Crocodilians
Crocodilia
INDEX
WHAT ARE CROCODILIANS?
TYPES OF CROCODILIANS
CROCODILIAN FEATURES
CROCODILIANS MAKE GOOD PARENTS
WHERE DID CROCODILIANS COME FROM?
CROCODILIANS, MAN AND CONSERVATION
CROCODILIANS THAT ONCE ROAMED THE BAHAMAS
CROCODILIANS OF ARDASTRA GARDENS
WHAT ARE CROCODILIANS?
Crocodilians are the world’s largest reptiles and like all reptiles they are cold-blooded animals with scaly skin, they lay eggs and have lungs for breathing. There are 23 recorded species of crocodilians found throughout the tropical areas of the world (though a couple species live in temperate regions) and they all live in areas where the water meets the land (marshes, rivers, coastal areas, etc). The majority of species prefer fresh water but a couple of species prefer salt water. Crocodilians grow continuously throughout their lives, some can grow as large as 20 feet long and some may only get to about 5 feet in length. These animals can live a long time. A crocodilian in a zoo has lived to be 56 years old, but scientists do say that some crocodilians probably live up to about 100 years in the wild.
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TYPES OF CROCODILIANS
There are 8 living genera divided into 3 major groups, the alligators and caimans, the true and dwarf crocodiles and the true and false gharials. Collectively they are all known as crocodilians. The table below shows the differences between these groups and the different species.
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Types and descriptions
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Nest building
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Different species and where they are found
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Crocodiles
- Long triangle-shaped heads.
- When mouth is closed you can see the upper and lower teeth showing.
- Teeth vary in size.
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Nest under the ground.
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- American croc. (Crocodylus acutus) - North and central South America.
- Cuban croc. (C. rhombifer) - Cuba.
- Nile croc. (C. niloticus) - Africa, Madagascar
- Morelet's croc. (C. moreletii) - Central America
- Saltwater croc. (C. porosus) - S.E. Asia
- Jonston's croc. (C. johnstoni) - Australia
- Mugger croc. (C. palustris) - Indian subcontinent
- Orinoco croc. (C. intermedius) - South America
- Siamese croc. (C. siamensis) - S.E. Asia
- New Guinea croc. (C. novaeguineae) - Papua New Guinea, Irian Jaya
- Phillipine croc. (C. mindorensis) - Phillipines
- Slender-snouted croc. (C. cataphractus) - Africa
- West Africa dwarf croc. (Osteolaemus tetraspis) - Africa
- False Gharial (Tomistoma schegeli) - S.E. Asia
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Alligators
- Wide flat heads with round noses.
- When mouth is closed only the upper teeth are showing.
- Teeth vary in size.
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Nest above the ground.
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- American Alligator (Alligator mississipiensis) - South east Northen America.
- Chinese Alligator (A. sinensis) - East China.
- Spectacled Caiman (Caiman crocodilus) - South and central America
- Broad-snouted Caiman (C. latirostris) - South America
- Jacare Caiman (C. yacare) - South America
- Black Caiman (Melanosuchus niger) - South America
- Schneider's Caiman (Paleosuchus trigonatus) - South America
- Cuvier's Dwarf Caiman (P. palpebrosus) - South America
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Gharials
- Odd looking crocodilians.
- Snouts are long and thin, looks like a frying pan handle.
- Teeth are similar in size.
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Nest under the ground.
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- Indian Gharial (Gavialus gangeticus) - Indian subcontinent
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Click here for more information on the different types of crocodilians.
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CROCODILIAN FEATURES
The body of a crocodilian is made for living on land and in water. Crocodiles, alligators and gharials all have legs and feet for walking on land and long powerful tails for swimming. The tail is longer than the rest of the body and is equipped with very strong muscles,
providing the power behind the crocodilian as it swims through the water.
Crocodilians often have bony plates on their backs called, osteoderms, which help to protect them like small shields.
