What are crocodilians?
Crocodiles, alligators, caiman, false gharials and
gharials make up the crocodilian group, which has survived for about
200 million years. There are three families included in the
- Alligatoridae: the American and Chinese alligators, South
American caimans; 7 species
- Crocodylidae: crocodiles and the false gharial; 14 species
Gavialidae: the gharial; 1 species which is the Indian Gharial
Where do crocodilians live?
They are widely distributed throughout the tropical
and subtropical regions of Africa, India, South-east Asia,
Australia, North, Central and South America. They are found in
habitats such as swamps, ponds, rivers, lakes and marshes.
What is the difference between a crocodile and an
The main difference is in the shape of the heads.
Alligators have broad, rounded snouts whereas crocodiles have more
narrow snouts that taper to a point. The other difference is with
their teeth. Alligators have a wider upper jaw than lower jaw so
when their mouth is closed the teeth in the lower jaw are almost
completely hidden and fit into sockets of the upper jaw. In
crocodiles, the upper and lower jaw are the same width and so teeth
in the lower jaw fit outside when the mouth is closed. This makes
them look like they have interlocking teeth. Another difference is
the skin of a crocodile which is covered in sensory pits, whereas
alligators only have these pits near their jaws.
Are crocodiles more dangerous than alligators?
Some crocodiles are more aggressive than alligators.
There are probably more incidents of humans being attacked by
crocodiles than alligators because there are more crocodiles in
What do crocodiles and alligators eat?
Their diet is diverse. They prey on anything from
dragonflies and bats to sharks, antelopes and even buffalo. Although
attacks on humans have occurred, most species of crocodilian don't
include humans as a food source. In fact, it has been suggested that
a person bending down over a water source may resemble an antelope
in the eyes of a crocodile and this is why the attacks occur. The
species that habitually hunt humans are the Nile and Indo-Pacific
crocodiles. The American crocodile, black caiman and the Indian
mugger will on occasion kill humans for food or to defend their
nests or territories.
Why don't crocodiles and alligators eat very
Crocodilians are extremely energy efficient. They are
poikilotherms (cold-blooded), and so depend on external heat sources
to regulate their body temperature. Because of this, they do not
have to heat themselves using energy fueled by food as humans and
other mammals do. Usually crocodilians need only eat once a week or
less to maintain their energy levels.
Why do alligators and crocodiles often sit with
their mouths open?
This behaviour is called gaping and it is done when
the crocodile or alligator is basking in the sun. It is thought that
this may act in cooling the crocodile, however, since they also do
this during rain and at night it could suggest that gaping has a
social function as well.
How are they adapted to an aquatic
Crocodilians are well adapted to water, as well as
land. They are excellent swimmers and can hold their posture in
water. When submerging underwater they close their ear and nostril
flaps. When feeding underwater the back of the tongue acts as a
valve to stop water from going into their lungs. Crocodiles and
alligators can dive for long periods of time due to their slow
metabolic rate. Vibration sensors and touch receptors help them to
feel movements of prey in the water. They have a third eyelid,
called the nictitating membrane that protects their eyes underwater.
Why are many species of crocodilian
Some species are endangered due to habitat destruction
such as the Nile crocodile whose nesting areas along the river are
disrupted by boat traffic. Nearly all crocodilians live in the
rainforests and wetlands of developing countries which are being
destroyed by logging, development and other industries. Poaching
also lowers the crocodilian population. A multi-million dollar
business exists in the illegal trade of crocodilian hides. The
common caiman is the most hunted crocodile, and makes up 60% - 80%
of skins in the trade. However, their bony hides only receive a
tenth of the price that is paid for alligator or crocodile skins.
The American alligator was one of the first animals to receive
protection under the United States Endangered Species Act, they are
now no longer endangered but listed as 'threatened' instead. Steps
are being taken to alleviate poaching and repopulate species of
crocodilians by setting up crocodile farms.
How do crocodiles and alligators catch their
Prey is seized using the element of surprise.
Crocodiles sit camouflaged and motionless in the water waiting for
prey to come to them. Their eyes and nostrils are high on their head
so the rest of their body can be hidden under water. When prey is
only a short distance away the crocodile quickly snaps its muscular
jaws around the prey and drags it below the water to drown and
Where do they lay their eggs?
Females lay their eggs in holes they dig in the sand
or in large nests made of vegetation and mud. The mother will guard
the nest until she hears the cry of her babies, which break their
shells with an "egg" tooth. Without the babies call of distress the
hatchlings may never see light, since it is the mother who digs them
out of the mound of mud. She then picks up her babies in her mouth
and carries them to water, breaking the remaining shells and
swallowing them. The smallest of the crocodilians may lay 10 to 15
eggs, but larger species like the Indo-Pacific crocodile may lay 50.
Are there any crocodilians at the
The Aquarium houses three caimans that were born in
1978 at Fort Worth, Texas. They were sent here in 1983 from the
National Zoological Park in Washington, D.C. The Aquarium is the
temporary home for the Golden Crocodiles until April 2000. While
these rare and endangered crocs are with us, the caiman will be
removed from the exhibit. The Golden Crocodiles, also known as the
Indo-Pacific crocodiles, were born in Samutprakan Crocodile Farm in
Do crocodilians make good pets?
No. Some people keep baby alligators and crocodiles,
but when they grow to over 2 metres long and are difficult to house,
they no longer make ideal pets and often have to be put down. They
can be dangerous to keep as pets, potentially harming other pets or
How long can they hold their breath
Usually they can hold their breath from 4 - 15 minutes
but can remain underwater for 2 hours if needed and if they aren't
stressed. The record time spent underwater is 8 hours in freezing
conditions, this is because a colder crocodile uses less energy and
oxygen and can hold its breath longer than a warmer one.
Did you know?
- Shed their teeth regularly. No cavities, no dentists, they
have it easy.
- Can last months without feeding as long as their body
temperature remains low.
- Roar like lions. They also snort, jaw snap and tail slap to
establish courtships, dominance, territory, and aggression.
Crocodiles and alligators also communicate visually through body
language and with sub-audible vibrations which are transmitted to
animals both in the water and on the surface. These vibrations are
created by contracting their trunk muscles.
- Are only distantly related to the dinosaurs, while birds are
the closest living relative to dinosaurs.
- When the American alligator's swamp freezes over most of the
reptiles will survive by maintaining a hole through the ice in
which to breath.
- Mothers respond to the distress call of juveniles and defend
them against predators.
- Are the only reptile to have a four-chambered heart (all other
reptiles have a three-chambered heart).
- Have a muscular gizzard similar to birds - which is used to
grind up food prior to entering the stomach.
- Incubation temperature will determine what sex the juvenile
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