Aussie Crocs: Predator Extraordinaire
Updated: Feb 6, 2018
Michael Hutchins on April 29, 2016
Two types of crocodiles inhabit Australia and nature travelers to the northern, western and eastern parts of the country need to familiarize themselves with both the joys and the dangers of watching and being in proximity to these formidable predators.
A large saltwater crocodile basking at the waters edge.
Adult saltwater crocodiles or “Salties” (Crocodylus porosus) are the largest of all living reptiles. An adult male can reach over 20 feet in length and weigh in at over 2,000 pounds. Typical lengths and weights, however, are in 14-17 foot and 800-2000 pound range. Females are much smaller than males and usually do not surpass 10 feet in length.
These formidable, opportunistic, ambush predators should not frighten you away from a trip to Australia, but knowledge is power and, like any large predator, they deserve your respect and caution. Many areas are dangerous to swim in and even venturing too close to the shoreline or into shallow water is a bad idea in saltwater crocodile country. That being said, tourists are perfectly safe if they remain cautious.
Warning signs are common in crocodile habitat. They should be heeded at all times.
Though many areas of high danger are marked with warning signs, many are not and saltwater crocodiles do take an occasional unsuspecting, less knowledgeable tourist who gets too close to the water’s edge or tries to go swimming in crocodile country. On average, one or two people are killed annually in Australia. Saltwater crocodiles are known to swim long distances at sea and occasionally do show up on the Great Barrier Reef, but only rarely, which is fortunate for the snorkeling and scuba diving industry. In Australia, saltwater crocodiles have ventured as far south as Fraser Island, even showing up near Brisbane on occasion, especially during the warmer wet season.
Saltwater crocodiles will attempt to tackle prey of large size, including kangaroos, cattle and humans. Their hunting behavior is similar to that of other crocodilians. They swim slowly towards their prey, and with most of their cryptically-colored body underwater, and can go totally undetected until it is too late. Once close enough to strike, the animals can move remarkably fast to capture, grip and clamp down on prey with their tooth filled jaws. Saltwater crocodiles have the most powerful bite ever recorded under laboratory conditions, with a bite-strength of 3,690 pounds-force. Small prey are swallowed whole, but larger prey are dragged into deeper water where they drown. Often, the predator performs a “death roll”, spinning rapidly to kill the prey or to tear off large chunks of meat for consumption. Once the crocodile eats its fill, the remaining food is sometimes stored for later consumption.
Swimming crocodiles are very difficult to see as they maintain a low profile in the water and look like floating logs.
Once rare due to over-hunting, saltwater crocodiles are now thriving in parts of Australia, notably the northernmost parts of Northern Territory around Darwin, Western Australia and Queensland. Kakadu National Park, just east of Darwin is one of the best places to see them, and large individuals more than 16 feet in length are common there.
Saltwater crocodiles spend the tropical wet season in freshwater swamps and rivers, moving downstream to marine estuaries in the dry season. Coastal and estuarine mangrove forests are ideal places for them to hide and feed.
Typical mangrove habitat in northern Queensland.
Saltwater crocodiles are not as social as other crocodilians. For one, adult males are highly territorial and thus less tolerant of their own kind. A male will share his territory with a number of breeding females, but any rivals will be driven off as soon as they are detected, especially during the wet season when mating occurs. In Australia, courtship and mating generally occur in September and October, with egg laying occurring between November and March. Females build nests out of mud and vegetation. Fermentation of the vegetation creates warmth, which may aid in incubation. Sex of hatchlings is determined by ambient temperature.
Females typically lay between 40-60 leathery shelled eggs and are highly protective of their nests and young. They will guard the nest for 80-90 days after egg-laying. However, loss of eggs is still often high due to flooding and predation. Large goanna lizards, in particular, like to prey on crocodile nests. Once they hatch, baby crocodiles are eaten by a wide range of predators, ranging from predatory birds, such as storks to large fish, such as barramundi. Larger crocodiles will also prey on the young. Losses are heavy, with only around 1% of hatchlings surviving to adulthood. If they do reach adulthood, they can survive for more than 70 years.
Saltwater crocodiles are aggressive towards member of their species; this one is threatening another which got too close.
Salt water crocodiles have the most valuable skin of any crocodilian. In the 20th century, they were nearly hunted to extinction, but the advent of full legal protection in the wild, combined with the establishment of crocodile farming, saved the species from extinction. The greatest challenge to conservation has been negative human attitudes because of the danger that they occasionally pose to humans.
The other crocodile inhabiting Australia is the freshwater crocodile (Crocodylus johnstoni) or “Freshie.” Unlike the much larger and aggressive saltwater crocodile, the freshwater crocodile is a docile fish-eater and is not dangerous to humans, although it will bite if cornered or harrassed. This species has a more slender snout. A relatively small crocodilian, males can grow up to 9 feet and weigh 200 pounds, but the average range is 7 to just under 10 feet and 150 pounds.
The freshwater crocodile has a more narrow snout and is comparatively docile.
Freshwater crocodiles are found in the Australian states of Western Australia, Queensland and Northern Territory. As the name implies they are found primarily in freshwater wetlands, waterholes (billibongs), rivers and creeks. One of the best places to see them is in Katherine Gorge National Park in Northern Territory. It is generally considered safe to swim in areas inhabited only by freshwater crocodiles, and I have been in the water with them in Katherine Gorge. They can be found in the same areas as saltwater crocodiles and are saltwater tolerant, but complete poorly with them.
The author holding a baby freshwater crocodile in a water hole in Northern Territory, 1985.
Eggs are laid in holes dug in soft sand or soil during the dry season, usually in August. Nests are not defended during incubation, but around five days prior to hatching, the young start calling from their eggs. This both synchronizes hatching in the clutch and stimulates the adults to open the nest. As the young emerge, the adult picks them up in their mouth and transports them to water.
A freshwater crocodile egg. The nest had been raided by a sand goanna in Northern Territory.
Seeing these large Australian predators in the wild is akin to seeing lions and leopards in Africa. They should be admired at a distance and in safety, but they are magnificent animals and play an extremely important ecological role in their natural habitats. Let World Safaris show you the natural wonders of Australia.