Crocodilians also have many features that make them powerful predators. They have large jaws with at least 60 teeth which are used to capture prey. These animals constantly replace lost or worn out teeth and a single crocodilian can go through as many as 3,000 teeth during its life-time. The jaws of crocodilians have powerful muscles for snapping shut, making it impossible for an animal to escape. However, the muscles that open their jaws are very weak.
As a rule, crocodilians eat fish most of the time, but large crocodilians will also eat turtles, mammals and birds. Most of the large animals are caught as they come to the water to take a drink.
Crocodilians are also good at stalking their prey. Their eyes and nostrils are located on the tops of their heads so they can breathe and look above the surface whilst hiding under water. These animals can easily be mistaken for a floating log by an unsuspecting animal coming to take a drink from the water. The attack starts when the crocodilian dives quietly under the water and swims toward its prey without being seen. When the animal takes a drink from the water the crocodilian uses it powerful tail to propel it forward and snag its prey.
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CROCODILIANS MAKE GOOD PARENTS
Most reptiles just lay their eggs and leave them to hatch on their own, but the crocodilian babies are heavily protected by their mothers. Crocodilians defend their nests and some species look after their young for several months after they hatch. This is necessary to ensure the survival of the young as many animals prey on the eggs and young of all the crocodilians. In some places only one out of every 25 crocodilians will survive to become an adult.
Crocodilians begin the parenting process by building a nest:
- Crocodiles and gharials dig a hole under-ground and lay their eggs inside, carefully arranging them into two or three layers separated by layers of leaves and they are then covered by a mound of sand.
- Alligators and caimans build their nests on top of the ground out of leaves, sticks and mud, arranging it into a 3 foot high by six foot wide dome. They scoop out a hole and lay the eggs inside.
The mother will remain close to the nest. Covering it with more leaves or splashing it with water to keep the eggs cool or warm as needed. The temperature of the eggs are important as that is how the sex of the young is determined. This is called Temperature dependant sex determination (TSD). For the majority of animals on the planet, the sex is determined by genes. For example, the genes (or sex chromosomes) that determine sex in humans are: XX (females), XY(males). Crocodilians lack sex chromosomes all together and rely on the environment to determine the sexes. For most species, temperatures around 89.6ºF (32ºC) will produce males and any temperature above or below this will produce females.
The incubation of the eggs depends on the species and the temperature. Generally, incubation can take anywhere between 45-90 days. When the eggs are ready to hatch the babies begin to “chirp” from inside the egg and this lets the mother know that her babies are ready to emerge.
Click here to hear the sounds of crocodilians
Baby crocodilians have a sharp scale on the end of their noses called an egg tooth, to help them break the shell open and disappears a couple of months after hatching.
The mother will often help her young by breaking open the nest, digging up the eggs or removing the leaves and then she will help the babies break out of the egg by gently crushing the shell in her mouth. She will also provide a safe haven for her young by letting them all scramble inside her mouth whenever danger approaches. She will continue to protect her babies for a few days before they begin to explore new territory.
WHERE DID CROCODILIANS COME FROM?
Crocodilians belong to a large and ancient group of reptiles known as the archosaurs or “ruling reptiles”, along with the dinosaurs (and later, the birds as well). This group first appeared more than 250 million years ago. The ancestors to the crocodilians appeared about 220 million years ago and were land-based animals called the Junggarsuchus sloani. These had the snapping jaws of a crocodilian but the limbs were built for walking on land. It was around 150 million years ago when dinosaurs began to take over the world, forcing many animals to find new niches, the crocodilian ancestors began to move to the water and the early bird ancestors took to the skies. It wasn’t until the dinosaurs went extinct around 65 million years ago that the crocodilians began to live the semi aquatic lives that they do today and they haven’t changed very much since.
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CROCODILIANS, MAN AND CONSERVATION
The future of these ancient animals is in human hands or rather on their feet. This is because people still desire to have products made from crocodilian skin, such as handbags, shoes and belts. Unless people stop buying these products, the crocodilians will end up like the dinosaurs, extinct. In the past 50 years, it is estimated that some 20 million crocodilians have been killed for the fashion industry alone.
