Saltwater Crocodile Safety Information

I awoke to the sobering news that a visitor to our rainforest had been attacked and presumably killed by an Estuarine Crocodile or Salty, last night. According to the ABC:


A 46-year-old woman, from Lithgow in New South Wales, was swimming with a friend at Thornton Beach about 10:30pm on Sunday.

Senior Constable Russell Parker said the women were waist-deep in the water when one of them was taken by the crocodile. ^


For her family and friends this is an appalling and traumatic event. And I have no interest in adding to their pain by focusing any more on the attack itself.

Instead I thought I'd put together a post on our crocodilian neighbours - including some info on how to co-exist with them, as hype free and fact based as I can. Because I know from past experience that this latest attack will fuel the fire for those who would like to see crocodiles culled, or even wiped out entirely from the region. And that, in my opinion, would turn a tragedy into a disaster.

The Estuarine, or 'Saltwater' crocodile is the largest living reptile on the planet today. It is known for its aggressiveness and has the strongest bite force of any animal recorded, (with 3,700 pounds per square inch (psi), or 16,460 newtons of pressure ^). They can weigh over 1,000 kilograms and are able to exit the water with explosive speed and power when attempting to ambush prey (around 12 metres per second or 43 kph ^). However, such speeds last a very short time and are not maintained.

As I mentioned, Crocs are primarily ambush predators, they rely on their superb camouflage and their highly evolved senses to capture food. These senses include ISO's or DPR's (integumentary sense organs or dome pressure receptors). Such organs help the crocodile to feel pressure changes in the water and vibrations caused by other animals such as fish as they swim.

The term 'Salty' is a bit of a problem as the Estuarine crocodile can be found in any water-way within its range, irrespective of salinity. For a croc, consistent temperature gradients and food availability are far more pressing concerns. That said, they are often found in salty to brackish water and have developed special glands to deal with the build up of sodium chloride in their bodies.


The apparent absence of salt glands in marine and estuarine Crocodilia has long been a puzzle. However, we have identified glands in the tongue of Crocodylus porosus which exude a concentrated secretion of sodium chloride. The glands are similar in ultrastructure to other reptilian salt glands and undoubtedly play a major role in electrolyte regulation.

In the estuarine crocodile, Crocodylus porosus, clear fluid exudes from numerous pores scattered over the upper surface of the tongue. The secretion is stimulated by injection of methacholine chloride, ishyperosmotic to the body fluids, and contains high concentrations of both sodium and chloride, pointing to the existence of a major and hitherto unknown salt gland in the Crocodilia ^


Although as adults estuarine crocodiles are northern Australia's undisputed apex predators, life in the beginning is tenuous at best:


Breeding territories are usually established along tidal rivers, creeks and freshwater areas. Females reach sexual maturity at lengths of 2.2 to 2.5 m (10 to 12 years old). Males mature later (3.2 m, at around 16 years old). Females on average lay 40 to 60 eggs (this can range from 25 to 90) in mound nests made from vegetation (usually grasses and vines) and mud. These are normally constructed between the months of November and March during the wet season, but this varies slightly geographically. The mound helps to insulate the eggs from temperature extremes, hides them from predators, stops them from dehydrating, and also serves to raise the eggs above the ground to minimise the risk of flooding. Many nests are still flooded every year, however, killing all the unhatched embryos - in saltwater crocodiles flooding is the main cause of embryo mortality, not destruction by predators.

Although the female stays near the nest, eggs do occasionally fall foul of predators (e.g. monitor lizards, feral wild pigs in Australia) and human egg collectors. Juveniles normally hatch after 80 to 90 days but this varies with temperature (80 days at a sustained 32 celsius, longer if cooler). The female digs the hatchlings out of the nest when they start their characteristic chirping sounds, assisting some of them to the water by picking them up carefully and carrying them within the mouth.

It is estimated that less than 1% of hatchlings will survive to reach maturity, due to flooding, predation (e.g. turtles, goannas, C. johnstoni), competition for resources, and social pressures (territorial males will kill and eat juveniles - they are one of the limiting factors in population growth along with competition) ^


Juv Crocodylus porosus 7-8 weeks old atop a broken tree stump





The little guy above had climbed some considerable distance up that stump and according to Ray, a local guide with Bruce Belcher’s Daintree River Cruises, will leap to the safety of the water at the first hint of danger. Thus earning the moniker of 'High Diver'.

Crocodiles are at home in the water - it is their preferred environment and normally only venture onto land to lay their eggs or thermo-regulate. They do not, as a rule actively hunt on land ... of course, you know what they say about rules ...


A NINETEEN-year-old man is in hospital in Katherine after he was attacked by a crocodile in his tent this morning.

Peter Roswell was on a camping trip with his family at Palm Creek near Bradshaw when he was attacked at 4.30am.

