Dangerous Australian Marine Wildlife Part I

Aussie, Oz, Down-under - no matter what moniker it goes by there's one thing that visitors to this land all seem to ask at one time or another: 'Why is everything trying to kill me?'.

At first glance, it's a fair question. Australia is indeed endowed with some of the most venomous, toxic and potentially dangerous animals and plants on the planet.

However, context is important, so I thought we'd take an unordered look at some of our less than loved critters and see just how "Dangerous" they really are.

Beginning with: Chironex fleckeri, the infamous Box Jellyfish.


Chironex fleckeri Source: ViralPortal





Carybdea branchi Sth Africa Source: Two Oceans Aquarium


Carukia barnesi Credit: Dr Lisa-ann Gershwin CSIRO 


Carukia barnesi, (The Common Irukandji pictured above), is one of the worlds smallest Box Jellies and is one of an unknown number of species believed to be responsible for Irukandji Syndrome. An extremely unpleasant reaction to the animals venom that can include:


Excruciating muscle cramps in the arms and legs, severe pain in the back and kidneys, a burning sensation of the skin and face, headaches, nausea, restlessness, sweating, vomiting, an increase in heart rate and blood pressure, and psychological phenomena such as the feeling of impending doom.

The sting is moderately irritating; the severe syndrome is delayed for 5–120 minutes (30 minutes on average). With symptoms lasting from hours to weeks. Victims usually require hospitalisation. ^


Only two deaths have been attributed to the Irukandji, although this figure could be low due to misappropriation. Around 50-100 people are hospitalised annually in Australia.

In Oz, the Box Jelly (or 'Marine Stinger'), has been responsible for the deaths of at least 70 people but probably more, with an average of one person a year being killed after coming in contact with them. As dangerous as these animals undoubtedly are, here in Australia we actually get off pretty lightly:


In parts of the Malay Archipelago, the number of lethal cases is far higher (in the Philippines alone, an estimated 20-40 people die annually from Chirodropid stings), likely due to limited access to medical facilities and antivenom ^


It would be nigh on impossible to overlook our next dangerous Australians. The Sharks:

Sharks have been getting a bad rap for as long as people have ventured into and on to the sea. Tales of catastrophic losses of life abound - with one in particular being forever immortalised by the movie Jaws (1975).


The USS Indianapolis was sunk by the Japanese on July 29 1945. Of the 1,196 men aboard, an est 900 made it into the water alive. Their ordeal, considered the worst shark attack in history, was just beginning.

The first night, the sharks focused on the floating dead. But the survivors’ struggles in the water and the scent of blood only attracted more sharks. As the sharks turned their attentions toward the living, especially the injured and the bleeding, sailors tried to quarantine themselves from anyone with an open wound, when someone died, they would push the body away.

When eventually rescued, only 317 of the Indianapolis’ original 1,196-man crew remained.

Estimates of the number who died from shark attacks range from a few dozen to almost 150. ^


In Australia, shark attacks are heavily reported by the media: Fatal shark attacks in WA since 2000

Recently people (often those most at risk from shark attack), have been rallying to the animals defence:


A navy clearance diver who lost a leg and a forearm in a shark attack has come out against the Western Australian shark cull, describing it as "stupid" and a "knee-jerk reaction".

Paul de Gelder was on exercises in Sydney Harbour in 2009 when he was attacked by a bull shark that bit off his arm and leg. Since then he has had to use specially made prosthetics.

But despite his experience, Mr de Gelder, originally of Canberra, said he was completely against Premier Colin Barnett's proposed shark cull, spelling out his opposition in a blog post on Wednesday morning. ^


The above quote is referencing the push by Western Australias' premier Colin Barnett to introduce shark culls following a spate of attacks.

What many Australians (and therefore visitors to these shores may not be aware of), is the continued and long-term culling of sharks in other states and territories:


Nearly 700 sharks have been killed in the last year*, in Queensland's shark control program.

Figures from the Fisheries Department reveal that in the 12 months to August, 667 sharks including endangered species such as the great white and grey nurses were killed.

Around 100 dolphins, turtles and dugongs were also unintentionally killed. ^

*Article quoted was published in 2014


Lemon Shark (Negaprion acutidens) Credit Albert kok 


The Lemon Shark (above), is classed as potentially dangerous and has attacked people. However, according to the good people at The International Shark Attack File none of these attacks were in Australian waters - so we can (respectfully), move on.

The following shark is another story entirely. The mighty, and highly aggressive Bull Shark.


Bull Shark (Carcharhinus leucas) Credit: Albert kok



Studies have shown that the Bull Shark has the highest levels of testosterone ever measured in any animal - land or sea. A while ago I learnt first-hand just how pugilistic these animals can be:

A friend and I were working in the Top End (Cape York), and had decided to cruise out to a river mouth to do a spot of fishing. We settled in and I managed to snag myself a 'Barra' ... things were looking up when suddenly Dan's line went ballistic. After a short but violent struggle he managed to get the fish close to the beach.

Being a helpful sort'a bloke I splashed in and grasped the shark by the tail in order to get it onto land where we could remove the hook (we had no intention of killing the shark). Unfortunately, the shark wasn't aware of this, and with astonishing speed promptly brought its head around in an impossible arch, its gnashing teeth barely missing my exposed calf.

The accuracy and speed of the 'strike' was mind blowing ... and this while the animal was out of the water!.


About 1.8m T/L (The hook was removed and the shark released)


Obviously, the shark was simply defending itself - I've included the experience just to highlight how easy it can be to inadvertently place yourself at risk, and perhaps even more importantly skew animal 'attack' statistics.

So what's the reality? Are our sharks really that dangerous?. Regrettably, the statistical answer is yes. Oz is a world leader when it comes to fatal unprovoked shark attacks.

I wonder though, if this doesn't say more about us and our behaviour, than it does about our sharks and theirs?.

Time to move on to some of our perhaps less known potentially dangerous critters.

The Blue-ringed octopus:


Hapalochlaena sp Credit: David Breneman 


Credit: Elias Levy


Despite its small size the blue-ringed octopus carries enough venom to kill up to twenty-six adult humans within minutes.

Bites are often painless, with many victims not realising they have been envenomated until respiratory distress and paralysis start to set in.

No blue-ringed octopus antivenom is available yet, making it one of the potentially deadliest reef inhabitants in the ocean. Edited ^


This exquisite octopus is, perhaps, a bit of a stretch for this list as it's so shy and retiring - with (so far as I am aware), all known envenomations a result of the octopus being harrassed. That said, it has caused at least three fatalities (two in Australia and one in Singapore ^).

Not to mention that its venom is really quite remarkable. So on the list it stays.


The major neurotoxin component of the blue-ringed octopus is a compound that was originally known as maculotoxin but was later found to be identical to tetrodotoxin, a neurotoxin also found in pufferfish, and in some poison dart frogs.

Tetrodotoxin is 1,200 times more toxic than cyanide. Its action blocks sodium channels, causing motor paralysis and respiratory arrest within minutes of exposure.


As noted above - this small animal is of little actual threat to people when left alone, however its 'reputation' belies this fact. Perhaps there's more going on here than an ancient continent jam-packed with bloody thirsty wildlife eh?

More to come in Part II



END OF PART I


Huge thanks to everyone who made their beautiful photographs and research available for use. I have done my utmost to credit accurately. However, if I haven't gotten it right, please contact me either through the comments section or by PM on twitter via @Garden_Guests. And I'll sort it out ASAP.

Till next time, take care -

Paul :)

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