Similar to all wild animals, crocodilians are also suffering from habitat loss as people continue to build in their territories and shoot them when they return to their former homes and nesting sites.
Fortunately, there are organizations trying to help save these magnificent creatures. Land is being put aside for them and many countries have enforced laws to control hunting. Also, many crocodilians are now being farmed to satisfy the demand for crocodilian skins, which does mean that fewer wild crocodilians will be killed but it still perpetuates the industry. If the market for crocodilian skins exists, then people will still take from the wild stocks as it is cheaper to take from the wild than to grow your own. Making it illegal to sell animal skin products all together and changing the way people view animals is fundamental to their survival.
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CROCODILIANS THAT ONCE ROAMED THE BAHAMAS
At some point, there was a type of crocodile roaming the Bahamas. Skeletal remains of Cuban crocodiles (Crocodylus rhombifer) have been found in a Blue hole in Abaco.
Cuban crocodile
(Crocodylus rhombifer)
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Endangered species
These crocodiles have the smallest range of any other crocodile. It is known that Cuban crocodiles used to be found throughout all of Cuba, the Cayman islands and the Bahamas but populations have become extinct in much of their former range and are now only found in the Zapata Swamp in the northwest of Cuba and in the Lanier Swamp on the Isla de Juventud just South of Cuba.
These crocodiles prefer fresh water habitats like swamps and marshes and rarely swim in sea water.
They are medium-sized and can grow to about 10 feet in length, with the males being slightly bigger than the females. They are typically darker on the top than the bottom and the top is speckled with a black and yellow pattern.
The juveniles tend to feed on arthropods and small fish and the adult Cuban Crocodiles eat mainly fish, turtles and small mammals. The Cuban crocodile has an extremely powerful tail and is noted for its ability to leap out of the water to capture small mammals in trees above the water. Fossil records suggest that they once fed on now-extinct giant ground sloths, which may have led to the evolution of their blunt and very wide rear teeth, now used for crushing turtle shells.
These crocodiles have been heavily hunted by people as their skins are used for purses, boots, wallets and briefcases and their meat is considered a delicacy. Today there are about 3000-6000 left in the wild and these numbers are declining. Still, much needs to be done to help save this species from extinction. Many zoos in North America have begun breeding programs with this species with the hope that one day they can be re-introduced to areas that they once roamed.
CROCODILIANS OF ARDASTRA
Ardastra has a crocodilian known as the Spectacled Caiman.
Spectacled Caiman
(Caiman crocodilus)
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Threatened species
The Spectacled Caiman earned its name from a bony ridge that exists between the front of its eyes called the infra-orbital bridge and makes the crocodilian look like it is wearing a pair of spectacles.
Caimans are small alligators that are found in Central and South America. There are nine different species and out of them all, the Spectacled Caiman is the most common and has quite a large range. They are native to Brazil, Colombia, Costa Rica, Ecuador, El Salvador, Guyana, French Guiana, Guatemala, Honduras, Mexico, Nicaragua, Panama, Peru, Suriname, Tobago, Trinidad and Venezuela. They have also been introduced to Cuba, Puerto Rico and parts of the Southern United States. This caiman is highly adaptable and is found in any wet, lowland habitat throughout its range. There are over one million individuals in the wild and this species has actually benefited from the fact that its skin does not tan very well, making it less of a target in the crocodilian skin trade. As other species have been removed from several habitats from over-hunting, the Spectacled Caiman has actually expanded its range over the past few decades. However, this good fortune is only temporary as when all the other crocodilians disappear, the Spectacled Caiman will be next. The Spectacled Caiman is also a popular choice for the black market pet trade as their smaller size makes them a more handle able target. However, they are naturally more aggressive than other species of alligators and so they do not make a good pet.
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