Friday, Jul 27, 2007 at 10:51
Crocodiles Does this answer your question?
Never trust a crocodile smile.
A crocodile has 66 teeth, each of which can be replaced many times during a lifetime.
Crocodile tears.
Crocodiles have a see-through third eyelid which is closed when it swims underwater.
Did you know?
The temperature at which crocodile eggs are kept during incubation determines the gender of the hatchlings. Low and high temperatures produce females while temperatures of 31-33deg.C produce males.
With snapping jaws and prehistoric looks, crocodiles are one of Australia's most feared animals.
Australia is home to two types of crocodile: the freshwater crocodile (Crocodylus johnstoni), and the estuarine (saltwater) crocodile (Crocodylus porosus). Both live in northern Australia, mainly across the top of Queensland, Northern Territory and Western Australia.
Both types are important to conserve, because Australia is the only country inhabited by the freshwater crocodile, and the estuarine crocodile is a threatened species.
In fact, Australia is one of the very few
places in the world where estuarine crocodiles have a chance to survive.
Beware! Although these animals are important to conserve, they can pose a serious threat to people. Freshwater crocodiles pose less danger but estuarine crocodiles are very dangerous animals.
What does it look like?
Freshwater crocodiles are
grey or olive-brown with ragged dark mottling. A freshwater crocodile can be distinguished from an estuarine by its narrow snout, needle-like teeth and row of four large scales on
the neck immediately behind its head.
A male freshwater crocodile rarely grows larger than 2.5m in length while the female is usually under 2m.
Estuarine crocodiles are
grey, olive-brown or almost black, with ragged dark mottling. Unlike the freshwater crocodile, the estuarine crocodile has a broad snout, thick teeth and no row of large scales on its neck.
An adult male can reach 7m in length, although most are less than 5m. Females are usually under 4m.
Where does it live?
Freshwater crocodiles make their home in inland freshwater rivers, billabongs and swamps of northern Australia. These crocodiles move into new areas during the wet season (November-April).As the floodwaters recede, the crocodiles return to their usual habitats.
The freshwater crocodile is found only in Australia. In Queensland, they are found mainly in rivers of
Cape York Peninsula and the Gulf of Carpentaria.
Estuarine crocodiles are found throughout south-east Asia - from India all the way south to Australia.
They are found across northern Australia in fresh and salt
water habitats. In Queensland, estuarine crocodiles lives mainly in coastal waters between
Rockhampton and
Cape York and throughout the Gulf of Carpentaria.
Although it lives mainly in the tidal reachers of rivers, the estuarine crocodile is also common in freshwater lagoons and swamps and beaches. This crocodile can even be seen in inland waterways hundreds of kilometres from the sea and on Great Barrier Reef islands.
What does it eat?
Crocodiles are top of the food chain in wetland environments, preying on many different animals.
Freshwater crocodiles are active during the day but forage mostly at night. They eat small things like insects, fish, frogs, lizards, turtles, bats and birds.
Mainly nocturnal,
young estuarine crocodiles munch on fish, frogs, prawns, crabs and insects. Larger crocodiles eat larger prey such as pigs, wallabies and even other crocodiles.
To capture prey, both types of crocodile wait in ambush at the
water's edge and then lunge or snap sideways at animals which come to feed or drink. Another method is dragging prey underwater, then twisting it in a 'death-roll' until it dies or disintergrates.
How does it breed?
Freshwater crocodiles nest in August and september during the dry season. About 12 eggs are laid in simple holes dug in sand or soil near the
water's edge. Incubation takes 65-90 days, so the
young usually hatch before the first floods of the wet season.
When about 12 years old, a female estuarine crocodile will make a nest, a large mound of soil and vegetation, on the banks of a watercourse or freshwater swamp. She will then lay about 50 eggs and guard the nest during incubation, which takes about 90 days.
Sex of the offspring is determined by incubation temperature: low and high temperatures produce females and temperatures of 31-33 deg.C produce males.
When the
young estuarine crocodile hatches from its egg, it squeaks to attract the mother.
The female protects the estuarine crocodile hatchlings for four to five weeks. Distressed hatchlings squawk loudly to attract the mother's attention. The mother comes immediatly to defend her offspring from predators.
Where is it seen?
Seeing crocodiles in the wild is difficult - they are very wary and may stay underwater when people are around.
However, if you are careful you might see a crocodile. Crocodiles spend much of their day basking in the sun, sheltering among plants or in mud. Slide marks along river banks and beaches are a good indicator they may be close.
Threats to survival
Less that one percent of the eggs laid by an estuarine crocodile reach adulthood. Floods destroy many crocodile nests.
Young crocodiles are eaten by other animals, even other crocodiles!
Public antagonism towards crocodiles is also a threat to their survival. Unless the community values crocodiles and their habitats, it will be difficult to promote their long-term conservation.
Protection
While crocodiles are killed in other countries for their skins, Australia's two species of crocodiles are protected. In Queensland, interfering with crocodiles or their eggs and possessing or taking parts of crocodiles are illegal without a licence from the Queensland Parks and Wildlife Service.
The Service has been conducting research on the biology of freshwater and estuarine crocodiles for many years. Through research, it hopes to:
assess crocodile numbers and locations;
determine their ecological role in
water ecosystems;
understand their reproductive biology and
population traits; and
encourage conservation and management of healthy wild populations, while keeping the risk to people as low as possible.
Keeping the balance between protecting crocodiles and protecting people from crocodiles is a challenge for the Environmental Protection Agency.
The Agency is concerned about crocodiles being in
places where people live. Potentially dangerous crocodiles are often captured and relocated away from people or made available to zoos.
The future
Crocodiles are one of few remaining links to our prehistoric past. As predator and prey, crocodiles play an important role in keeping our wetlands healthy.
Grrr!!!
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