Dangerous animals of the
Great Barrier Reef
Australia has long held a reputation for hosting many of the world's most dangerous animals, and the Great Barrier Reef makes no exceptions!
It's not at all uncommon to find dangerous marine animals in warm tropical waters throughout the world, and given the diversity of animal species that live on the Reef it's normal to find quite a variety of ones that will sting or bite.
The more common dangerous animals of the Great Barrier Reef include jellyfish, sea snakes, several species of fish and - believe it or not - a certain species of shellfish and octopus.
In no particular order, here are the most common of these dangerous animals:
Box Jellyfish
Without doubt the Box Jellyfish is the most infamous of the Reef's jellies and can be found swimming close to the shoreline in the summer months.
Box Jellyfish are so named because of the box shaped bell (body), with tentacles that can reach lengths of up to 3 meters. Their near-invisible transparency makes them very difficult to spot and many swimmers have fallen victim to the agonising stinging and burning that the highly toxic venom produces.
Box jellies breed in the mangrove swamps of northern Australia, which is why they are found so close to the shore. During the summer months, most popular beaches have netted swimming areas and it's a very good idea to keep inside them!
A single sting from a Box Jellyfish can be painful but bearable, but a sting normally results in the swimmer panicking in the water and thrashing around - this usually results in 'tentacle entanglement' and lots more stings.
While enough venom can kill an adult, another danger is death by drowning as a result of the panic. Box jellyfish tentacles on a victim can be neutralised by pouring vinegar on the effected area.
Irukandji Jellyfish
The Irukandji has made quite a reputation for itself, based on it being an undetected danger until relatively recently.
Only a few centimeters across, it is to be found in the more northern waters of the Great Barrier Reef - in fact its name comes from the name of the Aboriginal Tribe that lived around the Cairns area.
"Irukandji Syndrome" is a term used when these critters appear (summer months) and start stinging innocent swimmers. The effects of an Irukandji sting go unnoticed at first, maybe for up to half an hour. But when the venom does kick in, it's powerful enough to hospitalize an adult human.
This very small but dangerous animal of the Reef is almost impossible to see at a glance, making the danger even greater.
Blue Ringed Octopus
The Blue Ringed (or Blue Ring) Octopus is the only dangerous octopus in the world, and makes its home all around Australia including the Great Barrier Reef.
The octopus is browny-yellow in color with dark patterns all over its body and tentacles. The blue rings appear when the octopus is agitated or threatened.
As octopi go, it's pretty small - not much larger than an adult hand. It can be found very close to shore and quite often in rockpools, making it an easy target for human curiosity. Touching the Blue Ringed Octopus is harmless but not advised - the problem comes when they are picked up. The octopus will bite with its tiny beak and inject a very powerful venom into the victim.
The bite can be very subtle though, barely noticeable in many cases. The venom kicks in a few minutes later, resulting in breathing difficulties and nausea, often leading to fainting or worse if the venom triggers an allergic reaction.
If you see one, take a photo and leave it at that!
Cone shells
Most people are unaware that one of the most dangerous animals on the Great Barrier Reef is a shellfish.
There are many different species of Cone Shells all over the Reef, some harmless and others deadly. Rather like the Blue Ringed Octopus, Cone Shells can be found in rockpools and their attractive shells make them good for picking up.
If threatened, the shellfish will fire a harpoon-like dart into the victim, injecting a very strong venom that is powerful enough to kill a human in some cases.
Another danger of course is accidentally stepping on one while bathing. Unlike the octopus, the sting will be felt immediately.
Stonefish
Stonefish are rather ugly looking creatures, a mottled greeny-brown in color.
They prefer the warmer waters so are more commonly found in the northern half of the Reef. Stonefish lay motionless on top of rocks or the seabed, where their camouflage colors make them very hard to see.
Stepping on a Stonefish is a very painful experience - 13 spines along the back of the fish inject a highly toxic venom if pressure is put on them, ie by a foot. The level of pain depends on how deeply the spines penetrated the skin, but even a light amount of pressure will still be excruciating.
Lion Fish
Members of the Scorpion Fish family, Lion Fish can be found all over the Great Barrier Reef. Their exotic looks are a big attraction, but seeing one isn't that easy - they like to lay low around crevices and small caves, although shallow waters are common territory for the Lion Fish which makes them a threat to swimmers.
The unusually elongated fins double up as lethal spines that will penetrate skin given the chance. A Lion Fish sting is very painful and immediate, resulting in muscle swelling and cramps, nausea, fainting and even death in certain circumstances.
For more information about the Animals of the Great Barrier Reef take a look at our pages on theAnimals of the Reef; the Endangered Animals of the Reef; and the Hammerhead Shark.