Department of Health spokeswoman Gail Liston told the NT News the crocodile bit his right foot. The man managed to free himself from the crocodile’s jaws. The crocodile then slid back into the water. ^



The snippet above is really just the tip of the iceberg. A simple online search will turn up numerous accounts of people being attacked on land, usually while sleeping. This points to some other salient facts regarding crocodile behaviour:

1. They are nocturnal (although often seen moving about during the day)
2. They are opportunistic hunters

Knowing this - it stands to reason that the recommended safe distance to camp from waterways in croc country is at least 50 metres - no, seriously.

Here are some guidelines to take note of if you're unfamiliar with crocodiles (or, in fact - if you've been around them your entire life)


Originally compiled by the N.T Govt.

  • Obey crocodile warning signs - they are there for your safety and protection.
  • Never swim in water where crocodiles may live even if there is no warning sign present.
  • Swimming or standing in water above knee-height near a crocodile warning sign or where estuarine crocodiles are frequently seen, is illegal in protected areas (you can still enter the water if you have a reasonable excuse, e.g. launching a boat).
  • When fishing, always stand a few metres back from the water's edge and never stand on logs or branches overhanging the water.
  • Never clean fish or discard fish scraps near the water's edge, around campsites or at boat ramps.
  • Stay well back from any crocodile slide marks. Crocodiles may be close by and may approach people and boats.
  • Boats and vehicles must never be brought within 10m of an estuarine crocodile in the wild - it is illegal unless part of a commercial crocodile viewing tour, or there is a reasonable excuse, e.g. where a creek is less than 10m wide.
  • Never dangle your arms or legs over the side of a boat. If you fall out of a boat, get out of the water as quickly as possible.
  • Never provoke, harass or interfere with crocodiles, even small ones.
  • Never feed crocodiles - it is illegal and dangerous.
  • Camp at least 2m above the high water mark and at least 50m from the water's edge. Avoid places where native animals and domestic stock drink.
  • Never leave food scraps, fish frames or bait at your campsite. Always check that previous campers have not left these behind.
  • Never prepare food, wash dishes or pursue any other activities near the water's edge or adjacent sloping banks.
  • Be more aware of crocodiles at night and during the breeding season, September to April. ^


Always keep in mind that the estuarine crocodile is one of the very few animals (along with the polar bear and tiger shark) who view human beings as prey.


Only In Oz ...
Between 1838 and 1902 it was illegal to swim at the beach during the day!


'Yawning'


A little surprisingly crocodiles are quite communicative - both by using body language and audible sounds. The croc above yawned spectacularly (the jaws in this pic are about half-way open) and such displays are probably a warning to interlopers that the animal is not in the mood to be trifled with. But please remember that on the whole, stealth and camouflage are their forte, just because you cannot see a crocodile does not mean that it hasn't seen you.

Although some crocs are seemingly better at such strategies than others ...


Ummm


At the end of the day, we might accept that life is a risk. However in the case of crocodiles we really only need to be informed and willing to modify our behavior when venturing into their habitats to mitigate the risks that crocs pose. It also pays to keep in mind that in Australia:


According to statistics compiled by the National Coroners Information System, horses are the animals most likely to cause a human death.

Cows are the next most dangerous, followed by dogs. Sharks are in fourth position, while crocodiles and spiders account for only slightly more deaths than emus, cats and fish. ^

Despite these facts, ya don't see anyone calling for a cull of horses do you?


Something to think about - especially now that those daft bloody politicians are, as predicted, calling for a croc cull.

Anyway, I hope you got something out of this post - and for Gods sake, take care eh?
 - Paul.




The saltwater crocodile (Crocodylus porosus), also known as the estuarine crocodile, Indo-Pacific crocodile, marine crocodile, sea-going crocodile or informally as salty, is the largest of all living reptiles, as well as the largest terrestrial and riparian predator in the world. Males of this species can reach sizes up to at least 6.30 m (20.7 ft) and possibly up to 7.0 m (23.0 ft) in length. However, an adult male saltwater crocodile rarely exceeds a size of 6 m (19.7 ft) weighing 1,000 to 1,200 kg (2,200–2,600 lb),[4] females are much smaller and often do not surpass 3 m (9.8 ft). As its name implies, this species of crocodile can live in salt water, but usually resides in mangrove swamps, estuaries, deltas, lagoons, and lower stretches of rivers. They have the broadest distribution of any modern crocodile, ranging from the eastern coast of India, throughout most of Southeast Asia, and northern Australia.

This crocodile is a formidable and opportunistic hypercarnivorous apex predator. Most prey are ambushed and then drowned or swallowed whole. It is capable of taking almost any animal that enters its territory, including other apex predators such as sharks, a variety of freshwater and marine fish, including pelagic species, invertebrates, such as crustaceans, various reptiles, birds and mammals, including humans. Due to their size, aggression and distribution, saltwater crocodiles are regarded as the most dangerous extant crocodilian to humans ^

If you're interested in learning more - head to: CrocBITE and/or CROCODILIANS Natural History & Conservation

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