, Asia and Africa.
Meat is eaten in Australia, Ethiopia, South Africa, Cuba and Thailand.
Skins are made into wallets, briefcases, handbags, shoes, belts and hats. Only the underside of the croc skin is used.

Largest crocodile was 8.6 metres long and weighed 1352kg. Killed in Australia in 1957

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Caimans are common throughout South America and Central America. They live in wetlands and the Amazon river basin. Caimans have a bony ridge above their eyes. They are nocturnal and eat birds, turtles, fish and reptiles which they swallow whole.

Spectacled Caiman

The spectacled caiman can grow quite large. It's bony growth makes it look like it's wearing spectacles.

Schneider's Dwaft Caiman

Also called The Jacare - mostly green in colour and smaller in size.

Black Caiman

Has dark brown to black skin and flatter skull and a narrow snout. This caiman also has red eyes which no other species of caiman has. Can grow quite large. Similar to an American alligator.

Broad-snouted caiman

This caiman has a broad snout with a large mouth. Eats snails, fish and frogs. This caiman is endangered.

Cuvier's Dwarf caiman

This caiman is the smallest of all crocodilia. Sometimes kept as a pet in South America. Eats rodents, fish and insects.

The spectacled caiman is the most common. Reasons for this are believed to be that:-

1. The caiman is more adaptable to environmental changes than other crocodilia.
2. They can survive quite well in both salt and fresh water.
3. They are more maternal than other crocodilia. The babies are looked after in creches by an adult female, so more survive into adulthood.
4. The caimans are not as suitable for skinning as other crocodilia, so their numbers have increased as a result.

The Indian Gharial (garial) is a crocodile like reptile. It is critically endangered.
Only the saltwater crocodile lives longer than the gharial.
The gharial has a very long narrow snout. Male adult gharials have a bulbous growth on the tip of the snout. This growth is called a 'ghara' (pot).
The gharial lives mainly in calm areas of rapidly moving rivers in the sub-continent. The only time the gharial leaves the water is to bake in the sun or to build a nest on the riverbank.
They eat mainly fish which they can catch easily and hold onto with their numerous very sharp teeth.
They don't have the strength in the jaws to catch and kill larger animals.
The adult gharials are dark olive in colour and babies are pale olive with some brown spots.

Gharials are found in Pakistan (river Indus) - almost extinct.
Bangladesh, Bhutan and North East India (river Brahmaputra) - almost extinct.
Bangladesh, India and Nepal (river Ganges) - small numbers on the increase.