We have the largest of all living reptiles in North Queensland. These ‘saltie’ Indo-Pacific monsters measure up to 6 meters (20 feet), and originally arrived in our estuaries from the open ocean. Since then, they have settled into our mangrove swamps, deltas, estuaries, lagoons, and the lower stretches of our rivers. Salt water crocodiles are large, stealthy hunters best not taken at face value. They are the most dangerous of their species, and formidable and opportunistic predators to boot.
How Salt Water Crocodiles Bear Their Young
‘Salties’ court annually between September and October, when seasonal monsoons ensure water levels are at their highest. The female lays her eggs two months later. She often chooses the nursery site on a shoreline, alongside a tidal river, or on the edge of a freshwater swamp. Once chosen, she and her mate will defend the site against all comers.
The nest is a mound of mud and vegetation 1.75 meters long (69 inches), by 50 centimetres wide (21 inches). And with an entrance of half a meter diameter. A layer of leaves scratched over it helps keep 40 to 60 eggs warm and incubating happily. These eggs are relatively small by species standards, at 8 centimetres long (5 inches) by 5 centimetres (2 inches) wide.
The gender of the newly hatched salt water crocodiles weighing 70 grams (2.5 ounces), depends on the incubation temperature. They are invariably girls when incubated between 28 to 30 °C (82 to 86 °F). Between 30 to 32 °C, 86% are boys. Above that point, girls predominate again. We have no idea why this is the case. However, the system clearly works, since salt water crocs have been around for at least 6 million years.
Salt Water Crocodiles Make Good Mothers But Not Pets
Do not let a loving crocodile mother fool you for a moment. She is constantly on the lookout for an opportunistic meal as she responds to the yelping cries of hatchlings in the nest, and gently rolls stubborn eggs in her mouth to crack them open. Then she gathers her babies in her mouth and carries them to the nearest patch of open water. By now dad has lost interest, and may already be courting another girl.
Baby salt water crocodiles have a tough life, with just 1% surviving to adulthood. They are exceptionally aggressive – even against each other – and fight among themselves almost immediately after their mother takes them to open water. Here, they hone their fighting skills, and a sense of territoriality that ensures their survival. This is another good reason to back off when encountering an adult in the wild, even in the presence of a guide.
Salties Have Sheer Brute Force in Adulthood When Biting Down
While it takes 10 years for crocs to become sexually mature, they can live for 70 years, with some centenarians reported. Their young are open season for goanna monitor lizards, barramundi fish, wild boars, rats, and flying raptors. However, once they reach adulthood they are generally invincible, with their heads alone weighing 200 kilograms (440 pounds), and the highest bite force of all mammals, including the spotted hyena.
Despite this immense power, salt water crocodiles have a weak point. Nature invested most of their jaw muscles for chomping, leaving just a few to open their jaws again. They say a few layers of duct tape can keep them tightly shut. We are not about to try this gig. We prefer our crocs under controlled circumstances behind a stout fence.
Salt Water Crocodiles in Aboriginal Tradition
We will let the indigenous Wandjina legends from the mythology of ancient Australians have the final say about Australian salt water crocodiles. For the Wandjina are cloud and rain spirits who have watched over everything since time immemorial, and feature prominently in rock art. Dreamtime legends hold the Wandjina created our landscape, and our nation’s inhabitants that live here. Then they painted their images on cave walls when they died.
When they are angry, they punish the unjust with lightning, floods, and cyclones. According to their tradition, they banished salt water crocodiles from fresh water for becoming full of bad spirits, and growing too large, unlike the freshwater crocodile they somewhat revered. Hence, salt water crocodiles are largely absent in rock art, although a few examples from 3,000 years ago remain in Kakadu and Arnhem caves.
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